ui/base/resource: Roll our own version of ReadBigEndian() function.

net/base/big_endian.h

-// Copyright (c) 2011 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 NET_BASE_BIG_ENDIAN_H_
-#define NET_BASE_BIG_ENDIAN_H_
-
-#include "base/basictypes.h"
-#include "base/strings/string_piece.h"
-#include "net/base/net_export.h"
-
-namespace net {
-
-// 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 NET_EXPORT BigEndianReader {
- public:
-  BigEndianReader(const void* 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);
-
- 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 NET_EXPORT BigEndianWriter {
- public:
-  BigEndianWriter(void* 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);
-
- private:
-  // Hidden to promote type safety.
-  template<typename T>
-  bool Write(T v);
-
-  char* ptr_;
-  char* end_;
-};
-
-}  // namespace net
-
-#endif  // NET_BASE_BIG_ENDIAN_H_
-