File: bit_cast.h

package info (click to toggle)
chromium 138.0.7204.183-1
  • links: PTS, VCS
  • area: main
  • in suites: trixie
  • size: 6,071,908 kB
  • sloc: cpp: 34,937,088; ansic: 7,176,967; javascript: 4,110,704; python: 1,419,953; asm: 946,768; xml: 739,971; pascal: 187,324; sh: 89,623; perl: 88,663; objc: 79,944; sql: 50,304; cs: 41,786; fortran: 24,137; makefile: 21,806; php: 13,980; tcl: 13,166; yacc: 8,925; ruby: 7,485; awk: 3,720; lisp: 3,096; lex: 1,327; ada: 727; jsp: 228; sed: 36
file content (45 lines) | stat: -rw-r--r-- 1,726 bytes parent folder | download | duplicates (6)
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
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_BIT_CAST_H_
#define BASE_BIT_CAST_H_

#include <type_traits>

namespace base {

// This is an equivalent to C++20's std::bit_cast<>(), but with additional
// warnings. It morally does what `*reinterpret_cast<Dest*>(&source)` does, but
// the cast/deref pair is undefined behavior, while bit_cast<>() isn't.
//
// This is not a magic "get out of UB free" card. This must only be used on
// values, not on references or pointers. For pointers, use
// reinterpret_cast<>(), and then look at https://eel.is/c++draft/basic.lval#11
// as that's probably UB also.

template <class Dest, class Source>
constexpr Dest bit_cast(const Source& source) {
  static_assert(!std::is_pointer_v<Source>,
                "bit_cast must not be used on pointer types");
  static_assert(!std::is_pointer_v<Dest>,
                "bit_cast must not be used on pointer types");
  static_assert(!std::is_reference_v<Source>,
                "bit_cast must not be used on reference types");
  static_assert(!std::is_reference_v<Dest>,
                "bit_cast must not be used on reference types");
  static_assert(
      sizeof(Dest) == sizeof(Source),
      "bit_cast requires source and destination types to be the same size");
  static_assert(std::is_trivially_copyable_v<Source>,
                "bit_cast requires the source type to be trivially copyable");
  static_assert(
      std::is_trivially_copyable_v<Dest>,
      "bit_cast requires the destination type to be trivially copyable");

  return __builtin_bit_cast(Dest, source);
}

}  // namespace base

#endif  // BASE_BIT_CAST_H_