eventsource-parser - npm Package Compare versions

Comparing version 3.0.6 to 3.0.7

dist/index.cjs

@@ -8,2 +8,3 @@ "use strict";
 }
+const LF = 10, CR = 13, SPACE = 32;
 function noop(_arg) {
@@ -17,25 +18,91 @@ }
   const { onEvent = noop, onError = noop, onRetry = noop, onComment } = callbacks;
-  let incompleteLine = "", isFirstChunk = !0, id, data = "", eventType = "";
-  function feed(newChunk) {
-    const chunk = isFirstChunk ? newChunk.replace(/^\xEF\xBB\xBF/, "") : newChunk, [complete, incomplete] = splitLines(`${incompleteLine}${chunk}`);
-    for (const line of complete)
-      parseLine(line);
-    incompleteLine = incomplete, isFirstChunk = !1;
+  let incompleteLine = "", isFirstChunk = !0, id, data = "", dataLines = 0, eventType;
+  function feed(chunk) {
+    if (isFirstChunk) {
+      isFirstChunk = !1, feedFirst(chunk);
+      return;
+    }
+    const input = incompleteLine === "" ? chunk : incompleteLine + chunk;
+    incompleteLine = processLines(input);
   }
-  function parseLine(line) {
-    if (line === "") {
+  function feedFirst(chunk) {
+    chunk.charCodeAt(0) === 239 && chunk.charCodeAt(1) === 187 && chunk.charCodeAt(2) === 191 && (chunk = chunk.slice(3));
+    const input = incompleteLine === "" ? chunk : incompleteLine + chunk;
+    incompleteLine = processLines(input);
+  }
+  function processLines(chunk) {
+    let searchIndex = 0;
+    if (chunk.indexOf("\r") === -1) {
+      let lfIndex = chunk.indexOf(`
+`, searchIndex);
+      for (; lfIndex !== -1; ) {
+        if (searchIndex === lfIndex) {
+          dataLines > 0 && onEvent({ id, event: eventType, data }), id = void 0, data = "", dataLines = 0, eventType = void 0, searchIndex = lfIndex + 1, lfIndex = chunk.indexOf(`
+`, searchIndex);
+          continue;
+        }
+        const firstCharCode = chunk.charCodeAt(searchIndex);
+        if (isDataPrefix(chunk, searchIndex, firstCharCode)) {
+          const valueStart = chunk.charCodeAt(searchIndex + 5) === SPACE ? searchIndex + 6 : searchIndex + 5, value = chunk.slice(valueStart, lfIndex);
+          if (dataLines === 0 && chunk.charCodeAt(lfIndex + 1) === LF) {
+            onEvent({ id, event: eventType, data: value }), id = void 0, data = "", eventType = void 0, searchIndex = lfIndex + 2, lfIndex = chunk.indexOf(`
+`, searchIndex);
+            continue;
+          }
+          data = dataLines === 0 ? value : `${data}
+${value}`, dataLines++;
+        } else isEventPrefix(chunk, searchIndex, firstCharCode) ? eventType = chunk.slice(
+          chunk.charCodeAt(searchIndex + 6) === SPACE ? searchIndex + 7 : searchIndex + 6,
+          lfIndex
+        ) || void 0 : parseLine(chunk, searchIndex, lfIndex);
+        searchIndex = lfIndex + 1, lfIndex = chunk.indexOf(`
+`, searchIndex);
+      }
+      return chunk.slice(searchIndex);
+    }
+    for (; searchIndex < chunk.length; ) {
+      const crIndex = chunk.indexOf("\r", searchIndex), lfIndex = chunk.indexOf(`
+`, searchIndex);
+      let lineEnd = -1;
+      if (crIndex !== -1 && lfIndex !== -1 ? lineEnd = crIndex < lfIndex ? crIndex : lfIndex : crIndex !== -1 ? crIndex === chunk.length - 1 ? lineEnd = -1 : lineEnd = crIndex : lfIndex !== -1 && (lineEnd = lfIndex), lineEnd === -1)
+        break;
+      parseLine(chunk, searchIndex, lineEnd), searchIndex = lineEnd + 1, chunk.charCodeAt(searchIndex - 1) === CR && chunk.charCodeAt(searchIndex) === LF && searchIndex++;
+    }
+    return chunk.slice(searchIndex);
+  }
+  function parseLine(chunk, start, end) {
+    if (start === end) {
       dispatchEvent();
       return;
     }
-    if (line.startsWith(":")) {
-      onComment && onComment(line.slice(line.startsWith(": ") ? 2 : 1));
+    const firstCharCode = chunk.charCodeAt(start);
+    if (isDataPrefix(chunk, start, firstCharCode)) {
+      const valueStart = chunk.charCodeAt(start + 5) === SPACE ? start + 6 : start + 5, value2 = chunk.slice(valueStart, end);
+      data = dataLines === 0 ? value2 : `${data}
+${value2}`, dataLines++;
       return;
     }
-    const fieldSeparatorIndex = line.indexOf(":");
-    if (fieldSeparatorIndex !== -1) {
-      const field = line.slice(0, fieldSeparatorIndex), offset = line[fieldSeparatorIndex + 1] === " " ? 2 : 1, value = line.slice(fieldSeparatorIndex + offset);
-      processField(field, value, line);
+    if (isEventPrefix(chunk, start, firstCharCode)) {
+      eventType = chunk.slice(chunk.charCodeAt(start + 6) === SPACE ? start + 7 : start + 6, end) || void 0;
       return;
     }
-    processField(line, "", line);
+    if (firstCharCode === 105 && chunk.charCodeAt(start + 1) === 100 && chunk.charCodeAt(start + 2) === 58) {
+      const value2 = chunk.slice(chunk.charCodeAt(start + 3) === SPACE ? start + 4 : start + 3, end);
+      id = value2.includes("\0") ? void 0 : value2;
+      return;
+    }
+    if (firstCharCode === 58) {
+      if (onComment) {
+        const line2 = chunk.slice(start, end);
+        onComment(line2.slice(chunk.charCodeAt(start + 1) === SPACE ? 2 : 1));
+      }
+      return;
+    }
+    const line = chunk.slice(start, end), fieldSeparatorIndex = line.indexOf(":");
+    if (fieldSeparatorIndex === -1) {
+      processField(line, "", line);
+      return;
+    }
+    const field = line.slice(0, fieldSeparatorIndex), offset = line.charCodeAt(fieldSeparatorIndex + 1) === SPACE ? 2 : 1, value = line.slice(fieldSeparatorIndex + offset);
+    processField(field, value, line);
   }
@@ -45,7 +112,7 @@ function processField(field, value, line) {
       case "event":
-        eventType = value;
+        eventType = value || void 0;
         break;
       case "data":
-        data = `${data}${value}
-`;
+        data = dataLines === 0 ? value : `${data}
+${value}`, dataLines++;
         break;
@@ -75,36 +142,21 @@ case "id":
   function dispatchEvent() {
-    data.length > 0 && onEvent({
+    dataLines > 0 && onEvent({
       id,
-      event: eventType || void 0,
-      // If the data buffer's last character is a U+000A LINE FEED (LF) character,
-      // then remove the last character from the data buffer.
-      data: data.endsWith(`
-`) ? data.slice(0, -1) : data
-    }), id = void 0, data = "", eventType = "";
+      event: eventType,
+      data
+    }), id = void 0, data = "", dataLines = 0, eventType = void 0;
   }
   function reset(options = {}) {
-    incompleteLine && options.consume && parseLine(incompleteLine), isFirstChunk = !0, id = void 0, data = "", eventType = "", incompleteLine = "";
+    incompleteLine && options.consume && parseLine(incompleteLine, 0, incompleteLine.length), isFirstChunk = !0, id = void 0, data = "", dataLines = 0, eventType = void 0, incompleteLine = "";
   }
   return { feed, reset };
 }
-function splitLines(chunk) {
-  const lines = [];
-  let incompleteLine = "", searchIndex = 0;
-  for (; searchIndex < chunk.length; ) {
-    const crIndex = chunk.indexOf("\r", searchIndex), lfIndex = chunk.indexOf(`
-`, searchIndex);
-    let lineEnd = -1;
-    if (crIndex !== -1 && lfIndex !== -1 ? lineEnd = Math.min(crIndex, lfIndex) : crIndex !== -1 ? crIndex === chunk.length - 1 ? lineEnd = -1 : lineEnd = crIndex : lfIndex !== -1 && (lineEnd = lfIndex), lineEnd === -1) {
-      incompleteLine = chunk.slice(searchIndex);
-      break;
-    } else {
-      const line = chunk.slice(searchIndex, lineEnd);
-      lines.push(line), searchIndex = lineEnd + 1, chunk[searchIndex - 1] === "\r" && chunk[searchIndex] === `
-` && searchIndex++;
-    }
-  }
-  return [lines, incompleteLine];
+function isDataPrefix(chunk, i, firstCharCode) {
+  return firstCharCode === 100 && chunk.charCodeAt(i + 1) === 97 && chunk.charCodeAt(i + 2) === 116 && chunk.charCodeAt(i + 3) === 97 && chunk.charCodeAt(i + 4) === 58;
 }
+function isEventPrefix(chunk, i, firstCharCode) {
+  return firstCharCode === 101 && chunk.charCodeAt(i + 1) === 118 && chunk.charCodeAt(i + 2) === 101 && chunk.charCodeAt(i + 3) === 110 && chunk.charCodeAt(i + 4) === 116 && chunk.charCodeAt(i + 5) === 58;
+}
 exports.ParseError = ParseError;
 exports.createParser = createParser;
 //# sourceMappingURL=index.cjs.map

