coded_stream.h

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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Author: [email protected] (Kenton Varda)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// This file contains the CodedInputStream and CodedOutputStream classes,
// which wrap a ZeroCopyInputStream or ZeroCopyOutputStream, respectively,
// and allow you to read or write individual pieces of data in various
// formats. In particular, these implement the varint encoding for
// integers, a simple variable-length encoding in which smaller numbers
// take fewer bytes.
//
// Typically these classes will only be used internally by the protocol
// buffer library in order to encode and decode protocol buffers. Clients
// of the library only need to know about this class if they wish to write
// custom message parsing or serialization procedures.
//
// CodedOutputStream example:
// // Write some data to "myfile". First we write a 4-byte "magic number"
// // to identify the file type, then write a length-delimited string. The
// // string is composed of a varint giving the length followed by the raw
// // bytes.
// int fd = open("myfile", O_WRONLY);
// ZeroCopyOutputStream* raw_output = new FileOutputStream(fd);
// CodedOutputStream* coded_output = new CodedOutputStream(raw_output);
//
// int magic_number = 1234;
// char text[] = "Hello world!";
// coded_output->WriteLittleEndian32(magic_number);
// coded_output->WriteVarint32(strlen(text));
// coded_output->WriteRaw(text, strlen(text));
//
// delete coded_output;
// delete raw_output;
// close(fd);
//
// CodedInputStream example:
// // Read a file created by the above code.
// int fd = open("myfile", O_RDONLY);
// ZeroCopyInputStream* raw_input = new FileInputStream(fd);
// CodedInputStream coded_input = new CodedInputStream(raw_input);
//
// coded_input->ReadLittleEndian32(&magic_number);
// if (magic_number != 1234) {
// cerr << "File not in expected format." << endl;
// return;
// }
//
// uint32 size;
// coded_input->ReadVarint32(&size);
//
// char* text = new char[size + 1];
// coded_input->ReadRaw(buffer, size);
// text[size] = '\0';
//
// delete coded_input;
// delete raw_input;
// close(fd);
//
// cout << "Text is: " << text << endl;
// delete [] text;
//
// For those who are interested, varint encoding is defined as follows:
//
// The encoding operates on unsigned integers of up to 64 bits in length.
// Each byte of the encoded value has the format:
// * bits 0-6: Seven bits of the number being encoded.
// * bit 7: Zero if this is the last byte in the encoding (in which
// case all remaining bits of the number are zero) or 1 if
// more bytes follow.
// The first byte contains the least-significant 7 bits of the number, the
// second byte (if present) contains the next-least-significant 7 bits,
// and so on. So, the binary number 1011000101011 would be encoded in two
// bytes as "10101011 00101100".
//
// In theory, varint could be used to encode integers of any length.
// However, for practicality we set a limit at 64 bits. The maximum encoded
// length of a number is thus 10 bytes.

#ifndef GOOGLE_PROTOBUF_IO_CODED_STREAM_H__
#define GOOGLE_PROTOBUF_IO_CODED_STREAM_H__

#include <string>
#ifdef _MSC_VER
 #if defined(_M_IX86) && \
 !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
 #define PROTOBUF_LITTLE_ENDIAN 1
 #endif
 #if _MSC_VER >= 1300
 // If MSVC has "/RTCc" set, it will complain about truncating casts at
 // runtime. This file contains some intentional truncating casts.
 #pragma runtime_checks("c", off)
 #endif
#else
 #include <sys/param.h> // __BYTE_ORDER
 #if defined(__BYTE_ORDER) && __BYTE_ORDER == __LITTLE_ENDIAN && \
 !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
 #define PROTOBUF_LITTLE_ENDIAN 1
 #endif
#endif
#include <google/protobuf/stubs/common.h>


namespace google {
namespace protobuf {

class DescriptorPool;
class MessageFactory;

namespace io {

// Defined in this file.
class CodedInputStream;
class CodedOutputStream;

// Defined in other files.
class ZeroCopyInputStream; // zero_copy_stream.h
class ZeroCopyOutputStream; // zero_copy_stream.h

// Class which reads and decodes binary data which is composed of varint-
// encoded integers and fixed-width pieces. Wraps a ZeroCopyInputStream.
// Most users will not need to deal with CodedInputStream.
//
// Most methods of CodedInputStream that return a bool return false if an
// underlying I/O error occurs or if the data is malformed. Once such a
// failure occurs, the CodedInputStream is broken and is no longer useful.
class LIBPROTOBUF_EXPORT CodedInputStream {
 public:
 // Create a CodedInputStream that reads from the given ZeroCopyInputStream.
 explicit CodedInputStream(ZeroCopyInputStream* input);

 // Create a CodedInputStream that reads from the given flat array. This is
 // faster than using an ArrayInputStream. PushLimit(size) is implied by
 // this constructor.
 explicit CodedInputStream(const uint8* buffer, int size);

 // Destroy the CodedInputStream and position the underlying
 // ZeroCopyInputStream at the first unread byte. If an error occurred while
 // reading (causing a method to return false), then the exact position of
 // the input stream may be anywhere between the last value that was read
 // successfully and the stream's byte limit.
 ~CodedInputStream();

 // Return true if this CodedInputStream reads from a flat array instead of
 // a ZeroCopyInputStream.
 inline bool IsFlat() const;

 // Skips a number of bytes. Returns false if an underlying read error
 // occurs.
 bool Skip(int count);

 // Sets *data to point directly at the unread part of the CodedInputStream's
 // underlying buffer, and *size to the size of that buffer, but does not
 // advance the stream's current position. This will always either produce
 // a non-empty buffer or return false. If the caller consumes any of
 // this data, it should then call Skip() to skip over the consumed bytes.
 // This may be useful for implementing external fast parsing routines for
 // types of data not covered by the CodedInputStream interface.
 bool GetDirectBufferPointer(const void** data, int* size);

