arithmetic-coding - npm Package Compare versions

Comparing version 1.0.0 to 1.1.0

CHANGELOG.md

@@ -7,2 +7,8 @@ # arithmetic-coding CHANGELOG
 
-Finished API and CLI support.
+- Finished API and CLI support.
+
+## v1.1.0
+
+2019.03.30
+
+- Added Buffer support.

package.json

 {
   "name": "arithmetic-coding",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "Arithmetic coding implementation",
@@ -38,3 +38,4 @@ "main": "src/index.js",
     "concat-stream": "^2.0.0",
-    "long": "^4.0.0"
+    "long": "^4.0.0",
+    "which": "^1.3.1"
   },
@@ -41,0 +42,0 @@ "devDependencies": {

README.md

@@ -12,3 +12,3 @@ # arithmetic-coding
 
-Install as module:
+Install as module for API usage:
 
@@ -27,12 +27,24 @@ ```js
 
-Simply call `encode` and `decode` function.
+From file path:
 
 ```js
 const ariCoding = require('arithmetic-coding');
-// Encode
+// Encode from file
 ariCoding.encode(__dirname + '/txt/long.txt', __dirname + '/txt/long-encoded.txt');
-// Decode
+// Decode from file
 ariCoding.decode(__dirname + '/txt/long-encoded.txt', __dirname + '/txt/long-decoded.txt');
 ```
 
+From `Buffer`:
+
+```js
+let data = Buffer.from('Example data', 'utf8');
+// Encode from Buffer
+let encoded = encode.encodeFromBuffer(data);
+console.log(`encoded = ${encoded}`);
+// Decode from buffer
+let decoded = decode.decodeFromBuffer(encoded);
+console.log(`decoded = ${decoded}`);
+```
+
 ## Command-line interface
@@ -53,3 +65,3 @@
 
-## About algorithm
+## About the algorithm
 
@@ -56,0 +68,0 @@ 1. [Wikipedia](https://en.wikipedia.org/wiki/Arithmetic_coding)

src/bit-input-stream.js

 const fs = require('fs');
+
+const CACHE_SIZE = 20000;
+
 /**
@@ -24,2 +27,5 @@ * A stream where bits can be read.
     this._numbitsremaining = 0;
+
+    this._cachedBytes = Buffer.alloc(0);
+    this._streamEnded = false;
   }
@@ -38,12 +44,18 @@
     if (this._numbitsremaining === 0) {
-      // console.log(`this._numbitsremaining0 = ${this._numbitsremaining}`);
-      let temp = Buffer.alloc(1);
-      let numOfBytesRead = fs.readSync(this._input, temp, 0, 1, null);
-      // console.log(`numOfBytes read: ${numOfBytesRead}`);
-      // console.log(`position = ${this._position}`);
-      if (numOfBytesRead === 0) {
-        this._currentbyte = -1;
-        return -1;
+      if (this._cachedBytes.length === 0) {
+        if (this._streamEnded) {
+          this._currentbyte = -1;
+          return -1;
+        } else {
+          let temp = Buffer.alloc(CACHE_SIZE);
+          let numOfBytesRead = fs.readSync(this._input, temp, 0, CACHE_SIZE, null);
+          this._cachedBytes = Buffer.concat([this._cachedBytes, temp], numOfBytesRead);
+          if (numOfBytesRead < CACHE_SIZE) {
+            this._streamEnded = true;
+          }
+        }
       }
-      this._currentbyte = temp[0];
+      // console.log(`this._cachedBytes = ${this._cachedBytes}`);
+      this._currentbyte = this._cachedBytes[0];
+      this._cachedBytes = this._cachedBytes.slice(1);
       // console.log('Byte read:', temp);
@@ -59,3 +71,3 @@ // console.log(this._currentbyte);
     // console.log(`this._numbitsremaining = ${this._numbitsremaining}`);
-    return (this._currentbyte >> this._numbitsremaining) & 1; 
+    return (this._currentbyte >> this._numbitsremaining) & 1;
   }
@@ -62,0 +74,0 @@

src/decode.js

 const fs = require('fs');
 const FrequencyTable = require('./frequency-table');
 const BitInputStream = require('./bit-input-stream');
+const BitInputStreamFromBuffer = require('./bit-input-stream-buffer');
 const Long = require('long');
@@ -8,3 +9,3 @@ const ArithmeticDecoder = require('./arithmetic-decoder');
 /**
- * Encode a file using arithmetic coding algorithm
+ * Decode a file using arithmetic coding algorithm
  * @param {string} inputfile Absolute path of the input file
@@ -22,2 +23,15 @@ * @param {string} outputfile Absolute path of the output file
 
