michael@0: // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #include "base/pickle.h"
michael@0: 
michael@0: #include "mozilla/Alignment.h"
michael@0: #include "mozilla/Endian.h"
michael@0: #include "mozilla/TypeTraits.h"
michael@0: 
michael@0: #include <stdlib.h>
michael@0: 
michael@0: #include <limits>
michael@0: #include <string>
michael@0: #include <algorithm>
michael@0: 
michael@0: #include "nsDebug.h"
michael@0: 
michael@0: //------------------------------------------------------------------------------
michael@0: 
michael@0: static_assert(MOZ_ALIGNOF(Pickle::memberAlignmentType) >= MOZ_ALIGNOF(uint32_t),
michael@0:               "Insufficient alignment");
michael@0: 
michael@0: // static
michael@0: const int Pickle::kPayloadUnit = 64;
michael@0: 
michael@0: // We mark a read only pickle with a special capacity_.
michael@0: static const uint32_t kCapacityReadOnly = (uint32_t) -1;
michael@0: 
michael@0: static const char kBytePaddingMarker = char(0xbf);
michael@0: 
michael@0: namespace {
michael@0: 
michael@0: // We want to copy data to our payload as efficiently as possible.
michael@0: // memcpy fits the bill for copying, but not all compilers or
michael@0: // architectures support inlining memcpy from void*, which has unknown
michael@0: // static alignment.  However, we know that all the members of our
michael@0: // payload will be aligned on memberAlignmentType boundaries.  We
michael@0: // therefore use that knowledge to construct a copier that will copy
michael@0: // efficiently (via standard C++ assignment mechanisms) if the datatype
michael@0: // needs that alignment or less, and memcpy otherwise.  (The compiler
michael@0: // may still inline memcpy, of course.)
michael@0: 
michael@0: template<typename T, size_t size, bool hasSufficientAlignment>
michael@0: struct Copier
michael@0: {
michael@0:   static void Copy(T* dest, void** iter) {
michael@0:     memcpy(dest, *iter, sizeof(T));
michael@0:   }
michael@0: };
michael@0: 
michael@0: // Copying 64-bit quantities happens often enough and can easily be made
michael@0: // worthwhile on 32-bit platforms, so handle it specially.  Only do it
michael@0: // if 64-bit types aren't sufficiently aligned; the alignment
michael@0: // requirements for them vary between 32-bit platforms.
michael@0: #ifndef HAVE_64BIT_OS
michael@0: template<typename T>
michael@0: struct Copier<T, sizeof(uint64_t), false>
michael@0: {
michael@0:   static void Copy(T* dest, void** iter) {
michael@0: #if MOZ_LITTLE_ENDIAN
michael@0:     static const int loIndex = 0, hiIndex = 1;
michael@0: #else
michael@0:     static const int loIndex = 1, hiIndex = 0;
michael@0: #endif
michael@0:     static_assert(MOZ_ALIGNOF(uint32_t*) == MOZ_ALIGNOF(void*),
michael@0:                   "Pointers have different alignments");
michael@0:     uint32_t* src = *reinterpret_cast<uint32_t**>(iter);
michael@0:     uint32_t* uint32dest = reinterpret_cast<uint32_t*>(dest);
michael@0:     uint32dest[loIndex] = src[loIndex];
michael@0:     uint32dest[hiIndex] = src[hiIndex];
michael@0:   }
michael@0: };
michael@0: #endif
michael@0: 
michael@0: template<typename T, size_t size>
michael@0: struct Copier<T, size, true>
michael@0: {
michael@0:   static void Copy(T* dest, void** iter) {
michael@0:     // The reinterpret_cast is only safe if two conditions hold:
michael@0:     // (1) If the alignment of T* is the same as void*;
michael@0:     // (2) The alignment of the data in *iter is at least as
michael@0:     //     big as MOZ_ALIGNOF(T).
michael@0:     // Check the first condition, as the second condition is already
michael@0:     // known to be true, or we wouldn't be here.