 // Like GetDirectBufferPointer, but this method is inlined, and does not
 // attempt to Refresh() if the buffer is currently empty.
 inline void GetDirectBufferPointerInline(const void** data,
 int* size) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // Read raw bytes, copying them into the given buffer.
 bool ReadRaw(void* buffer, int size);

 // Like ReadRaw, but reads into a string.
 //
 // Implementation Note: ReadString() grows the string gradually as it
 // reads in the data, rather than allocating the entire requested size
 // upfront. This prevents denial-of-service attacks in which a client
 // could claim that a string is going to be MAX_INT bytes long in order to
 // crash the server because it can't allocate this much space at once.
 bool ReadString(string* buffer, int size);
 // Like the above, with inlined optimizations. This should only be used
 // by the protobuf implementation.
 inline bool InternalReadStringInline(string* buffer,
 int size) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;


 // Read a 32-bit little-endian integer.
 bool ReadLittleEndian32(uint32* value);
 // Read a 64-bit little-endian integer.
 bool ReadLittleEndian64(uint64* value);

 // These methods read from an externally provided buffer. The caller is
 // responsible for ensuring that the buffer has sufficient space.
 // Read a 32-bit little-endian integer.
 static const uint8* ReadLittleEndian32FromArray(const uint8* buffer,
 uint32* value);
 // Read a 64-bit little-endian integer.
 static const uint8* ReadLittleEndian64FromArray(const uint8* buffer,
 uint64* value);

 // Read an unsigned integer with Varint encoding, truncating to 32 bits.
 // Reading a 32-bit value is equivalent to reading a 64-bit one and casting
 // it to uint32, but may be more efficient.
 bool ReadVarint32(uint32* value);
 // Read an unsigned integer with Varint encoding.
 bool ReadVarint64(uint64* value);

 // Read a tag. This calls ReadVarint32() and returns the result, or returns
 // zero (which is not a valid tag) if ReadVarint32() fails. Also, it updates
 // the last tag value, which can be checked with LastTagWas().
 // Always inline because this is only called in one place per parse loop
 // but it is called for every iteration of said loop, so it should be fast.
 // GCC doesn't want to inline this by default.
 uint32 ReadTag() GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // This usually a faster alternative to ReadTag() when cutoff is a manifest
 // constant. It does particularly well for cutoff >= 127. The first part
 // of the return value is the tag that was read, though it can also be 0 in
 // the cases where ReadTag() would return 0. If the second part is true
 // then the tag is known to be in [0, cutoff]. If not, the tag either is
 // above cutoff or is 0. (There's intentional wiggle room when tag is 0,
 // because that can arise in several ways, and for best performance we want
 // to avoid an extra "is tag == 0?" check here.)
 inline std::pair<uint32, bool> ReadTagWithCutoff(uint32 cutoff)
 GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // Usually returns true if calling ReadVarint32() now would produce the given
 // value. Will always return false if ReadVarint32() would not return the
 // given value. If ExpectTag() returns true, it also advances past
 // the varint. For best performance, use a compile-time constant as the
 // parameter.
 // Always inline because this collapses to a small number of instructions
 // when given a constant parameter, but GCC doesn't want to inline by default.
 bool ExpectTag(uint32 expected) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // Like above, except this reads from the specified buffer. The caller is
 // responsible for ensuring that the buffer is large enough to read a varint
 // of the expected size. For best performance, use a compile-time constant as
 // the expected tag parameter.
 //
 // Returns a pointer beyond the expected tag if it was found, or NULL if it
 // was not.
 static const uint8* ExpectTagFromArray(
 const uint8* buffer,
 uint32 expected) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // Usually returns true if no more bytes can be read. Always returns false
 // if more bytes can be read. If ExpectAtEnd() returns true, a subsequent
 // call to LastTagWas() will act as if ReadTag() had been called and returned
 // zero, and ConsumedEntireMessage() will return true.
 bool ExpectAtEnd();

 // If the last call to ReadTag() or ReadTagWithCutoff() returned the
 // given value, returns true. Otherwise, returns false;
 //
 // This is needed because parsers for some types of embedded messages
 // (with field type TYPE_GROUP) don't actually know that they've reached the
 // end of a message until they see an ENDGROUP tag, which was actually part
 // of the enclosing message. The enclosing message would like to check that
 // tag to make sure it had the right number, so it calls LastTagWas() on
 // return from the embedded parser to check.
 bool LastTagWas(uint32 expected);

 // When parsing message (but NOT a group), this method must be called
 // immediately after MergeFromCodedStream() returns (if it returns true)
 // to further verify that the message ended in a legitimate way. For
 // example, this verifies that parsing did not end on an end-group tag.
 // It also checks for some cases where, due to optimizations,
 // MergeFromCodedStream() can incorrectly return true.
 bool ConsumedEntireMessage();

 // Limits ----------------------------------------------------------
 // Limits are used when parsing length-delimited embedded messages.
 // After the message's length is read, PushLimit() is used to prevent
 // the CodedInputStream from reading beyond that length. Once the
 // embedded message has been parsed, PopLimit() is called to undo the
 // limit.

