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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_BIG_ENDIAN_H_
#define BASE_BIG_ENDIAN_H_
#include "base/base_export.h"
#include "base/basictypes.h"
#include "base/strings/string_piece.h"
namespace base {
// Read an integer (signed or unsigned) from |buf| in Big Endian order.
// Note: this loop is unrolled with -O1 and above.
// NOTE(szym): glibc dns-canon.c and SpdyFrameBuilder use
// ntohs(*(uint16_t*)ptr) which is potentially unaligned.
// This would cause SIGBUS on ARMv5 or earlier and ARMv6-M.
template<typename T>
inline void ReadBigEndian(const char buf[], T* out) {
*out = buf[0];
for (size_t i = 1; i < sizeof(T); ++i) {
*out <<= 8;
// Must cast to uint8 to avoid clobbering by sign extension.
*out |= static_cast<uint8>(buf[i]);
}
}
// Write an integer (signed or unsigned) |val| to |buf| in Big Endian order.
// Note: this loop is unrolled with -O1 and above.
template<typename T>
inline void WriteBigEndian(char buf[], T val) {
for (size_t i = 0; i < sizeof(T); ++i) {
buf[sizeof(T)-i-1] = static_cast<char>(val & 0xFF);
val >>= 8;
}
}
// Specializations to make clang happy about the (dead code) shifts above.
template<>
inline void ReadBigEndian<uint8>(const char buf[], uint8* out) {
*out = buf[0];
}
template<>
inline void WriteBigEndian<uint8>(char buf[], uint8 val) {
buf[0] = static_cast<char>(val);
}
// Allows reading integers in network order (big endian) while iterating over
// an underlying buffer. All the reading functions advance the internal pointer.
class BASE_EXPORT BigEndianReader {
public:
BigEndianReader(const char* buf, size_t len);
const char* ptr() const { return ptr_; }
int remaining() const { return end_ - ptr_; }
bool Skip(size_t len);
bool ReadBytes(void* out, size_t len);
// Creates a StringPiece in |out| that points to the underlying buffer.
bool ReadPiece(base::StringPiece* out, size_t len);
bool ReadU8(uint8* value);
bool ReadU16(uint16* value);
bool ReadU32(uint32* value);
bool ReadU64(uint64* value);
private:
// Hidden to promote type safety.
template<typename T>
bool Read(T* v);
const char* ptr_;
const char* end_;
};
// Allows writing integers in network order (big endian) while iterating over
// an underlying buffer. All the writing functions advance the internal pointer.
class BASE_EXPORT BigEndianWriter {
public:
BigEndianWriter(char* buf, size_t len);
char* ptr() const { return ptr_; }
int remaining() const { return end_ - ptr_; }
bool Skip(size_t len);
bool WriteBytes(const void* buf, size_t len);
bool WriteU8(uint8 value);
bool WriteU16(uint16 value);
bool WriteU32(uint32 value);
bool WriteU64(uint64 value);
private:
// Hidden to promote type safety.
template<typename T>
bool Write(T v);
char* ptr_;
char* end_;
};
} // namespace base
#endif // BASE_BIG_ENDIAN_H_
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