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tfarina@chromium.org5e7e6732014-02-27 03:14:57 +09001// 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);
benchan@chromium.orgc9993402014-07-31 08:24:48 +090066 bool ReadU64(uint64* value);
tfarina@chromium.org5e7e6732014-02-27 03:14:57 +090067
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);
benchan@chromium.orgc9993402014-07-31 08:24:48 +090091 bool WriteU64(uint64 value);
tfarina@chromium.org5e7e6732014-02-27 03:14:57 +090092
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_