dist/index.cjs.map

@@ -1,1 +0,1 @@
-{"version":3,"file":"index.cjs","sources":["../src/errors.ts","../src/parse.ts"],"sourcesContent":["/**\n * The type of error that occurred.\n * @public\n */\nexport type ErrorType = 'invalid-retry' | 'unknown-field'\n\n/**\n * Error thrown when encountering an issue during parsing.\n *\n * @public\n */\nexport class ParseError extends Error {\n  /**\n   * The type of error that occurred.\n   */\n  type: ErrorType\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the field name.\n   */\n  field?: string | undefined\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the value of the field.\n   */\n  value?: string | undefined\n\n  /**\n   * The line that caused the error, if available.\n   */\n  line?: string | undefined\n\n  constructor(\n    message: string,\n    options: {type: ErrorType; field?: string; value?: string; line?: string},\n  ) {\n    super(message)\n    this.name = 'ParseError'\n    this.type = options.type\n    this.field = options.field\n    this.value = options.value\n    this.line = options.line\n  }\n}\n","/**\n * EventSource/Server-Sent Events parser\n * @see https://html.spec.whatwg.org/multipage/server-sent-events.html\n */\nimport {ParseError} from './errors.ts'\nimport type {EventSourceParser, ParserCallbacks} from './types.ts'\n\n// eslint-disable-next-line @typescript-eslint/no-unused-vars\nfunction noop(_arg: unknown) {\n  // intentional noop\n}\n\n/**\n * Creates a new EventSource parser.\n *\n * @param callbacks - Callbacks to invoke on different parsing events:\n *   - `onEvent` when a new event is parsed\n *   - `onError` when an error occurs\n *   - `onRetry` when a new reconnection interval has been sent from the server\n *   - `onComment` when a comment is encountered in the stream\n *\n * @returns A new EventSource parser, with `parse` and `reset` methods.\n * @public\n */\nexport function createParser(callbacks: ParserCallbacks): EventSourceParser {\n  if (typeof callbacks === 'function') {\n    throw new TypeError(\n      '`callbacks` must be an object, got a function instead. Did you mean `{onEvent: fn}`?',\n    )\n  }\n\n  const {onEvent = noop, onError = noop, onRetry = noop, onComment} = callbacks\n\n  let incompleteLine = ''\n\n  let isFirstChunk = true\n  let id: string | undefined\n  let data = ''\n  let eventType = ''\n\n  function feed(newChunk: string) {\n    // Strip any UTF8 byte order mark (BOM) at the start of the stream\n    const chunk = isFirstChunk ? newChunk.replace(/^\\xEF\\xBB\\xBF/, '') : newChunk\n\n    // If there was a previous incomplete line, append it to the new chunk,\n    // so we may process it together as a new (hopefully complete) chunk.\n    const [complete, incomplete] = splitLines(`${incompleteLine}${chunk}`)\n\n    for (const line of complete) {\n      parseLine(line)\n    }\n\n    incompleteLine = incomplete\n    isFirstChunk = false\n  }\n\n  function parseLine(line: string) {\n    // If the line is empty (a blank line), dispatch the event\n    if (line === '') {\n      dispatchEvent()\n      return\n    }\n\n    // If the line starts with a U+003A COLON character (:), ignore the line.\n    if (line.startsWith(':')) {\n      if (onComment) {\n        onComment(line.slice(line.startsWith(': ') ? 2 : 1))\n      }\n      return\n    }\n\n    // If the line contains a U+003A COLON character (:)\n    const fieldSeparatorIndex = line.indexOf(':')\n    if (fieldSeparatorIndex !== -1) {\n      // Collect the characters on the line before the first U+003A COLON character (:),\n      // and let `field` be that string.\n      const field = line.slice(0, fieldSeparatorIndex)\n\n      // Collect the characters on the line after the first U+003A COLON character (:),\n      // and let `value` be that string. If value starts with a U+0020 SPACE character,\n      // remove it from value.\n      const offset = line[fieldSeparatorIndex + 1] === ' ' ? 2 : 1\n      const value = line.slice(fieldSeparatorIndex + offset)\n\n      processField(field, value, line)\n      return\n    }\n\n    // Otherwise, the string is not empty but does not contain a U+003A COLON character (:)\n    // Process the field using the whole line as the field name, and an empty string as the field value.\n    // 👆 This is according to spec. That means that a line that has the value `data` will result in\n    // a newline being added to the current `data` buffer, for instance.\n    processField(line, '', line)\n  }\n\n  function processField(field: string, value: string, line: string) {\n    // Field names must be compared literally, with no case folding performed.\n    switch (field) {\n      case 'event':\n        // Set the `event type` buffer to field value\n        eventType = value\n        break\n      case 'data':\n        // Append the field value to the `data` buffer, then append a single U+000A LINE FEED(LF)\n        // character to the `data` buffer.\n        data = `${data}${value}\\n`\n        break\n      case 'id':\n        // If the field value does not contain U+0000 NULL, then set the `ID` buffer to\n        // the field value. Otherwise, ignore the field.\n        id = value.includes('\\0') ? undefined : value\n        break\n      case 'retry':\n        // If the field value consists of only ASCII digits, then interpret the field value as an\n        // integer in base ten, and set the event stream's reconnection time to that integer.\n        // Otherwise, ignore the field.\n        if (/^\\d+$/.test(value)) {\n          onRetry(parseInt(value, 10))\n        } else {\n          onError(\n            new ParseError(`Invalid \\`retry\\` value: \"${value}\"`, {\n              type: 'invalid-retry',\n              value,\n              line,\n            }),\n          )\n        }\n        break\n      default:\n        // Otherwise, the field is ignored.\n        onError(\n          new ParseError(\n            `Unknown field \"${field.length > 20 ? `${field.slice(0, 20)}…` : field}\"`,\n            {type: 'unknown-field', field, value, line},\n          ),\n        )\n        break\n    }\n  }\n\n  function dispatchEvent() {\n    const shouldDispatch = data.length > 0\n    if (shouldDispatch) {\n      onEvent({\n        id,\n        event: eventType || undefined,\n        // If the data buffer's last character is a U+000A LINE FEED (LF) character,\n        // then remove the last character from the data buffer.\n        data: data.endsWith('\\n') ? data.slice(0, -1) : data,\n      })\n    }\n\n    // Reset for the next event\n    id = undefined\n    data = ''\n    eventType = ''\n  }\n\n  function reset(options: {consume?: boolean} = {}) {\n    if (incompleteLine && options.consume) {\n      parseLine(incompleteLine)\n    }\n\n    isFirstChunk = true\n    id = undefined\n    data = ''\n    eventType = ''\n    incompleteLine = ''\n  }\n\n  return {feed, reset}\n}\n\n/**\n * For the given `chunk`, split it into lines according to spec, and return any remaining incomplete line.\n *\n * @param chunk - The chunk to split into lines\n * @returns A tuple containing an array of complete lines, and any remaining incomplete line\n * @internal\n */\nfunction splitLines(chunk: string): [complete: Array<string>, incomplete: string] {\n  /**\n   * According to the spec, a line is terminated by either:\n   * - U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair\n   * - a single U+000A LINE FEED(LF) character not preceded by a U+000D CARRIAGE RETURN(CR) character\n   * - a single U+000D CARRIAGE RETURN(CR) character not followed by a U+000A LINE FEED(LF) character\n   */\n  const lines: Array<string> = []\n  let incompleteLine = ''\n  let searchIndex = 0\n\n  while (searchIndex < chunk.length) {\n    // Find next line terminator\n    const crIndex = chunk.indexOf('\\r', searchIndex)\n    const lfIndex = chunk.indexOf('\\n', searchIndex)\n\n    // Determine line end\n    let lineEnd = -1\n    if (crIndex !== -1 && lfIndex !== -1) {\n      // CRLF case\n      lineEnd = Math.min(crIndex, lfIndex)\n    } else if (crIndex !== -1) {\n      // CR at the end of a chunk might be part of a CRLF sequence that spans chunks,\n      // so we shouldn't treat it as a line terminator (yet)\n      if (crIndex === chunk.length - 1) {\n        lineEnd = -1\n      } else {\n        lineEnd = crIndex\n      }\n    } else if (lfIndex !== -1) {\n      lineEnd = lfIndex\n    }\n\n    // Extract line if terminator found\n    if (lineEnd === -1) {\n      // No terminator found, rest is incomplete\n      incompleteLine = chunk.slice(searchIndex)\n      break\n    } else {\n      const line = chunk.slice(searchIndex, lineEnd)\n      lines.push(line)\n\n      // Move past line terminator\n      searchIndex = lineEnd + 1\n      if (chunk[searchIndex - 1] === '\\r' && chunk[searchIndex] === '\\n') {\n        searchIndex++\n      }\n    }\n  }\n\n  return [lines, incompleteLine]\n}\n"],"names":[],"mappings":";;AAWO,MAAM,mBAAmB,MAAM;AAAA,EAqBpC,YACE,SACA,SACA;AACA,UAAM,OAAO,GACb,KAAK,OAAO,cACZ,KAAK,OAAO,QAAQ,MACpB,KAAK,QAAQ,QAAQ,OACrB,KAAK,QAAQ,QAAQ,OACrB,KAAK,OAAO,QAAQ;AAAA,EACtB;AACF;ACnCA,SAAS,KAAK,MAAe;AAE7B;AAcO,SAAS,aAAa,WAA+C;AAC1E,MAAI,OAAO,aAAc;AACvB,UAAM,IAAI;AAAA,MACR;AAAA,IAAA;AAIJ,QAAM,EAAC,UAAU,MAAM,UAAU,MAAM,UAAU,MAAM,cAAa;AAEpE,MAAI,iBAAiB,IAEjB,eAAe,IACf,IACA,OAAO,IACP,YAAY;AAEhB,WAAS,KAAK,UAAkB;AAE9B,UAAM,QAAQ,eAAe,SAAS,QAAQ,iBAAiB,EAAE,IAAI,UAI/D,CAAC,UAAU,UAAU,IAAI,WAAW,GAAG,cAAc,GAAG,KAAK,EAAE;AAErE,eAAW,QAAQ;AACjB,gBAAU,IAAI;AAGhB,qBAAiB,YACjB,eAAe;AAAA,EACjB;AAEA,WAAS,UAAU,MAAc;AAE/B,QAAI,SAAS,IAAI;AACf,oBAAA;AACA;AAAA,IACF;AAGA,QAAI,KAAK,WAAW,GAAG,GAAG;AACpB,mBACF,UAAU,KAAK,MAAM,KAAK,WAAW,IAAI,IAAI,IAAI,CAAC,CAAC;AAErD;AAAA,IACF;AAGA,UAAM,sBAAsB,KAAK,QAAQ,GAAG;AAC5C,QAAI,wBAAwB,IAAI;AAG9B,YAAM,QAAQ,KAAK,MAAM,GAAG,mBAAmB,GAKzC,SAAS,KAAK,sBAAsB,CAAC,MAAM,MAAM,IAAI,GACrD,QAAQ,KAAK,MAAM,sBAAsB,MAAM;AAErD,mBAAa,OAAO,OAAO,IAAI;AAC/B;AAAA,IACF;AAMA,iBAAa,MAAM,IAAI,IAAI;AAAA,EAC7B;AAEA,WAAS,aAAa,OAAe,OAAe,MAAc;AAEhE,YAAQ,OAAA;AAAA,MACN,KAAK;AAEH,oBAAY;AACZ;AAAA,MACF,KAAK;AAGH,eAAO,GAAG,IAAI,GAAG,KAAK;AAAA;AACtB;AAAA,MACF,KAAK;AAGH,aAAK,MAAM,SAAS,IAAI,IAAI,SAAY;AACxC;AAAA,MACF,KAAK;AAIC,gBAAQ,KAAK,KAAK,IACpB,QAAQ,SAAS,OAAO,EAAE,CAAC,IAE3B;AAAA,UACE,IAAI,WAAW,6BAA6B,KAAK,KAAK;AAAA,YACpD,MAAM;AAAA,YACN;AAAA,YACA;AAAA,UAAA,CACD;AAAA,QAAA;AAGL;AAAA,MACF;AAEE;AAAA,UACE,IAAI;AAAA,YACF,kBAAkB,MAAM,SAAS,KAAK,GAAG,MAAM,MAAM,GAAG,EAAE,CAAC,WAAM,KAAK;AAAA,YACtE,EAAC,MAAM,iBAAiB,OAAO,OAAO,KAAA;AAAA,UAAI;AAAA,QAC5C;AAEF;AAAA,IAAA;AAAA,EAEN;AAEA,WAAS,gBAAgB;AACA,SAAK,SAAS,KAEnC,QAAQ;AAAA,MACN;AAAA,MACA,OAAO,aAAa;AAAA;AAAA;AAAA,MAGpB,MAAM,KAAK,SAAS;AAAA,CAAI,IAAI,KAAK,MAAM,GAAG,EAAE,IAAI;AAAA,IAAA,CACjD,GAIH,KAAK,QACL,OAAO,IACP,YAAY;AAAA,EACd;AAEA,WAAS,MAAM,UAA+B,IAAI;AAC5C,sBAAkB,QAAQ,WAC5B,UAAU,cAAc,GAG1B,eAAe,IACf,KAAK,QACL,OAAO,IACP,YAAY,IACZ,iBAAiB;AAAA,EACnB;AAEA,SAAO,EAAC,MAAM,MAAA;AAChB;AASA,SAAS,WAAW,OAA8D;AAOhF,QAAM,QAAuB,CAAA;AAC7B,MAAI,iBAAiB,IACjB,cAAc;AAElB,SAAO,cAAc,MAAM,UAAQ;AAEjC,UAAM,UAAU,MAAM,QAAQ,MAAM,WAAW,GACzC,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AAG/C,QAAI,UAAU;AAiBd,QAhBI,YAAY,MAAM,YAAY,KAEhC,UAAU,KAAK,IAAI,SAAS,OAAO,IAC1B,YAAY,KAGjB,YAAY,MAAM,SAAS,IAC7B,UAAU,KAEV,UAAU,UAEH,YAAY,OACrB,UAAU,UAIR,YAAY,IAAI;AAElB,uBAAiB,MAAM,MAAM,WAAW;AACxC;AAAA,IACF,OAAO;AACL,YAAM,OAAO,MAAM,MAAM,aAAa,OAAO;AAC7C,YAAM,KAAK,IAAI,GAGf,cAAc,UAAU,GACpB,MAAM,cAAc,CAAC,MAAM,QAAQ,MAAM,WAAW,MAAM;AAAA,KAC5D;AAAA,IAEJ;AAAA,EACF;AAEA,SAAO,CAAC,OAAO,cAAc;AAC/B;;;"}
+{"version":3,"file":"index.cjs","sources":["../src/errors.ts","../src/parse.ts"],"sourcesContent":["/**\n * The type of error that occurred.\n * @public\n */\nexport type ErrorType = 'invalid-retry' | 'unknown-field'\n\n/**\n * Error thrown when encountering an issue during parsing.\n *\n * @public\n */\nexport class ParseError extends Error {\n  /**\n   * The type of error that occurred.\n   */\n  type: ErrorType\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the field name.\n   */\n  field?: string | undefined\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the value of the field.\n   */\n  value?: string | undefined\n\n  /**\n   * The line that caused the error, if available.\n   */\n  line?: string | undefined\n\n  constructor(\n    message: string,\n    options: {type: ErrorType; field?: string; value?: string; line?: string},\n  ) {\n    super(message)\n    this.name = 'ParseError'\n    this.type = options.type\n    this.field = options.field\n    this.value = options.value\n    this.line = options.line\n  }\n}\n","/**\n * EventSource/Server-Sent Events parser\n * @see https://html.spec.whatwg.org/multipage/server-sent-events.html\n */\nimport {ParseError} from './errors.ts'\nimport type {EventSourceParser, ParserCallbacks} from './types.ts'\n\n// ASCII codes used in the hot parsing paths.\nconst LF = 10\nconst CR = 13\nconst SPACE = 32\n\n// oxlint-disable-next-line no-unused-vars\nfunction noop(_arg: unknown) {\n  // intentional noop\n}\n\n/**\n * Creates a new EventSource parser.\n *\n * @param callbacks - Callbacks to invoke on different parsing events:\n *   - `onEvent` when a new event is parsed\n *   - `onError` when an error occurs\n *   - `onRetry` when a new reconnection interval has been sent from the server\n *   - `onComment` when a comment is encountered in the stream\n *\n * @returns A new EventSource parser, with `parse` and `reset` methods.\n * @public\n */\nexport function createParser(callbacks: ParserCallbacks): EventSourceParser {\n  if (typeof callbacks === 'function') {\n    throw new TypeError(\n      '`callbacks` must be an object, got a function instead. Did you mean `{onEvent: fn}`?',\n    )\n  }\n\n  const {onEvent = noop, onError = noop, onRetry = noop, onComment} = callbacks\n\n  let incompleteLine = ''\n\n  let isFirstChunk = true\n  let id: string | undefined\n  let data = ''\n  let dataLines = 0\n  let eventType: string | undefined\n\n  /**\n   * Feeds a chunk of the SSE stream to the parser. Any trailing bytes that do\n   * not yet form a complete line are held back and prepended to the next chunk,\n   * so callers can pass arbitrary slices of the stream without worrying about\n   * line boundaries.\n   *\n   * The first chunk is dispatched to {@link feedFirst} so the leading UTF-8\n   * BOM can be stripped before parsing begins.\n   */\n  function feed(chunk: string) {\n    if (isFirstChunk) {\n      isFirstChunk = false\n      feedFirst(chunk)\n      return\n    }\n    const input = incompleteLine === '' ? chunk : incompleteLine + chunk\n    incompleteLine = processLines(input)\n  }\n\n  /**\n   * Handles the very first chunk of the stream. Per the SSE spec, a UTF-8 BOM\n   * (0xEF 0xBB 0xBF) at the start of the stream must be stripped before\n   * parsing. After BOM handling, behaves identically to {@link feed}.\n   *\n   * @see https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream\n   */\n  function feedFirst(chunk: string) {\n    if (\n      chunk.charCodeAt(0) === 0xef &&\n      chunk.charCodeAt(1) === 0xbb &&\n      chunk.charCodeAt(2) === 0xbf\n    ) {\n      chunk = chunk.slice(3)\n    }\n    const input = incompleteLine === '' ? chunk : incompleteLine + chunk\n    incompleteLine = processLines(input)\n  }\n\n  /**\n   * Splits `chunk` into SSE lines and dispatches each to the appropriate handler.\n   * Returns any trailing bytes that did not terminate with a line break, so the\n   * caller can prepend them to the next chunk.\n   *\n   * The SSE spec permits three line terminators: `\\n`, `\\r`, and `\\r\\n`. Real-world\n   * streams almost always use plain `\\n`, so we take a fast path when no `\\r` is\n   * present in the chunk. The slow path is spec-correct but does more work per line.\n   */\n  function processLines(chunk: string): string {\n    let searchIndex = 0\n\n    // Fast path: LF-only chunk (the common case for typical SSE servers).\n    // We can scan forward with a single `indexOf('\\n')` per line and inline\n    // the hot-path branches for `data:` and `event:` without the CR bookkeeping\n    // the slow path needs.\n    if (chunk.indexOf('\\r') === -1) {\n      let lfIndex = chunk.indexOf('\\n', searchIndex)\n      while (lfIndex !== -1) {\n        // Blank line: end-of-event marker. Dispatch the accumulated event (if any)\n        // and reset the buffered fields. This is hoisted out of `parseLine` because\n        // it's the single most common line shape after `data:` lines.\n        if (searchIndex === lfIndex) {\n          if (dataLines > 0) {\n            onEvent({id, event: eventType, data})\n          }\n          id = undefined\n          data = ''\n          dataLines = 0\n          eventType = undefined\n          searchIndex = lfIndex + 1\n          lfIndex = chunk.indexOf('\\n', searchIndex)\n          continue\n        }\n        const firstCharCode = chunk.charCodeAt(searchIndex)\n        if (isDataPrefix(chunk, searchIndex, firstCharCode)) {\n          // `data:` line — append the value to the event's data buffer.\n          // 'data:'.length === 5, 'data: '.length === 6\n          const valueStart =\n            chunk.charCodeAt(searchIndex + 5) === SPACE ? searchIndex + 6 : searchIndex + 5\n          const value = chunk.slice(valueStart, lfIndex)\n          // Fast path within a fast path: if this is the first data line AND the\n          // next char is another LF (i.e. `data:foo\\n\\n`), dispatch immediately\n          // without ever writing to the `data` buffer. This is the shape of a\n          // typical single-line SSE event (ChatGPT-style streams, etc.) and is\n          // hot enough to be worth the duplication.\n          if (dataLines === 0 && chunk.charCodeAt(lfIndex + 1) === LF) {\n            onEvent({id, event: eventType, data: value})\n            id = undefined\n            data = ''\n            eventType = undefined\n            searchIndex = lfIndex + 2\n            lfIndex = chunk.indexOf('\\n', searchIndex)\n            continue\n          }\n          // Multi-line data: concatenate with newline separator per spec.\n          data = dataLines === 0 ? value : `${data}\\n${value}`\n          dataLines++\n        } else if (isEventPrefix(chunk, searchIndex, firstCharCode)) {\n          // `event:` line — set the event type for the next dispatch. Per spec,\n          // an empty value resets `event type` to its default (undefined here).\n          // 'event:'.length === 6, 'event: '.length === 7\n          eventType =\n            chunk.slice(\n              chunk.charCodeAt(searchIndex + 6) === SPACE ? searchIndex + 7 : searchIndex + 6,\n              lfIndex,\n            ) || undefined\n        } else {\n          // Everything else: `id:`, `retry:`, comment lines (`:` prefix), unknown\n          // fields, or malformed lines. These are rarer and go through the full\n          // per-line parser, which handles the SSE field grammar in detail.\n          parseLine(chunk, searchIndex, lfIndex)\n        }\n        searchIndex = lfIndex + 1\n        lfIndex = chunk.indexOf('\\n', searchIndex)\n      }\n      return chunk.slice(searchIndex)\n    }\n\n    // Slow path: the chunk contains at least one `\\r`, so lines may be terminated\n    // by `\\r`, `\\n`, or `\\r\\n`. We locate the next terminator by looking at both\n    // the nearest `\\r` and `\\n` and picking whichever comes first.\n    while (searchIndex < chunk.length) {\n      const crIndex = chunk.indexOf('\\r', searchIndex)\n      const lfIndex = chunk.indexOf('\\n', searchIndex)\n\n      let lineEnd = -1\n      if (crIndex !== -1 && lfIndex !== -1) {\n        lineEnd = crIndex < lfIndex ? crIndex : lfIndex\n      } else if (crIndex !== -1) {\n        // A trailing `\\r` at the very end of the chunk is ambiguous: it could be\n        // a bare-CR terminator, or the first half of a `\\r\\n` whose `\\n` arrives\n        // in the next chunk. Defer until we see more input.\n        if (crIndex === chunk.length - 1) {\n          lineEnd = -1\n        } else {\n          lineEnd = crIndex\n        }\n      } else if (lfIndex !== -1) {\n        lineEnd = lfIndex\n      }\n\n      if (lineEnd === -1) {\n        break\n      }\n\n      parseLine(chunk, searchIndex, lineEnd)\n      searchIndex = lineEnd + 1\n      // If we just consumed a `\\r` and the next char is `\\n`, skip it so the\n      // pair is treated as a single terminator rather than an empty line.\n      if (chunk.charCodeAt(searchIndex - 1) === CR && chunk.charCodeAt(searchIndex) === LF) {\n        searchIndex++\n      }\n    }\n\n    return chunk.slice(searchIndex)\n  }\n\n  function parseLine(chunk: string, start: number, end: number) {\n    if (start === end) {\n      dispatchEvent()\n      return\n    }\n\n    const firstCharCode = chunk.charCodeAt(start)\n\n    if (isDataPrefix(chunk, start, firstCharCode)) {\n      // 'data:'.length === 5, 'data: '.length === 6\n      const valueStart = chunk.charCodeAt(start + 5) === SPACE ? start + 6 : start + 5\n      const value = chunk.slice(valueStart, end)\n      data = dataLines === 0 ? value : `${data}\\n${value}`\n      dataLines++\n      return\n    }\n\n    if (isEventPrefix(chunk, start, firstCharCode)) {\n      // 'event:'.length === 6, 'event: '.length === 7\n      eventType =\n        chunk.slice(chunk.charCodeAt(start + 6) === SPACE ? start + 7 : start + 6, end) || undefined\n      return\n    }\n\n    // Fast path for \"id:\" — 'i' = 105, 'd' = 100, ':' = 58\n    if (\n      firstCharCode === 105 &&\n      chunk.charCodeAt(start + 1) === 100 &&\n      chunk.charCodeAt(start + 2) === 58\n    ) {\n      // 'id:'.length === 3, 'id: '.length === 4\n      const value = chunk.slice(chunk.charCodeAt(start + 3) === SPACE ? start + 4 : start + 3, end)\n      id = value.includes('\\0') ? undefined : value\n      return\n    }\n\n    // Comment line — ':' = 58\n    if (firstCharCode === 58) {\n      if (onComment) {\n        const line = chunk.slice(start, end)\n        // skip ':' (+1), or ': ' (+2) when a space follows\n        onComment(line.slice(chunk.charCodeAt(start + 1) === SPACE ? 2 : 1))\n      }\n      return\n    }\n\n    const line = chunk.slice(start, end)\n    const fieldSeparatorIndex = line.indexOf(':')\n    if (fieldSeparatorIndex === -1) {\n      processField(line, '', line)\n      return\n    }\n\n    const field = line.slice(0, fieldSeparatorIndex)\n    // skip ':' (+1), or ': ' (+2) when a space follows\n    const offset = line.charCodeAt(fieldSeparatorIndex + 1) === SPACE ? 2 : 1\n    const value = line.slice(fieldSeparatorIndex + offset)\n    processField(field, value, line)\n  }\n\n  function processField(field: string, value: string, line: string) {\n    // Field names must be compared literally, with no case folding performed.\n    switch (field) {\n      case 'event':\n        // Set the `event type` buffer to field value\n        eventType = value || undefined\n        break\n      case 'data':\n        data = dataLines === 0 ? value : `${data}\\n${value}`\n        dataLines++\n        break\n      case 'id':\n        // If the field value does not contain U+0000 NULL, then set the `ID` buffer to\n        // the field value. Otherwise, ignore the field.\n        id = value.includes('\\0') ? undefined : value\n        break\n      case 'retry':\n        // If the field value consists of only ASCII digits, then interpret the field value as an\n        // integer in base ten, and set the event stream's reconnection time to that integer.\n        // Otherwise, ignore the field.\n        if (/^\\d+$/.test(value)) {\n          onRetry(parseInt(value, 10))\n        } else {\n          onError(\n            new ParseError(`Invalid \\`retry\\` value: \"${value}\"`, {\n              type: 'invalid-retry',\n              value,\n              line,\n            }),\n          )\n        }\n        break\n      default:\n        // Otherwise, the field is ignored.\n        onError(\n          new ParseError(\n            `Unknown field \"${field.length > 20 ? `${field.slice(0, 20)}…` : field}\"`,\n            {type: 'unknown-field', field, value, line},\n          ),\n        )\n        break\n    }\n  }\n\n  function dispatchEvent() {\n    if (dataLines > 0) {\n      onEvent({\n        id,\n        event: eventType,\n        data,\n      })\n    }\n\n    id = undefined\n    data = ''\n    dataLines = 0\n    eventType = undefined\n  }\n\n  function reset(options: {consume?: boolean} = {}) {\n    if (incompleteLine && options.consume) {\n      parseLine(incompleteLine, 0, incompleteLine.length)\n    }\n\n    isFirstChunk = true\n    id = undefined\n    data = ''\n    dataLines = 0\n    eventType = undefined\n    incompleteLine = ''\n  }\n\n  return {feed, reset}\n}\n\n/**\n * Checks if `chunk` starts with the literal `data:` at index `i`.\n *\n * Equivalent to `chunk.startsWith('data:', i)`, but benchmarks show this\n * hand-unrolled char-code comparison is ~20% faster on common event types.\n * The caller passes `firstCharCode` (the code at `i`) so it can be reused\n * across prefix checks.\n *\n * ASCII: 'd' = 100, 'a' = 97, 't' = 116, 'a' = 97, ':' = 58\n */\nfunction isDataPrefix(chunk: string, i: number, firstCharCode: number): boolean {\n  return (\n    firstCharCode === 100 &&\n    chunk.charCodeAt(i + 1) === 97 &&\n    chunk.charCodeAt(i + 2) === 116 &&\n    chunk.charCodeAt(i + 3) === 97 &&\n    chunk.charCodeAt(i + 4) === 58\n  )\n}\n\n/**\n * Checks if `chunk` starts with the literal `event:` at index `i`.\n *\n * See {@link isDataPrefix} for why this is hand-unrolled rather than using\n * `String.prototype.startsWith`.\n *\n * ASCII: 'e' = 101, 'v' = 118, 'e' = 101, 'n' = 110, 't' = 116, ':' = 58\n */\nfunction isEventPrefix(chunk: string, i: number, firstCharCode: number): boolean {\n  return (\n    firstCharCode === 101 &&\n    chunk.charCodeAt(i + 1) === 118 &&\n    chunk.charCodeAt(i + 2) === 101 &&\n    chunk.charCodeAt(i + 3) === 110 &&\n    chunk.charCodeAt(i + 4) === 116 &&\n    chunk.charCodeAt(i + 5) === 58\n  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dist/index.d.cts