 // Opaque type used with PushLimit() and PopLimit(). Do not modify
 // values of this type yourself. The only reason that this isn't a
 // struct with private internals is for efficiency.
 typedef int Limit;

 // Places a limit on the number of bytes that the stream may read,
 // starting from the current position. Once the stream hits this limit,
 // it will act like the end of the input has been reached until PopLimit()
 // is called.
 //
 // As the names imply, the stream conceptually has a stack of limits. The
 // shortest limit on the stack is always enforced, even if it is not the
 // top limit.
 //
 // The value returned by PushLimit() is opaque to the caller, and must
 // be passed unchanged to the corresponding call to PopLimit().
 Limit PushLimit(int byte_limit);

 // Pops the last limit pushed by PushLimit(). The input must be the value
 // returned by that call to PushLimit().
 void PopLimit(Limit limit);

 // Returns the number of bytes left until the nearest limit on the
 // stack is hit, or -1 if no limits are in place.
 int BytesUntilLimit() const;

 // Returns current position relative to the beginning of the input stream.
 int CurrentPosition() const;

 // Total Bytes Limit -----------------------------------------------
 // To prevent malicious users from sending excessively large messages
 // and causing integer overflows or memory exhaustion, CodedInputStream
 // imposes a hard limit on the total number of bytes it will read.

 // Sets the maximum number of bytes that this CodedInputStream will read
 // before refusing to continue. To prevent integer overflows in the
 // protocol buffers implementation, as well as to prevent servers from
 // allocating enormous amounts of memory to hold parsed messages, the
 // maximum message length should be limited to the shortest length that
 // will not harm usability. The theoretical shortest message that could
 // cause integer overflows is 512MB. The default limit is 64MB. Apps
 // should set shorter limits if possible. If warning_threshold is not -1,
 // a warning will be printed to stderr after warning_threshold bytes are
 // read. For backwards compatibility all negative values get squashed to -1,
 // as other negative values might have special internal meanings.
 // An error will always be printed to stderr if the limit is reached.
 //
 // This is unrelated to PushLimit()/PopLimit().
 //
 // Hint: If you are reading this because your program is printing a
 // warning about dangerously large protocol messages, you may be
 // confused about what to do next. The best option is to change your
 // design such that excessively large messages are not necessary.
 // For example, try to design file formats to consist of many small
 // messages rather than a single large one. If this is infeasible,
 // you will need to increase the limit. Chances are, though, that
 // your code never constructs a CodedInputStream on which the limit
 // can be set. You probably parse messages by calling things like
 // Message::ParseFromString(). In this case, you will need to change
 // your code to instead construct some sort of ZeroCopyInputStream
 // (e.g. an ArrayInputStream), construct a CodedInputStream around
 // that, then call Message::ParseFromCodedStream() instead. Then
 // you can adjust the limit. Yes, it's more work, but you're doing
 // something unusual.
 void SetTotalBytesLimit(int total_bytes_limit, int warning_threshold);

 // The Total Bytes Limit minus the Current Position, or -1 if there
 // is no Total Bytes Limit.
 int BytesUntilTotalBytesLimit() const;

 // Recursion Limit -------------------------------------------------
 // To prevent corrupt or malicious messages from causing stack overflows,
 // we must keep track of the depth of recursion when parsing embedded
 // messages and groups. CodedInputStream keeps track of this because it
 // is the only object that is passed down the stack during parsing.

 // Sets the maximum recursion depth. The default is 100.
 void SetRecursionLimit(int limit);


 // Increments the current recursion depth. Returns true if the depth is
 // under the limit, false if it has gone over.
 bool IncrementRecursionDepth();

 // Decrements the recursion depth.
 void DecrementRecursionDepth();

 // Extension Registry ----------------------------------------------
 // ADVANCED USAGE: 99.9% of people can ignore this section.
 //
 // By default, when parsing extensions, the parser looks for extension
 // definitions in the pool which owns the outer message's Descriptor.
 // However, you may call SetExtensionRegistry() to provide an alternative
 // pool instead. This makes it possible, for example, to parse a message
 // using a generated class, but represent some extensions using
 // DynamicMessage.

 // Set the pool used to look up extensions. Most users do not need to call
 // this as the correct pool will be chosen automatically.
 //
 // WARNING: It is very easy to misuse this. Carefully read the requirements
 // below. Do not use this unless you are sure you need it. Almost no one
 // does.
 //
 // Let's say you are parsing a message into message object m, and you want
 // to take advantage of SetExtensionRegistry(). You must follow these
 // requirements:
 //
 // The given DescriptorPool must contain m->GetDescriptor(). It is not
 // sufficient for it to simply contain a descriptor that has the same name
 // and content -- it must be the *exact object*. In other words:
 // assert(pool->FindMessageTypeByName(m->GetDescriptor()->full_name()) ==
 // m->GetDescriptor());
 // There are two ways to satisfy this requirement:
 // 1) Use m->GetDescriptor()->pool() as the pool. This is generally useless
 // because this is the pool that would be used anyway if you didn't call
 // SetExtensionRegistry() at all.
 // 2) Use a DescriptorPool which has m->GetDescriptor()->pool() as an
 // "underlay". Read the documentation for DescriptorPool for more
 // information about underlays.
 //
 // You must also provide a MessageFactory. This factory will be used to
 // construct Message objects representing extensions. The factory's
 // GetPrototype() MUST return non-NULL for any Descriptor which can be found
 // through the provided pool.
 //
 // If the provided factory might return instances of protocol-compiler-
 // generated (i.e. compiled-in) types, or if the outer message object m is
 // a generated type, then the given factory MUST have this property: If
 // GetPrototype() is given a Descriptor which resides in
 // DescriptorPool::generated_pool(), the factory MUST return the same
 // prototype which MessageFactory::generated_factory() would return. That
 // is, given a descriptor for a generated type, the factory must return an
 // instance of the generated class (NOT DynamicMessage). However, when
 // given a descriptor for a type that is NOT in generated_pool, the factory
 // is free to return any implementation.
 //
 // The reason for this requirement is that generated sub-objects may be
 // accessed via the standard (non-reflection) extension accessor methods,
 // and these methods will down-cast the object to the generated class type.
 // If the object is not actually of that type, the results would be undefined.
 // On the other hand, if an extension is not compiled in, then there is no
 // way the code could end up accessing it via the standard accessors -- the
 // only way to access the extension is via reflection. When using reflection,
 // DynamicMessage and generated messages are indistinguishable, so it's fine
 // if these objects are represented using DynamicMessage.
 //
 // Using DynamicMessageFactory on which you have called
 // SetDelegateToGeneratedFactory(true) should be sufficient to satisfy the
 // above requirement.
 //
 // If either pool or factory is NULL, both must be NULL.
 //
 // Note that this feature is ignored when parsing "lite" messages as they do
 // not have descriptors.
 void SetExtensionRegistry(const DescriptorPool* pool,
 MessageFactory* factory);

