72 lines
2.4 KiB
JavaScript
72 lines
2.4 KiB
JavaScript
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/* crc32.js (C) 2014 SheetJS -- http://sheetjs.com */
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/* vim: set ts=2: */
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var CRC32 = {};
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(function(CRC32) {
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CRC32.version = '0.1.0';
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/* see perf/crc32table.js */
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function signed_crc_table() {
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var c, table = new Array(256);
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for(var n =0; n != 256; ++n){
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c = n;
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
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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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var table = signed_crc_table();
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/* charCodeAt is the best approach for binary strings */
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function crc32_bstr(bstr) {
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for(var crc = -1, i = 0, L=bstr.length-1; i < L;) {
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crc = (crc >>> 8) ^ table[(crc ^ bstr.charCodeAt(i++)) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ bstr.charCodeAt(i++)) & 0xFF];
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}
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if(i === L) crc = (crc >>> 8) ^ table[(crc ^ bstr.charCodeAt(i++)) & 0xFF];
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return crc ^ -1;
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}
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function crc32_buf(buf) {
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for(var crc = -1, i = 0; i != buf.length; ++i) {
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crc = (crc >>> 8) ^ table[(crc ^ buf[i]) & 0xFF];
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}
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return crc ^ -1;
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}
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/* much much faster to intertwine utf8 and crc */
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function crc32_str(str) {
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for(var crc = -1, i = 0, L=str.length, c, d; i < L;) {
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c = str.charCodeAt(i++);
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if(c < 0x80) {
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crc = (crc >>> 8) ^ table[(crc ^ c) & 0xFF];
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} else if(c < 0x800) {
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crc = (crc >>> 8) ^ table[(crc ^ (192|((c>>6)&31))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|(c&63))) & 0xFF];
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} else if(c >= 0xD800 && c < 0xE000) {
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c = (c&1023)+64; d = str.charCodeAt(i++) & 1023;
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crc = (crc >>> 8) ^ table[(crc ^ (240|((c>>8)&7))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|((c>>2)&63))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|((d>>6)&15)|(c&3))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|(d&63))) & 0xFF];
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} else {
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crc = (crc >>> 8) ^ table[(crc ^ (224|((c>>12)&15))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|((c>>6)&63))) & 0xFF];
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crc = (crc >>> 8) ^ table[(crc ^ (128|(c&63))) & 0xFF];
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}
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}
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return crc ^ -1;
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}
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CRC32.table = table;
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CRC32.bstr = crc32_bstr;
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CRC32.buf = crc32_buf;
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CRC32.str = crc32_str;
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})(typeof exports !== "undefined" && typeof DO_NOT_EXPORT_CRC === 'undefined' ? exports : CRC32);
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