| 1 | // Note: we can't get significant speed boost here. |
| 2 | // So write code to minimize size - no pregenerated tables |
| 3 | // and array tools dependencies. |
| 4 | |
| 5 | |
| 6 | // Use ordinary array, since untyped makes no boost here |
| 7 | export default function makeTable() { |
| 8 | var c, table = []; |
| 9 | |
| 10 | for (var n = 0; n < 256; n++) { |
| 11 | c = n; |
| 12 | for (var k = 0; k < 8; k++) { |
| 13 | c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1)); |
| 14 | } |
| 15 | table[n] = c; |
| 16 | } |
| 17 | |
| 18 | return table; |
| 19 | } |
| 20 | |
| 21 | // Create table on load. Just 255 signed longs. Not a problem. |
| 22 | var crcTable = makeTable(); |
| 23 | |
| 24 | |
| 25 | function crc32(crc, buf, len, pos) { |
| 26 | var t = crcTable, |
| 27 | end = pos + len; |
| 28 | |
| 29 | crc ^= -1; |
| 30 | |
| 31 | for (var i = pos; i < end; i++) { |
| 32 | crc = (crc >>> 8) ^ t[(crc ^ buf[i]) & 0xFF]; |
| 33 | } |
| 34 | |
| 35 | return (crc ^ (-1)); // >>> 0; |
| 36 | } |