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// Copyright (c) 2012 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_PICKLE_H_
#define BASE_PICKLE_H_
#include <string>
#include "base/base_export.h"
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/logging.h"
#include "base/strings/string16.h"
#include "base/strings/string_piece.h"
namespace base {
class Pickle;
// PickleIterator reads data from a Pickle. The Pickle object must remain valid
// while the PickleIterator object is in use.
class BASE_EXPORT PickleIterator {
PickleIterator() : payload_(NULL), read_index_(0), end_index_(0) {}
explicit PickleIterator(const Pickle& pickle);
// Methods for reading the payload of the Pickle. To read from the start of
// the Pickle, create a PickleIterator from a Pickle. If successful, these
// methods return true. Otherwise, false is returned to indicate that the
// result could not be extracted. It is not possible to read from the iterator
// after that.
bool ReadBool(bool* result) WARN_UNUSED_RESULT;
bool ReadInt(int* result) WARN_UNUSED_RESULT;
bool ReadLong(long* result) WARN_UNUSED_RESULT;
bool ReadUInt16(uint16* result) WARN_UNUSED_RESULT;
bool ReadUInt32(uint32* result) WARN_UNUSED_RESULT;
bool ReadInt64(int64* result) WARN_UNUSED_RESULT;
bool ReadUInt64(uint64* result) WARN_UNUSED_RESULT;
bool ReadSizeT(size_t* result) WARN_UNUSED_RESULT;
bool ReadFloat(float* result) WARN_UNUSED_RESULT;
bool ReadDouble(double* result) WARN_UNUSED_RESULT;
bool ReadString(std::string* result) WARN_UNUSED_RESULT;
// The StringPiece data will only be valid for the lifetime of the message.
bool ReadStringPiece(StringPiece* result) WARN_UNUSED_RESULT;
bool ReadString16(string16* result) WARN_UNUSED_RESULT;
// The StringPiece16 data will only be valid for the lifetime of the message.
bool ReadStringPiece16(StringPiece16* result) WARN_UNUSED_RESULT;
// A pointer to the data will be placed in |*data|, and the length will be
// placed in |*length|. The pointer placed into |*data| points into the
// message's buffer so it will be scoped to the lifetime of the message (or
// until the message data is mutated). Do not keep the pointer around!
bool ReadData(const char** data, int* length) WARN_UNUSED_RESULT;
// A pointer to the data will be placed in |*data|. The caller specifies the
// number of bytes to read, and ReadBytes will validate this length. The
// pointer placed into |*data| points into the message's buffer so it will be
// scoped to the lifetime of the message (or until the message data is
// mutated). Do not keep the pointer around!
bool ReadBytes(const char** data, int length) WARN_UNUSED_RESULT;
// A safer version of ReadInt() that checks for the result not being negative.
// Use it for reading the object sizes.
bool ReadLength(int* result) WARN_UNUSED_RESULT {
return ReadInt(result) && *result >= 0;
// Skips bytes in the read buffer and returns true if there are at least
// num_bytes available. Otherwise, does nothing and returns false.
bool SkipBytes(int num_bytes) WARN_UNUSED_RESULT {
return !!GetReadPointerAndAdvance(num_bytes);
// Aligns 'i' by rounding it up to the next multiple of 'alignment'.
static size_t AlignInt(size_t i, int alignment) {
return i + (alignment - (i % alignment)) % alignment;
// Read Type from Pickle.
template <typename Type>
bool ReadBuiltinType(Type* result);
// Advance read_index_ but do not allow it to exceed end_index_.
// Keeps read_index_ aligned.
void Advance(size_t size);
// Get read pointer for Type and advance read pointer.
template<typename Type>
const char* GetReadPointerAndAdvance();
// Get read pointer for |num_bytes| and advance read pointer. This method
// checks num_bytes for negativity and wrapping.
const char* GetReadPointerAndAdvance(int num_bytes);
// Get read pointer for (num_elements * size_element) bytes and advance read
// pointer. This method checks for int overflow, negativity and wrapping.
const char* GetReadPointerAndAdvance(int num_elements,
size_t size_element);
const char* payload_; // Start of our pickle's payload.
size_t read_index_; // Offset of the next readable byte in payload.
size_t end_index_; // Payload size.
FRIEND_TEST_ALL_PREFIXES(PickleTest, GetReadPointerAndAdvance);
// This class provides facilities for basic binary value packing and unpacking.
// The Pickle class supports appending primitive values (ints, strings, etc.)
// to a pickle instance. The Pickle instance grows its internal memory buffer
// dynamically to hold the sequence of primitive values. The internal memory
// buffer is exposed as the "data" of the Pickle. This "data" can be passed
// to a Pickle object to initialize it for reading.
// When reading from a Pickle object, it is important for the consumer to know
// what value types to read and in what order to read them as the Pickle does
// not keep track of the type of data written to it.
// The Pickle's data has a header which contains the size of the Pickle's
// payload. It can optionally support additional space in the header. That
// space is controlled by the header_size parameter passed to the Pickle
// constructor.
class BASE_EXPORT Pickle {
// Initialize a Pickle object using the default header size.
// Initialize a Pickle object with the specified header size in bytes, which
// must be greater-than-or-equal-to sizeof(Pickle::Header). The header size
// will be rounded up to ensure that the header size is 32bit-aligned.
explicit Pickle(int header_size);
// Initializes a Pickle from a const block of data. The data is not copied;
// instead the data is merely referenced by this Pickle. Only const methods
// should be used on the Pickle when initialized this way. The header
// padding size is deduced from the data length.
