adler-32 - npm Package Compare versions

Comparing version 0.1.0 to 0.2.0

adler32.js

@@ -13,11 +13,11 @@ /* adler32.js (C) 2014 SheetJS -- http://sheetjs.com */
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += bstr.charCodeAt(i++);
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += bstr.charCodeAt(i);
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -28,11 +28,11 @@
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += buf[i++];
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += buf[i];
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -66,3 +66,3 @@
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return (b << 16) | a;
 }
@@ -69,0 +69,0 @@ ADLER32.bstr = adler32_bstr;

bits/40_adler.js

@@ -8,11 +8,11 @@ /* consult README.md for the magic number */
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += bstr.charCodeAt(i++);
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += bstr.charCodeAt(i);
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -23,11 +23,11 @@
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += buf[i++];
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += buf[i];
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -61,3 +61,3 @@
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return (b << 16) | a;
 }

ctest/adler32.js

@@ -13,11 +13,11 @@ /* adler32.js (C) 2014 SheetJS -- http://sheetjs.com */
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += bstr.charCodeAt(i++);
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += bstr.charCodeAt(i);
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -28,11 +28,11 @@
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
-		for(;M>0;--M) {
-			a += buf[i++];
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += buf[i];
 			b += a;
 		}
-		a %= 65521;
-		b %= 65521;
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return ((b%65521) << 16) | (a%65521);
 }
@@ -66,3 +66,3 @@
 	}
-	return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
+	return (b << 16) | a;
 }
@@ -69,0 +69,0 @@ ADLER32.bstr = adler32_bstr;

package.json

 {
 	"name": "adler-32",
-	"version": "0.1.0",
+	"version": "0.2.0",
 	"author": "sheetjs",
@@ -5,0 +5,0 @@ "description": "Pure-JS ADLER-32",

perf/bstr.js

@@ -1,3 +0,1 @@
-var table = require('../').table;
-
 function sheetjs1(bstr) {
@@ -17,3 +15,17 @@ var a = 1, b = 0, L = bstr.length;
 	for(var i = 0; i < L;) {
-		M = Math.min(L-i, 3854);
+		M = Math.min(L-i, 3850)+i;
+		for(;i<M;i++) {
+			a += bstr.charCodeAt(i);
+			b += a;
+		}
+		a = (15*(a>>>16)+(a&65535))
+		b = (15*(b>>>16)+(b&65535))
+	}
+	return ((b%65521) << 16) | (a%65521);
+}
+
+function sheetjs3(bstr) {
+	var a = 1, b = 0, L = bstr.length, M;
+	for(var i = 0; i < L;) {
+		M = Math.min(L-i, 5552);
 		for(;M>0;--M) {
@@ -29,12 +41,26 @@ a += bstr.charCodeAt(i++);
 
-var foobar = "foobarbazqux";
-for(var i = 0; i != 11; ++i) foobar += " " + foobar;
+var foobar = [255,255,255,255,255,255].map(function(x) { return String.fromCharCode(x); }).join("");
+foobar += foobar;
+foobar += foobar;
+foobar += foobar;
+foobar += foobar;
+foobar += foobar;
+foobar += foobar;
+foobar.charCodeAt(0);
+var m = 2048;
 var assert = require('assert');
-assert.equal(sheetjs1(foobar), sheetjs2(foobar));
-
 var BM = require('./bm');
-var suite = new BM('binary string');
+for(var i = 0; i != 14; ++i) {
+	foobar += foobar;
+	foobar.charCodeAt(0);
+	assert.equal(sheetjs1(foobar), sheetjs3(foobar));
+	assert.equal(sheetjs1(foobar), sheetjs2(foobar));
+	//for(var j = 0; j != 200; ++j) assert.equal(sheetjs2(foobar), sheetjs3(foobar));
+	var suite = new BM('binary string (' + foobar.length + ')');
 
-suite.add('sheetjs 1', function() { for(var j = 0; j != 1000; ++j) sheetjs1(foobar); });
-suite.add('sheetjs 2', function() { for(var j = 0; j != 1000; ++j) sheetjs2(foobar); });
-suite.run();
+	if(i<3) suite.add('sheetjs 1', function() { for(var j = 0; j != m; ++j) sheetjs1(foobar); });
+	suite.add('sheetjs 2', function() { for(var j = 0; j != m; ++j) sheetjs2(foobar); });
+	suite.add('sheetjs 3', function() { for(var j = 0; j != m; ++j) sheetjs3(foobar); });
+	suite.run();
+	m>>>=1; if(m < 10) m = 10;
+}

README.md

@@ -54,2 +54,13 @@ # adler32
 
+Bit twiddling is much faster than taking the mod on Safari and older Firefoxes.
+Instead of taking the literal mod 65521, it is faster to keep it in the integers
+by bit-shifting: `65536 ~ 15 mod 65521` so for nonnegative integer `a`:
+
+```
+    a = (a >>> 16) * 65536 + (a & 65535)            [equality]
+    a ~ (a >>> 16) * 15    + (a & 65535) mod 65521
+```
+
+The mod is taken at the very end, since the intermediate result may exceed 65521
+
 ## Magic Number
@@ -56,0 +67,0 @@

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Improved metrics

Total package byte prevSize

146855

increased by0.74%

Lines of code

5430

increased by0.5%

Number of lines in readme file

88

increased by14.29%

No dependency changes