+/**
+ * Decode a Buffer using arithmetic coding algorithm
+ * @param {Buffer} inBuffer Input buffer
+ */
+function decodeFromBuffer(inBuffer) {
+  // const inStream = fs.createReadStream(inputfile);
+  // const outStream = fs.createWriteStream(outputfile);
+  const bitin = new BitInputStreamFromBuffer(inBuffer);
+  let freqs = readFrequencies(bitin);
+  // console.log(`freqs.total = ${freqs.total}`);
+  return decompressToBuffer(freqs, bitin);
+}
+
 function readFrequencies(bitin) {
@@ -64,5 +78,27 @@ function readInt(n) {
 
+/**
+ * 
+ * @param {FrequencyTable} freqs 
+ * @param {BitInputStreamFromBuffer} bitin 
+ */
+function decompressToBuffer(freqs, bitin) {
+  let buffer = Buffer.alloc(0);
+  const dec = new ArithmeticDecoder(32, bitin);
+  for (;;) {
+    let symbol = dec.read(freqs);
+    // EOF symbol
+    if (symbol === 256) {
+      dec.finish();
+      break;
+    }
+    // console.log(`writing ${symbol}`);
+    buffer = Buffer.concat([buffer, Buffer.from([symbol])]);
+  }
+  return buffer;
+}
+
 module.exports = {
   readFrequencies,
-  decode
+  decode,
+  decodeFromBuffer
 };

src/encode.js

 const fs = require('fs');
 const FrequencyTable = require('./frequency-table');
 const BitOutputStream = require('./bit-output-stream');
+const BitOutputStreamToBuffer = require('./bit-output-stream-buffer');
 const ArithmeticEncoder = require('./arithmetic-encoder');
 
+const CACHE_SIZE = 20000;
+
 /**
@@ -18,3 +21,3 @@ * Returns a frequency table based on the bytes
   );
-  const temp = Buffer.alloc(100);
+  const temp = Buffer.alloc(CACHE_SIZE);
   let bytesRead;
@@ -34,3 +37,20 @@ for (;;) {
 /**
- * Decode a file using arithmetic coding algorithm
+ * Returns a frequency table based on the bytes 
+ * in the given Buffer.
+ * Also contains an extra entry for symbol 256,
+ * whose frequency is set to 0.
+ * @param {Buffer} buffer 
+ */
+function getFrequenciesFromBuffer(buffer) {
+  let freqs = new FrequencyTable(
+    new Array(257).fill(0)
+  );
+  for (let byte of buffer) {
+    freqs.increment(byte);
+  }
+  return freqs;
+}
+
+/**
+ * Encode a file using arithmetic coding algorithm
  * @param {string} inputfile Absolute path of the input file
@@ -51,2 +71,18 @@ * @param {string} outputfile Absolute path of the output file
 /**
+ * Encode a Buffer using arithmetic coding algorithm
+ * @param {Buffer} inBuffer Input buffer
+ */
+function encodeFromBuffer(inBuffer) {
+  let freqs = getFrequenciesFromBuffer(inBuffer);
+  // EOF symbol gets a frequency of 1
+  freqs.increment(256);
+  
+  const bitout = new BitOutputStreamToBuffer();
+  
+  writeFrequencies(bitout, freqs);
+  compressFromBuffer(freqs, inBuffer, bitout);
+  return bitout.buffer;
+}
+
+/**
  * Write the frequency table to encoded file.
@@ -86,3 +122,3 @@ * @param {BitOutputStream} bitout the output stream
   for(;;) {
-    const temp = Buffer.alloc(100);
+    const temp = Buffer.alloc(CACHE_SIZE);
     let bytesRead;
@@ -104,5 +140,24 @@ if ((bytesRead = fs.readSync(input, temp, 0, temp.length, null)) === 0) {
 
