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function crc32(s/*, polynomial = 0x04C11DB7, initialValue = 0xFFFFFFFF, finalXORValue = 0xFFFFFFFF*/) { | |
s = String(s); | |
var polynomial = arguments.length < 2 ? 0x04C11DB7 : arguments[1], | |
initialValue = arguments.length < 3 ? 0xFFFFFFFF : arguments[2], | |
finalXORValue = arguments.length < 4 ? 0xFFFFFFFF : arguments[3], | |
crc = initialValue, | |
table = [], i, j, c; | |
function reverse(x, n) { | |
var b = 0; | |
while (n) { | |
b = b * 2 + x % 2; | |
x /= 2; | |
x -= x % 1; | |
n--; | |
} | |
return b; | |
} | |
for (i = 255; i >= 0; i--) { | |
c = reverse(i, 32); | |
for (j = 0; j < 8; j++) { | |
c = ((c * 2) ^ (((c >>> 31) % 2) * polynomial)) >>> 0; | |
} | |
table[i] = reverse(c, 32); | |
} | |
for (i = 0; i < s.length; i++) { | |
c = s.charCodeAt(i); | |
if (c > 255) { | |
throw new RangeError(); | |
} | |
j = (crc % 256) ^ c; | |
crc = ((crc / 256) ^ table[j]) >>> 0; | |
} | |
return (crc ^ finalXORValue) >>> 0; | |
} | |
alert(crc32('test').toString(16));//D87F7E0C | |
alert(crc32('test', 0x04c11db7, 0, 0xFFFFFFFF).toString(16));//6C45EEF | |
alert(crc32('test', 0x04c11db7, 0xFFFFFFFF, 0).toString(16));//278081F3 | |
alert(crc32('test', 0x04c11db7, 0, 0).toString(16));//F93BA110 |
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