123 lines
3.6 KiB
C++
123 lines
3.6 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_BIG_ENDIAN_H_
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#define BASE_BIG_ENDIAN_H_
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#include <stddef.h>
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#include <stdint.h>
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#include "base/base_export.h"
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#include "base/strings/string_piece.h"
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namespace base {
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// Read an integer (signed or unsigned) from |buf| in Big Endian order.
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// Note: this loop is unrolled with -O1 and above.
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// NOTE(szym): glibc dns-canon.c use ntohs(*(uint16_t*)ptr) which is
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// potentially unaligned.
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// This would cause SIGBUS on ARMv5 or earlier and ARMv6-M.
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template<typename T>
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inline void ReadBigEndian(const char buf[], T* out) {
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*out = buf[0];
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for (size_t i = 1; i < sizeof(T); ++i) {
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*out <<= 8;
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// Must cast to uint8_t to avoid clobbering by sign extension.
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*out |= static_cast<uint8_t>(buf[i]);
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}
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}
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// Write an integer (signed or unsigned) |val| to |buf| in Big Endian order.
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// Note: this loop is unrolled with -O1 and above.
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template<typename T>
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inline void WriteBigEndian(char buf[], T val) {
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for (size_t i = 0; i < sizeof(T); ++i) {
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buf[sizeof(T)-i-1] = static_cast<char>(val & 0xFF);
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val >>= 8;
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}
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}
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// Specializations to make clang happy about the (dead code) shifts above.
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template <>
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inline void ReadBigEndian<uint8_t>(const char buf[], uint8_t* out) {
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*out = buf[0];
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}
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template <>
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inline void WriteBigEndian<uint8_t>(char buf[], uint8_t val) {
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buf[0] = static_cast<char>(val);
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}
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// Allows reading integers in network order (big endian) while iterating over
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// an underlying buffer. All the reading functions advance the internal pointer.
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class BASE_EXPORT BigEndianReader {
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public:
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BigEndianReader(const char* buf, size_t len);
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const char* ptr() const { return ptr_; }
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size_t remaining() const { return end_ - ptr_; }
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bool Skip(size_t len);
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bool ReadBytes(void* out, size_t len);
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// Creates a StringPiece in |out| that points to the underlying buffer.
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bool ReadPiece(base::StringPiece* out, size_t len);
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bool ReadU8(uint8_t* value);
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bool ReadU16(uint16_t* value);
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bool ReadU32(uint32_t* value);
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bool ReadU64(uint64_t* value);
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// Reads a length-prefixed region:
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// 1. reads a big-endian length L from the buffer;
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// 2. sets |*out| to a StringPiece over the next L many bytes
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// of the buffer (beyond the end of the bytes encoding the length); and
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// 3. skips the main reader past this L-byte substring.
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//
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// Fails if reading a U8 or U16 fails, or if the parsed length is greater
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// than the number of bytes remaining in the stream.
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//
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// On failure, leaves the stream at the same position
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// as before the call.
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bool ReadU8LengthPrefixed(base::StringPiece* out);
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bool ReadU16LengthPrefixed(base::StringPiece* out);
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private:
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// Hidden to promote type safety.
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template<typename T>
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bool Read(T* v);
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template <typename T>
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bool ReadLengthPrefixed(base::StringPiece* out);
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const char* ptr_;
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const char* end_;
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};
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// Allows writing integers in network order (big endian) while iterating over
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// an underlying buffer. All the writing functions advance the internal pointer.
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class BASE_EXPORT BigEndianWriter {
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public:
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BigEndianWriter(char* buf, size_t len);
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char* ptr() const { return ptr_; }
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size_t remaining() const { return end_ - ptr_; }
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bool Skip(size_t len);
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bool WriteBytes(const void* buf, size_t len);
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bool WriteU8(uint8_t value);
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bool WriteU16(uint16_t value);
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bool WriteU32(uint32_t value);
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bool WriteU64(uint64_t value);
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private:
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// Hidden to promote type safety.
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template<typename T>
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bool Write(T v);
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char* ptr_;
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char* end_;
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};
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} // namespace base
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#endif // BASE_BIG_ENDIAN_H_
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