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acl/include/google/protobuf/wire_format_lite.h

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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
// 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: kenton@google.com (Kenton Varda)
// atenasio@google.com (Chris Atenasio) (ZigZag transform)
// wink@google.com (Wink Saville) (refactored from wire_format.h)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// This header is logically internal, but is made public because it is used
// from protocol-compiler-generated code, which may reside in other components.
#ifndef GOOGLE_PROTOBUF_WIRE_FORMAT_LITE_H__
#define GOOGLE_PROTOBUF_WIRE_FORMAT_LITE_H__
#include <string>
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/message_lite.h>
#include <google/protobuf/io/coded_stream.h> // for CodedOutputStream::Varint32Size
namespace google {
namespace protobuf {
template <typename T> class RepeatedField; // repeated_field.h
}
namespace protobuf {
namespace internal {
class StringPieceField;
// This class is for internal use by the protocol buffer library and by
// protocol-complier-generated message classes. It must not be called
// directly by clients.
//
// This class contains helpers for implementing the binary protocol buffer
// wire format without the need for reflection. Use WireFormat when using
// reflection.
//
// This class is really a namespace that contains only static methods.
class LIBPROTOBUF_EXPORT WireFormatLite {
public:
// -----------------------------------------------------------------
// Helper constants and functions related to the format. These are
// mostly meant for internal and generated code to use.
// The wire format is composed of a sequence of tag/value pairs, each
// of which contains the value of one field (or one element of a repeated
// field). Each tag is encoded as a varint. The lower bits of the tag
// identify its wire type, which specifies the format of the data to follow.
// The rest of the bits contain the field number. Each type of field (as
// declared by FieldDescriptor::Type, in descriptor.h) maps to one of
// these wire types. Immediately following each tag is the field's value,
// encoded in the format specified by the wire type. Because the tag
// identifies the encoding of this data, it is possible to skip
// unrecognized fields for forwards compatibility.
enum WireType {
WIRETYPE_VARINT = 0,
WIRETYPE_FIXED64 = 1,
WIRETYPE_LENGTH_DELIMITED = 2,
WIRETYPE_START_GROUP = 3,
WIRETYPE_END_GROUP = 4,
WIRETYPE_FIXED32 = 5,
};
// Lite alternative to FieldDescriptor::Type. Must be kept in sync.
enum FieldType {
TYPE_DOUBLE = 1,
TYPE_FLOAT = 2,
TYPE_INT64 = 3,
TYPE_UINT64 = 4,
TYPE_INT32 = 5,
TYPE_FIXED64 = 6,
TYPE_FIXED32 = 7,
TYPE_BOOL = 8,
TYPE_STRING = 9,
TYPE_GROUP = 10,
TYPE_MESSAGE = 11,
TYPE_BYTES = 12,
TYPE_UINT32 = 13,
TYPE_ENUM = 14,
TYPE_SFIXED32 = 15,
TYPE_SFIXED64 = 16,
TYPE_SINT32 = 17,
TYPE_SINT64 = 18,
MAX_FIELD_TYPE = 18,
};
// Lite alternative to FieldDescriptor::CppType. Must be kept in sync.
enum CppType {
CPPTYPE_INT32 = 1,
CPPTYPE_INT64 = 2,
CPPTYPE_UINT32 = 3,
CPPTYPE_UINT64 = 4,
CPPTYPE_DOUBLE = 5,
CPPTYPE_FLOAT = 6,
CPPTYPE_BOOL = 7,
CPPTYPE_ENUM = 8,
CPPTYPE_STRING = 9,
CPPTYPE_MESSAGE = 10,
MAX_CPPTYPE = 10,
};
// Helper method to get the CppType for a particular Type.
static CppType FieldTypeToCppType(FieldType type);
// Given a FieldSescriptor::Type return its WireType
static inline WireFormatLite::WireType WireTypeForFieldType(
WireFormatLite::FieldType type) {
return kWireTypeForFieldType[type];
}
// Number of bits in a tag which identify the wire type.
static const int kTagTypeBits = 3;
// Mask for those bits.