@@ -13,3 +13,5 @@ /**
  */
-export declare function createParser(callbacks: ParserCallbacks): EventSourceParser
+export declare function createParser(
+  callbacks: ParserCallbacks,
+): EventSourceParser;
 
@@ -20,3 +22,3 @@ /**
  */
-export declare type ErrorType = 'invalid-retry' | 'unknown-field'
+export declare type ErrorType = "invalid-retry" | "unknown-field";
 
@@ -34,3 +36,3 @@ /**
    */
-  event?: string | undefined
+  event?: string | undefined;
   /**
@@ -40,7 +42,7 @@ * ID of the message, if any was provided by the server. Can be used by clients to keep the
    */
-  id?: string | undefined
+  id?: string | undefined;
   /**
    * The data received for this message
    */
-  data: string
+  data: string;
 }
@@ -64,3 +66,3 @@
    */
-  feed(chunk: string): void
+  feed(chunk: string): void;
   /**
@@ -77,3 +79,3 @@ * Resets the parser state. This is required when you have a new stream of messages -
    */
-  reset(options?: {consume?: boolean}): void
+  reset(options?: { consume?: boolean }): void;
 }
@@ -90,24 +92,24 @@
    */
-  type: ErrorType
+  type: ErrorType;
   /**
    * In the case of an unknown field encountered in the stream, this will be the field name.
    */
-  field?: string | undefined
+  field?: string | undefined;
   /**
    * In the case of an unknown field encountered in the stream, this will be the value of the field.
    */
-  value?: string | undefined
+  value?: string | undefined;
   /**
    * The line that caused the error, if available.
    */
-  line?: string | undefined
+  line?: string | undefined;
   constructor(
     message: string,
     options: {
-      type: ErrorType
-      field?: string
-      value?: string
-      line?: string
+      type: ErrorType;
+      field?: string;
+      value?: string;
+      line?: string;
     },
-  )
+  );
 }
@@ -128,3 +130,3 @@
    */
-  onEvent?: ((event: EventSourceMessage) => void) | undefined
+  onEvent?: ((event: EventSourceMessage) => void) | undefined;
   /**
@@ -135,3 +137,3 @@ * Callback for when the server sends a new reconnection interval through the `retry` field.
    */
-  onRetry?: ((retry: number) => void) | undefined
+  onRetry?: ((retry: number) => void) | undefined;
   /**
@@ -142,3 +144,3 @@ * Callback for when a comment is encountered in the stream.
    */
-  onComment?: ((comment: string) => void) | undefined
+  onComment?: ((comment: string) => void) | undefined;
   /**
@@ -151,5 +153,5 @@ * Callback for when an error occurs during parsing. This is a catch-all for any errors
    */
-  onError?: ((error: ParseError) => void) | undefined
+  onError?: ((error: ParseError) => void) | undefined;
 }
 