 // Get the DescriptorPool set via SetExtensionRegistry(), or NULL if no pool
 // has been provided.
 const DescriptorPool* GetExtensionPool();

 // Get the MessageFactory set via SetExtensionRegistry(), or NULL if no
 // factory has been provided.
 MessageFactory* GetExtensionFactory();

 private:
 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CodedInputStream);

 ZeroCopyInputStream* input_;
 const uint8* buffer_;
 const uint8* buffer_end_; // pointer to the end of the buffer.
 int total_bytes_read_; // total bytes read from input_, including
 // the current buffer

 // If total_bytes_read_ surpasses INT_MAX, we record the extra bytes here
 // so that we can BackUp() on destruction.
 int overflow_bytes_;

 // LastTagWas() stuff.
 uint32 last_tag_; // result of last ReadTag() or ReadTagWithCutoff().

 // This is set true by ReadTag{Fallback/Slow}() if it is called when exactly
 // at EOF, or by ExpectAtEnd() when it returns true. This happens when we
 // reach the end of a message and attempt to read another tag.
 bool legitimate_message_end_;

 // See EnableAliasing().
 bool aliasing_enabled_;

 // Limits
 Limit current_limit_; // if position = -1, no limit is applied

 // For simplicity, if the current buffer crosses a limit (either a normal
 // limit created by PushLimit() or the total bytes limit), buffer_size_
 // only tracks the number of bytes before that limit. This field
 // contains the number of bytes after it. Note that this implies that if
 // buffer_size_ == 0 and buffer_size_after_limit_ > 0, we know we've
 // hit a limit. However, if both are zero, it doesn't necessarily mean
 // we aren't at a limit -- the buffer may have ended exactly at the limit.
 int buffer_size_after_limit_;

 // Maximum number of bytes to read, period. This is unrelated to
 // current_limit_. Set using SetTotalBytesLimit().
 int total_bytes_limit_;

 // If positive/0: Limit for bytes read after which a warning due to size
 // should be logged.
 // If -1: Printing of warning disabled. Can be set by client.
 // If -2: Internal: Limit has been reached, print full size when destructing.
 int total_bytes_warning_threshold_;

 // Current recursion depth, controlled by IncrementRecursionDepth() and
 // DecrementRecursionDepth().
 int recursion_depth_;
 // Recursion depth limit, set by SetRecursionLimit().
 int recursion_limit_;

 // See SetExtensionRegistry().
 const DescriptorPool* extension_pool_;
 MessageFactory* extension_factory_;

 // Private member functions.

 // Advance the buffer by a given number of bytes.
 void Advance(int amount);

 // Back up input_ to the current buffer position.
 void BackUpInputToCurrentPosition();

 // Recomputes the value of buffer_size_after_limit_. Must be called after
 // current_limit_ or total_bytes_limit_ changes.
 void RecomputeBufferLimits();

 // Writes an error message saying that we hit total_bytes_limit_.
 void PrintTotalBytesLimitError();

 // Called when the buffer runs out to request more data. Implies an
 // Advance(BufferSize()).
 bool Refresh();

 // When parsing varints, we optimize for the common case of small values, and
 // then optimize for the case when the varint fits within the current buffer
 // piece. The Fallback method is used when we can't use the one-byte
 // optimization. The Slow method is yet another fallback when the buffer is
 // not large enough. Making the slow path out-of-line speeds up the common
 // case by 10-15%. The slow path is fairly uncommon: it only triggers when a
 // message crosses multiple buffers.
 bool ReadVarint32Fallback(uint32* value);
 bool ReadVarint64Fallback(uint64* value);
 bool ReadVarint32Slow(uint32* value);
 bool ReadVarint64Slow(uint64* value);
 bool ReadLittleEndian32Fallback(uint32* value);
 bool ReadLittleEndian64Fallback(uint64* value);
 // Fallback/slow methods for reading tags. These do not update last_tag_,
 // but will set legitimate_message_end_ if we are at the end of the input
 // stream.
 uint32 ReadTagFallback();
 uint32 ReadTagSlow();
 bool ReadStringFallback(string* buffer, int size);

 // Return the size of the buffer.
 int BufferSize() const;

 static const int kDefaultTotalBytesLimit = 64 << 20; // 64MB

 static const int kDefaultTotalBytesWarningThreshold = 32 << 20; // 32MB

 static int default_recursion_limit_; // 100 by default.
};

