mirror of
https://github.com/google/leveldb.git
synced 2024-12-01 03:19:07 +08:00
107 lines
3.8 KiB
C++
107 lines
3.8 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
//
|
|
// Endian-neutral encoding:
|
|
// * Fixed-length numbers are encoded with least-significant byte first
|
|
// * In addition we support variable length "varint" encoding
|
|
// * Strings are encoded prefixed by their length in varint format
|
|
|
|
#ifndef STORAGE_LEVELDB_UTIL_CODING_H_
|
|
#define STORAGE_LEVELDB_UTIL_CODING_H_
|
|
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
|
|
#include <string>
|
|
|
|
#include "leveldb/slice.h"
|
|
#include "port/port.h"
|
|
|
|
namespace leveldb {
|
|
|
|
// Standard Put... routines append to a string
|
|
void PutFixed32(std::string* dst, uint32_t value);
|
|
void PutFixed64(std::string* dst, uint64_t value);
|
|
void PutVarint32(std::string* dst, uint32_t value);
|
|
void PutVarint64(std::string* dst, uint64_t value);
|
|
void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
|
|
|
|
// Standard Get... routines parse a value from the beginning of a Slice
|
|
// and advance the slice past the parsed value.
|
|
bool GetVarint32(Slice* input, uint32_t* value);
|
|
bool GetVarint64(Slice* input, uint64_t* value);
|
|
bool GetLengthPrefixedSlice(Slice* input, Slice* result);
|
|
|
|
// Pointer-based variants of GetVarint... These either store a value
|
|
// in *v and return a pointer just past the parsed value, or return
|
|
// nullptr on error. These routines only look at bytes in the range
|
|
// [p..limit-1]
|
|
const char* GetVarint32Ptr(const char* p, const char* limit, uint32_t* v);
|
|
const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* v);
|
|
|
|
// Returns the length of the varint32 or varint64 encoding of "v"
|
|
int VarintLength(uint64_t v);
|
|
|
|
// Lower-level versions of Put... that write directly into a character buffer
|
|
// REQUIRES: dst has enough space for the value being written
|
|
void EncodeFixed32(char* dst, uint32_t value);
|
|
void EncodeFixed64(char* dst, uint64_t value);
|
|
|
|
// Lower-level versions of Put... that write directly into a character buffer
|
|
// and return a pointer just past the last byte written.
|
|
// REQUIRES: dst has enough space for the value being written
|
|
char* EncodeVarint32(char* dst, uint32_t value);
|
|
char* EncodeVarint64(char* dst, uint64_t value);
|
|
|
|
// Lower-level versions of Get... that read directly from a character buffer
|
|
// without any bounds checking.
|
|
|
|
inline uint32_t DecodeFixed32(const char* ptr) {
|
|
if (port::kLittleEndian) {
|
|
// Load the raw bytes
|
|
uint32_t result;
|
|
memcpy(&result, ptr, sizeof(result)); // gcc optimizes this to a plain load
|
|
return result;
|
|
} else {
|
|
return ((static_cast<uint32_t>(static_cast<unsigned char>(ptr[0])))
|
|
| (static_cast<uint32_t>(static_cast<unsigned char>(ptr[1])) << 8)
|
|
| (static_cast<uint32_t>(static_cast<unsigned char>(ptr[2])) << 16)
|
|
| (static_cast<uint32_t>(static_cast<unsigned char>(ptr[3])) << 24));
|
|
}
|
|
}
|
|
|
|
inline uint64_t DecodeFixed64(const char* ptr) {
|
|
if (port::kLittleEndian) {
|
|
// Load the raw bytes
|
|
uint64_t result;
|
|
memcpy(&result, ptr, sizeof(result)); // gcc optimizes this to a plain load
|
|
return result;
|
|
} else {
|
|
uint64_t lo = DecodeFixed32(ptr);
|
|
uint64_t hi = DecodeFixed32(ptr + 4);
|
|
return (hi << 32) | lo;
|
|
}
|
|
}
|
|
|
|
// Internal routine for use by fallback path of GetVarint32Ptr
|
|
const char* GetVarint32PtrFallback(const char* p,
|
|
const char* limit,
|
|
uint32_t* value);
|
|
inline const char* GetVarint32Ptr(const char* p,
|
|
const char* limit,
|
|
uint32_t* value) {
|
|
if (p < limit) {
|
|
uint32_t result = *(reinterpret_cast<const unsigned char*>(p));
|
|
if ((result & 128) == 0) {
|
|
*value = result;
|
|
return p + 1;
|
|
}
|
|
}
|
|
return GetVarint32PtrFallback(p, limit, value);
|
|
}
|
|
|
|
} // namespace leveldb
|
|
|
|
#endif // STORAGE_LEVELDB_UTIL_CODING_H_
|