michael@0:     static_assert(MOZ_ALIGNOF(T*) == MOZ_ALIGNOF(void*),
michael@0:                   "Pointers have different alignments");
michael@0:     *dest = *(*reinterpret_cast<T**>(iter));
michael@0:   }
michael@0: };
michael@0: 
michael@0: template<typename T>
michael@0: void CopyFromIter(T* dest, void** iter) {
michael@0:   static_assert(mozilla::IsPod<T>::value, "Copied type must be a POD type");
michael@0:   Copier<T, sizeof(T), (MOZ_ALIGNOF(T) <= sizeof(Pickle::memberAlignmentType))>::Copy(dest, iter);
michael@0: }
michael@0: 
michael@0: } // anonymous namespace
michael@0: 
michael@0: // Payload is sizeof(Pickle::memberAlignmentType) aligned.
michael@0: 
michael@0: Pickle::Pickle()
michael@0:     : header_(NULL),
michael@0:       header_size_(sizeof(Header)),
michael@0:       capacity_(0),
michael@0:       variable_buffer_offset_(0) {
michael@0:   Resize(kPayloadUnit);
michael@0:   header_->payload_size = 0;
michael@0: }
michael@0: 
michael@0: Pickle::Pickle(int header_size)
michael@0:     : header_(NULL),
michael@0:       header_size_(AlignInt(header_size)),
michael@0:       capacity_(0),
michael@0:       variable_buffer_offset_(0) {
michael@0:   DCHECK(static_cast<memberAlignmentType>(header_size) >= sizeof(Header));
michael@0:   DCHECK(header_size <= kPayloadUnit);
michael@0:   Resize(kPayloadUnit);
michael@0:   if (!header_) {
michael@0:     NS_ABORT_OOM(kPayloadUnit);
michael@0:   }
michael@0:   header_->payload_size = 0;
michael@0: }
michael@0: 
michael@0: Pickle::Pickle(const char* data, int data_len)
michael@0:     : header_(reinterpret_cast<Header*>(const_cast<char*>(data))),
michael@0:       header_size_(data_len - header_->payload_size),
michael@0:       capacity_(kCapacityReadOnly),
michael@0:       variable_buffer_offset_(0) {
michael@0:   DCHECK(header_size_ >= sizeof(Header));
michael@0:   DCHECK(header_size_ == AlignInt(header_size_));
michael@0: }
michael@0: 
michael@0: Pickle::Pickle(const Pickle& other)
michael@0:     : header_(NULL),
michael@0:       header_size_(other.header_size_),
michael@0:       capacity_(0),
michael@0:       variable_buffer_offset_(other.variable_buffer_offset_) {
michael@0:   uint32_t payload_size = header_size_ + other.header_->payload_size;
michael@0:   bool resized = Resize(payload_size);
michael@0:   if (!resized) {
michael@0:     NS_ABORT_OOM(payload_size);
michael@0:   }
michael@0:   memcpy(header_, other.header_, payload_size);
michael@0: }
michael@0: 
michael@0: Pickle::~Pickle() {
michael@0:   if (capacity_ != kCapacityReadOnly)
michael@0:     free(header_);
michael@0: }
michael@0: 
michael@0: Pickle& Pickle::operator=(const Pickle& other) {
michael@0:   if (header_size_ != other.header_size_ && capacity_ != kCapacityReadOnly) {
michael@0:     free(header_);
michael@0:     header_ = NULL;
michael@0:     header_size_ = other.header_size_;
michael@0:   }
michael@0:   bool resized = Resize(other.header_size_ + other.header_->payload_size);
michael@0:   if (!resized) {
michael@0:     NS_ABORT_OOM(other.header_size_ + other.header_->payload_size);
michael@0:   }
michael@0:   memcpy(header_, other.header_, header_size_ + other.header_->payload_size);
michael@0:   variable_buffer_offset_ = other.variable_buffer_offset_;
michael@0:   return *this;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadBool(void** iter, bool* result) const {
michael@0:   DCHECK(iter);
michael@0: 
michael@0:   int tmp;
michael@0:   if (!ReadInt(iter, &tmp))
michael@0:     return false;
michael@0:   DCHECK(0 == tmp || 1 == tmp);
michael@0:   *result = tmp ? true : false;
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadInt16(void** iter, int16_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadUInt16(void** iter, uint16_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadInt(void** iter, int* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // Always written as a 64-bit value since the size for this type can
michael@0: // differ between architectures.
