1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_BIG_ENDIAN_H_
6#define BASE_BIG_ENDIAN_H_
7
8#include "base/base_export.h"
9#include "base/basictypes.h"
10#include "base/strings/string_piece.h"
11
12namespace base {
13
14// Read an integer (signed or unsigned) from |buf| in Big Endian order.
15// Note: this loop is unrolled with -O1 and above.
16// NOTE(szym): glibc dns-canon.c and SpdyFrameBuilder use
17// ntohs(*(uint16_t*)ptr) which is potentially unaligned.
18// This would cause SIGBUS on ARMv5 or earlier and ARMv6-M.
19template<typename T>
20inline void ReadBigEndian(const char buf[], T* out) {
21  *out = buf[0];
22  for (size_t i = 1; i < sizeof(T); ++i) {
23    *out <<= 8;
24    // Must cast to uint8 to avoid clobbering by sign extension.
25    *out |= static_cast<uint8>(buf[i]);
26  }
27}
28
29// Write an integer (signed or unsigned) |val| to |buf| in Big Endian order.
30// Note: this loop is unrolled with -O1 and above.
31template<typename T>
32inline void WriteBigEndian(char buf[], T val) {
33  for (size_t i = 0; i < sizeof(T); ++i) {
34    buf[sizeof(T)-i-1] = static_cast<char>(val & 0xFF);
35    val >>= 8;
36  }
37}
38
39// Specializations to make clang happy about the (dead code) shifts above.
40template<>
41inline void ReadBigEndian<uint8>(const char buf[], uint8* out) {
42  *out = buf[0];
43}
44
45template<>
46inline void WriteBigEndian<uint8>(char buf[], uint8 val) {
47  buf[0] = static_cast<char>(val);
48}
49
50// Allows reading integers in network order (big endian) while iterating over
51// an underlying buffer. All the reading functions advance the internal pointer.
52class BASE_EXPORT BigEndianReader {
53 public:
54  BigEndianReader(const char* buf, size_t len);
55
56  const char* ptr() const { return ptr_; }
57  int remaining() const { return end_ - ptr_; }
58
59  bool Skip(size_t len);
60  bool ReadBytes(void* out, size_t len);
61  // Creates a StringPiece in |out| that points to the underlying buffer.
62  bool ReadPiece(base::StringPiece* out, size_t len);
63  bool ReadU8(uint8* value);
64  bool ReadU16(uint16* value);
65  bool ReadU32(uint32* value);
66  bool ReadU64(uint64* value);
67
68 private:
69  // Hidden to promote type safety.
70  template<typename T>
71  bool Read(T* v);
72
73  const char* ptr_;
74  const char* end_;
75};
76
77// Allows writing integers in network order (big endian) while iterating over
78// an underlying buffer. All the writing functions advance the internal pointer.
79class BASE_EXPORT BigEndianWriter {
80 public:
81  BigEndianWriter(char* buf, size_t len);
82
83  char* ptr() const { return ptr_; }
84  int remaining() const { return end_ - ptr_; }
85
86  bool Skip(size_t len);
87  bool WriteBytes(const void* buf, size_t len);
88  bool WriteU8(uint8 value);
89  bool WriteU16(uint16 value);
90  bool WriteU32(uint32 value);
91  bool WriteU64(uint64 value);
92
93 private:
94  // Hidden to promote type safety.
95  template<typename T>
96  bool Write(T v);
97
98  char* ptr_;
99  char* end_;
100};
101
102}  // namespace base
103
104#endif  // BASE_BIG_ENDIAN_H_
105