js-crc32/bits/40_crc.js
2022-01-24 13:00:36 -08:00

97 lines
3.1 KiB
JavaScript

/*# charCodeAt is the best approach for binary strings */
function crc32_bstr(bstr/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
if(bstr.length > 10000) return crc32_bstr_16(bstr, seed);
var C = seed/*:: ? 0 : 0 */ ^ -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];
}
if(i === L) C = (C>>>8) ^ T[(C ^ bstr.charCodeAt(i))&0xFF];
return C ^ -1;
}
function crc32_bstr_16(bstr/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
var C = seed/*:: ? 0 : 0 */ ^ -1, L = bstr.length - 15;
for(var i = 0; i < L;) C =
Tf[bstr.charCodeAt(i++) ^ (C & 255)] ^
Te[bstr.charCodeAt(i++) ^ ((C >> 8) & 255)] ^
Td[bstr.charCodeAt(i++) ^ ((C >> 16) & 255)] ^
Tc[bstr.charCodeAt(i++) ^ (C >>> 24)] ^
Tb[bstr.charCodeAt(i++)] ^
Ta[bstr.charCodeAt(i++)] ^
T9[bstr.charCodeAt(i++)] ^
T8[bstr.charCodeAt(i++)] ^
T7[bstr.charCodeAt(i++)] ^
T6[bstr.charCodeAt(i++)] ^
T5[bstr.charCodeAt(i++)] ^
T4[bstr.charCodeAt(i++)] ^
T3[bstr.charCodeAt(i++)] ^
T2[bstr.charCodeAt(i++)] ^
T1[bstr.charCodeAt(i++)] ^
T[bstr.charCodeAt(i++)];
L += 15;
while(i < L) C = (C>>>8) ^ T[(C^bstr.charCodeAt(i++))&0xFF];
return C ^ -1;
}
function crc32_buf(buf/*:ABuf*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
if(buf.length > 2000) return crc32_buf_16(buf, seed);
var C = seed/*:: ? 0 : 0 */ ^ -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];
}
while(i < L+3) C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
return C ^ -1;
}
function crc32_buf_16(buf/*:ABuf*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
var C = seed/*:: ? 0 : 0 */ ^ -1, L = buf.length - 15;
for(var i = 0; i < L;) C =
Tf[buf[i++] ^ (C & 255)] ^
Te[buf[i++] ^ ((C >> 8) & 255)] ^
Td[buf[i++] ^ ((C >> 16) & 255)] ^
Tc[buf[i++] ^ (C >>> 24)] ^
Tb[buf[i++]] ^
Ta[buf[i++]] ^
T9[buf[i++]] ^
T8[buf[i++]] ^
T7[buf[i++]] ^
T6[buf[i++]] ^
T5[buf[i++]] ^
T4[buf[i++]] ^
T3[buf[i++]] ^
T2[buf[i++]] ^
T1[buf[i++]] ^
T[buf[i++]];
L += 15;
while(i < L) C = (C>>>8) ^ T[(C^buf[i++])&0xFF];
return C ^ -1;
}
/*# much much faster to intertwine utf8 and crc, slower to slice by 8 or 16 */
function crc32_str(str/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
var C = seed/*:: ? 0 : 0 */ ^ -1;
for(var i = 0, L = str.length, c = 0, d = 0; i < L;) {
c = str.charCodeAt(i++);
if(c < 0x80) {
C = (C>>>8) ^ T[(C ^ c)&0xFF];
} else if(c < 0x800) {
C = (C>>>8) ^ T[(C ^ (192|((c>>6)&31)))&0xFF];
C = (C>>>8) ^ T[(C ^ (128|(c&63)))&0xFF];
} 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];
} 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];
}
}
return C ^ -1;
}