base/pickle.h - chromium/src - Git at Google

 // 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"

 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 {
  public:
   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 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;
   bool ReadWString(std::wstring* result) WARN_UNUSED_RESULT;
   bool ReadString16(base::string16* result) WARN_UNUSED_RESULT;
   bool ReadData(const char** data, int* length) WARN_UNUSED_RESULT;
   bool ReadBytes(const char** data, int length) WARN_UNUSED_RESULT;

   // Safer version of ReadInt() 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);
   }

  private:
   // 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 {
  public:
   // Initialize a Pickle object using the default header size.
   Pickle();

   // 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 size of the Pickle's data.
   size_t size() const { return header_size_ + header_->payload_size; }

   // Returns the data for this Pickle.
   const void* data() const { return header_; }

   // For compatibility, these older style read methods pass through to the
   // PickleIterator methods.
   // TODO(jbates) Remove these methods.
   bool ReadBool(PickleIterator* iter,
                 bool* result) const WARN_UNUSED_RESULT {
     return iter->ReadBool(result);
   }
   bool ReadInt(PickleIterator* iter,
                int* result) const WARN_UNUSED_RESULT {
     return iter->ReadInt(result);
   }
   bool ReadLong(PickleIterator* iter,
                 long* result) const WARN_UNUSED_RESULT {
     return iter->ReadLong(result);
   }
   bool ReadUInt16(PickleIterator* iter,
                   uint16* result) const WARN_UNUSED_RESULT {
     return iter->ReadUInt16(result);
   }
   bool ReadUInt32(PickleIterator* iter,
                   uint32* result) const WARN_UNUSED_RESULT {
     return iter->ReadUInt32(result);
   }
   bool ReadInt64(PickleIterator* iter,
                  int64* result) const WARN_UNUSED_RESULT {
     return iter->ReadInt64(result);
   }
   bool ReadUInt64(PickleIterator* iter,
                   uint64* result) const WARN_UNUSED_RESULT {
     return iter->ReadUInt64(result);
   }
   bool ReadSizeT(PickleIterator* iter,
                  size_t* result) const WARN_UNUSED_RESULT {
     return iter->ReadSizeT(result);
   }
   bool ReadFloat(PickleIterator* iter,
                  float* result) const WARN_UNUSED_RESULT {
     return iter->ReadFloat(result);
   }
   bool ReadDouble(PickleIterator* iter,
                   double* result) const WARN_UNUSED_RESULT {
     return iter->ReadDouble(result);
   }
   bool ReadString(PickleIterator* iter,
                   std::string* result) const WARN_UNUSED_RESULT {
     return iter->ReadString(result);
   }
   bool ReadWString(PickleIterator* iter,
                    std::wstring* result) const WARN_UNUSED_RESULT {
     return iter->ReadWString(result);
   }
   bool ReadString16(PickleIterator* iter,
                     base::string16* result) const WARN_UNUSED_RESULT {
     return iter->ReadString16(result);
   }
   // A pointer to the data will be placed in *data, and the length will be
   // placed in *length. This buffer will be into the message's buffer so will
   // be scoped to the lifetime of the message (or until the message data is
   // mutated).
   bool ReadData(PickleIterator* iter,
                 const char** data,
                 int* length) const WARN_UNUSED_RESULT {
     return iter->ReadData(data, length);
   }
   // 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
   // returned buffer will be into the message's buffer so will be scoped to the
   // lifetime of the message (or until the message data is mutated).
   bool ReadBytes(PickleIterator* iter,
                  const char** data,
                  int length) const WARN_UNUSED_RESULT {
     return iter->ReadBytes(data, length);
   }

   // Safer version of ReadInt() checks for the result not being negative.
   // Use it for reading the object sizes.
   bool ReadLength(PickleIterator* iter,
                   int* result) const  WARN_UNUSED_RESULT {
     return iter->ReadLength(result);
   }

   // 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);
   }
   // WARNING: DO NOT USE THIS METHOD IF PICKLES ARE PERSISTED IN ANY WAY.
   // 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 std::string& value);
   bool WriteWString(const std::wstring& value);
   bool WriteString16(const base::string16& 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;
   }

  protected:
   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;

  private:
   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) {
     WriteBytesStatic<sizeof(data)>(&data);
     return true;
   }
   inline void WriteBytesCommon(const void* data, size_t length);

   FRIEND_TEST_ALL_PREFIXES(PickleTest, Resize);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNext);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextOverflow);
 };

