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https://gitee.com/onvia/ccc-tnt-psd2ui
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60 lines
1.7 KiB
JavaScript
60 lines
1.7 KiB
JavaScript
'use strict';
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// Note: we can't get significant speed boost here.
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// So write code to minimize size - no pregenerated tables
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// and array tools dependencies.
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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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// Use ordinary array, since untyped makes no boost here
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const makeTable = () => {
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let c, table = [];
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for (var n = 0; n < 256; n++) {
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c = n;
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for (var k = 0; k < 8; k++) {
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c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
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}
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table[n] = c;
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}
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return table;
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};
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// Create table on load. Just 255 signed longs. Not a problem.
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const crcTable = new Uint32Array(makeTable());
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const crc32 = (crc, buf, len, pos) => {
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const t = crcTable;
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const end = pos + len;
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crc ^= -1;
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for (let i = pos; i < end; i++) {
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crc = (crc >>> 8) ^ t[(crc ^ buf[i]) & 0xFF];
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}
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return (crc ^ (-1)); // >>> 0;
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};
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module.exports = crc32;
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