static const uint32 kTagTypeMask = (1 << kTagTypeBits) - 1;
// Helper functions for encoding and decoding tags. (Inlined below and in
// _inl.h)
//
// This is different from MakeTag(field->number(), field->type()) in the case
// of packed repeated fields.
static uint32 MakeTag(int field_number, WireType type);
static WireType GetTagWireType(uint32 tag);
static int GetTagFieldNumber(uint32 tag);
// Compute the byte size of a tag. For groups, this includes both the start
// and end tags.
static inline int TagSize(int field_number, WireFormatLite::FieldType type);
// Skips a field value with the given tag. The input should start
// positioned immediately after the tag. Skipped values are simply discarded,
// not recorded anywhere. See WireFormat::SkipField() for a version that
// records to an UnknownFieldSet.
static bool SkipField(io::CodedInputStream* input, uint32 tag);
// Skips a field value with the given tag. The input should start
// positioned immediately after the tag. Skipped values are recorded to a
// CodedOutputStream.
static bool SkipField(io::CodedInputStream* input, uint32 tag,
io::CodedOutputStream* output);
// Reads and ignores a message from the input. Skipped values are simply
// discarded, not recorded anywhere. See WireFormat::SkipMessage() for a
// version that records to an UnknownFieldSet.
static bool SkipMessage(io::CodedInputStream* input);
// Reads and ignores a message from the input. Skipped values are recorded
// to a CodedOutputStream.
static bool SkipMessage(io::CodedInputStream* input,
io::CodedOutputStream* output);
// This macro does the same thing as WireFormatLite::MakeTag(), but the
// result is usable as a compile-time constant, which makes it usable
// as a switch case or a template input. WireFormatLite::MakeTag() is more
// type-safe, though, so prefer it if possible.
#define GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(FIELD_NUMBER, TYPE) \
static_cast<uint32>( \
((FIELD_NUMBER) << ::google::protobuf::internal::WireFormatLite::kTagTypeBits) \
| (TYPE))
// These are the tags for the old MessageSet format, which was defined as:
// message MessageSet {
// repeated group Item = 1 {
// required int32 type_id = 2;
// required string message = 3;
// }
// }
static const int kMessageSetItemNumber = 1;
static const int kMessageSetTypeIdNumber = 2;
static const int kMessageSetMessageNumber = 3;
static const int kMessageSetItemStartTag =
GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(kMessageSetItemNumber,
WireFormatLite::WIRETYPE_START_GROUP);
static const int kMessageSetItemEndTag =
GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(kMessageSetItemNumber,
WireFormatLite::WIRETYPE_END_GROUP);
static const int kMessageSetTypeIdTag =
GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(kMessageSetTypeIdNumber,
WireFormatLite::WIRETYPE_VARINT);
static const int kMessageSetMessageTag =
GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(kMessageSetMessageNumber,
WireFormatLite::WIRETYPE_LENGTH_DELIMITED);
// Byte size of all tags of a MessageSet::Item combined.
static const int kMessageSetItemTagsSize;
// Helper functions for converting between floats/doubles and IEEE-754
// uint32s/uint64s so that they can be written. (Assumes your platform
// uses IEEE-754 floats.)
static uint32 EncodeFloat(float value);
static float DecodeFloat(uint32 value);
static uint64 EncodeDouble(double value);
static double DecodeDouble(uint64 value);
// Helper functions for mapping signed integers to unsigned integers in
// such a way that numbers with small magnitudes will encode to smaller
// varints. If you simply static_cast a negative number to an unsigned
// number and varint-encode it, it will always take 10 bytes, defeating
// the purpose of varint. So, for the "sint32" and "sint64" field types,
// we ZigZag-encode the values.
static uint32 ZigZagEncode32(int32 n);
static int32 ZigZagDecode32(uint32 n);
static uint64 ZigZagEncode64(int64 n);
static int64 ZigZagDecode64(uint64 n);
// =================================================================
// Methods for reading/writing individual field. The implementations
// of these methods are defined in wire_format_lite_inl.h; you must #include
// that file to use these.