-export {}
+export {};

dist/index.d.ts

@@ -13,3 +13,5 @@ /**
  */
-export declare function createParser(callbacks: ParserCallbacks): EventSourceParser
+export declare function createParser(
+  callbacks: ParserCallbacks,
+): EventSourceParser;
 
@@ -20,3 +22,3 @@ /**
  */
-export declare type ErrorType = 'invalid-retry' | 'unknown-field'
+export declare type ErrorType = "invalid-retry" | "unknown-field";
 
@@ -34,3 +36,3 @@ /**
    */
-  event?: string | undefined
+  event?: string | undefined;
   /**
@@ -40,7 +42,7 @@ * ID of the message, if any was provided by the server. Can be used by clients to keep the
    */
-  id?: string | undefined
+  id?: string | undefined;
   /**
    * The data received for this message
    */
-  data: string
+  data: string;
 }
@@ -64,3 +66,3 @@
    */
-  feed(chunk: string): void
+  feed(chunk: string): void;
   /**
@@ -77,3 +79,3 @@ * Resets the parser state. This is required when you have a new stream of messages -
    */
-  reset(options?: {consume?: boolean}): void
+  reset(options?: { consume?: boolean }): void;
 }
@@ -90,24 +92,24 @@
    */
-  type: ErrorType
+  type: ErrorType;
   /**
    * In the case of an unknown field encountered in the stream, this will be the field name.
    */
-  field?: string | undefined
+  field?: string | undefined;
   /**
    * In the case of an unknown field encountered in the stream, this will be the value of the field.
    */
-  value?: string | undefined
+  value?: string | undefined;
   /**
    * The line that caused the error, if available.
    */
-  line?: string | undefined
+  line?: string | undefined;
   constructor(
     message: string,
     options: {
-      type: ErrorType
-      field?: string
-      value?: string
-      line?: string
+      type: ErrorType;
+      field?: string;
+      value?: string;
+      line?: string;
     },
-  )
+  );
 }
@@ -128,3 +130,3 @@
    */
-  onEvent?: ((event: EventSourceMessage) => void) | undefined
+  onEvent?: ((event: EventSourceMessage) => void) | undefined;
   /**
@@ -135,3 +137,3 @@ * Callback for when the server sends a new reconnection interval through the `retry` field.
    */
-  onRetry?: ((retry: number) => void) | undefined
+  onRetry?: ((retry: number) => void) | undefined;
   /**
@@ -142,3 +144,3 @@ * Callback for when a comment is encountered in the stream.
    */
-  onComment?: ((comment: string) => void) | undefined
+  onComment?: ((comment: string) => void) | undefined;
   /**
@@ -151,5 +153,5 @@ * Callback for when an error occurs during parsing. This is a catch-all for any errors
    */
-  onError?: ((error: ParseError) => void) | undefined
+  onError?: ((error: ParseError) => void) | undefined;
 }
 
-export {}
+export {};

dist/index.js

@@ -6,2 +6,3 @@ class ParseError extends Error {
 }
+const LF = 10, CR = 13, SPACE = 32;
 function noop(_arg) {
@@ -15,25 +16,91 @@ }
   const { onEvent = noop, onError = noop, onRetry = noop, onComment } = callbacks;
-  let incompleteLine = "", isFirstChunk = !0, id, data = "", eventType = "";
-  function feed(newChunk) {
-    const chunk = isFirstChunk ? newChunk.replace(/^\xEF\xBB\xBF/, "") : newChunk, [complete, incomplete] = splitLines(`${incompleteLine}${chunk}`);
-    for (const line of complete)
-      parseLine(line);
-    incompleteLine = incomplete, isFirstChunk = !1;
+  let incompleteLine = "", isFirstChunk = !0, id, data = "", dataLines = 0, eventType;
+  function feed(chunk) {
+    if (isFirstChunk) {
+      isFirstChunk = !1, feedFirst(chunk);
+      return;
+    }
+    const input = incompleteLine === "" ? chunk : incompleteLine + chunk;
+    incompleteLine = processLines(input);
   }
-  function parseLine(line) {
-    if (line === "") {
+  function feedFirst(chunk) {
+    chunk.charCodeAt(0) === 239 && chunk.charCodeAt(1) === 187 && chunk.charCodeAt(2) === 191 && (chunk = chunk.slice(3));
+    const input = incompleteLine === "" ? chunk : incompleteLine + chunk;
+    incompleteLine = processLines(input);
+  }
+  function processLines(chunk) {
+    let searchIndex = 0;
+    if (chunk.indexOf("\r") === -1) {
+      let lfIndex = chunk.indexOf(`
+`, searchIndex);
+      for (; lfIndex !== -1; ) {
+        if (searchIndex === lfIndex) {
+          dataLines > 0 && onEvent({ id, event: eventType, data }), id = void 0, data = "", dataLines = 0, eventType = void 0, searchIndex = lfIndex + 1, lfIndex = chunk.indexOf(`
+`, searchIndex);
+          continue;
+        }
+        const firstCharCode = chunk.charCodeAt(searchIndex);
+        if (isDataPrefix(chunk, searchIndex, firstCharCode)) {
+          const valueStart = chunk.charCodeAt(searchIndex + 5) === SPACE ? searchIndex + 6 : searchIndex + 5, value = chunk.slice(valueStart, lfIndex);
+          if (dataLines === 0 && chunk.charCodeAt(lfIndex + 1) === LF) {
+            onEvent({ id, event: eventType, data: value }), id = void 0, data = "", eventType = void 0, searchIndex = lfIndex + 2, lfIndex = chunk.indexOf(`
+`, searchIndex);
+            continue;
+          }
+          data = dataLines === 0 ? value : `${data}
+${value}`, dataLines++;
+        } else isEventPrefix(chunk, searchIndex, firstCharCode) ? eventType = chunk.slice(
+          chunk.charCodeAt(searchIndex + 6) === SPACE ? searchIndex + 7 : searchIndex + 6,
+          lfIndex
+        ) || void 0 : parseLine(chunk, searchIndex, lfIndex);
+        searchIndex = lfIndex + 1, lfIndex = chunk.indexOf(`
+`, searchIndex);
+      }
+      return chunk.slice(searchIndex);
+    }
+    for (; searchIndex < chunk.length; ) {
+      const crIndex = chunk.indexOf("\r", searchIndex), lfIndex = chunk.indexOf(`
+`, searchIndex);
+      let lineEnd = -1;
+      if (crIndex !== -1 && lfIndex !== -1 ? lineEnd = crIndex < lfIndex ? crIndex : lfIndex : crIndex !== -1 ? crIndex === chunk.length - 1 ? lineEnd = -1 : lineEnd = crIndex : lfIndex !== -1 && (lineEnd = lfIndex), lineEnd === -1)
+        break;
+      parseLine(chunk, searchIndex, lineEnd), searchIndex = lineEnd + 1, chunk.charCodeAt(searchIndex - 1) === CR && chunk.charCodeAt(searchIndex) === LF && searchIndex++;
+    }
+    return chunk.slice(searchIndex);
+  }
+  function parseLine(chunk, start, end) {
+    if (start === end) {
       dispatchEvent();
       return;
     }
-    if (line.startsWith(":")) {
-      onComment && onComment(line.slice(line.startsWith(": ") ? 2 : 1));
+    const firstCharCode = chunk.charCodeAt(start);
+    if (isDataPrefix(chunk, start, firstCharCode)) {
+      const valueStart = chunk.charCodeAt(start + 5) === SPACE ? start + 6 : start + 5, value2 = chunk.slice(valueStart, end);
+      data = dataLines === 0 ? value2 : `${data}
+${value2}`, dataLines++;
       return;
     }
-    const fieldSeparatorIndex = line.indexOf(":");
-    if (fieldSeparatorIndex !== -1) {
-      const field = line.slice(0, fieldSeparatorIndex), offset = line[fieldSeparatorIndex + 1] === " " ? 2 : 1, value = line.slice(fieldSeparatorIndex + offset);
-      processField(field, value, line);
+    if (isEventPrefix(chunk, start, firstCharCode)) {
+      eventType = chunk.slice(chunk.charCodeAt(start + 6) === SPACE ? start + 7 : start + 6, end) || void 0;
       return;
     }
-    processField(line, "", line);
+    if (firstCharCode === 105 && chunk.charCodeAt(start + 1) === 100 && chunk.charCodeAt(start + 2) === 58) {
+      const value2 = chunk.slice(chunk.charCodeAt(start + 3) === SPACE ? start + 4 : start + 3, end);
+      id = value2.includes("\0") ? void 0 : value2;
+      return;
+    }
+    if (firstCharCode === 58) {
+      if (onComment) {
+        const line2 = chunk.slice(start, end);
+        onComment(line2.slice(chunk.charCodeAt(start + 1) === SPACE ? 2 : 1));
+      }
+      return;
+    }
+    const line = chunk.slice(start, end), fieldSeparatorIndex = line.indexOf(":");
+    if (fieldSeparatorIndex === -1) {
+      processField(line, "", line);
+      return;
+    }
+    const field = line.slice(0, fieldSeparatorIndex), offset = line.charCodeAt(fieldSeparatorIndex + 1) === SPACE ? 2 : 1, value = line.slice(fieldSeparatorIndex + offset);
+    processField(field, value, line);
   }
@@ -43,7 +110,7 @@ function processField(field, value, line) {
       case "event":
-        eventType = value;
+        eventType = value || void 0;
         break;
       case "data":
-        data = `${data}${value}
-`;
+        data = dataLines === 0 ? value : `${data}
+${value}`, dataLines++;
         break;
@@ -73,34 +140,19 @@ case "id":
   function dispatchEvent() {
-    data.length > 0 && onEvent({
+    dataLines > 0 && onEvent({
       id,
-      event: eventType || void 0,
-      // If the data buffer's last character is a U+000A LINE FEED (LF) character,
-      // then remove the last character from the data buffer.
-      data: data.endsWith(`
-`) ? data.slice(0, -1) : data
-    }), id = void 0, data = "", eventType = "";
+      event: eventType,
+      data
+    }), id = void 0, data = "", dataLines = 0, eventType = void 0;
   }
   function reset(options = {}) {
-    incompleteLine && options.consume && parseLine(incompleteLine), isFirstChunk = !0, id = void 0, data = "", eventType = "", incompleteLine = "";
+    incompleteLine && options.consume && parseLine(incompleteLine, 0, incompleteLine.length), isFirstChunk = !0, id = void 0, data = "", dataLines = 0, eventType = void 0, incompleteLine = "";
   }
   return { feed, reset };
 }
-function splitLines(chunk) {
-  const lines = [];
-  let incompleteLine = "", searchIndex = 0;
-  for (; searchIndex < chunk.length; ) {
-    const crIndex = chunk.indexOf("\r", searchIndex), lfIndex = chunk.indexOf(`
-`, searchIndex);
-    let lineEnd = -1;
-    if (crIndex !== -1 && lfIndex !== -1 ? lineEnd = Math.min(crIndex, lfIndex) : crIndex !== -1 ? crIndex === chunk.length - 1 ? lineEnd = -1 : lineEnd = crIndex : lfIndex !== -1 && (lineEnd = lfIndex), lineEnd === -1) {
-      incompleteLine = chunk.slice(searchIndex);
-      break;
-    } else {
-      const line = chunk.slice(searchIndex, lineEnd);
-      lines.push(line), searchIndex = lineEnd + 1, chunk[searchIndex - 1] === "\r" && chunk[searchIndex] === `
-` && searchIndex++;
-    }
-  }
-  return [lines, incompleteLine];
+function isDataPrefix(chunk, i, firstCharCode) {
+  return firstCharCode === 100 && chunk.charCodeAt(i + 1) === 97 && chunk.charCodeAt(i + 2) === 116 && chunk.charCodeAt(i + 3) === 97 && chunk.charCodeAt(i + 4) === 58;
 }
+function isEventPrefix(chunk, i, firstCharCode) {
+  return firstCharCode === 101 && chunk.charCodeAt(i + 1) === 118 && chunk.charCodeAt(i + 2) === 101 && chunk.charCodeAt(i + 3) === 110 && chunk.charCodeAt(i + 4) === 116 && chunk.charCodeAt(i + 5) === 58;
+}
 export {
@@ -107,0 +159,0 @@ ParseError,

