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51 lines
1.6 KiB
51 lines
1.6 KiB
'use strict'; |
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// Note: adler32 takes 12% for level 0 and 2% for level 6. |
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// It isn't worth it to make additional optimizations as in original. |
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// Small size is preferable. |
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// (C) 1995-2013 Jean-loup Gailly and Mark Adler |
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// (C) 2014-2017 Vitaly Puzrin and Andrey Tupitsin |
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// |
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// This software is provided 'as-is', without any express or implied |
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// warranty. In no event will the authors be held liable for any damages |
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// arising from the use of this software. |
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// |
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// Permission is granted to anyone to use this software for any purpose, |
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// including commercial applications, and to alter it and redistribute it |
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// freely, subject to the following restrictions: |
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// |
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// 1. The origin of this software must not be misrepresented; you must not |
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// claim that you wrote the original software. If you use this software |
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// in a product, an acknowledgment in the product documentation would be |
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// appreciated but is not required. |
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// 2. Altered source versions must be plainly marked as such, and must not be |
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// misrepresented as being the original software. |
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// 3. This notice may not be removed or altered from any source distribution. |
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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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module.exports = adler32;
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