// Class which encodes and writes binary data which is composed of varint-
// encoded integers and fixed-width pieces. Wraps a ZeroCopyOutputStream.
// Most users will not need to deal with CodedOutputStream.
//
// Most methods of CodedOutputStream which return a bool return false if an
// underlying I/O error occurs. Once such a failure occurs, the
// CodedOutputStream is broken and is no longer useful. The Write* methods do
// not return the stream status, but will invalidate the stream if an error
// occurs. The client can probe HadError() to determine the status.
//
// Note that every method of CodedOutputStream which writes some data has
// a corresponding static "ToArray" version. These versions write directly
// to the provided buffer, returning a pointer past the last written byte.
// They require that the buffer has sufficient capacity for the encoded data.
// This allows an optimization where we check if an output stream has enough
// space for an entire message before we start writing and, if there is, we
// call only the ToArray methods to avoid doing bound checks for each
// individual value.
// i.e., in the example above:
//
// CodedOutputStream coded_output = new CodedOutputStream(raw_output);
// int magic_number = 1234;
// char text[] = "Hello world!";
//
// int coded_size = sizeof(magic_number) +
// CodedOutputStream::VarintSize32(strlen(text)) +
// strlen(text);
//
// uint8* buffer =
// coded_output->GetDirectBufferForNBytesAndAdvance(coded_size);
// if (buffer != NULL) {
// // The output stream has enough space in the buffer: write directly to
// // the array.
// buffer = CodedOutputStream::WriteLittleEndian32ToArray(magic_number,
// buffer);
// buffer = CodedOutputStream::WriteVarint32ToArray(strlen(text), buffer);
// buffer = CodedOutputStream::WriteRawToArray(text, strlen(text), buffer);
// } else {
// // Make bound-checked writes, which will ask the underlying stream for
// // more space as needed.
// coded_output->WriteLittleEndian32(magic_number);
// coded_output->WriteVarint32(strlen(text));
// coded_output->WriteRaw(text, strlen(text));
// }
//
// delete coded_output;
class LIBPROTOBUF_EXPORT CodedOutputStream {
 public:
 // Create an CodedOutputStream that writes to the given ZeroCopyOutputStream.
 explicit CodedOutputStream(ZeroCopyOutputStream* output);

 // Destroy the CodedOutputStream and position the underlying
 // ZeroCopyOutputStream immediately after the last byte written.
 ~CodedOutputStream();

 // Skips a number of bytes, leaving the bytes unmodified in the underlying
 // buffer. Returns false if an underlying write error occurs. This is
 // mainly useful with GetDirectBufferPointer().
 bool Skip(int count);

 // Sets *data to point directly at the unwritten part of the
 // CodedOutputStream's underlying buffer, and *size to the size of that
 // buffer, but does not advance the stream's current position. This will
 // always either produce a non-empty buffer or return false. If the caller
 // writes any data to this buffer, it should then call Skip() to skip over
 // the consumed bytes. This may be useful for implementing external fast
 // serialization routines for types of data not covered by the
 // CodedOutputStream interface.
 bool GetDirectBufferPointer(void** data, int* size);

 // If there are at least "size" bytes available in the current buffer,
 // returns a pointer directly into the buffer and advances over these bytes.
 // The caller may then write directly into this buffer (e.g. using the
 // *ToArray static methods) rather than go through CodedOutputStream. If
 // there are not enough bytes available, returns NULL. The return pointer is
 // invalidated as soon as any other non-const method of CodedOutputStream
 // is called.
 inline uint8* GetDirectBufferForNBytesAndAdvance(int size);

 // Write raw bytes, copying them from the given buffer.
 void WriteRaw(const void* buffer, int size);
 // Like WriteRaw() but will try to write aliased data if aliasing is
 // turned on.
 void WriteRawMaybeAliased(const void* data, int size);
 // Like WriteRaw() but writing directly to the target array.
 // This is _not_ inlined, as the compiler often optimizes memcpy into inline
 // copy loops. Since this gets called by every field with string or bytes
 // type, inlining may lead to a significant amount of code bloat, with only a
 // minor performance gain.
 static uint8* WriteRawToArray(const void* buffer, int size, uint8* target);

 // Equivalent to WriteRaw(str.data(), str.size()).
 void WriteString(const string& str);
 // Like WriteString() but writing directly to the target array.
 static uint8* WriteStringToArray(const string& str, uint8* target);
 // Write the varint-encoded size of str followed by str.
 static uint8* WriteStringWithSizeToArray(const string& str, uint8* target);


 // Instructs the CodedOutputStream to allow the underlying
 // ZeroCopyOutputStream to hold pointers to the original structure instead of
 // copying, if it supports it (i.e. output->AllowsAliasing() is true). If the
 // underlying stream does not support aliasing, then enabling it has no
 // affect. For now, this only affects the behavior of
 // WriteRawMaybeAliased().
 //
 // NOTE: It is caller's responsibility to ensure that the chunk of memory
 // remains live until all of the data has been consumed from the stream.
 void EnableAliasing(bool enabled);

 // Write a 32-bit little-endian integer.
 void WriteLittleEndian32(uint32 value);
 // Like WriteLittleEndian32() but writing directly to the target array.
 static uint8* WriteLittleEndian32ToArray(uint32 value, uint8* target);
 // Write a 64-bit little-endian integer.
 void WriteLittleEndian64(uint64 value);
 // Like WriteLittleEndian64() but writing directly to the target array.
 static uint8* WriteLittleEndian64ToArray(uint64 value, uint8* target);

 // Write an unsigned integer with Varint encoding. Writing a 32-bit value
 // is equivalent to casting it to uint64 and writing it as a 64-bit value,
 // but may be more efficient.
 void WriteVarint32(uint32 value);
 // Like WriteVarint32() but writing directly to the target array.
 static uint8* WriteVarint32ToArray(uint32 value, uint8* target);
 // Write an unsigned integer with Varint encoding.
 void WriteVarint64(uint64 value);
 // Like WriteVarint64() but writing directly to the target array.
 static uint8* WriteVarint64ToArray(uint64 value, uint8* target);

 // Equivalent to WriteVarint32() except when the value is negative,
 // in which case it must be sign-extended to a full 10 bytes.
 void WriteVarint32SignExtended(int32 value);
 // Like WriteVarint32SignExtended() but writing directly to the target array.
 static uint8* WriteVarint32SignExtendedToArray(int32 value, uint8* target);

