js-crc32/bits/40_crc.js

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/*# charCodeAt is the best approach for binary strings */
/*global Buffer */
var use_buffer = typeof Buffer !== 'undefined';
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function crc32_bstr(bstr/*:string*/)/*:CRC32Type*/ {
if(bstr.length > 32768) if(use_buffer) return crc32_buf_8(new Buffer(bstr));
var C = -1, L = bstr.length - 1;
for(var i = 0; i < L;) {
C = (C>>>8) ^ T[(C^bstr.charCodeAt(i++))&0xFF];
C = (C>>>8) ^ T[(C^bstr.charCodeAt(i++))&0xFF];
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}
if(i === L) C = (C>>>8) ^ T[(C ^ bstr.charCodeAt(i))&0xFF];
return C ^ -1;
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}
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function crc32_buf(buf/*:ABuf*/)/*:CRC32Type*/ {
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if(buf.length > 10000) return crc32_buf_8(buf);
var C = -1, L = buf.length - 3;
for(var i = 0; i < L;) {
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
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}
while(i < L+3) C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
return C ^ -1;
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}
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function crc32_buf_8(buf/*:ABuf*/)/*:CRC32Type*/ {
var C = -1, L = buf.length - 7;
for(var i = 0; i < L;) {
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
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}
while(i < L+7) C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
return C ^ -1;
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}
/*# much much faster to intertwine utf8 and C */
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function crc32_str(str/*:string*/)/*:CRC32Type*/ {
var C = -1;
for(var i = 0, L=str.length, c, d; i < L;) {
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c = str.charCodeAt(i++);
if(c < 0x80) {
C = (C>>>8) ^ T[(C ^ c)&0xFF];
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} else if(c < 0x800) {
C = (C>>>8) ^ T[(C ^ (192|((c>>6)&31)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|(c&63)))&0xFF];
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} else if(c >= 0xD800 && c < 0xE000) {
c = (c&1023)+64; d = str.charCodeAt(i++)&1023;
C = (C>>>8) ^ T[(C ^ (240|((c>>8)&7)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|((c>>2)&63)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|((d>>6)&15)|((c&3)<<4)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|(d&63)))&0xFF];
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} else {
C = (C>>>8) ^ T[(C ^ (224|((c>>12)&15)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|((c>>6)&63)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|(c&63)))&0xFF];
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}
}
return C ^ -1;
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}