michael@0: bool Pickle::ReadLong(void** iter, long* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   int64_t bigResult = 0;
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(bigResult)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(&bigResult, iter);
michael@0:   DCHECK(bigResult <= LONG_MAX && bigResult >= LONG_MIN);
michael@0:   *result = static_cast<long>(bigResult);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(bigResult));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // Always written as a 64-bit value since the size for this type can
michael@0: // differ between architectures.
michael@0: bool Pickle::ReadULong(void** iter, unsigned long* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   uint64_t bigResult = 0;
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(bigResult)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(&bigResult, iter);
michael@0:   DCHECK(bigResult <= ULONG_MAX);
michael@0:   *result = static_cast<unsigned long>(bigResult);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(bigResult));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadLength(void** iter, int* result) const {
michael@0:   if (!ReadInt(iter, result))
michael@0:     return false;
michael@0:   return ((*result) >= 0);
michael@0: }
michael@0: 
michael@0: // Always written as a 64-bit value since the size for this type can
michael@0: // differ between architectures.
michael@0: bool Pickle::ReadSize(void** iter, size_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   uint64_t bigResult = 0;
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(bigResult)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(&bigResult, iter);
michael@0:   DCHECK(bigResult <= std::numeric_limits<size_t>::max());
michael@0:   *result = static_cast<size_t>(bigResult);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(bigResult));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadInt32(void** iter, int32_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadUInt32(void** iter, uint32_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadInt64(void** iter, int64_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadUInt64(void** iter, uint64_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadDouble(void** iter, double* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // Always written as a 64-bit value since the size for this type can
michael@0: // differ between architectures.
michael@0: bool Pickle::ReadIntPtr(void** iter, intptr_t* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   int64_t bigResult = 0;
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(bigResult)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(&bigResult, iter);
michael@0:   DCHECK(bigResult <= std::numeric_limits<intptr_t>::max() && bigResult >= std::numeric_limits<intptr_t>::min());
michael@0:   *result = static_cast<intptr_t>(bigResult);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(bigResult));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadUnsignedChar(void** iter, unsigned char* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, sizeof(*result)))
michael@0:     return false;
michael@0: 
michael@0:   CopyFromIter(result, iter);
michael@0: 
michael@0:   UpdateIter(iter, sizeof(*result));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadString(void** iter, std::string* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   int len;
michael@0:   if (!ReadLength(iter, &len))
michael@0:     return false;
michael@0:   if (!IteratorHasRoomFor(*iter, len))
michael@0:     return false;
michael@0: 
michael@0:   char* chars = reinterpret_cast<char*>(*iter);
michael@0:   result->assign(chars, len);
michael@0: 
michael@0:   UpdateIter(iter, len);
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadWString(void** iter, std::wstring* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   int len;
michael@0:   if (!ReadLength(iter, &len))
michael@0:     return false;
michael@0:   if (!IteratorHasRoomFor(*iter, len * sizeof(wchar_t)))
