| // 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 |
| extern void PutFixed32(std::string* dst, uint32_t value); |
| extern void PutFixed64(std::string* dst, uint64_t value); |
| extern void PutVarint32(std::string* dst, uint32_t value); |
| extern void PutVarint64(std::string* dst, uint64_t value); |
| extern 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. |
| extern bool GetVarint32(Slice* input, uint32_t* value); |
| extern bool GetVarint64(Slice* input, uint64_t* value); |
| extern 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 |
| // NULL on error. These routines only look at bytes in the range |
| // [p..limit-1] |
| extern const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v); |
| extern const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v); |
| |
| // Returns the length of the varint32 or varint64 encoding of "v" |
| extern 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 |
| extern void EncodeFixed32(char* dst, uint32_t value); |
| extern 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 |
| extern char* EncodeVarint32(char* dst, uint32_t value); |
| extern 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 |
| extern 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_ |