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Automatically resize chunks to prevent splitting UTF-8 characters #1099

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Automatically resize chunks to prevent splitting UTF-8 characters #1099

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25 changes: 21 additions & 4 deletions papaparse.js
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Original file line number Diff line number Diff line change
Expand Up @@ -739,6 +739,7 @@ License: MIT
ChunkStreamer.call(this, config);

var reader, slice;
var decoder = new TextDecoder(config.encoding || 'utf-8');

// FileReader is better than FileReaderSync (even in worker) - see http://stackoverflow.com/q/24708649/1048862
// But Firefox is a pill, too - see issue #76: https://github.com/mholt/PapaParse/issues/76
Expand Down Expand Up @@ -775,17 +776,33 @@ License: MIT
var end = Math.min(this._start + this._config.chunkSize, this._input.size);
input = slice.call(input, this._start, end);
}
var txt = reader.readAsText(input, this._config.encoding);
var buffer = reader.readAsArrayBuffer(input);
if (!usingAsyncReader)
this._chunkLoaded({ target: { result: txt } }); // mimic the async signature
this._chunkLoaded({ target: { result: buffer } }); // mimic the async signature
};

this._chunkLoaded = function(event)
{
var buffer = event.target.result;
var resize = 0;

// Bugfix: #751 Avoid splitting chunks in the middle of UTF-8 characters
if (decoder.encoding === 'utf-8') {
var bytes = new Uint8Array(buffer.slice(-3)); // UTF-8 characters can be up to four bytes
if ((bytes[0] & 0xF8) === 0xF0) resize = 3; // Four-byte sequence
else if ((bytes[1] & 0xF0) >= 0xE0) resize = 2; // Three-byte or four-byte sequence
else if ((bytes[2] & 0xE0) >= 0xC0) resize = 1; // Two-byte, three-byte or four-byte sequence
}

if (resize > 0)
buffer = buffer.slice(0, -resize);

var chunk = decoder.decode(buffer);

// Very important to increment start each time before handling results
this._start += this._config.chunkSize;
this._start += this._config.chunkSize - resize;
this._finished = !this._config.chunkSize || this._start >= this._input.size;
this.parseChunk(event.target.result);
this.parseChunk(chunk);
};

this._chunkError = function()
Expand Down