+/**
+ * 
+ * @param {FrequencyTable} freqs 
+ * @param {Buffer} inBuffer 
+ * @param {BitOutputStreamToBuffer} bitout 
+ */
+function compressFromBuffer(freqs, inBuffer, bitout) {
+  let enc = new ArithmeticEncoder(32, bitout);
+  for (let byte of inBuffer) {
+    enc.write(freqs, byte);
+  }
+  // EOF
+  enc.write(freqs, 256);
+  // Flush remaining code bit
+  enc.finish();
+  // console.log('Encoded okay!');
+}
+
 module.exports = {
   getFrequencies,
-  encode
+  encode,
+  encodeFromBuffer
 };

src/index.js

@@ -1,6 +0,8 @@
-let encode = require('./encode').encode;
-let decode = require('./decode').decode;
+let encode = require('./encode');
+let decode = require('./decode');
 module.exports = {
-  encode,
-  decode
+  encode: encode.encode,
+  encodeFromBuffer: encode.encodeFromBuffer,
+  decode: decode.decode,
+  decodeFromBuffer: decode.decodeFromBuffer
 };

test/2_decode.test.js

@@ -8,2 +8,4 @@ var fs = require('fs');
     decode.decode(__dirname + '/txt/short-encoded.txt', __dirname + '/txt/short-decoded.txt');
+  });
+  it('should decode & encode equal', function () {
     let originalText = fs.readFileSync(__dirname + '/txt/short.txt');
@@ -10,0 +12,0 @@ let decodedText = fs.readFileSync(__dirname + '/txt/short-decoded.txt');

test/3_index.test.js

@@ -19,2 +19,12 @@ require('should');
   });
+  describe('Buffer support', function() {
+    it('should encode and decode Buffer okay', function() {
+      let data = Buffer.from('Example data', 'utf8');
+      let encoded = ariCoding.encodeFromBuffer(data);
+      // console.log(`encoded = ${encoded}`);
+      let decoded = ariCoding.decodeFromBuffer(encoded);
+      // console.log(`decoded = ${decoded}`);
+      data.should.eql(decoded);
+    });
+  });
 });

test/4_cli.test.js

@@ -17,3 +17,3 @@ const cmd = require('./cmd');
   });
-  it('should encode & encode okay', async () => {
+  it('should encode okay', async () => {
     await cmd.execute(
@@ -23,2 +23,4 @@ path.resolve(__dirname, '../bin/index.js'),
     );
+  });
+  it('should decode okay', async () => {
     await cmd.execute(
@@ -28,2 +30,4 @@ path.resolve(__dirname, '../bin/index.js'),
     );
+  });
+  it('should encode & decode equal', async () => {
     let originalText = fs.readFileSync(__dirname + '/txt/long.txt');
@@ -30,0 +34,0 @@ let decodedText = fs.readFileSync(__dirname + '/txt/long-decoded.txt');

test/cmd.js

@@ -0,1 +1,2 @@
+require('should');
 // https://medium.com/@zorrodg/integration-tests-on-node-js-cli-part-1-why-and-how-fa5b1ba552fe
@@ -6,3 +7,8 @@ const spawn = require('child_process').spawn;
 
-  return spawn('node', args, {
+  // Require which and child_process
+  const which = require('which');
+  // Find node in PATH
+  const node = which.sync('node');
+
+  return spawn(node, args, {
     env: Object.assign(
@@ -9,0 +15,0 @@ {

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Improved metrics

Total package byte prevSize

162202

increased by5.12%

Number of package files

27

increased by12.5%

Lines of code

1262

increased by22.76%

Number of lines in readme file

67

increased by21.82%

Worsened metrics

Dependency count

5

increased by25%

Dependency changes

• + Addedwhich@^1.3.1

• + Addedisexe@2.0.0(transitive)

• + Addedwhich@1.3.1(transitive)