dist/index.js.map

@@ -1,1 +0,1 @@
-{"version":3,"file":"index.js","sources":["../src/errors.ts","../src/parse.ts"],"sourcesContent":["/**\n * The type of error that occurred.\n * @public\n */\nexport type ErrorType = 'invalid-retry' | 'unknown-field'\n\n/**\n * Error thrown when encountering an issue during parsing.\n *\n * @public\n */\nexport class ParseError extends Error {\n  /**\n   * The type of error that occurred.\n   */\n  type: ErrorType\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the field name.\n   */\n  field?: string | undefined\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the value of the field.\n   */\n  value?: string | undefined\n\n  /**\n   * The line that caused the error, if available.\n   */\n  line?: string | undefined\n\n  constructor(\n    message: string,\n    options: {type: ErrorType; field?: string; value?: string; line?: string},\n  ) {\n    super(message)\n    this.name = 'ParseError'\n    this.type = options.type\n    this.field = options.field\n    this.value = options.value\n    this.line = options.line\n  }\n}\n","/**\n * EventSource/Server-Sent Events parser\n * @see https://html.spec.whatwg.org/multipage/server-sent-events.html\n */\nimport {ParseError} from './errors.ts'\nimport type {EventSourceParser, ParserCallbacks} from './types.ts'\n\n// eslint-disable-next-line @typescript-eslint/no-unused-vars\nfunction noop(_arg: unknown) {\n  // intentional noop\n}\n\n/**\n * Creates a new EventSource parser.\n *\n * @param callbacks - Callbacks to invoke on different parsing events:\n *   - `onEvent` when a new event is parsed\n *   - `onError` when an error occurs\n *   - `onRetry` when a new reconnection interval has been sent from the server\n *   - `onComment` when a comment is encountered in the stream\n *\n * @returns A new EventSource parser, with `parse` and `reset` methods.\n * @public\n */\nexport function createParser(callbacks: ParserCallbacks): EventSourceParser {\n  if (typeof callbacks === 'function') {\n    throw new TypeError(\n      '`callbacks` must be an object, got a function instead. Did you mean `{onEvent: fn}`?',\n    )\n  }\n\n  const {onEvent = noop, onError = noop, onRetry = noop, onComment} = callbacks\n\n  let incompleteLine = ''\n\n  let isFirstChunk = true\n  let id: string | undefined\n  let data = ''\n  let eventType = ''\n\n  function feed(newChunk: string) {\n    // Strip any UTF8 byte order mark (BOM) at the start of the stream\n    const chunk = isFirstChunk ? newChunk.replace(/^\\xEF\\xBB\\xBF/, '') : newChunk\n\n    // If there was a previous incomplete line, append it to the new chunk,\n    // so we may process it together as a new (hopefully complete) chunk.\n    const [complete, incomplete] = splitLines(`${incompleteLine}${chunk}`)\n\n    for (const line of complete) {\n      parseLine(line)\n    }\n\n    incompleteLine = incomplete\n    isFirstChunk = false\n  }\n\n  function parseLine(line: string) {\n    // If the line is empty (a blank line), dispatch the event\n    if (line === '') {\n      dispatchEvent()\n      return\n    }\n\n    // If the line starts with a U+003A COLON character (:), ignore the line.\n    if (line.startsWith(':')) {\n      if (onComment) {\n        onComment(line.slice(line.startsWith(': ') ? 2 : 1))\n      }\n      return\n    }\n\n    // If the line contains a U+003A COLON character (:)\n    const fieldSeparatorIndex = line.indexOf(':')\n    if (fieldSeparatorIndex !== -1) {\n      // Collect the characters on the line before the first U+003A COLON character (:),\n      // and let `field` be that string.\n      const field = line.slice(0, fieldSeparatorIndex)\n\n      // Collect the characters on the line after the first U+003A COLON character (:),\n      // and let `value` be that string. If value starts with a U+0020 SPACE character,\n      // remove it from value.\n      const offset = line[fieldSeparatorIndex + 1] === ' ' ? 2 : 1\n      const value = line.slice(fieldSeparatorIndex + offset)\n\n      processField(field, value, line)\n      return\n    }\n\n    // Otherwise, the string is not empty but does not contain a U+003A COLON character (:)\n    // Process the field using the whole line as the field name, and an empty string as the field value.\n    // 👆 This is according to spec. That means that a line that has the value `data` will result in\n    // a newline being added to the current `data` buffer, for instance.\n    processField(line, '', line)\n  }\n\n  function processField(field: string, value: string, line: string) {\n    // Field names must be compared literally, with no case folding performed.\n    switch (field) {\n      case 'event':\n        // Set the `event type` buffer to field value\n        eventType = value\n        break\n      case 'data':\n        // Append the field value to the `data` buffer, then append a single U+000A LINE FEED(LF)\n        // character to the `data` buffer.\n        data = `${data}${value}\\n`\n        break\n      case 'id':\n        // If the field value does not contain U+0000 NULL, then set the `ID` buffer to\n        // the field value. Otherwise, ignore the field.\n        id = value.includes('\\0') ? undefined : value\n        break\n      case 'retry':\n        // If the field value consists of only ASCII digits, then interpret the field value as an\n        // integer in base ten, and set the event stream's reconnection time to that integer.\n        // Otherwise, ignore the field.\n        if (/^\\d+$/.test(value)) {\n          onRetry(parseInt(value, 10))\n        } else {\n          onError(\n            new ParseError(`Invalid \\`retry\\` value: \"${value}\"`, {\n              type: 'invalid-retry',\n              value,\n              line,\n            }),\n          )\n        }\n        break\n      default:\n        // Otherwise, the field is ignored.\n        onError(\n          new ParseError(\n            `Unknown field \"${field.length > 20 ? `${field.slice(0, 20)}…` : field}\"`,\n            {type: 'unknown-field', field, value, line},\n          ),\n        )\n        break\n    }\n  }\n\n  function dispatchEvent() {\n    const shouldDispatch = data.length > 0\n    if (shouldDispatch) {\n      onEvent({\n        id,\n        event: eventType || undefined,\n        // If the data buffer's last character is a U+000A LINE FEED (LF) character,\n        // then remove the last character from the data buffer.\n        data: data.endsWith('\\n') ? 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+{"version":3,"file":"index.js","sources":["../src/errors.ts","../src/parse.ts"],"sourcesContent":["/**\n * The type of error that occurred.\n * @public\n */\nexport type ErrorType = 'invalid-retry' | 'unknown-field'\n\n/**\n * Error thrown when encountering an issue during parsing.\n *\n * @public\n */\nexport class ParseError extends Error {\n  /**\n   * The type of error that occurred.\n   */\n  type: ErrorType\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the field name.\n   */\n  field?: string | undefined\n\n  /**\n   * In the case of an unknown field encountered in the stream, this will be the value of the field.\n   */\n  value?: string | undefined\n\n  /**\n   * The line that caused the error, if available.\n   */\n  line?: string | undefined\n\n  constructor(\n    message: string,\n    options: {type: ErrorType; field?: string; value?: string; line?: string},\n  ) {\n    super(message)\n    this.name = 'ParseError'\n    this.type = options.type\n    this.field = options.field\n    this.value = options.value\n    this.line = options.line\n  }\n}\n","/**\n * EventSource/Server-Sent Events parser\n * @see https://html.spec.whatwg.org/multipage/server-sent-events.html\n */\nimport {ParseError} from './errors.ts'\nimport type {EventSourceParser, ParserCallbacks} from './types.ts'\n\n// ASCII codes used in the hot parsing paths.\nconst LF = 10\nconst CR = 13\nconst SPACE = 32\n\n// oxlint-disable-next-line no-unused-vars\nfunction noop(_arg: unknown) {\n  // intentional noop\n}\n\n/**\n * Creates a new EventSource parser.\n *\n * @param callbacks - Callbacks to invoke on different parsing events:\n *   - `onEvent` when a new event is parsed\n *   - `onError` when an error occurs\n *   - `onRetry` when a new reconnection interval has been sent from the server\n *   - `onComment` when a comment is encountered in the stream\n *\n * @returns A new EventSource parser, with `parse` and `reset` methods.\n * @public\n */\nexport function createParser(callbacks: ParserCallbacks): EventSourceParser {\n  if (typeof callbacks === 'function') {\n    throw new TypeError(\n      '`callbacks` must be an object, got a function instead. Did you mean `{onEvent: fn}`?',\n    )\n  }\n\n  const {onEvent = noop, onError = noop, onRetry = noop, onComment} = callbacks\n\n  let incompleteLine = ''\n\n  let isFirstChunk = true\n  let id: string | undefined\n  let data = ''\n  let dataLines = 0\n  let eventType: string | undefined\n\n  /**\n   * Feeds a chunk of the SSE stream to the parser. Any trailing bytes that do\n   * not yet form a complete line are held back and prepended to the next chunk,\n   * so callers can pass arbitrary slices of the stream without worrying about\n   * line boundaries.\n   *\n   * The first chunk is dispatched to {@link feedFirst} so the leading UTF-8\n   * BOM can be stripped before parsing begins.\n   */\n  function feed(chunk: string) {\n    if (isFirstChunk) {\n      isFirstChunk = false\n      feedFirst(chunk)\n      return\n    }\n    const input = incompleteLine === '' ? chunk : incompleteLine + chunk\n    incompleteLine = processLines(input)\n  }\n\n  /**\n   * Handles the very first chunk of the stream. Per the SSE spec, a UTF-8 BOM\n   * (0xEF 0xBB 0xBF) at the start of the stream must be stripped before\n   * parsing. After BOM handling, behaves identically to {@link feed}.\n   *\n   * @see https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream\n   */\n  function feedFirst(chunk: string) {\n    if (\n      chunk.charCodeAt(0) === 0xef &&\n      chunk.charCodeAt(1) === 0xbb &&\n      chunk.charCodeAt(2) === 0xbf\n    ) {\n      chunk = chunk.slice(3)\n    }\n    const input = incompleteLine === '' ? chunk : incompleteLine + chunk\n    incompleteLine = processLines(input)\n  }\n\n  /**\n   * Splits `chunk` into SSE lines and dispatches each to the appropriate handler.\n   * Returns any trailing bytes that did not terminate with a line break, so the\n   * caller can prepend them to the next chunk.\n   *\n   * The SSE spec permits three line terminators: `\\n`, `\\r`, and `\\r\\n`. Real-world\n   * streams almost always use plain `\\n`, so we take a fast path when no `\\r` is\n   * present in the chunk. The slow path is spec-correct but does more work per line.\n   */\n  function processLines(chunk: string): string {\n    let searchIndex = 0\n\n    // Fast path: LF-only chunk (the common case for typical SSE servers).\n    // We can scan forward with a single `indexOf('\\n')` per line and inline\n    // the hot-path branches for `data:` and `event:` without the CR bookkeeping\n    // the slow path needs.\n    if (chunk.indexOf('\\r') === -1) {\n      let lfIndex = chunk.indexOf('\\n', searchIndex)\n      while (lfIndex !== -1) {\n        // Blank line: end-of-event marker. Dispatch the accumulated event (if any)\n        // and reset the buffered fields. This is hoisted out of `parseLine` because\n        // it's the single most common line shape after `data:` lines.\n        if (searchIndex === lfIndex) {\n          if (dataLines > 0) {\n            onEvent({id, event: eventType, data})\n          }\n          id = undefined\n          data = ''\n          dataLines = 0\n          eventType = undefined\n          searchIndex = lfIndex + 1\n          lfIndex = chunk.indexOf('\\n', searchIndex)\n          continue\n        }\n        const firstCharCode = chunk.charCodeAt(searchIndex)\n        if (isDataPrefix(chunk, searchIndex, firstCharCode)) {\n          // `data:` line — append the value to the event's data buffer.\n          // 'data:'.length === 5, 'data: '.length === 6\n          const valueStart =\n            chunk.charCodeAt(searchIndex + 5) === SPACE ? searchIndex + 6 : searchIndex + 5\n          const value = chunk.slice(valueStart, lfIndex)\n          // Fast path within a fast path: if this is the first data line AND the\n          // next char is another LF (i.e. `data:foo\\n\\n`), dispatch immediately\n          // without ever writing to the `data` buffer. This is the shape of a\n          // typical single-line SSE event (ChatGPT-style streams, etc.) and is\n          // hot enough to be worth the duplication.