 #endif  // BASE_PICKLE_H__
	// 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"

	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 {
	public:
	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 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;
	bool ReadWString(std::wstring* result) WARN_UNUSED_RESULT;
	bool ReadString16(base::string16* result) WARN_UNUSED_RESULT;
	bool ReadData(const char** data, int* length) WARN_UNUSED_RESULT;
	bool ReadBytes(const char** data, int length) WARN_UNUSED_RESULT;

	// Safer version of ReadInt() 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);
	}

	private:
	// 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 {
	public:
	// Initialize a Pickle object using the default header size.
	Pickle();

	// 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 size of the Pickle's data.
	size_t size() const { return header_size_ + header_->payload_size; }

	// Returns the data for this Pickle.
	const void* data() const { return header_; }

	// For compatibility, these older style read methods pass through to the
	// PickleIterator methods.
	// TODO(jbates) Remove these methods.
	bool ReadBool(PickleIterator* iter,
	bool* result) const WARN_UNUSED_RESULT {
	return iter->ReadBool(result);
	}
	bool ReadInt(PickleIterator* iter,
	int* result) const WARN_UNUSED_RESULT {
	return iter->ReadInt(result);
	}
	bool ReadLong(PickleIterator* iter,
	long* result) const WARN_UNUSED_RESULT {
	return iter->ReadLong(result);
	}
	bool ReadUInt16(PickleIterator* iter,
	uint16* result) const WARN_UNUSED_RESULT {
	return iter->ReadUInt16(result);
	}
	bool ReadUInt32(PickleIterator* iter,
	uint32* result) const WARN_UNUSED_RESULT {
	return iter->ReadUInt32(result);
	}
	bool ReadInt64(PickleIterator* iter,
	int64* result) const WARN_UNUSED_RESULT {
	return iter->ReadInt64(result);
	}
	bool ReadUInt64(PickleIterator* iter,
	uint64* result) const WARN_UNUSED_RESULT {
	return iter->ReadUInt64(result);
	}
	bool ReadSizeT(PickleIterator* iter,
	size_t* result) const WARN_UNUSED_RESULT {
	return iter->ReadSizeT(result);
	}
	bool ReadFloat(PickleIterator* iter,
	float* result) const WARN_UNUSED_RESULT {
	return iter->ReadFloat(result);
	}
	bool ReadDouble(PickleIterator* iter,
	double* result) const WARN_UNUSED_RESULT {
	return iter->ReadDouble(result);
	}
	bool ReadString(PickleIterator* iter,
	std::string* result) const WARN_UNUSED_RESULT {
	return iter->ReadString(result);
	}
	bool ReadWString(PickleIterator* iter,
	std::wstring* result) const WARN_UNUSED_RESULT {
	return iter->ReadWString(result);
	}
	bool ReadString16(PickleIterator* iter,
	base::string16* result) const WARN_UNUSED_RESULT {
	return iter->ReadString16(result);
	}
	// A pointer to the data will be placed in *data, and the length will be
	// placed in *length. This buffer will be into the message's buffer so will
	// be scoped to the lifetime of the message (or until the message data is
	// mutated).
	bool ReadData(PickleIterator* iter,
	const char** data,
	int* length) const WARN_UNUSED_RESULT {
	return iter->ReadData(data, length);
	}
	// 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
	// returned buffer will be into the message's buffer so will be scoped to the
	// lifetime of the message (or until the message data is mutated).
	bool ReadBytes(PickleIterator* iter,
	const char** data,
	int length) const WARN_UNUSED_RESULT {
	return iter->ReadBytes(data, length);
	}

	// Safer version of ReadInt() checks for the result not being negative.
	// Use it for reading the object sizes.
	bool ReadLength(PickleIterator* iter,
	int* result) const WARN_UNUSED_RESULT {
	return iter->ReadLength(result);
	}

	// 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);
	}
	// WARNING: DO NOT USE THIS METHOD IF PICKLES ARE PERSISTED IN ANY WAY.
	// 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 std::string& value);
	bool WriteWString(const std::wstring& value);
	bool WriteString16(const base::string16& 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;
	}

	protected:
	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;

	private:
	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) {
	WriteBytesStatic<sizeof(data)>(&data);
	return true;
	}
	inline void WriteBytesCommon(const void* data, size_t length);

	FRIEND_TEST_ALL_PREFIXES(PickleTest, Resize);
	FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNext);
	FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
	FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextOverflow);
	};

	#endif // BASE_PICKLE_H__