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@ -25,6 +25,14 @@ function assertEncoding(encoding) { |
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} |
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} |
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// StringDecoder provides an interface for efficiently splitting a series of
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// buffers into a series of JS strings without breaking apart multi-byte
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// characters. CESU-8 is handled as part of the UTF-8 encoding.
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//
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// @TODO Handling all encodings inside a single object makes it very difficult
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// to reason about this code, so it should be split up in the future.
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// @TODO There should be a utf8-strict encoding that rejects invalid UTF-8 code
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// points as used by CESU-8.
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var StringDecoder = exports.StringDecoder = function(encoding) { |
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this.encoding = (encoding || 'utf8').toLowerCase().replace(/[-_]/, ''); |
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assertEncoding(encoding); |
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@ -49,12 +57,25 @@ var StringDecoder = exports.StringDecoder = function(encoding) { |
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return; |
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} |
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// Enough space to store all bytes of a single character. UTF-8 needs 4
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// bytes, but CESU-8 may require up to 6 (3 bytes per surrogate).
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this.charBuffer = new Buffer(6); |
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// Number of bytes received for the current incomplete multi-byte character.
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this.charReceived = 0; |
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// Number of bytes expected for the current incomplete multi-byte character.
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this.charLength = 0; |
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}; |
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// write decodes the given buffer and returns it as JS string that is
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// guaranteed to not contain any partial multi-byte characters. Any partial
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// character found at the end of the buffer is buffered up, and will be
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// returned when calling write again with the remaining bytes.
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//
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// Note: Converting a Buffer containing an orphan surrogate to a String
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// currently works, but converting a String to a Buffer (via `new Buffer`, or
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// Buffer#write) will replace incomplete surrogates with the unicode
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// replacement character. See https://codereview.chromium.org/121173009/ .
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StringDecoder.prototype.write = function(buffer) { |
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var charStr = ''; |
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// if our last write ended with an incomplete multibyte character
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@ -123,6 +144,10 @@ StringDecoder.prototype.write = function(buffer) { |
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return charStr; |
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}; |
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// detectIncompleteChar determines if there is an incomplete UTF-8 character at
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// the end of the given buffer. If so, it sets this.charLength to the byte
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// length that character, and sets this.charReceived to the number of bytes
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// that are available for this character.
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StringDecoder.prototype.detectIncompleteChar = function(buffer) { |
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// determine how many bytes we have to check at the end of this buffer
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var i = (buffer.length >= 3) ? 3 : buffer.length; |
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