Version 0.2.4: Optimized single-byte encodings (4.5x performance incr…

…ease).
ashtuchkin · Aug 24, 2012 · d57c271 · d57c271
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diff --git a/README.md b/README.md
@@ -8,7 +8,7 @@ iconv-lite - pure javascript character encoding conversion
 *   Pure javascript. Doesn't need native code compilation.
 *   Easy API.
 *   Works on Windows and in sandboxed environments like [Cloud9](http://c9.io).
-*   Encoding is faster than node-iconv, decoding slightly slower (see below for performance comparison).
+*   Encoding is much faster than node-iconv (see below for performance comparison).
 
 ## Usage
 
@@ -39,10 +39,10 @@ Not supported yet: Big5, EUC family, Shift_JIS.
 Comparison with node-iconv module (1000x256kb, on Ubuntu 12.04, Core i5/2.5 GHz, Node v0.8.7). 
 Note: your results may vary, so please always check on your hardware.
 
-    operation             iconv@1.1.3   iconv-lite@0.2.3 
+    operation             iconv@1.1.3   iconv-lite@0.2.4 
     ----------------------------------------------------------
-    encode('win1251')     ~36 Mb/s      ~50 Mb/s
-    decode('win1251')     ~38 Mb/s      ~29 Mb/s
+    encode('win1251')     ~36 Mb/s      ~230 Mb/s
+    decode('win1251')     ~38 Mb/s      ~130 Mb/s
 
 
 ## Notes

diff --git a/index.js b/index.js
@@ -58,13 +58,13 @@ var iconv = module.exports = {
         // Codepage single-byte encodings.
         singlebyte: function(options) {
             // Prepare chars if needed
-            if (!options.chars || (options.chars.length !== 128 && options.chars.length !== 256))
-                throw new Error("Encoding '"+options.type+"' has incorrect 'chars' (must be of len 128 or 256)");
-
-            if (options.chars.length === 128)
-                options.chars = asciiString + options.chars;
-
             if (!options.charsBuf) {
+                if (!options.chars || (options.chars.length !== 128 && options.chars.length !== 256))
+                    throw new Error("Encoding '"+options.type+"' has incorrect 'chars' (must be of len 128 or 256)");
+
+                if (options.chars.length === 128)
+                    options.chars = asciiString + options.chars;
+
                 options.charsBuf = new Buffer(options.chars, 'ucs2');
             }
 
@@ -76,33 +76,14 @@ var iconv = module.exports = {
                 for (var i = 0; i < options.chars.length; i++)
                     options.revCharsBuf[options.chars.charCodeAt(i)] = i;
             }
-            
+
             return {
-                toEncoding: function(str) {
-                    str = ensureString(str);
-
-                    var buf = new Buffer(str.length);
-                    var revCharsBuf = options.revCharsBuf;
-                    for (var i = 0; i < str.length; i++)
-                        buf[i] = revCharsBuf[str.charCodeAt(i)];
-
-                    return buf;
-                },
-                fromEncoding: function(buf) {
-                    buf = ensureBuffer(buf);
-
-                    // Strings are immutable in JS -> we use ucs2 buffer to speed up computations.
-                    var charsBuf = options.charsBuf;
-                    var newBuf = new Buffer(buf.length*2);
-                    var idx1 = 0, idx2 = 0;
-                    for (var i = 0, _len = buf.length; i < _len; i++) {
-                        idx1 = buf[i]*2; idx2 = i*2;
-                        newBuf[idx2] = charsBuf[idx1];
-                        newBuf[idx2+1] = charsBuf[idx1+1];
-                    }
-                    return newBuf.toString('ucs2');
-                }
-            };
+                // Seems that V8 is not optimizing functions if they are created again and again.
+                // TODO: Make same optimization for other encodings.
+                toEncoding: toSingleByteEncoding,
+                fromEncoding: fromSingleByteEncoding,
+                options: options,
+            }
         },
 
         // Codepage double-byte encodings.
@@ -171,6 +152,32 @@ var iconv = module.exports = {
     }
 };
 
+function toSingleByteEncoding(str) {
+    str = ensureString(str);
+
+    var buf = new Buffer(str.length);
+    var revCharsBuf = this.options.revCharsBuf;
+    for (var i = 0; i < str.length; i++)
+        buf[i] = revCharsBuf[str.charCodeAt(i)];
+
+    return buf;
+}
+
+function fromSingleByteEncoding(buf) {
+    buf = ensureBuffer(buf);
+
+    // Strings are immutable in JS -> we use ucs2 buffer to speed up computations.
+    var charsBuf = this.options.charsBuf;
+    var newBuf = new Buffer(buf.length*2);
+    var idx1 = 0, idx2 = 0;
+    for (var i = 0, _len = buf.length; i < _len; i++) {
+        idx1 = buf[i]*2; idx2 = i*2;
+        newBuf[idx2] = charsBuf[idx1];
+        newBuf[idx2+1] = charsBuf[idx1+1];
+    }
+    return newBuf.toString('ucs2');
+}
+
 // Add aliases to convert functions
 iconv.encode = iconv.toEncoding;
 iconv.decode = iconv.fromEncoding;

diff --git a/package.json b/package.json
@@ -1,7 +1,7 @@
 {
     "name": "iconv-lite",
     "description": "Convert character encodings in pure javascript.",
-    "version": "0.2.3",
+    "version": "0.2.4",
 
     "keywords": ["iconv", "convert", "charset"],
     "author": "Alexander Shtuchkin <ashtuchkin@gmail.com>",