File: crc32.cc

package info (click to toggle)
chromium 139.0.7258.127-2
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid
  • size: 6,122,156 kB
  • sloc: cpp: 35,100,771; ansic: 7,163,530; javascript: 4,103,002; python: 1,436,920; asm: 946,517; xml: 746,709; pascal: 187,653; perl: 88,691; sh: 88,436; objc: 79,953; sql: 51,488; cs: 44,583; fortran: 24,137; makefile: 22,147; tcl: 15,277; php: 13,980; yacc: 8,984; ruby: 7,485; awk: 3,720; lisp: 3,096; lex: 1,327; ada: 727; jsp: 228; sed: 36
file content (28 lines) | stat: -rw-r--r-- 919 bytes parent folder | download | duplicates (3) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
 
// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/metrics/crc32.h"
#include "third_party/zlib/zlib.h"

namespace base {

uint32_t Crc32(uint32_t sum, span<const uint8_t> data) {
  if (data.empty()) {
    return sum;
  }

  // Make sure zlib checks CPU features before further calls to crc32_z.
  // zlib's crc32_z implementation says it's a convention to call
  // crc32(0, NULL, 0); before making calls to crc32(), so it uses it as
  // a place to cache CPU features if needed.
  // There's no need to cache the results, since there's an internal zlib
  // caching mechanism, so this function will just return if called multiple
  // times.
  (void)crc32_z(0L, Z_NULL, 0);

  return static_cast<uint32_t>(
      (~crc32_z((~sum) & 0xffffffff, data.data(), data.size())) & 0xffffffff);
}

}  // namespace base