60 lines
1.7 KiB
JavaScript
60 lines
1.7 KiB
JavaScript
'use strict';
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var HUFFMAN_EOF = -1;
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function huffmanDecodeBuf(inBuf, inBufCharacterCount, huffmanTree, huffmanLenIndex)
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{
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var code = 0;
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var codeLen = 0;
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var testBit = 0x80;
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var eof = false;
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var outBuf = [];
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while (!eof && inBuf.byteLength != 0) {
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if (outBuf.length == inBufCharacterCount) {
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// we've exhausted the input stream, discard any odd bits on the end
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break;
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}
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if (inBuf.byteLength == 0) {
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throw new Error('unexpected');
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}
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// get the next bit from the input buffer
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code <<= 1;
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++codeLen;
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if (inBuf[0] & testBit) {
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code |= 0x01;
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}
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testBit >>= 1;
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if (testBit == 0) {
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testBit = 0x80;
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inBuf = inBuf.subarray(1);
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}
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// check if the code is a leaf node or an interior node
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if (huffmanLenIndex[codeLen] != -1) {
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// look for the code in the tree, only leaf nodes are stored in the tree
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for (var i = huffmanLenIndex[codeLen]; (i < huffmanTree.length) && (huffmanTree[i].codeLen == codeLen); ++i) {
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if (huffmanTree[i].code == code) {
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// we've found the code, so it is a leaf node
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var value = huffmanTree[i].value;
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if (value == HUFFMAN_EOF) {
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eof = true;
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} else {
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// output the value
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outBuf.push(value);
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}
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// reset the code to continue decompressing the input buffer
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code = 0;
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codeLen = 0;
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break;
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}
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}
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}
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}
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return new Uint8Array(outBuf);
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} |