28 lines
666 B
JavaScript
28 lines
666 B
JavaScript
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// Note: adler32 takes 12% for level 0 and 2% for level 6.
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// It doesn't worth to make additional optimizationa as in original.
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// Small size is preferable.
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export default function adler32(adler, buf, len, pos) {
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var s1 = (adler & 0xffff) |0,
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s2 = ((adler >>> 16) & 0xffff) |0,
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n = 0;
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while (len !== 0) {
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// Set limit ~ twice less than 5552, to keep
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// s2 in 31-bits, because we force signed ints.
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// in other case %= will fail.
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n = len > 2000 ? 2000 : len;
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len -= n;
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do {
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s1 = (s1 + buf[pos++]) |0;
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s2 = (s2 + s1) |0;
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} while (--n);
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s1 %= 65521;
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s2 %= 65521;
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}
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return (s1 | (s2 << 16)) |0;
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}
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