From c58bfccd1b87d00c7eaacc829bdeb6b46cd8acb0 Mon Sep 17 00:00:00 2001
From: Vitaly Puzrin <vitaly@rcdesign.ru>
Date: Mon, 14 Apr 2014 01:57:08 +0400
Subject: [PATCH] More utf8 decoder opts

---
 lib/utils/strings.js | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/lib/utils/strings.js b/lib/utils/strings.js
index 317dc72..656fef7 100644
--- a/lib/utils/strings.js
+++ b/lib/utils/strings.js
@@ -112,18 +112,11 @@ exports.buf2string = function (buf, max) {
       buf.subarray ? buf.subarray(0, max) : buf.slice(0, max)
   )));*/
 
-  var str = '', i, out, part, char_len;
+  var str, i, out, part, char_len;
   var len = max || buf.length;
-  var out_len = 0;
-  var utf16buf;
 
-  // Calculate output length
-  for (i=0; i < len;) {
-    i += utf8len[buf[i]];
-    out_len++;
-  }
-
-  utf16buf = new utils.Buf32(out_len);
+  // Reserve max possibli length
+  var utf16buf = new utils.Buf16(len*2);
 
   for (out=0, i=0; i<len; i++) {
     part = buf[i];
@@ -131,7 +124,7 @@ exports.buf2string = function (buf, max) {
 
     // edge case - broken sequence
     if (i + char_len > len) {
-      utf16buf[out++] = 0x7f;
+      utf16buf[out++] = 0xfffd;
       break;
     }
     switch (char_len) {
@@ -145,17 +138,21 @@ exports.buf2string = function (buf, max) {
         utf16buf[out++] = ((part & 0x0f) << 12) | ((buf[++i] & 0x3f) << 6) | (buf[++i] & 0x3f);
         break;
       case 4:
-        utf16buf[out++] = ((part & 0x07) << 18) | ((buf[++i] & 0x3f) << 12) | ((buf[++i] & 0x3f) << 6) + (buf[++i] & 0x3f);
+        // surrogate pair
+        part = ((part & 0x07) << 18) | ((buf[++i] & 0x3f) << 12) | ((buf[++i] & 0x3f) << 6) + (buf[++i] & 0x3f);
+        part -= 0x10000;
+        utf16buf[out++] = 0xd800 | ((part >> 10) & 0x3ff);
+        utf16buf[out++] = 0xdc00 | (part & 0x3ff);
         break;
       // 5 & 6 bytes uticodes not supported in UTF16 (JS), so fill with dummy symbol
       case 5:
         i += 4;
-        utf16buf[out++] = 0x7f;
+        utf16buf[out++] = 0xfffd;
         //utf16buf[out++] = (part - 248 << 24) + (buf[++i] - 128 << 18) + (buf[++i] - 128 << 12) + (buf[++i] - 128 << 6) + buf[++i] - 128;
         break;
       case 6:
         i += 5;
-        utf16buf[out++] = 0x7f;
+        utf16buf[out++] = 0xfffd;
                           // (part - 252 << 32) is not possible in ECMAScript! So...:
         //utf16buf[out++] = (part - 252) * 1073741824 + (buf[++i] - 128 << 24) + (buf[++i] - 128 << 18) + (buf[++i] - 128 << 12) + (buf[++i] - 128 << 6) + buf[++i] - 128;
         break;
@@ -163,11 +160,12 @@ exports.buf2string = function (buf, max) {
   }
 
   if (STR_APPLY_OK) {
-    return String.fromCharCode.apply(null, utf16buf);
+    return String.fromCharCode.apply(null, utils.shrinkBuf(utf16buf, out));
   }
 
   // Fallback, when String.fromCharCode.apply not available
-  for (i=0, len=utf16buf.length; i<len; i++) {
+  str = '';
+  for (i=0, len=out; i<len; i++) {
     str += String.fromCharCode(utf16buf[i]);
   }
   return str;