 // This is identical to WriteVarint32(), but optimized for writing tags.
 // In particular, if the input is a compile-time constant, this method
 // compiles down to a couple instructions.
 // Always inline because otherwise the aformentioned optimization can't work,
 // but GCC by default doesn't want to inline this.
 void WriteTag(uint32 value);
 // Like WriteTag() but writing directly to the target array.
 static uint8* WriteTagToArray(
 uint32 value, uint8* target) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 // Returns the number of bytes needed to encode the given value as a varint.
 static int VarintSize32(uint32 value);
 // Returns the number of bytes needed to encode the given value as a varint.
 static int VarintSize64(uint64 value);

 // If negative, 10 bytes. Otheriwse, same as VarintSize32().
 static int VarintSize32SignExtended(int32 value);

 // Compile-time equivalent of VarintSize32().
 template <uint32 Value>
 struct StaticVarintSize32 {
 static const int value =
 (Value < (1 << 7))
 ? 1
 : (Value < (1 << 14))
 ? 2
 : (Value < (1 << 21))
 ? 3
 : (Value < (1 << 28))
 ? 4
 : 5;
 };

 // Returns the total number of bytes written since this object was created.
 inline int ByteCount() const;

 // Returns true if there was an underlying I/O error since this object was
 // created.
 bool HadError() const { return had_error_; }

 private:
 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CodedOutputStream);

 ZeroCopyOutputStream* output_;
 uint8* buffer_;
 int buffer_size_;
 int total_bytes_; // Sum of sizes of all buffers seen so far.
 bool had_error_; // Whether an error occurred during output.
 bool aliasing_enabled_; // See EnableAliasing().

 // Advance the buffer by a given number of bytes.
 void Advance(int amount);

 // Called when the buffer runs out to request more data. Implies an
 // Advance(buffer_size_).
 bool Refresh();

 // Like WriteRaw() but may avoid copying if the underlying
 // ZeroCopyOutputStream supports it.
 void WriteAliasedRaw(const void* buffer, int size);

 static uint8* WriteVarint32FallbackToArray(uint32 value, uint8* target);

 // Always-inlined versions of WriteVarint* functions so that code can be
 // reused, while still controlling size. For instance, WriteVarint32ToArray()
 // should not directly call this: since it is inlined itself, doing so
 // would greatly increase the size of generated code. Instead, it should call
 // WriteVarint32FallbackToArray. Meanwhile, WriteVarint32() is already
 // out-of-line, so it should just invoke this directly to avoid any extra
 // function call overhead.
 static uint8* WriteVarint32FallbackToArrayInline(
 uint32 value, uint8* target) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
 static uint8* WriteVarint64ToArrayInline(
 uint64 value, uint8* target) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;

 static int VarintSize32Fallback(uint32 value);
};

// inline methods ====================================================
// The vast majority of varints are only one byte. These inline
// methods optimize for that case.

inline bool CodedInputStream::ReadVarint32(uint32* value) {
 if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_) && *buffer_ < 0x80) {
 *value = *buffer_;
 Advance(1);
 return true;
 } else {
 return ReadVarint32Fallback(value);
 }
}

inline bool CodedInputStream::ReadVarint64(uint64* value) {
 if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_) && *buffer_ < 0x80) {
 *value = *buffer_;
 Advance(1);
 return true;
 } else {
 return ReadVarint64Fallback(value);
 }
}

// static
inline const uint8* CodedInputStream::ReadLittleEndian32FromArray(
 const uint8* buffer,
 uint32* value) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 memcpy(value, buffer, sizeof(*value));
 return buffer + sizeof(*value);
#else
 *value = (static_cast<uint32>(buffer[0]) ) |
 (static_cast<uint32>(buffer[1]) << 8) |
 (static_cast<uint32>(buffer[2]) << 16) |
 (static_cast<uint32>(buffer[3]) << 24);
 return buffer + sizeof(*value);
#endif
}
// static
inline const uint8* CodedInputStream::ReadLittleEndian64FromArray(
 const uint8* buffer,
 uint64* value) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 memcpy(value, buffer, sizeof(*value));
 return buffer + sizeof(*value);
#else
 uint32 part0 = (static_cast<uint32>(buffer[0]) ) |
 (static_cast<uint32>(buffer[1]) << 8) |
 (static_cast<uint32>(buffer[2]) << 16) |
 (static_cast<uint32>(buffer[3]) << 24);
 uint32 part1 = (static_cast<uint32>(buffer[4]) ) |
 (static_cast<uint32>(buffer[5]) << 8) |
 (static_cast<uint32>(buffer[6]) << 16) |
 (static_cast<uint32>(buffer[7]) << 24);
 *value = static_cast<uint64>(part0) |
 (static_cast<uint64>(part1) << 32);
 return buffer + sizeof(*value);
#endif
}

inline bool CodedInputStream::ReadLittleEndian32(uint32* value) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 if (GOOGLE_PREDICT_TRUE(BufferSize() >= static_cast<int>(sizeof(*value)))) {
 memcpy(value, buffer_, sizeof(*value));
 Advance(sizeof(*value));
 return true;
 } else {
 return ReadLittleEndian32Fallback(value);
 }
#else
 return ReadLittleEndian32Fallback(value);
#endif
}

inline bool CodedInputStream::ReadLittleEndian64(uint64* value) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 if (GOOGLE_PREDICT_TRUE(BufferSize() >= static_cast<int>(sizeof(*value)))) {
 memcpy(value, buffer_, sizeof(*value));
 Advance(sizeof(*value));
 return true;
 } else {
 return ReadLittleEndian64Fallback(value);
 }
#else
 return ReadLittleEndian64Fallback(value);
#endif
}

inline uint32 CodedInputStream::ReadTag() {
 if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_) && buffer_[0] < 0x80) {
 last_tag_ = buffer_[0];
 Advance(1);
 return last_tag_;
 } else {
 last_tag_ = ReadTagFallback();
 return last_tag_;
 }
}

