| 1 | // Note: adler32 takes 12% for level 0 and 2% for level 6. |
| 2 | // It doesn't worth to make additional optimizationa as in original. |
| 3 | // Small size is preferable. |
| 4 | |
| 5 | export default function adler32(adler, buf, len, pos) { |
| 6 | var s1 = (adler & 0xffff) |0, |
| 7 | s2 = ((adler >>> 16) & 0xffff) |0, |
| 8 | n = 0; |
| 9 | |
| 10 | while (len !== 0) { |
| 11 | // Set limit ~ twice less than 5552, to keep |
| 12 | // s2 in 31-bits, because we force signed ints. |
| 13 | // in other case %= will fail. |
| 14 | n = len > 2000 ? 2000 : len; |
| 15 | len -= n; |
| 16 | |
| 17 | do { |
| 18 | s1 = (s1 + buf[pos++]) |0; |
| 19 | s2 = (s2 + s1) |0; |
| 20 | } while (--n); |
| 21 | |
| 22 | s1 %= 65521; |
| 23 | s2 %= 65521; |
| 24 | } |
| 25 | |
| 26 | return (s1 | (s2 << 16)) |0; |
| 27 | } |