// Avoid ugly line wrapping
#define input io::CodedInputStream* input
#define output io::CodedOutputStream* output
#define field_number int field_number
#define INL GOOGLE_ATTRIBUTE_ALWAYS_INLINE
// Read fields, not including tags. The assumption is that you already
// read the tag to determine what field to read.
// For primitive fields, we just use a templatized routine parameterized by
// the represented type and the FieldType. These are specialized with the
// appropriate definition for each declared type.
template <typename CType, enum FieldType DeclaredType>
static inline bool ReadPrimitive(input, CType* value) INL;
// Reads repeated primitive values, with optimizations for repeats.
// tag_size and tag should both be compile-time constants provided by the
// protocol compiler.
template <typename CType, enum FieldType DeclaredType>
static inline bool ReadRepeatedPrimitive(int tag_size,
uint32 tag,
input,
RepeatedField<CType>* value) INL;
// Identical to ReadRepeatedPrimitive, except will not inline the
// implementation.
template <typename CType, enum FieldType DeclaredType>
static bool ReadRepeatedPrimitiveNoInline(int tag_size,
uint32 tag,
input,
RepeatedField<CType>* value);
// Reads a primitive value directly from the provided buffer. It returns a
// pointer past the segment of data that was read.
//
// This is only implemented for the types with fixed wire size, e.g.
// float, double, and the (s)fixed* types.
template <typename CType, enum FieldType DeclaredType>
static inline const uint8* ReadPrimitiveFromArray(const uint8* buffer,
CType* value) INL;
// Reads a primitive packed field.
//
// This is only implemented for packable types.
template <typename CType, enum FieldType DeclaredType>
static inline bool ReadPackedPrimitive(input,
RepeatedField<CType>* value) INL;
// Identical to ReadPackedPrimitive, except will not inline the
// implementation.
template <typename CType, enum FieldType DeclaredType>
static bool ReadPackedPrimitiveNoInline(input, RepeatedField<CType>* value);
// Read a packed enum field. Values for which is_valid() returns false are
// dropped.
static bool ReadPackedEnumNoInline(input,
bool (*is_valid)(int),
RepeatedField<int>* value);
static bool ReadString(input, string* value);
static bool ReadBytes (input, string* value);
static inline bool ReadGroup (field_number, input, MessageLite* value);
static inline bool ReadMessage(input, MessageLite* value);
// Like above, but de-virtualize the call to MergePartialFromCodedStream().
// The pointer must point at an instance of MessageType, *not* a subclass (or
// the subclass must not override MergePartialFromCodedStream()).
template<typename MessageType>
static inline bool ReadGroupNoVirtual(field_number, input,
MessageType* value);
template<typename MessageType>
static inline bool ReadMessageNoVirtual(input, MessageType* value);
// Write a tag. The Write*() functions typically include the tag, so
// normally there's no need to call this unless using the Write*NoTag()
// variants.
static inline void WriteTag(field_number, WireType type, output) INL;
// Write fields, without tags.
static inline void WriteInt32NoTag (int32 value, output) INL;
static inline void WriteInt64NoTag (int64 value, output) INL;
static inline void WriteUInt32NoTag (uint32 value, output) INL;
static inline void WriteUInt64NoTag (uint64 value, output) INL;
static inline void WriteSInt32NoTag (int32 value, output) INL;
static inline void WriteSInt64NoTag (int64 value, output) INL;
static inline void WriteFixed32NoTag (uint32 value, output) INL;
static inline void WriteFixed64NoTag (uint64 value, output) INL;
static inline void WriteSFixed32NoTag(int32 value, output) INL;
static inline void WriteSFixed64NoTag(int64 value, output) INL;
static inline void WriteFloatNoTag (float value, output) INL;
static inline void WriteDoubleNoTag (double value, output) INL;
static inline void WriteBoolNoTag (bool value, output) INL;
static inline void WriteEnumNoTag (int value, output) INL;
// Write fields, including tags.