michael@0:     return false;
michael@0: 
michael@0:   wchar_t* chars = reinterpret_cast<wchar_t*>(*iter);
michael@0:   result->assign(chars, len);
michael@0: 
michael@0:   UpdateIter(iter, len * sizeof(wchar_t));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadString16(void** iter, string16* result) const {
michael@0:   DCHECK(iter);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   int len;
michael@0:   if (!ReadLength(iter, &len))
michael@0:     return false;
michael@0:   if (!IteratorHasRoomFor(*iter, len))
michael@0:     return false;
michael@0: 
michael@0:   char16* chars = reinterpret_cast<char16*>(*iter);
michael@0:   result->assign(chars, len);
michael@0: 
michael@0:   UpdateIter(iter, len * sizeof(char16));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadBytes(void** iter, const char** data, int length,
michael@0:                        uint32_t alignment) const {
michael@0:   DCHECK(iter);
michael@0:   DCHECK(data);
michael@0:   DCHECK(alignment == 4 || alignment == 8);
michael@0:   DCHECK(intptr_t(header_) % alignment == 0);
michael@0: 
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   uint32_t paddingLen = intptr_t(*iter) % alignment;
michael@0:   if (paddingLen) {
michael@0: #ifdef DEBUG
michael@0:     {
michael@0:       const char* padding = static_cast<const char*>(*iter);
michael@0:       for (uint32_t i = 0; i < paddingLen; i++) {
michael@0:         DCHECK(*(padding + i) == kBytePaddingMarker);
michael@0:       }
michael@0:     }
michael@0: #endif
michael@0:     length += paddingLen;
michael@0:   }
michael@0: 
michael@0:   if (!IteratorHasRoomFor(*iter, length))
michael@0:     return false;
michael@0: 
michael@0:   *data = static_cast<const char*>(*iter) + paddingLen;
michael@0:   DCHECK(intptr_t(*data) % alignment == 0);
michael@0: 
michael@0:   UpdateIter(iter, length);
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::ReadData(void** iter, const char** data, int* length) const {
michael@0:   DCHECK(iter);
michael@0:   DCHECK(data);
michael@0:   DCHECK(length);
michael@0:   if (!*iter)
michael@0:     *iter = const_cast<char*>(payload());
michael@0: 
michael@0:   if (!ReadLength(iter, length))
michael@0:     return false;
michael@0: 
michael@0:   return ReadBytes(iter, data, *length);
michael@0: }
michael@0: 
michael@0: char* Pickle::BeginWrite(uint32_t length, uint32_t alignment) {
michael@0:   DCHECK(alignment % 4 == 0) << "Must be at least 32-bit aligned!";
michael@0: 
michael@0:   // write at an alignment-aligned offset from the beginning of the header
michael@0:   uint32_t offset = AlignInt(header_->payload_size);
michael@0:   uint32_t padding = (header_size_ + offset) %  alignment;
michael@0:   uint32_t new_size = offset + padding + AlignInt(length);
michael@0:   uint32_t needed_size = header_size_ + new_size;
michael@0: 
michael@0:   if (needed_size > capacity_ && !Resize(std::max(capacity_ * 2, needed_size)))
michael@0:     return NULL;
michael@0: 
michael@0:   DCHECK(intptr_t(header_) % alignment == 0);
michael@0: 
michael@0: #ifdef ARCH_CPU_64_BITS
michael@0:   DCHECK_LE(length, std::numeric_limits<uint32_t>::max());
michael@0: #endif
michael@0: 
michael@0:   char* buffer = payload() + offset;
michael@0: 
michael@0:   if (padding) {
michael@0:     memset(buffer, kBytePaddingMarker, padding);
michael@0:     buffer += padding;
michael@0:   }
michael@0: 
michael@0:   DCHECK(intptr_t(buffer) % alignment == 0);
michael@0: 
michael@0:   header_->payload_size = new_size;
michael@0: 
michael@0: #ifdef MOZ_VALGRIND
michael@0:   // pad the trailing end as well, so that valgrind
michael@0:   // doesn't complain when we write the buffer
michael@0:   padding = AlignInt(length) - length;
michael@0:   if (padding) {
michael@0:     memset(buffer + length, kBytePaddingMarker, padding);
michael@0:   }
michael@0: #endif
michael@0: 
michael@0:   return buffer;
michael@0: }
michael@0: 
michael@0: void Pickle::EndWrite(char* dest, int length) {
michael@0:   // Zero-pad to keep tools like purify from complaining about uninitialized
michael@0:   // memory.