Pickle(const char* data, int data_len);
// Initializes a Pickle as a deep copy of another Pickle.
Pickle(const Pickle& other);
// Note: There are no virtual methods in this class. This destructor is
// virtual as an element of defensive coding. Other classes have derived from
// this class, and there is a *chance* that they will cast into this base
// class before destruction. At least one such class does have a virtual
// destructor, suggesting at least some need to call more derived destructors.
virtual ~Pickle();
// Performs a deep copy.
Pickle& operator=(const Pickle& other);
// Returns the number of bytes written in the Pickle, including the header.
size_t size() const { return header_size_ + header_->payload_size; }
// Returns the data for this Pickle.
const void* data() const { return header_; }
// Returns the effective memory capacity of this Pickle, that is, the total
// number of bytes currently dynamically allocated or 0 in the case of a
// read-only Pickle. This should be used only for diagnostic / profiling
// purposes.
size_t GetTotalAllocatedSize() const;
// Methods for adding to the payload of the Pickle. These values are
// appended to the end of the Pickle's payload. When reading values from a
// Pickle, it is important to read them in the order in which they were added
// to the Pickle.
bool WriteBool(bool value) {
return WriteInt(value ? 1 : 0);
bool WriteInt(int value) {
return WritePOD(value);
// It will write whatever a "long" is on this architecture. On 32-bit
// platforms, it is 32 bits. On 64-bit platforms, it is 64 bits. If persisted
// pickles are still around after upgrading to 64-bit, or if they are copied
// between dissimilar systems, YOUR PICKLES WILL HAVE GONE BAD.
bool WriteLongUsingDangerousNonPortableLessPersistableForm(long value) {
return WritePOD(value);
bool WriteUInt16(uint16 value) {
return WritePOD(value);
bool WriteUInt32(uint32 value) {
return WritePOD(value);
bool WriteInt64(int64 value) {
return WritePOD(value);
bool WriteUInt64(uint64 value) {
return WritePOD(value);
bool WriteSizeT(size_t value) {
// Always write size_t as a 64-bit value to ensure compatibility between
// 32-bit and 64-bit processes.
return WritePOD(static_cast<uint64>(value));
bool WriteFloat(float value) {
return WritePOD(value);
bool WriteDouble(double value) {
return WritePOD(value);
bool WriteString(const StringPiece& value);
bool WriteString16(const StringPiece16& value);
// "Data" is a blob with a length. When you read it out you will be given the
// length. See also WriteBytes.
bool WriteData(const char* data, int length);
// "Bytes" is a blob with no length. The caller must specify the length both
// when reading and writing. It is normally used to serialize PoD types of a
// known size. See also WriteData.
bool WriteBytes(const void* data, int length);
// Reserves space for upcoming writes when multiple writes will be made and
// their sizes are computed in advance. It can be significantly faster to call
// Reserve() before calling WriteFoo() multiple times.
void Reserve(size_t additional_capacity);
// Payload follows after allocation of Header (header size is customizable).
struct Header {
uint32 payload_size; // Specifies the size of the payload.
// Returns the header, cast to a user-specified type T. The type T must be a
// subclass of Header and its size must correspond to the header_size passed
// to the Pickle constructor.
template <class T>
T* headerT() {
DCHECK_EQ(header_size_, sizeof(T));
return static_cast<T*>(header_);
template <class T>
const T* headerT() const {
DCHECK_EQ(header_size_, sizeof(T));
return static_cast<const T*>(header_);
// The payload is the pickle data immediately following the header.
size_t payload_size() const {
return header_ ? header_->payload_size : 0;
const char* payload() const {
return reinterpret_cast<const char*>(header_) + header_size_;
// Returns the address of the byte immediately following the currently valid
// header + payload.
const char* end_of_payload() const {
// This object may be invalid.
return header_ ? payload() + payload_size() : NULL;
char* mutable_payload() {
return reinterpret_cast<char*>(header_) + header_size_;
size_t capacity_after_header() const {
return capacity_after_header_;
// Resize the capacity, note that the input value should not include the size
// of the header.
void Resize(size_t new_capacity);
// Aligns 'i' by rounding it up to the next multiple of 'alignment'
static size_t AlignInt(size_t i, int alignment) {
return i + (alignment - (i % alignment)) % alignment;
// Find the end of the pickled data that starts at range_start. Returns NULL
// if the entire Pickle is not found in the given data range.
static const char* FindNext(size_t header_size,
const char* range_start,
const char* range_end);
// The allocation granularity of the payload.
static const int kPayloadUnit;
friend class PickleIterator;
Header* header_;
size_t header_size_; // Supports extra data between header and payload.
// Allocation size of payload (or -1 if allocation is const). Note: this
// doesn't count the header.
size_t capacity_after_header_;
// The offset at which we will write the next field. Note: this doesn't count
// the header.
size_t write_offset_;
// Just like WriteBytes, but with a compile-time size, for performance.
template<size_t length> void BASE_EXPORT WriteBytesStatic(const void* data);
// Writes a POD by copying its bytes.
template <typename T> bool WritePOD(const T& data) {
return true;
inline void WriteBytesCommon(const void* data, size_t length);
FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextOverflow);
} // namespace base
#endif // BASE_PICKLE_H_