static void WriteInt32 (field_number, int32 value, output);
static void WriteInt64 (field_number, int64 value, output);
static void WriteUInt32 (field_number, uint32 value, output);
static void WriteUInt64 (field_number, uint64 value, output);
static void WriteSInt32 (field_number, int32 value, output);
static void WriteSInt64 (field_number, int64 value, output);
static void WriteFixed32 (field_number, uint32 value, output);
static void WriteFixed64 (field_number, uint64 value, output);
static void WriteSFixed32(field_number, int32 value, output);
static void WriteSFixed64(field_number, int64 value, output);
static void WriteFloat (field_number, float value, output);
static void WriteDouble (field_number, double value, output);
static void WriteBool (field_number, bool value, output);
static void WriteEnum (field_number, int value, output);
static void WriteString(field_number, const string& value, output);
static void WriteBytes (field_number, const string& value, output);
static void WriteStringMaybeAliased(
field_number, const string& value, output);
static void WriteBytesMaybeAliased(
field_number, const string& value, output);
static void WriteGroup(
field_number, const MessageLite& value, output);
static void WriteMessage(
field_number, const MessageLite& value, output);
// Like above, but these will check if the output stream has enough
// space to write directly to a flat array.
static void WriteGroupMaybeToArray(
field_number, const MessageLite& value, output);
static void WriteMessageMaybeToArray(
field_number, const MessageLite& value, output);
// Like above, but de-virtualize the call to SerializeWithCachedSizes(). The
// pointer must point at an instance of MessageType, *not* a subclass (or
// the subclass must not override SerializeWithCachedSizes()).
template<typename MessageType>
static inline void WriteGroupNoVirtual(
field_number, const MessageType& value, output);
template<typename MessageType>
static inline void WriteMessageNoVirtual(
field_number, const MessageType& value, output);
#undef output
#define output uint8* target
// Like above, but use only *ToArray methods of CodedOutputStream.
static inline uint8* WriteTagToArray(field_number, WireType type, output) INL;
// Write fields, without tags.
static inline uint8* WriteInt32NoTagToArray (int32 value, output) INL;
static inline uint8* WriteInt64NoTagToArray (int64 value, output) INL;
static inline uint8* WriteUInt32NoTagToArray (uint32 value, output) INL;
static inline uint8* WriteUInt64NoTagToArray (uint64 value, output) INL;
static inline uint8* WriteSInt32NoTagToArray (int32 value, output) INL;
static inline uint8* WriteSInt64NoTagToArray (int64 value, output) INL;
static inline uint8* WriteFixed32NoTagToArray (uint32 value, output) INL;
static inline uint8* WriteFixed64NoTagToArray (uint64 value, output) INL;
static inline uint8* WriteSFixed32NoTagToArray(int32 value, output) INL;
static inline uint8* WriteSFixed64NoTagToArray(int64 value, output) INL;
static inline uint8* WriteFloatNoTagToArray (float value, output) INL;
static inline uint8* WriteDoubleNoTagToArray (double value, output) INL;
static inline uint8* WriteBoolNoTagToArray (bool value, output) INL;
static inline uint8* WriteEnumNoTagToArray (int value, output) INL;
// Write fields, including tags.
static inline uint8* WriteInt32ToArray(
field_number, int32 value, output) INL;
static inline uint8* WriteInt64ToArray(
field_number, int64 value, output) INL;
static inline uint8* WriteUInt32ToArray(
field_number, uint32 value, output) INL;
static inline uint8* WriteUInt64ToArray(
field_number, uint64 value, output) INL;
static inline uint8* WriteSInt32ToArray(
field_number, int32 value, output) INL;
static inline uint8* WriteSInt64ToArray(
field_number, int64 value, output) INL;
static inline uint8* WriteFixed32ToArray(
field_number, uint32 value, output) INL;
static inline uint8* WriteFixed64ToArray(
field_number, uint64 value, output) INL;
static inline uint8* WriteSFixed32ToArray(
field_number, int32 value, output) INL;
static inline uint8* WriteSFixed64ToArray(
field_number, int64 value, output) INL;
static inline uint8* WriteFloatToArray(
field_number, float value, output) INL;
static inline uint8* WriteDoubleToArray(
field_number, double value, output) INL;
static inline uint8* WriteBoolToArray(
field_number, bool value, output) INL;
static inline uint8* WriteEnumToArray(
field_number, int value, output) INL;
static inline uint8* WriteStringToArray(
field_number, const string& value, output) INL;
static inline uint8* WriteBytesToArray(
field_number, const string& value, output) INL;
static inline uint8* WriteGroupToArray(
field_number, const MessageLite& value, output) INL;
static inline uint8* WriteMessageToArray(
field_number, const MessageLite& value, output) INL;
// Like above, but de-virtualize the call to SerializeWithCachedSizes(). The
// pointer must point at an instance of MessageType, *not* a subclass (or
// the subclass must not override SerializeWithCachedSizes()).
