js-adler32/bits/40_adler.js
2021-02-11 13:10:28 -08:00

63 lines
1.9 KiB
JavaScript

/*# consult README.md for the magic number */
/*# charCodeAt is the best approach for binary strings */
function adler32_bstr(bstr/*:string*/, seed/*:?ADLER32Type*/)/*:ADLER32Type*/ {
var a = 1, b = 0, L = bstr.length, M = 0;
if(typeof seed === 'number') { a = seed & 0xFFFF; b = seed >>> 16; }
for(var i = 0; i < L;) {
M = Math.min(L-i, 2654)+i;
for(;i<M;i++) {
a += bstr.charCodeAt(i)&0xFF;
b += a;
}
a = (15*(a>>>16)+(a&65535));
b = (15*(b>>>16)+(b&65535));
}
return ((b%65521) << 16) | (a%65521);
}
function adler32_buf(buf/*:ABuf*/, seed/*:?ADLER32Type*/)/*:ADLER32Type*/ {
var a = 1, b = 0, L = buf.length, M = 0;
if(typeof seed === 'number') { a = seed & 0xFFFF; b = (seed >>> 16) & 0xFFFF; }
for(var i = 0; i < L;) {
M = Math.min(L-i, 2654)+i;
for(;i<M;i++) {
a += buf[i]&0xFF;
b += a;
}
a = (15*(a>>>16)+(a&65535));
b = (15*(b>>>16)+(b&65535));
}
return ((b%65521) << 16) | (a%65521);
}
/*# much much faster to intertwine utf8 and adler */
function adler32_str(str/*:string*/, seed/*:?ADLER32Type*/)/*:ADLER32Type*/ {
var a = 1, b = 0, L = str.length, M = 0, c = 0, d = 0;
if(typeof seed === 'number') { a = seed & 0xFFFF; b = seed >>> 16; }
for(var i = 0; i < L;) {
M = Math.min(L-i, 2918);
while(M>0) {
c = str.charCodeAt(i++);
if(c < 0x80) { a += c; }
else if(c < 0x800) {
a += 192|((c>>6)&31); b += a; --M;
a += 128|(c&63);
} else if(c >= 0xD800 && c < 0xE000) {
c = (c&1023)+64; d = str.charCodeAt(i++) & 1023;
a += 240|((c>>8)&7); b += a; --M;
a += 128|((c>>2)&63); b += a; --M;
a += 128|((d>>6)&15)|((c&3)<<4); b += a; --M;
a += 128|(d&63);
} else {
a += 224|((c>>12)&15); b += a; --M;
a += 128|((c>>6)&63); b += a; --M;
a += 128|(c&63);
}
b += a; --M;
}
a = (15*(a>>>16)+(a&65535));
b = (15*(b>>>16)+(b&65535));
}
return ((b%65521) << 16) | (a%65521);
}