inline std::pair<uint32, bool> CodedInputStream::ReadTagWithCutoff(
 uint32 cutoff) {
 // In performance-sensitive code we can expect cutoff to be a compile-time
 // constant, and things like "cutoff >= kMax1ByteVarint" to be evaluated at
 // compile time.
 if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_)) {
 // Hot case: buffer_ non_empty, buffer_[0] in [1, 128).
 // TODO(gpike): Is it worth rearranging this? E.g., if the number of fields
 // is large enough then is it better to check for the two-byte case first?
 if (static_cast<int8>(buffer_[0]) > 0) {
 const uint32 kMax1ByteVarint = 0x7f;
 uint32 tag = last_tag_ = buffer_[0];
 Advance(1);
 return make_pair(tag, cutoff >= kMax1ByteVarint || tag <= cutoff);
 }
 // Other hot case: cutoff >= 0x80, buffer_ has at least two bytes available,
 // and tag is two bytes. The latter is tested by bitwise-and-not of the
 // first byte and the second byte.
 if (cutoff >= 0x80 &&
 GOOGLE_PREDICT_TRUE(buffer_ + 1 < buffer_end_) &&
 GOOGLE_PREDICT_TRUE((buffer_[0] & ~buffer_[1]) >= 0x80)) {
 const uint32 kMax2ByteVarint = (0x7f << 7) + 0x7f;
 uint32 tag = last_tag_ = (1u << 7) * buffer_[1] + (buffer_[0] - 0x80);
 Advance(2);
 // It might make sense to test for tag == 0 now, but it is so rare that
 // that we don't bother. A varint-encoded 0 should be one byte unless
 // the encoder lost its mind. The second part of the return value of
 // this function is allowed to be either true or false if the tag is 0,
 // so we don't have to check for tag == 0. We may need to check whether
 // it exceeds cutoff.
 bool at_or_below_cutoff = cutoff >= kMax2ByteVarint || tag <= cutoff;
 return make_pair(tag, at_or_below_cutoff);
 }
 }
 // Slow path
 last_tag_ = ReadTagFallback();
 return make_pair(last_tag_, static_cast<uint32>(last_tag_ - 1) < cutoff);
}

inline bool CodedInputStream::LastTagWas(uint32 expected) {
 return last_tag_ == expected;
}

inline bool CodedInputStream::ConsumedEntireMessage() {
 return legitimate_message_end_;
}

inline bool CodedInputStream::ExpectTag(uint32 expected) {
 if (expected < (1 << 7)) {
 if (GOOGLE_PREDICT_TRUE(buffer_ < buffer_end_) && buffer_[0] == expected) {
 Advance(1);
 return true;
 } else {
 return false;
 }
 } else if (expected < (1 << 14)) {
 if (GOOGLE_PREDICT_TRUE(BufferSize() >= 2) &&
 buffer_[0] == static_cast<uint8>(expected | 0x80) &&
 buffer_[1] == static_cast<uint8>(expected >> 7)) {
 Advance(2);
 return true;
 } else {
 return false;
 }
 } else {
 // Don't bother optimizing for larger values.
 return false;
 }
}

inline const uint8* CodedInputStream::ExpectTagFromArray(
 const uint8* buffer, uint32 expected) {
 if (expected < (1 << 7)) {
 if (buffer[0] == expected) {
 return buffer + 1;
 }
 } else if (expected < (1 << 14)) {
 if (buffer[0] == static_cast<uint8>(expected | 0x80) &&
 buffer[1] == static_cast<uint8>(expected >> 7)) {
 return buffer + 2;
 }
 }
 return NULL;
}

inline void CodedInputStream::GetDirectBufferPointerInline(const void** data,
 int* size) {
 *data = buffer_;
 *size = buffer_end_ - buffer_;
}

inline bool CodedInputStream::ExpectAtEnd() {
 // If we are at a limit we know no more bytes can be read. Otherwise, it's
 // hard to say without calling Refresh(), and we'd rather not do that.

 if (buffer_ == buffer_end_ &&
 ((buffer_size_after_limit_ != 0) ||
 (total_bytes_read_ == current_limit_))) {
 last_tag_ = 0; // Pretend we called ReadTag()...
 legitimate_message_end_ = true; // ... and it hit EOF.
 return true;
 } else {
 return false;
 }
}

inline int CodedInputStream::CurrentPosition() const {
 return total_bytes_read_ - (BufferSize() + buffer_size_after_limit_);
}

inline uint8* CodedOutputStream::GetDirectBufferForNBytesAndAdvance(int size) {
 if (buffer_size_ < size) {
 return NULL;
 } else {
 uint8* result = buffer_;
 Advance(size);
 return result;
 }
}

inline uint8* CodedOutputStream::WriteVarint32ToArray(uint32 value,
 uint8* target) {
 if (value < 0x80) {
 *target = value;
 return target + 1;
 } else {
 return WriteVarint32FallbackToArray(value, target);
 }
}

inline void CodedOutputStream::WriteVarint32SignExtended(int32 value) {
 if (value < 0) {
 WriteVarint64(static_cast<uint64>(value));
 } else {
 WriteVarint32(static_cast<uint32>(value));
 }
}

inline uint8* CodedOutputStream::WriteVarint32SignExtendedToArray(
 int32 value, uint8* target) {
 if (value < 0) {
 return WriteVarint64ToArray(static_cast<uint64>(value), target);
 } else {
 return WriteVarint32ToArray(static_cast<uint32>(value), target);
 }
}