\n          if (dataLines === 0 && chunk.charCodeAt(lfIndex + 1) === LF) {\n            onEvent({id, event: eventType, data: value})\n            id = undefined\n            data = ''\n            eventType = undefined\n            searchIndex = lfIndex + 2\n            lfIndex = chunk.indexOf('\\n', searchIndex)\n            continue\n          }\n          // Multi-line data: concatenate with newline separator per spec.\n          data = dataLines === 0 ? value : `${data}\\n${value}`\n          dataLines++\n        } else if (isEventPrefix(chunk, searchIndex, firstCharCode)) {\n          // `event:` line — set the event type for the next dispatch. Per spec,\n          // an empty value resets `event type` to its default (undefined here).\n          // 'event:'.length === 6, 'event: '.length === 7\n          eventType =\n            chunk.slice(\n              chunk.charCodeAt(searchIndex + 6) === SPACE ? searchIndex + 7 : searchIndex + 6,\n              lfIndex,\n            ) || undefined\n        } else {\n          // Everything else: `id:`, `retry:`, comment lines (`:` prefix), unknown\n          // fields, or malformed lines. These are rarer and go through the full\n          // per-line parser, which handles the SSE field grammar in detail.\n          parseLine(chunk, searchIndex, lfIndex)\n        }\n        searchIndex = lfIndex + 1\n        lfIndex = chunk.indexOf('\\n', searchIndex)\n      }\n      return chunk.slice(searchIndex)\n    }\n\n    // Slow path: the chunk contains at least one `\\r`, so lines may be terminated\n    // by `\\r`, `\\n`, or `\\r\\n`. We locate the next terminator by looking at both\n    // the nearest `\\r` and `\\n` and picking whichever comes first.\n    while (searchIndex < chunk.length) {\n      const crIndex = chunk.indexOf('\\r', searchIndex)\n      const lfIndex = chunk.indexOf('\\n', searchIndex)\n\n      let lineEnd = -1\n      if (crIndex !== -1 && lfIndex !== -1) {\n        lineEnd = crIndex < lfIndex ? crIndex : lfIndex\n      } else if (crIndex !== -1) {\n        // A trailing `\\r` at the very end of the chunk is ambiguous: it could be\n        // a bare-CR terminator, or the first half of a `\\r\\n` whose `\\n` arrives\n        // in the next chunk. Defer until we see more input.\n        if (crIndex === chunk.length - 1) {\n          lineEnd = -1\n        } else {\n          lineEnd = crIndex\n        }\n      } else if (lfIndex !== -1) {\n        lineEnd = lfIndex\n      }\n\n      if (lineEnd === -1) {\n        break\n      }\n\n      parseLine(chunk, searchIndex, lineEnd)\n      searchIndex = lineEnd + 1\n      // If we just consumed a `\\r` and the next char is `\\n`, skip it so the\n      // pair is treated as a single terminator rather than an empty line.\n      if (chunk.charCodeAt(searchIndex - 1) === CR && chunk.charCodeAt(searchIndex) === LF) {\n        searchIndex++\n      }\n    }\n\n    return chunk.slice(searchIndex)\n  }\n\n  function parseLine(chunk: string, start: number, end: number) {\n    if (start === end) {\n      dispatchEvent()\n      return\n    }\n\n    const firstCharCode = chunk.charCodeAt(start)\n\n    if (isDataPrefix(chunk, start, firstCharCode)) {\n      // 'data:'.length === 5, 'data: '.length === 6\n      const valueStart = chunk.charCodeAt(start + 5) === SPACE ? start + 6 : start + 5\n      const value = chunk.slice(valueStart, end)\n      data = dataLines === 0 ? value : `${data}\\n${value}`\n      dataLines++\n      return\n    }\n\n    if (isEventPrefix(chunk, start, firstCharCode)) {\n      // 'event:'.length === 6, 'event: '.length === 7\n      eventType =\n        chunk.slice(chunk.charCodeAt(start + 6) === SPACE ? start + 7 : start + 6, end) || undefined\n      return\n    }\n\n    // Fast path for \"id:\" — 'i' = 105, 'd' = 100, ':' = 58\n    if (\n      firstCharCode === 105 &&\n      chunk.charCodeAt(start + 1) === 100 &&\n      chunk.charCodeAt(start + 2) === 58\n    ) {\n      // 'id:'.length === 3, 'id: '.length === 4\n      const value = chunk.slice(chunk.charCodeAt(start + 3) === SPACE ? start + 4 : start + 3, end)\n      id = value.includes('\\0') ? undefined : value\n      return\n    }\n\n    // Comment line — ':' = 58\n    if (firstCharCode === 58) {\n      if (onComment) {\n        const line = chunk.slice(start, end)\n        // skip ':' (+1), or ': ' (+2) when a space follows\n        onComment(line.slice(chunk.charCodeAt(start + 1) === SPACE ? 2 : 1))\n      }\n      return\n    }\n\n    const line = chunk.slice(start, end)\n    const fieldSeparatorIndex = line.indexOf(':')\n    if (fieldSeparatorIndex === -1) {\n      processField(line, '', line)\n      return\n    }\n\n    const field = line.slice(0, fieldSeparatorIndex)\n    // skip ':' (+1), or ': ' (+2) when a space follows\n    const offset = line.charCodeAt(fieldSeparatorIndex + 1) === SPACE ? 2 : 1\n    const value = line.slice(fieldSeparatorIndex + offset)\n    processField(field, value, line)\n  }\n\n  function processField(field: string, value: string, line: string) {\n    // Field names must be compared literally, with no case folding performed.\n    switch (field) {\n      case 'event':\n        // Set the `event type` buffer to field value\n        eventType = value || undefined\n        break\n      case 'data':\n        data = dataLines === 0 ? value : `${data}\\n${value}`\n        dataLines++\n        break\n      case 'id':\n        // If the field value does not contain U+0000 NULL, then set the `ID` buffer to\n        // the field value. Otherwise, ignore the field.\n        id = value.includes('\\0') ? undefined : value\n        break\n      case 'retry':\n        // If the field value consists of only ASCII digits, then interpret the field value as an\n        // integer in base ten, and set the event stream's reconnection time to that integer.\n        // Otherwise, ignore the field.\n        if (/^\\d+$/.test(value)) {\n          onRetry(parseInt(value, 10))\n        } else {\n          onError(\n            new ParseError(`Invalid \\`retry\\` value: \"${value}\"`, {\n              type: 'invalid-retry',\n              value,\n              line,\n            }),\n          )\n        }\n        break\n      default:\n        // Otherwise, the field is ignored.\n        onError(\n          new ParseError(\n            `Unknown field \"${field.length > 20 ? `${field.slice(0, 20)}…` : field}\"`,\n            {type: 'unknown-field', field, value, line},\n          ),\n        )\n        break\n    }\n  }\n\n  function dispatchEvent() {\n    if (dataLines > 0) {\n      onEvent({\n        id,\n        event: eventType,\n        data,\n      })\n    }\n\n    id = undefined\n    data = ''\n    dataLines = 0\n    eventType = undefined\n  }\n\n  function reset(options: {consume?: boolean} = {}) {\n    if (incompleteLine && options.consume) {\n      parseLine(incompleteLine, 0, incompleteLine.length)\n    }\n\n    isFirstChunk = true\n    id = undefined\n    data = ''\n    dataLines = 0\n    eventType = undefined\n    incompleteLine = ''\n  }\n\n  return {feed, reset}\n}\n\n/**\n * Checks if `chunk` starts with the literal `data:` at index `i`.\n *\n * Equivalent to `chunk.startsWith('data:', i)`, but benchmarks show this\n * hand-unrolled char-code comparison is ~20% faster on common event types.\n * The caller passes `firstCharCode` (the code at `i`) so it can be reused\n * across prefix checks.\n *\n * ASCII: 'd' = 100, 'a' = 97, 't' = 116, 'a' = 97, ':' = 58\n */\nfunction isDataPrefix(chunk: string, 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)\n}\n"],"names":["value","line"],"mappings":"AAWO,MAAM,mBAAmB,MAAM;AAAA,EAqBpC,YACE,SACA,SACA;AACA,UAAM,OAAO,GACb,KAAK,OAAO,cACZ,KAAK,OAAO,QAAQ,MACpB,KAAK,QAAQ,QAAQ,OACrB,KAAK,QAAQ,QAAQ,OACrB,KAAK,OAAO,QAAQ;AAAA,EACtB;AACF;ACnCA,MAAM,KAAK,IACL,KAAK,IACL,QAAQ;AAGd,SAAS,KAAK,MAAe;AAE7B;AAcO,SAAS,aAAa,WAA+C;AAC1E,MAAI,OAAO,aAAc;AACvB,UAAM,IAAI;AAAA,MACR;AAAA,IAAA;AAIJ,QAAM,EAAC,UAAU,MAAM,UAAU,MAAM,UAAU,MAAM,cAAa;AAEpE,MAAI,iBAAiB,IAEjB,eAAe,IACf,IACA,OAAO,IACP,YAAY,GACZ;AAWJ,WAAS,KAAK,OAAe;AAC3B,QAAI,cAAc;AAChB,qBAAe,IACf,UAAU,KAAK;AACf;AAAA,IACF;AACA,UAAM,QAAQ,mBAAmB,KAAK,QAAQ,iBAAiB;AAC/D,qBAAiB,aAAa,KAAK;AAAA,EACrC;AASA,WAAS,UAAU,OAAe;AAE9B,UAAM,WAAW,CAAC,MAAM,OACxB,MAAM,WAAW,CAAC,MAAM,OACxB,MAAM,WAAW,CAAC,MAAM,QAExB,QAAQ,MAAM,MAAM,CAAC;AAEvB,UAAM,QAAQ,mBAAmB,KAAK,QAAQ,iBAAiB;AAC/D,qBAAiB,aAAa,KAAK;AAAA,EACrC;AAWA,WAAS,aAAa,OAAuB;AAC3C,QAAI,cAAc;AAMlB,QAAI,MAAM,QAAQ,IAAI,MAAM,IAAI;AAC9B,UAAI,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AAC7C,aAAO,YAAY,MAAI;AAIrB,YAAI,gBAAgB,SAAS;AACvB,sBAAY,KACd,QAAQ,EAAC,IAAI,OAAO,WAAW,KAAA,CAAK,GAEtC,KAAK,QACL,OAAO,IACP,YAAY,GACZ,YAAY,QACZ,cAAc,UAAU,GACxB,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AACzC;AAAA,QACF;AACA,cAAM,gBAAgB,MAAM,WAAW,WAAW;AAClD,YAAI,aAAa,OAAO,aAAa,aAAa,GAAG;AAGnD,gBAAM,aACJ,MAAM,WAAW,cAAc,CAAC,MAAM,QAAQ,cAAc,IAAI,cAAc,GAC1E,QAAQ,MAAM,MAAM,YAAY,OAAO;AAM7C,cAAI,cAAc,KAAK,MAAM,WAAW,UAAU,CAAC,MAAM,IAAI;AAC3D,oBAAQ,EAAC,IAAI,OAAO,WAAW,MAAM,MAAA,CAAM,GAC3C,KAAK,QACL,OAAO,IACP,YAAY,QACZ,cAAc,UAAU,GACxB,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AACzC;AAAA,UACF;AAEA,iBAAO,cAAc,IAAI,QAAQ,GAAG,IAAI;AAAA,EAAK,KAAK,IAClD;AAAA,QACF,MAAW,eAAc,OAAO,aAAa,aAAa,IAIxD,YACE,MAAM;AAAA,UACJ,MAAM,WAAW,cAAc,CAAC,MAAM,QAAQ,cAAc,IAAI,cAAc;AAAA,UAC9E;AAAA,QAAA,KACG,SAKP,UAAU,OAAO,aAAa,OAAO;AAEvC,sBAAc,UAAU,GACxB,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AAAA,MAC3C;AACA,aAAO,MAAM,MAAM,WAAW;AAAA,IAChC;AAKA,WAAO,cAAc,MAAM,UAAQ;AACjC,YAAM,UAAU,MAAM,QAAQ,MAAM,WAAW,GACzC,UAAU,MAAM,QAAQ;AAAA,GAAM,WAAW;AAE/C,UAAI,UAAU;AAgBd,UAfI,YAAY,MAAM,YAAY,KAChC,UAAU,UAAU,UAAU,UAAU,UAC/B,YAAY,KAIjB,YAAY,MAAM,SAAS,IAC7B,UAAU,KAEV,UAAU,UAEH,YAAY,OACrB,UAAU,UAGR,YAAY;AACd;AAGF,gBAAU,OAAO,aAAa,OAAO,GACrC,cAAc,UAAU,GAGpB,MAAM,WAAW,cAAc,CAAC,MAAM,MAAM,MAAM,WAAW,WAAW,MAAM,MAChF;AAAA,IAEJ;AAEA,WAAO,MAAM,MAAM,WAAW;AAAA,EAChC;AAEA,WAAS,UAAU,OAAe,OAAe,KAAa;AAC5D,QAAI,UAAU,KAAK;AACjB,oBAAA;AACA;AAAA,IACF;AAEA,UAAM,gBAAgB,MAAM,WAAW,KAAK;AAE5C,QAAI,aAAa,OAAO,OAAO,aAAa,GAAG;AAE7C,YAAM,aAAa,MAAM,WAAW,QAAQ,CAAC,MAAM,QAAQ,QAAQ,IAAI,QAAQ,GACzEA,SAAQ,MAAM,MAAM,YAAY,GAAG;AACzC,aAAO,cAAc,IAAIA,SAAQ,GAAG,IAAI;AAAA,EAAKA,MAAK,IAClD;AACA;AAAA,IACF;AAEA,QAAI,cAAc,OAAO,OAAO,aAAa,GAAG;AAE9C,kBACE,MAAM,MAAM,MAAM,WAAW,QAAQ,CAAC,MAAM,QAAQ,QAAQ,IAAI,QAAQ,GAAG,GAAG,KAAK;AACrF;AAAA,IACF;AAGA,QACE,kBAAkB,OAClB,MAAM,WAAW,QAAQ,CAAC,MAAM,OAChC,MAAM,WAAW,QAAQ,CAAC,MAAM,IAChC;AAEA,YAAMA,SAAQ,MAAM,MAAM,MAAM,WAAW,QAAQ,CAAC,MAAM,QAAQ,QAAQ,IAAI,QAAQ,GAAG,GAAG;AAC5F,WAAKA,OAAM,SAAS,IAAI,IAAI,SAAYA;AACxC;AAAA,IACF;AAGA,QAAI,kBAAkB,IAAI;AACxB,UAAI,WAAW;AACb,cAAMC,QAAO,MAAM,MAAM,OAAO,GAAG;AAEnC,kBAAUA,MAAK,MAAM,MAAM,WAAW,QAAQ,CAAC,MAAM,QAAQ,IAAI,CAAC,CAAC;AAAA,MACrE;AACA;AAAA,IACF;AAEA,UAAM,OAAO,MAAM,MAAM,OAAO,GAAG,GAC7B,sBAAsB,KAAK,QAAQ,GAAG;AAC5C,QAAI,wBAAwB,IAAI;AAC9B,mBAAa,MAAM,IAAI,IAAI;AAC3B;AAAA,IACF;AAEA,UAAM,QAAQ,KAAK,MAAM,GAAG,mBAAmB,GAEzC,SAAS,KAAK,WAAW,sBAAsB,CAAC,MAAM,QAAQ,IAAI,GAClE,QAAQ,KAAK,MAAM,sBAAsB,MAAM;AACrD,iBAAa,OAAO,OAAO,IAAI;AAAA,EACjC;AAEA,WAAS,aAAa,OAAe,OAAe,MAAc;AAEhE,YAAQ,OAAA;AAAA,MACN,KAAK;AAEH,oBAAY,SAAS;AACrB;AAAA,MACF,KAAK;AACH,eAAO,cAAc,IAAI,QAAQ,GAAG,IAAI;AAAA,EAAK,KAAK,IAClD;AACA;AAAA,MACF,KAAK;AAGH,aAAK,MAAM,SAAS,IAAI,IAAI,SAAY;AACxC;AAAA,MACF,KAAK;AAIC,gBAAQ,KAAK,KAAK,IACpB,QAAQ,SAAS,OAAO,EAAE,CAAC,IAE3B;AAAA,UACE,IAAI,WAAW,6BAA6B,KAAK,KAAK;AAAA,YACpD,MAAM;AAAA,YACN;AAAA,YACA;AAAA,UAAA,CACD;AAAA,QAAA;AAGL;AAAA,MACF;AAEE;AAAA,UACE,IAAI;AAAA,YACF,kBAAkB,MAAM,SAAS,KAAK,GAAG,MAAM,MAAM,GAAG,EAAE,CAAC,WAAM,KAAK;AAAA,YACtE,EAAC,MAAM,iBAAiB,OAAO,OAAO,KAAA;AAAA,UAAI;AAAA,QAC5C;AAEF;AAAA,IAAA;AAAA,EAEN;AAEA,WAAS,gBAAgB;AACnB,gBAAY,KACd,QAAQ;AAAA,MACN;AAAA,MACA,OAAO;AAAA,MACP;AAAA,IAAA,CACD,GAGH,KAAK,QACL,OAAO,IACP,YAAY,GACZ,YAAY;AAAA,EACd;AAEA,WAAS,MAAM,UAA+B,IAAI;AAC5C,sBAAkB,QAAQ,WAC5B,UAAU,gBAAgB,GAAG,eAAe,MAAM,GAGpD,eAAe,IACf,KAAK,QACL,OAAO,IACP,YAAY,GACZ,YAAY,QACZ,iBAAiB;AAAA,EACnB;AAEA,SAAO,EAAC,MAAM,MAAA;AAChB;AAYA,SAAS,aAAa,OAAe,GAAW,eAAgC;AAC9E,SACE,kBAAkB,OAClB,MAAM,WAAW,IAAI,CAAC,MAAM,MAC5B,MAAM,WAAW,IAAI,CAAC,MAAM,OAC5B,MAAM,WAAW,IAAI,CAAC,MAAM,MAC5B,MAAM,WAAW,IAAI,CAAC,MAAM;AAEhC;AAUA,SAAS,cAAc,OAAe,GAAW,eAAgC;AAC/E,SACE,kBAAkB,OAClB,MAAM,WAAW,IAAI,CAAC,MAAM,OAC5B,MAAM,WAAW,IAAI,CAAC,MAAM,OAC5B,MAAM,WAAW,IAAI,CAAC,MAAM,OAC5B,MAAM,WAAW,IAAI,CAAC,MAAM,OAC5B,MAAM,WAAW,IAAI,CAAC,MAAM;AAEhC;"}

