79 lines
2.1 KiB
JavaScript
79 lines
2.1 KiB
JavaScript
'use strict';
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var Buffer = require('safer-buffer').Buffer;
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// Single-byte codec. Needs a 'chars' string parameter that contains 256 or 128 chars that
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// correspond to encoded bytes (if 128 - then lower half is ASCII).
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exports._sbcs = SBCSCodec;
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function SBCSCodec(codecOptions, iconv) {
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if (!codecOptions) throw new Error('SBCS codec is called without the data.');
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// Prepare char buffer for decoding.
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if (
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!codecOptions.chars ||
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(codecOptions.chars.length !== 128 && codecOptions.chars.length !== 256)
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)
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throw new Error(
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"Encoding '" +
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codecOptions.type +
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"' has incorrect 'chars' (must be of len 128 or 256)"
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);
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if (codecOptions.chars.length === 128) {
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var asciiString = '';
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for (var i = 0; i < 128; i++) asciiString += String.fromCharCode(i);
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codecOptions.chars = asciiString + codecOptions.chars;
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}
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this.decodeBuf = Buffer.from(codecOptions.chars, 'ucs2');
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// Encoding buffer.
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var encodeBuf = Buffer.alloc(
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65536,
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iconv.defaultCharSingleByte.charCodeAt(0)
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);
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for (var i = 0; i < codecOptions.chars.length; i++)
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encodeBuf[codecOptions.chars.charCodeAt(i)] = i;
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this.encodeBuf = encodeBuf;
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}
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SBCSCodec.prototype.encoder = SBCSEncoder;
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SBCSCodec.prototype.decoder = SBCSDecoder;
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function SBCSEncoder(options, codec) {
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this.encodeBuf = codec.encodeBuf;
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}
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SBCSEncoder.prototype.write = function (str) {
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var buf = Buffer.alloc(str.length);
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for (var i = 0; i < str.length; i++)
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buf[i] = this.encodeBuf[str.charCodeAt(i)];
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return buf;
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};
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SBCSEncoder.prototype.end = function () {};
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function SBCSDecoder(options, codec) {
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this.decodeBuf = codec.decodeBuf;
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}
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SBCSDecoder.prototype.write = function (buf) {
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// Strings are immutable in JS -> we use ucs2 buffer to speed up computations.
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var decodeBuf = this.decodeBuf;
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var newBuf = Buffer.alloc(buf.length * 2);
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var idx1 = 0,
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idx2 = 0;
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for (var i = 0; i < buf.length; i++) {
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idx1 = buf[i] * 2;
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idx2 = i * 2;
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newBuf[idx2] = decodeBuf[idx1];
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newBuf[idx2 + 1] = decodeBuf[idx1 + 1];
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}
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return newBuf.toString('ucs2');
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};
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SBCSDecoder.prototype.end = function () {};
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