| package brotli |
| |
| /* Copyright 2013 Google Inc. All Rights Reserved. |
| |
| Distributed under MIT license. |
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| */ |
| |
| /* Functions for encoding of integers into prefix codes the amount of extra |
| bits, and the actual values of the extra bits. */ |
| |
| /* Here distance_code is an intermediate code, i.e. one of the special codes or |
| the actual distance increased by BROTLI_NUM_DISTANCE_SHORT_CODES - 1. */ |
| func prefixEncodeCopyDistance(distance_code uint, num_direct_codes uint, postfix_bits uint, code *uint16, extra_bits *uint32) { |
| if distance_code < numDistanceShortCodes+num_direct_codes { |
| *code = uint16(distance_code) |
| *extra_bits = 0 |
| return |
| } else { |
| var dist uint = (uint(1) << (postfix_bits + 2)) + (distance_code - numDistanceShortCodes - num_direct_codes) |
| var bucket uint = uint(log2FloorNonZero(dist) - 1) |
| var postfix_mask uint = (1 << postfix_bits) - 1 |
| var postfix uint = dist & postfix_mask |
| var prefix uint = (dist >> bucket) & 1 |
| var offset uint = (2 + prefix) << bucket |
| var nbits uint = bucket - postfix_bits |
| *code = uint16(nbits<<10 | (numDistanceShortCodes + num_direct_codes + ((2*(nbits-1) + prefix) << postfix_bits) + postfix)) |
| *extra_bits = uint32((dist - offset) >> postfix_bits) |
| } |
| } |