tfarina@chromium.org | 5e7e673 | 2014-02-27 03:14:57 +0900 | [diff] [blame] | 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 | |
| 12 | namespace 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. |
| 19 | template<typename T> |
| 20 | inline 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. |
| 31 | template<typename T> |
| 32 | inline 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. |
| 40 | template<> |
| 41 | inline void ReadBigEndian<uint8>(const char buf[], uint8* out) { |
| 42 | *out = buf[0]; |
| 43 | } |
| 44 | |
| 45 | template<> |
| 46 | inline 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. |
| 52 | class 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.org | c999340 | 2014-07-31 08:24:48 +0900 | [diff] [blame] | 66 | bool ReadU64(uint64* value); |
tfarina@chromium.org | 5e7e673 | 2014-02-27 03:14:57 +0900 | [diff] [blame] | 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. |
| 79 | class 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.org | c999340 | 2014-07-31 08:24:48 +0900 | [diff] [blame] | 91 | bool WriteU64(uint64 value); |
tfarina@chromium.org | 5e7e673 | 2014-02-27 03:14:57 +0900 | [diff] [blame] | 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_ |