template<typename MessageType>
static inline uint8* WriteGroupNoVirtualToArray(
field_number, const MessageType& value, output) INL;
template<typename MessageType>
static inline uint8* WriteMessageNoVirtualToArray(
field_number, const MessageType& value, output) INL;
#undef output
#undef input
#undef INL
#undef field_number
// Compute the byte size of a field. The XxSize() functions do NOT include
// the tag, so you must also call TagSize(). (This is because, for repeated
// fields, you should only call TagSize() once and multiply it by the element
// count, but you may have to call XxSize() for each individual element.)
static inline int Int32Size ( int32 value);
static inline int Int64Size ( int64 value);
static inline int UInt32Size (uint32 value);
static inline int UInt64Size (uint64 value);
static inline int SInt32Size ( int32 value);
static inline int SInt64Size ( int64 value);
static inline int EnumSize ( int value);
// These types always have the same size.
static const int kFixed32Size = 4;
static const int kFixed64Size = 8;
static const int kSFixed32Size = 4;
static const int kSFixed64Size = 8;
static const int kFloatSize = 4;
static const int kDoubleSize = 8;
static const int kBoolSize = 1;
static inline int StringSize(const string& value);
static inline int BytesSize (const string& value);
static inline int GroupSize (const MessageLite& value);
static inline int MessageSize(const MessageLite& value);
// Like above, but de-virtualize the call to ByteSize(). The
// pointer must point at an instance of MessageType, *not* a subclass (or
// the subclass must not override ByteSize()).
template<typename MessageType>
static inline int GroupSizeNoVirtual (const MessageType& value);
template<typename MessageType>
static inline int MessageSizeNoVirtual(const MessageType& value);
// Given the length of data, calculate the byte size of the data on the
// wire if we encode the data as a length delimited field.
static inline int LengthDelimitedSize(int length);
private:
// A helper method for the repeated primitive reader. This method has
// optimizations for primitive types that have fixed size on the wire, and
// can be read using potentially faster paths.
template <typename CType, enum FieldType DeclaredType>
static inline bool ReadRepeatedFixedSizePrimitive(
int tag_size,
uint32 tag,
google::protobuf::io::CodedInputStream* input,
RepeatedField<CType>* value) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
// Like ReadRepeatedFixedSizePrimitive but for packed primitive fields.
template <typename CType, enum FieldType DeclaredType>
static inline bool ReadPackedFixedSizePrimitive(
google::protobuf::io::CodedInputStream* input,
RepeatedField<CType>* value) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
static const CppType kFieldTypeToCppTypeMap[];
static const WireFormatLite::WireType kWireTypeForFieldType[];
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(WireFormatLite);
};
// A class which deals with unknown values. The default implementation just
// discards them. WireFormat defines a subclass which writes to an
// UnknownFieldSet. This class is used by ExtensionSet::ParseField(), since
// ExtensionSet is part of the lite library but UnknownFieldSet is not.
class LIBPROTOBUF_EXPORT FieldSkipper {
public:
FieldSkipper() {}
virtual ~FieldSkipper() {}
// Skip a field whose tag has already been consumed.
virtual bool SkipField(io::CodedInputStream* input, uint32 tag);
// Skip an entire message or group, up to an end-group tag (which is consumed)
// or end-of-stream.