dist/stream.d.cts

@@ -5,3 +5,3 @@ /**
  */
-export declare type ErrorType = 'invalid-retry' | 'unknown-field'
+export declare type ErrorType = "invalid-retry" | "unknown-field";
 
@@ -19,3 +19,3 @@ /**
    */
-  event?: string | undefined
+  event?: string | undefined;
   /**
@@ -25,7 +25,7 @@ * ID of the message, if any was provided by the server. Can be used by clients to keep the
    */
-  id?: string | undefined
+  id?: string | undefined;
   /**
    * The data received for this message
    */
-  data: string
+  data: string;
 }
@@ -54,4 +54,7 @@
  */
-export declare class EventSourceParserStream extends TransformStream<string, EventSourceMessage> {
-  constructor({onError, onRetry, onComment}?: StreamOptions)
+export declare class EventSourceParserStream extends TransformStream<
+  string,
+  EventSourceMessage
+> {
+  constructor({ onError, onRetry, onComment }?: StreamOptions);
 }
@@ -68,24 +71,24 @@
    */
-  type: ErrorType
+  type: ErrorType;
   /**
    * In the case of an unknown field encountered in the stream, this will be the field name.
    */
-  field?: string | undefined
+  field?: string | undefined;
   /**
    * In the case of an unknown field encountered in the stream, this will be the value of the field.
    */
-  value?: string | undefined
+  value?: string | undefined;
   /**
    * The line that caused the error, if available.
    */
-  line?: string | undefined
+  line?: string | undefined;
   constructor(
     message: string,
     options: {
-      type: ErrorType
-      field?: string
-      value?: string
-      line?: string
+      type: ErrorType;
+      field?: string;
+      value?: string;
+      line?: string;
     },
-  )
+  );
 }
@@ -108,3 +111,3 @@
    */
-  onError?: ('terminate' | ((error: Error) => void)) | undefined
+  onError?: ("terminate" | ((error: Error) => void)) | undefined;
   /**
@@ -115,3 +118,3 @@ * Callback for when a reconnection interval is sent from the server.
    */
-  onRetry?: ((retry: number) => void) | undefined
+  onRetry?: ((retry: number) => void) | undefined;
   /**
@@ -122,5 +125,5 @@ * Callback for when a comment is encountered in the stream.
    */
-  onComment?: ((comment: string) => void) | undefined
+  onComment?: ((comment: string) => void) | undefined;
 }
 
-export {}
+export {};

dist/stream.d.ts

@@ -5,3 +5,3 @@ /**
  */
-export declare type ErrorType = 'invalid-retry' | 'unknown-field'
+export declare type ErrorType = "invalid-retry" | "unknown-field";
 
@@ -19,3 +19,3 @@ /**
    */
-  event?: string | undefined
+  event?: string | undefined;
   /**
@@ -25,7 +25,7 @@ * ID of the message, if any was provided by the server. Can be used by clients to keep the
    */
-  id?: string | undefined
+  id?: string | undefined;
   /**
    * The data received for this message
    */
-  data: string
+  data: string;
 }
@@ -54,4 +54,7 @@
  */
-export declare class EventSourceParserStream extends TransformStream<string, EventSourceMessage> {
-  constructor({onError, onRetry, onComment}?: StreamOptions)
+export declare class EventSourceParserStream extends TransformStream<
+  string,
+  EventSourceMessage
+> {
+  constructor({ onError, onRetry, onComment }?: StreamOptions);
 }
@@ -68,24 +71,24 @@
    */
-  type: ErrorType
+  type: ErrorType;
   /**
    * In the case of an unknown field encountered in the stream, this will be the field name.
    */
-  field?: string | undefined
+  field?: string | undefined;
   /**
    * In the case of an unknown field encountered in the stream, this will be the value of the field.
    */
-  value?: string | undefined
+  value?: string | undefined;
   /**
    * The line that caused the error, if available.
    */
-  line?: string | undefined
+  line?: string | undefined;
   constructor(
     message: string,
     options: {
-      type: ErrorType
-      field?: string
-      value?: string
-      line?: string
+      type: ErrorType;
+      field?: string;
+      value?: string;
+      line?: string;
     },
-  )
+  );
 }
@@ -108,3 +111,3 @@
    */
-  onError?: ('terminate' | ((error: Error) => void)) | undefined
+  onError?: ("terminate" | ((error: Error) => void)) | undefined;
   /**
@@ -115,3 +118,3 @@ * Callback for when a reconnection interval is sent from the server.
    */
-  onRetry?: ((retry: number) => void) | undefined
+  onRetry?: ((retry: number) => void) | undefined;
   /**
@@ -122,5 +125,5 @@ * Callback for when a comment is encountered in the stream.
    */
-  onComment?: ((comment: string) => void) | undefined
+  onComment?: ((comment: string) => void) | undefined;
 }
 
-export {}
+export {};

LICENSE

 MIT License
 
-Copyright (c) 2025 Espen Hovlandsdal <[e-mail]>
+Copyright (c) 2026 Espen Hovlandsdal <[e-mail]>
 
@@ -5,0 +5,0 @@ Permission is hereby granted, free of charge, to any person obtaining a copy

package.json

 {
   "name": "eventsource-parser",
-  "version": "3.0.6",
+  "version": "3.0.7",
   "description": "Streaming, source-agnostic EventSource/Server-Sent Events parser",
+  "keywords": [
+    "eventsource",
+    "server-sent-events",
+    "sse"
+  ],
+  "homepage": "https://github.com/rexxars/eventsource-parser#readme",
+  "bugs": {
+    "url": "https://github.com/rexxars/eventsource-parser/issues"
+  },
+  "license": "MIT",
+  "author": "Espen Hovlandsdal <[e-mail]>",
+  "repository": {
+    "type": "git",
+    "url": "git+ssh://[e-mail]/rexxars/eventsource-parser.git"
+  },
+  "files": [
+    "dist",
+    "!dist/stats.html",
+    "!dist/index.min.js",
+    "src",
+    "stream.js"
+  ],
+  "type": "module",
   "sideEffects": false,
-  "type": "module",
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.js",
   "types": "./dist/index.d.ts",
-  "module": "./dist/index.js",
-  "main": "./dist/index.cjs",
   "exports": {
@@ -25,29 +47,12 @@ ".": {
   },
-  "typesVersions": {
-    "*": {
-      "stream": [
-        "./dist/stream.d.ts"
-      ]
-    }
-  },
-  "engines": {
-    "node": ">=18.0.0"
-  },
-  "browserslist": [
-    "node >= 20",
-    "chrome >= 71",
-    "safari >= 14.1",
-    "firefox >= 105",
-    "edge >= 79"
-  ],
-  "files": [
-    "dist",
-    "!dist/stats.html",
-    "src",
-    "stream.js"
-  ],
   "scripts": {
     "build": "pkg-utils build && pkg-utils --strict",
     "clean": "rimraf dist coverage",
-    "lint": "eslint . && tsc --noEmit",
+    "check": "npm run clean && npm run format && npm run lint && npm run build && vitest run",
+    "format": "oxfmt",
+    "format:check": "oxfmt --check",
+    "bench": "node --expose-gc --experimental-strip-types --no-warnings=ExperimentalWarning bench/parse.bench.ts",
+    "bundle-size": "node --experimental-strip-types --no-warnings=ExperimentalWarning scripts/bundle-size.ts",
+    "knip": "knip",
+    "lint": "oxlint && tsc --noEmit",
     "posttest": "npm run lint",
@@ -61,57 +66,29 @@ "prebuild": "npm run clean",
   },
-  "author": "Espen Hovlandsdal <[e-mail]>",
-  "keywords": [
-    "sse",
-    "eventsource",
-    "server-sent-events"
-  ],
   "devDependencies": {
-    "@sanity/pkg-utils": "^8.0.0",
-    "@sanity/semantic-release-preset": "^5.0.0",
+    "@sanity/pkg-utils": "^10.4.15",
+    "@sanity/semantic-release-preset": "^6.0.0",
+    "@sanity/tsconfig": "^2.1.0",
     "@types/node": "^20.19.0",
-    "@typescript-eslint/eslint-plugin": "^7.0.0",
-    "@typescript-eslint/parser": "^7.0.0",
-    "eslint": "^8.51.0",
-    "eslint-config-prettier": "^9.1.0",
-    "eslint-config-sanity": "^7.1.2",
     "eventsource-encoder": "^1.0.1",
-    "prettier": "^3.5.3",
-    "rimraf": "^6.0.1",
+    "knip": "^6.4.1",
+    "mitata": "^1.0.34",
+    "oxfmt": "^0.45.0",
+    "oxlint": "^1.60.0",
+    "rimraf": "^6.1.3",
     "rollup-plugin-visualizer": "^6.0.3",
-    "semantic-release": "^24.2.3",
-    "typescript": "^5.8.3",
-    "vitest": "^3.1.3"
+    "semantic-release": "^25.0.3",
+    "terser": "^5.46.1",
+    "typescript": "^5.9.3",
+    "vitest": "^4.1.4"
   },
-  "homepage": "https://github.com/rexxars/eventsource-parser#readme",
-  "bugs": {
-    "url": "https://github.com/rexxars/eventsource-parser/issues"
-  },
-  "repository": {
-    "type": "git",
-    "url": "git+ssh://[e-mail]/rexxars/eventsource-parser.git"
-  },
-  "license": "MIT",
-  "prettier": {
-    "bracketSpacing": false,
-    "printWidth": 100,
-    "semi": false,
-    "singleQuote": true
-  },
-  "eslintConfig": {
-    "parserOptions": {
-      "ecmaFeatures": {
-        "modules": true
-      },
-      "ecmaVersion": 9,
-      "sourceType": "module"
-    },
-    "extends": [
-      "sanity",
-      "sanity/typescript",
-      "prettier"
-    ],
-    "ignorePatterns": [
-      "lib/**/"
-    ]
+  "browserslist": [
+    "node >= 18",
+    "chrome >= 71",
+    "safari >= 14.1",
+    "firefox >= 105",
+    "edge >= 79"
+  ],
+  "engines": {
+    "node": ">=18.0.0"
   }
 }

src/parse.ts

@@ -8,3 +8,8 @@ /**
 
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
+// ASCII codes used in the hot parsing paths.
+const LF = 10
+const CR = 13
+const SPACE = 32
+
+// oxlint-disable-next-line no-unused-vars
 function noop(_arg: unknown) {
@@ -40,23 +45,163 @@ // intentional noop
   let data = ''
-  let eventType = ''
+  let dataLines = 0
+  let eventType: string | undefined
 
-  function feed(newChunk: string) {
-    // Strip any UTF8 byte order mark (BOM) at the start of the stream
-    const chunk = isFirstChunk ? newChunk.replace(/^\xEF\xBB\xBF/, '') : newChunk
+  /**
+   * Feeds a chunk of the SSE stream to the parser. Any trailing bytes that do
+   * not yet form a complete line are held back and prepended to the next chunk,
+   * so callers can pass arbitrary slices of the stream without worrying about
+   * line boundaries.
+   *
+   * The first chunk is dispatched to {@link feedFirst} so the leading UTF-8
+   * BOM can be stripped before parsing begins.
+   */
+  function feed(chunk: string) {
+    if (isFirstChunk) {
+      isFirstChunk = false
+      feedFirst(chunk)
+      return
+    }
+    const input = incompleteLine === '' ? chunk : incompleteLine + chunk
+    incompleteLine = processLines(input)
+  }
 
-    // If there was a previous incomplete line, append it to the new chunk,
-    // so we may process it together as a new (hopefully complete) chunk.
-    const [complete, incomplete] = splitLines(`${incompleteLine}${chunk}`)
+  /**
+   * Handles the very first chunk of the stream. Per the SSE spec, a UTF-8 BOM
+   * (0xEF 0xBB 0xBF) at the start of the stream must be stripped before
+   * parsing. After BOM handling, behaves identically to {@link feed}.
+   *
+   * @see https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream
+   */
+  function feedFirst(chunk: string) {
+    if (
+      chunk.charCodeAt(0) === 0xef &&
+      chunk.charCodeAt(1) === 0xbb &&
+      chunk.charCodeAt(2) === 0xbf
+    ) {
+      chunk = chunk.slice(3)
+    }
+    const input = incompleteLine === '' ? chunk : incompleteLine + chunk
+    incompleteLine = processLines(input)
+  }
 
