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string_decoder: add support for CESU-8

Fixes #3217.
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koichik committed May 5, 2012
1 parent eaf607e commit ceb51ddaa187b188035dd0b01589f1d24d5e90c7
Showing with 78 additions and 14 deletions.
  1. +35 −14 lib/string_decoder.js
  2. +43 −0 test/simple/test-string-decoder.js
@@ -22,7 +22,7 @@
var StringDecoder = exports.StringDecoder = function(encoding) {
this.encoding = (encoding || 'utf8').toLowerCase().replace(/[-_]/, '');
if (this.encoding === 'utf8') {
this.charBuffer = new Buffer(4);
this.charBuffer = new Buffer(6);
this.charReceived = 0;
this.charLength = 0;
}
@@ -36,16 +36,18 @@ StringDecoder.prototype.write = function(buffer) {
}

var charStr = '';
var offset = 0;
// if our last write ended with an incomplete multibyte character
if (this.charLength) {
while (this.charLength) {
// determine how many remaining bytes this buffer has to offer for this char
var i = (buffer.length >= this.charLength - this.charReceived) ?
this.charLength - this.charReceived :
buffer.length;

// add the new bytes to the char buffer
buffer.copy(this.charBuffer, this.charReceived, 0, i);
this.charReceived += i;
buffer.copy(this.charBuffer, this.charReceived, offset, i);
this.charReceived += (i - offset);
offset = i;

if (this.charReceived < this.charLength) {
// still not enough chars in this buffer? wait for more ...
@@ -54,13 +56,24 @@ StringDecoder.prototype.write = function(buffer) {

// get the character that was split
charStr = this.charBuffer.slice(0, this.charLength).toString();

// lead surrogate (D800-DBFF) is also the incomplete character
if (this.charLength === 3) {
var charCode = charStr.charCodeAt(0);
if (charCode >= 0xD800 && charCode <= 0xDBFF) {
charStr = '';
this.charLength += 3; // size of trail surrogate (DC00-DFFF)
continue;
}
}
this.charReceived = this.charLength = 0;

// if there are no more bytes in this buffer, just emit our char
if (i == buffer.length) return charStr;

// otherwise cut off the characters end from the beginning of this buffer
buffer = buffer.slice(i, buffer.length);
break;
}


@@ -93,18 +106,26 @@ StringDecoder.prototype.write = function(buffer) {
}
}

if (!this.charLength) {
// no incomplete char at the end of this buffer, emit the whole thing
return charStr + buffer.toString();
var end = buffer.length;
if (this.charLength) {
// buffer the incomplete character bytes we got
buffer.copy(this.charBuffer, 0, buffer.length - i, buffer.length);
this.charReceived = i;
end -= i;
}

// buffer the incomplete character bytes we got
buffer.copy(this.charBuffer, 0, buffer.length - i, buffer.length);
this.charReceived = i;

if (buffer.length - i > 0) {
// buffer had more bytes before the incomplete char, emit them
return charStr + buffer.toString('utf8', 0, buffer.length - i);
charStr += buffer.toString('utf8', 0, end);

// lead surrogate (D800-DBFF) is also the incomplete character
end = charStr.length - 1;
var charCode = charStr.charCodeAt(end);
if (charCode >= 0xD800 && charCode <= 0xDBFF) {
// CESU-8 represents each of Surrogate Pair by 3-bytes
this.charLength += 3
this.charReceived += 3
this.charBuffer.copy(this.charBuffer, 3, 0, 3);
this.charBuffer.write(charStr.charAt(end));
return charStr.substring(0, end);
}

// or just emit the charStr
@@ -46,6 +46,49 @@ s += decoder.write(buffer.slice(2, 3));
s += decoder.write(buffer.slice(3, 4));
assert.ok(s.length > 0);

// CESU-8
buffer = new Buffer('EDA0BDEDB18D', 'hex'); // THUMBS UP SIGN (in CESU-8)
var s = '';
s += decoder.write(buffer.slice(0, 1));
s += decoder.write(buffer.slice(1, 2));
s += decoder.write(buffer.slice(2, 3)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(3, 4));
s += decoder.write(buffer.slice(4, 5));
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 2));
s += decoder.write(buffer.slice(2, 4)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(4, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 3)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(3, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 4)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(4, 5));
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 5)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 6));
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)


// A mixed ascii and non-ascii string
// Test stolen from deps/v8/test/cctest/test-strings.cc
// U+02E4 -> CB A4

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