virtual bool SkipMessage(io::CodedInputStream* input);
// Deal with an already-parsed unrecognized enum value. The default
// implementation does nothing, but the UnknownFieldSet-based implementation
// saves it as an unknown varint.
virtual void SkipUnknownEnum(int field_number, int value);
};
// Subclass of FieldSkipper which saves skipped fields to a CodedOutputStream.
class LIBPROTOBUF_EXPORT CodedOutputStreamFieldSkipper : public FieldSkipper {
public:
explicit CodedOutputStreamFieldSkipper(io::CodedOutputStream* unknown_fields)
: unknown_fields_(unknown_fields) {}
virtual ~CodedOutputStreamFieldSkipper() {}
// implements FieldSkipper -----------------------------------------
virtual bool SkipField(io::CodedInputStream* input, uint32 tag);
virtual bool SkipMessage(io::CodedInputStream* input);
virtual void SkipUnknownEnum(int field_number, int value);
protected:
io::CodedOutputStream* unknown_fields_;
};
// inline methods ====================================================
inline WireFormatLite::CppType
WireFormatLite::FieldTypeToCppType(FieldType type) {
return kFieldTypeToCppTypeMap[type];
}
inline uint32 WireFormatLite::MakeTag(int field_number, WireType type) {
return GOOGLE_PROTOBUF_WIRE_FORMAT_MAKE_TAG(field_number, type);
}
inline WireFormatLite::WireType WireFormatLite::GetTagWireType(uint32 tag) {
return static_cast<WireType>(tag & kTagTypeMask);
}
inline int WireFormatLite::GetTagFieldNumber(uint32 tag) {
return static_cast<int>(tag >> kTagTypeBits);
}
inline int WireFormatLite::TagSize(int field_number,
WireFormatLite::FieldType type) {
int result = io::CodedOutputStream::VarintSize32(
field_number << kTagTypeBits);
if (type == TYPE_GROUP) {
// Groups have both a start and an end tag.
return result * 2;
} else {
return result;
}
}
inline uint32 WireFormatLite::EncodeFloat(float value) {
union {float f; uint32 i;};
f = value;
return i;
}
inline float WireFormatLite::DecodeFloat(uint32 value) {
union {float f; uint32 i;};
i = value;
return f;
}
inline uint64 WireFormatLite::EncodeDouble(double value) {
union {double f; uint64 i;};
f = value;
return i;
}
inline double WireFormatLite::DecodeDouble(uint64 value) {
union {double f; uint64 i;};
i = value;
return f;
}
// ZigZag Transform: Encodes signed integers so that they can be
// effectively used with varint encoding.
//
// varint operates on unsigned integers, encoding smaller numbers into
// fewer bytes. If you try to use it on a signed integer, it will treat
// this number as a very large unsigned integer, which means that even
// small signed numbers like -1 will take the maximum number of bytes
// (10) to encode. ZigZagEncode() maps signed integers to unsigned
// in such a way that those with a small absolute value will have smaller
// encoded values, making them appropriate for encoding using varint.
//
// int32 -> uint32
// -------------------------
// 0 -> 0
// -1 -> 1
// 1 -> 2
// -2 -> 3
// ... -> ...
// 2147483647 -> 4294967294
// -2147483648 -> 4294967295
//
// >> encode >>
// << decode <<
inline uint32 WireFormatLite::ZigZagEncode32(int32 n) {
// Note: the right-shift must be arithmetic
return (n << 1) ^ (n >> 31);
}
inline int32 WireFormatLite::ZigZagDecode32(uint32 n) {
return (n >> 1) ^ -static_cast<int32>(n & 1);
}
inline uint64 WireFormatLite::ZigZagEncode64(int64 n) {
// Note: the right-shift must be arithmetic
return (n << 1) ^ (n >> 63);
}
inline int64 WireFormatLite::ZigZagDecode64(uint64 n) {
return (n >> 1) ^ -static_cast<int64>(n & 1);
}
} // namespace internal
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_WIRE_FORMAT_LITE_H__
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