-    for (const line of complete) {
-      parseLine(line)
+  /**
+   * Splits `chunk` into SSE lines and dispatches each to the appropriate handler.
+   * Returns any trailing bytes that did not terminate with a line break, so the
+   * caller can prepend them to the next chunk.
+   *
+   * The SSE spec permits three line terminators: `\n`, `\r`, and `\r\n`. Real-world
+   * streams almost always use plain `\n`, so we take a fast path when no `\r` is
+   * present in the chunk. The slow path is spec-correct but does more work per line.
+   */
+  function processLines(chunk: string): string {
+    let searchIndex = 0
+
+    // Fast path: LF-only chunk (the common case for typical SSE servers).
+    // We can scan forward with a single `indexOf('\n')` per line and inline
+    // the hot-path branches for `data:` and `event:` without the CR bookkeeping
+    // the slow path needs.
+    if (chunk.indexOf('\r') === -1) {
+      let lfIndex = chunk.indexOf('\n', searchIndex)
+      while (lfIndex !== -1) {
+        // Blank line: end-of-event marker. Dispatch the accumulated event (if any)
+        // and reset the buffered fields. This is hoisted out of `parseLine` because
+        // it's the single most common line shape after `data:` lines.
+        if (searchIndex === lfIndex) {
+          if (dataLines > 0) {
+            onEvent({id, event: eventType, data})
+          }
+          id = undefined
+          data = ''
+          dataLines = 0
+          eventType = undefined
+          searchIndex = lfIndex + 1
+          lfIndex = chunk.indexOf('\n', searchIndex)
+          continue
+        }
+        const firstCharCode = chunk.charCodeAt(searchIndex)
+        if (isDataPrefix(chunk, searchIndex, firstCharCode)) {
+          // `data:` line — append the value to the event's data buffer.
+          // 'data:'.length === 5, 'data: '.length === 6
+          const valueStart =
+            chunk.charCodeAt(searchIndex + 5) === SPACE ? searchIndex + 6 : searchIndex + 5
+          const value = chunk.slice(valueStart, lfIndex)
+          // Fast path within a fast path: if this is the first data line AND the
+          // next char is another LF (i.e. `data:foo\n\n`), dispatch immediately
+          // without ever writing to the `data` buffer. This is the shape of a
+          // typical single-line SSE event (ChatGPT-style streams, etc.) and is
+          // hot enough to be worth the duplication.
+          if (dataLines === 0 && chunk.charCodeAt(lfIndex + 1) === LF) {
+            onEvent({id, event: eventType, data: value})
+            id = undefined
+            data = ''
+            eventType = undefined
+            searchIndex = lfIndex + 2
+            lfIndex = chunk.indexOf('\n', searchIndex)
+            continue
+          }
+          // Multi-line data: concatenate with newline separator per spec.
+          data = dataLines === 0 ? value : `${data}\n${value}`
+          dataLines++
+        } else if (isEventPrefix(chunk, searchIndex, firstCharCode)) {
+          // `event:` line — set the event type for the next dispatch. Per spec,
+          // an empty value resets `event type` to its default (undefined here).
+          // 'event:'.length === 6, 'event: '.length === 7
+          eventType =
+            chunk.slice(
+              chunk.charCodeAt(searchIndex + 6) === SPACE ? searchIndex + 7 : searchIndex + 6,
+              lfIndex,
+            ) || undefined
+        } else {
+          // Everything else: `id:`, `retry:`, comment lines (`:` prefix), unknown
+          // fields, or malformed lines. These are rarer and go through the full
+          // per-line parser, which handles the SSE field grammar in detail.
+          parseLine(chunk, searchIndex, lfIndex)
+        }
+        searchIndex = lfIndex + 1
+        lfIndex = chunk.indexOf('\n', searchIndex)
+      }
+      return chunk.slice(searchIndex)
     }
 
-    incompleteLine = incomplete
-    isFirstChunk = false
+    // Slow path: the chunk contains at least one `\r`, so lines may be terminated
+    // by `\r`, `\n`, or `\r\n`. We locate the next terminator by looking at both
+    // the nearest `\r` and `\n` and picking whichever comes first.
+    while (searchIndex < chunk.length) {
+      const crIndex = chunk.indexOf('\r', searchIndex)
+      const lfIndex = chunk.indexOf('\n', searchIndex)
+
+      let lineEnd = -1
+      if (crIndex !== -1 && lfIndex !== -1) {
+        lineEnd = crIndex < lfIndex ? crIndex : lfIndex
+      } else if (crIndex !== -1) {
+        // A trailing `\r` at the very end of the chunk is ambiguous: it could be
+        // a bare-CR terminator, or the first half of a `\r\n` whose `\n` arrives
+        // in the next chunk. Defer until we see more input.
+        if (crIndex === chunk.length - 1) {
+          lineEnd = -1
+        } else {
+          lineEnd = crIndex
+        }
+      } else if (lfIndex !== -1) {
+        lineEnd = lfIndex
+      }
+
+      if (lineEnd === -1) {
+        break
+      }
+
+      parseLine(chunk, searchIndex, lineEnd)
+      searchIndex = lineEnd + 1
+      // If we just consumed a `\r` and the next char is `\n`, skip it so the
+      // pair is treated as a single terminator rather than an empty line.
+      if (chunk.charCodeAt(searchIndex - 1) === CR && chunk.charCodeAt(searchIndex) === LF) {
+        searchIndex++
+      }
+    }
+
+    return chunk.slice(searchIndex)
   }
 
-  function parseLine(line: string) {
-    // If the line is empty (a blank line), dispatch the event
-    if (line === '') {
+  function parseLine(chunk: string, start: number, end: number) {
+    if (start === end) {
       dispatchEvent()
@@ -66,6 +211,38 @@ return
 
-    // If the line starts with a U+003A COLON character (:), ignore the line.
-    if (line.startsWith(':')) {
+    const firstCharCode = chunk.charCodeAt(start)
+
+    if (isDataPrefix(chunk, start, firstCharCode)) {
+      // 'data:'.length === 5, 'data: '.length === 6
+      const valueStart = chunk.charCodeAt(start + 5) === SPACE ? start + 6 : start + 5
+      const value = chunk.slice(valueStart, end)
+      data = dataLines === 0 ? value : `${data}\n${value}`
+      dataLines++
+      return
+    }
+
+    if (isEventPrefix(chunk, start, firstCharCode)) {
+      // 'event:'.length === 6, 'event: '.length === 7
+      eventType =
+        chunk.slice(chunk.charCodeAt(start + 6) === SPACE ? start + 7 : start + 6, end) || undefined
+      return
+    }
+
+    // Fast path for "id:" — 'i' = 105, 'd' = 100, ':' = 58
+    if (
+      firstCharCode === 105 &&
+      chunk.charCodeAt(start + 1) === 100 &&
+      chunk.charCodeAt(start + 2) === 58
+    ) {
+      // 'id:'.length === 3, 'id: '.length === 4
+      const value = chunk.slice(chunk.charCodeAt(start + 3) === SPACE ? start + 4 : start + 3, end)
+      id = value.includes('\0') ? undefined : value
+      return
+    }
+
+    // Comment line — ':' = 58
+    if (firstCharCode === 58) {
       if (onComment) {
-        onComment(line.slice(line.startsWith(': ') ? 2 : 1))
+        const line = chunk.slice(start, end)
+        // skip ':' (+1), or ': ' (+2) when a space follows
+        onComment(line.slice(chunk.charCodeAt(start + 1) === SPACE ? 2 : 1))
       }
@@ -75,24 +252,14 @@ return
 
-    // If the line contains a U+003A COLON character (:)
+    const line = chunk.slice(start, end)
     const fieldSeparatorIndex = line.indexOf(':')
-    if (fieldSeparatorIndex !== -1) {
-      // Collect the characters on the line before the first U+003A COLON character (:),
-      // and let `field` be that string.
-      const field = line.slice(0, fieldSeparatorIndex)
-
-      // Collect the characters on the line after the first U+003A COLON character (:),
-      // and let `value` be that string. If value starts with a U+0020 SPACE character,
-      // remove it from value.
-      const offset = line[fieldSeparatorIndex + 1] === ' ' ? 2 : 1
-      const value = line.slice(fieldSeparatorIndex + offset)
-
-      processField(field, value, line)
+    if (fieldSeparatorIndex === -1) {
+      processField(line, '', line)
       return
     }
 
-    // Otherwise, the string is not empty but does not contain a U+003A COLON character (:)
-    // Process the field using the whole line as the field name, and an empty string as the field value.
-    // 👆 This is according to spec. That means that a line that has the value `data` will result in
-    // a newline being added to the current `data` buffer, for instance.
-    processField(line, '', line)
+    const field = line.slice(0, fieldSeparatorIndex)
+    // skip ':' (+1), or ': ' (+2) when a space follows
+    const offset = line.charCodeAt(fieldSeparatorIndex + 1) === SPACE ? 2 : 1
+    const value = line.slice(fieldSeparatorIndex + offset)
+    processField(field, value, line)
   }
@@ -105,8 +272,7 @@
         // Set the `event type` buffer to field value
-        eventType = value
+        eventType = value || undefined
         break
       case 'data':
-        // Append the field value to the `data` buffer, then append a single U+000A LINE FEED(LF)
-        // character to the `data` buffer.
-        data = `${data}${value}\n`
+        data = dataLines === 0 ? value : `${data}\n${value}`
+        dataLines++
         break
@@ -147,17 +313,14 @@ case 'id':
   function dispatchEvent() {
-    const shouldDispatch = data.length > 0
-    if (shouldDispatch) {
+    if (dataLines > 0) {
       onEvent({
         id,
-        event: eventType || undefined,
-        // If the data buffer's last character is a U+000A LINE FEED (LF) character,
-        // then remove the last character from the data buffer.
-        data: data.endsWith('\n') ? data.slice(0, -1) : data,
+        event: eventType,
+        data,
       })
     }
 
-    // Reset for the next event
     id = undefined
     data = ''
-    eventType = ''
+    dataLines = 0
+    eventType = undefined
   }
@@ -167,3 +330,3 @@
     if (incompleteLine && options.consume) {
-      parseLine(incompleteLine)
+      parseLine(incompleteLine, 0, incompleteLine.length)
     }
@@ -174,3 +337,4 @@
     data = ''
-    eventType = ''
+    dataLines = 0
+    eventType = undefined
     incompleteLine = ''
@@ -183,59 +347,38 @@ }
 /**
- * For the given `chunk`, split it into lines according to spec, and return any remaining incomplete line.
+ * Checks if `chunk` starts with the literal `data:` at index `i`.
  *
- * @param chunk - The chunk to split into lines
- * @returns A tuple containing an array of complete lines, and any remaining incomplete line
- * @internal
+ * Equivalent to `chunk.startsWith('data:', i)`, but benchmarks show this
+ * hand-unrolled char-code comparison is ~20% faster on common event types.
+ * The caller passes `firstCharCode` (the code at `i`) so it can be reused
+ * across prefix checks.
+ *
+ * ASCII: 'd' = 100, 'a' = 97, 't' = 116, 'a' = 97, ':' = 58
  */
-function splitLines(chunk: string): [complete: Array<string>, incomplete: string] {
-  /**
-   * According to the spec, a line is terminated by either:
-   * - U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair
-   * - a single U+000A LINE FEED(LF) character not preceded by a U+000D CARRIAGE RETURN(CR) character
-   * - a single U+000D CARRIAGE RETURN(CR) character not followed by a U+000A LINE FEED(LF) character
-   */
-  const lines: Array<string> = []
-  let incompleteLine = ''
-  let searchIndex = 0
+function isDataPrefix(chunk: string, i: number, firstCharCode: number): boolean {
+  return (
+    firstCharCode === 100 &&
+    chunk.charCodeAt(i + 1) === 97 &&
+    chunk.charCodeAt(i + 2) === 116 &&
+    chunk.charCodeAt(i + 3) === 97 &&
+    chunk.charCodeAt(i + 4) === 58
+  )
+}
 
-  while (searchIndex < chunk.length) {
-    // Find next line terminator
-    const crIndex = chunk.indexOf('\r', searchIndex)
-    const lfIndex = chunk.indexOf('\n', searchIndex)
-
-    // Determine line end
-    let lineEnd = -1
-    if (crIndex !== -1 && lfIndex !== -1) {
-      // CRLF case
-      lineEnd = Math.min(crIndex, lfIndex)
-    } else if (crIndex !== -1) {
-      // CR at the end of a chunk might be part of a CRLF sequence that spans chunks,
-      // so we shouldn't treat it as a line terminator (yet)
-      if (crIndex === chunk.length - 1) {
-        lineEnd = -1
-      } else {
-        lineEnd = crIndex
-      }
-    } else if (lfIndex !== -1) {
-      lineEnd = lfIndex
-    }
-
-    // Extract line if terminator found
-    if (lineEnd === -1) {
-      // No terminator found, rest is incomplete
-      incompleteLine = chunk.slice(searchIndex)
-      break
-    } else {
-      const line = chunk.slice(searchIndex, lineEnd)
-      lines.push(line)
-
-      // Move past line terminator
-      searchIndex = lineEnd + 1
-      if (chunk[searchIndex - 1] === '\r' && chunk[searchIndex] === '\n') {
-        searchIndex++
-      }
-    }
-  }
-
-  return [lines, incompleteLine]
+/**
+ * Checks if `chunk` starts with the literal `event:` at index `i`.
+ *
+ * See {@link isDataPrefix} for why this is hand-unrolled rather than using
+ * `String.prototype.startsWith`.
+ *
+ * ASCII: 'e' = 101, 'v' = 118, 'e' = 101, 'n' = 110, 't' = 116, ':' = 58
+ */
+function isEventPrefix(chunk: string, i: number, firstCharCode: number): boolean {
+  return (
+    firstCharCode === 101 &&
+    chunk.charCodeAt(i + 1) === 118 &&
+    chunk.charCodeAt(i + 2) === 101 &&
+    chunk.charCodeAt(i + 3) === 110 &&
+    chunk.charCodeAt(i + 4) === 116 &&
+    chunk.charCodeAt(i + 5) === 58
+  )
 }

No alert changes

Improved metrics

Total package byte prevSize

103275

35.15%

Lines of code

1186

26.44%

No dependency changes