michael@0:   if (length % sizeof(memberAlignmentType))
michael@0:     memset(dest + length, 0,
michael@0: 	   sizeof(memberAlignmentType) - (length % sizeof(memberAlignmentType)));
michael@0: }
michael@0: 
michael@0: bool Pickle::WriteBytes(const void* data, int data_len, uint32_t alignment) {
michael@0:   DCHECK(capacity_ != kCapacityReadOnly) << "oops: pickle is readonly";
michael@0:   DCHECK(alignment == 4 || alignment == 8);
michael@0:   DCHECK(intptr_t(header_) % alignment == 0);
michael@0: 
michael@0:   char* dest = BeginWrite(data_len, alignment);
michael@0:   if (!dest)
michael@0:     return false;
michael@0: 
michael@0:   memcpy(dest, data, data_len);
michael@0: 
michael@0:   EndWrite(dest, data_len);
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool Pickle::WriteString(const std::string& value) {
michael@0:   if (!WriteInt(static_cast<int>(value.size())))
michael@0:     return false;
michael@0: 
michael@0:   return WriteBytes(value.data(), static_cast<int>(value.size()));
michael@0: }
michael@0: 
michael@0: bool Pickle::WriteWString(const std::wstring& value) {
michael@0:   if (!WriteInt(static_cast<int>(value.size())))
michael@0:     return false;
michael@0: 
michael@0:   return WriteBytes(value.data(),
michael@0:                     static_cast<int>(value.size() * sizeof(wchar_t)));
michael@0: }
michael@0: 
michael@0: bool Pickle::WriteString16(const string16& value) {
michael@0:   if (!WriteInt(static_cast<int>(value.size())))
michael@0:     return false;
michael@0: 
michael@0:   return WriteBytes(value.data(),
michael@0:                     static_cast<int>(value.size()) * sizeof(char16));
michael@0: }
michael@0: 
michael@0: bool Pickle::WriteData(const char* data, int length) {
michael@0:   return WriteInt(length) && WriteBytes(data, length);
michael@0: }
michael@0: 
michael@0: char* Pickle::BeginWriteData(int length) {
michael@0:   DCHECK_EQ(variable_buffer_offset_, 0U) <<
michael@0:     "There can only be one variable buffer in a Pickle";
michael@0: 
michael@0:   if (!WriteInt(length))
michael@0:     return NULL;
michael@0: 
michael@0:   char *data_ptr = BeginWrite(length, sizeof(memberAlignmentType));
michael@0:   if (!data_ptr)
michael@0:     return NULL;
michael@0: 
michael@0:   variable_buffer_offset_ =
michael@0:       data_ptr - reinterpret_cast<char*>(header_) - sizeof(int);
michael@0: 
michael@0:   // EndWrite doesn't necessarily have to be called after the write operation,
michael@0:   // so we call it here to pad out what the caller will eventually write.
michael@0:   EndWrite(data_ptr, length);
michael@0:   return data_ptr;
michael@0: }
michael@0: 
michael@0: void Pickle::TrimWriteData(int new_length) {
michael@0:   DCHECK(variable_buffer_offset_ != 0);
michael@0: 
michael@0:   // Fetch the the variable buffer size
michael@0:   int* cur_length = reinterpret_cast<int*>(
michael@0:       reinterpret_cast<char*>(header_) + variable_buffer_offset_);
michael@0: 
michael@0:   if (new_length < 0 || new_length > *cur_length) {
michael@0:     NOTREACHED() << "Invalid length in TrimWriteData.";
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   // Update the payload size and variable buffer size
michael@0:   header_->payload_size -= (*cur_length - new_length);
michael@0:   *cur_length = new_length;
michael@0: }
michael@0: 
michael@0: bool Pickle::Resize(uint32_t new_capacity) {
michael@0:   new_capacity = ConstantAligner<kPayloadUnit>::align(new_capacity);
michael@0: 
michael@0:   void* p = realloc(header_, new_capacity);
michael@0:   if (!p)
michael@0:     return false;
michael@0: 
michael@0:   header_ = reinterpret_cast<Header*>(p);
michael@0:   capacity_ = new_capacity;
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // static
michael@0: const char* Pickle::FindNext(uint32_t header_size,
michael@0:                              const char* start,
michael@0:                              const char* end) {
michael@0:   DCHECK(header_size == AlignInt(header_size));
michael@0:   DCHECK(header_size <= static_cast<memberAlignmentType>(kPayloadUnit));
michael@0: 
michael@0:   const Header* hdr = reinterpret_cast<const Header*>(start);
michael@0:   const char* payload_base = start + header_size;
michael@0:   const char* payload_end = payload_base + hdr->payload_size;
michael@0:   if (payload_end < payload_base)
michael@0:     return NULL;
michael@0: 
michael@0:   return (payload_end > end) ? NULL : payload_end;
michael@0: }