inline uint8* CodedOutputStream::WriteLittleEndian32ToArray(uint32 value,
 uint8* target) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 memcpy(target, &value, sizeof(value));
#else
 target[0] = static_cast<uint8>(value);
 target[1] = static_cast<uint8>(value >> 8);
 target[2] = static_cast<uint8>(value >> 16);
 target[3] = static_cast<uint8>(value >> 24);
#endif
 return target + sizeof(value);
}

inline uint8* CodedOutputStream::WriteLittleEndian64ToArray(uint64 value,
 uint8* target) {
#if defined(PROTOBUF_LITTLE_ENDIAN)
 memcpy(target, &value, sizeof(value));
#else
 uint32 part0 = static_cast<uint32>(value);
 uint32 part1 = static_cast<uint32>(value >> 32);

 target[0] = static_cast<uint8>(part0);
 target[1] = static_cast<uint8>(part0 >> 8);
 target[2] = static_cast<uint8>(part0 >> 16);
 target[3] = static_cast<uint8>(part0 >> 24);
 target[4] = static_cast<uint8>(part1);
 target[5] = static_cast<uint8>(part1 >> 8);
 target[6] = static_cast<uint8>(part1 >> 16);
 target[7] = static_cast<uint8>(part1 >> 24);
#endif
 return target + sizeof(value);
}

inline void CodedOutputStream::WriteTag(uint32 value) {
 WriteVarint32(value);
}

inline uint8* CodedOutputStream::WriteTagToArray(
 uint32 value, uint8* target) {
 if (value < (1 << 7)) {
 target[0] = value;
 return target + 1;
 } else if (value < (1 << 14)) {
 target[0] = static_cast<uint8>(value | 0x80);
 target[1] = static_cast<uint8>(value >> 7);
 return target + 2;
 } else {
 return WriteVarint32FallbackToArray(value, target);
 }
}

inline int CodedOutputStream::VarintSize32(uint32 value) {
 if (value < (1 << 7)) {
 return 1;
 } else {
 return VarintSize32Fallback(value);
 }
}

inline int CodedOutputStream::VarintSize32SignExtended(int32 value) {
 if (value < 0) {
 return 10; // TODO(kenton): Make this a symbolic constant.
 } else {
 return VarintSize32(static_cast<uint32>(value));
 }
}

inline void CodedOutputStream::WriteString(const string& str) {
 WriteRaw(str.data(), static_cast<int>(str.size()));
}

inline void CodedOutputStream::WriteRawMaybeAliased(
 const void* data, int size) {
 if (aliasing_enabled_) {
 WriteAliasedRaw(data, size);
 } else {
 WriteRaw(data, size);
 }
}

inline uint8* CodedOutputStream::WriteStringToArray(
 const string& str, uint8* target) {
 return WriteRawToArray(str.data(), static_cast<int>(str.size()), target);
}

inline int CodedOutputStream::ByteCount() const {
 return total_bytes_ - buffer_size_;
}

inline void CodedInputStream::Advance(int amount) {
 buffer_ += amount;
}

inline void CodedOutputStream::Advance(int amount) {
 buffer_ += amount;
 buffer_size_ -= amount;
}

inline void CodedInputStream::SetRecursionLimit(int limit) {
 recursion_limit_ = limit;
}

inline bool CodedInputStream::IncrementRecursionDepth() {
 ++recursion_depth_;
 return recursion_depth_ <= recursion_limit_;
}

inline void CodedInputStream::DecrementRecursionDepth() {
 if (recursion_depth_ > 0) --recursion_depth_;
}

inline void CodedInputStream::SetExtensionRegistry(const DescriptorPool* pool,
 MessageFactory* factory) {
 extension_pool_ = pool;
 extension_factory_ = factory;
}

inline const DescriptorPool* CodedInputStream::GetExtensionPool() {
 return extension_pool_;
}

inline MessageFactory* CodedInputStream::GetExtensionFactory() {
 return extension_factory_;
}

inline int CodedInputStream::BufferSize() const {
 return buffer_end_ - buffer_;
}

inline CodedInputStream::CodedInputStream(ZeroCopyInputStream* input)
 : input_(input),
 buffer_(NULL),
 buffer_end_(NULL),
 total_bytes_read_(0),
 overflow_bytes_(0),
 last_tag_(0),
 legitimate_message_end_(false),
 aliasing_enabled_(false),
 current_limit_(kint32max),
 buffer_size_after_limit_(0),
 total_bytes_limit_(kDefaultTotalBytesLimit),
 total_bytes_warning_threshold_(kDefaultTotalBytesWarningThreshold),
 recursion_depth_(0),
 recursion_limit_(default_recursion_limit_),
 extension_pool_(NULL),
 extension_factory_(NULL) {
 // Eagerly Refresh() so buffer space is immediately available.
 Refresh();
}

inline CodedInputStream::CodedInputStream(const uint8* buffer, int size)
 : input_(NULL),
 buffer_(buffer),
 buffer_end_(buffer + size),
 total_bytes_read_(size),
 overflow_bytes_(0),
 last_tag_(0),
 legitimate_message_end_(false),
 aliasing_enabled_(false),
 current_limit_(size),
 buffer_size_after_limit_(0),
 total_bytes_limit_(kDefaultTotalBytesLimit),
 total_bytes_warning_threshold_(kDefaultTotalBytesWarningThreshold),
 recursion_depth_(0),
 recursion_limit_(default_recursion_limit_),
 extension_pool_(NULL),
 extension_factory_(NULL) {
 // Note that setting current_limit_ == size is important to prevent some
 // code paths from trying to access input_ and segfaulting.
}

inline bool CodedInputStream::IsFlat() const {
 return input_ == NULL;
}

} // namespace io
} // namespace protobuf


#if defined(_MSC_VER) && _MSC_VER >= 1300
 #pragma runtime_checks("c", restore)
#endif // _MSC_VER

} // namespace google
#endif // GOOGLE_PROTOBUF_IO_CODED_STREAM_H__