| 1 | "use strict";
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| 2 |
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| 3 | var pow2 = [1, 2, 4, 8, 16, 32, 64, 128, 256];
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| 4 | var neg = [127, 191, 223, 239, 247, 251, 253, 254];
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| 5 |
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| 6 |
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| 7 | function writeBits(target, source, bitoffset, sourcebitLength) {
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| 8 | if(sourcebitLength === undefined)
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| 9 | sourcebitLength = source.length << 3;
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| 10 |
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| 11 | if(!sourcebitLength)
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| 12 | return 0;
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| 13 |
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| 14 | var soucebitStart = sourcebitLength < 0 ? (source.length << 3) + sourcebitLength : 0;
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| 15 | sourcebitLength = Math.min(Math.abs(sourcebitLength), (target.length << 3) - bitoffset);
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| 16 | var sourceBitEnd = soucebitStart + sourcebitLength - 1;
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| 17 |
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| 18 | for(var i = soucebitStart, j = bitoffset; i <= sourceBitEnd; i++, j++) {
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| 19 | if(source[i >> 3] & pow2[7 - i % 8])
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| 20 | target[j >> 3] |= pow2[7 - j % 8];
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| 21 | else
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| 22 | target[j >> 3] &= neg[j % 8];
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| 23 | }
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| 24 |
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| 25 | return sourcebitLength;
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| 26 | }
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| 27 |
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| 28 |
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| 29 | module.exports = writeBits;
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