Line data    Source code

       1             : // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file. See the AUTHORS file for names of contributors.
       4             : //
       5             : // Endian-neutral encoding:
       6             : // * Fixed-length numbers are encoded with least-significant byte first
       7             : // * In addition we support variable length "varint" encoding
       8             : // * Strings are encoded prefixed by their length in varint format
       9             : 
      10             : #ifndef STORAGE_LEVELDB_UTIL_CODING_H_
      11             : #define STORAGE_LEVELDB_UTIL_CODING_H_
      12             : 
      13             : #include <stdint.h>
      14             : #include <string.h>
      15             : #include <string>
      16             : #include "leveldb/slice.h"
      17             : #include "port/port.h"
      18             : 
      19             : namespace leveldb {
      20             : 
      21             : // Standard Put... routines append to a string
      22             : extern void PutFixed32(std::string* dst, uint32_t value);
      23             : extern void PutFixed64(std::string* dst, uint64_t value);
      24             : extern void PutVarint32(std::string* dst, uint32_t value);
      25             : extern void PutVarint64(std::string* dst, uint64_t value);
      26             : extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
      27             : 
      28             : // Standard Get... routines parse a value from the beginning of a Slice
      29             : // and advance the slice past the parsed value.
      30             : extern bool GetVarint32(Slice* input, uint32_t* value);
      31             : extern bool GetVarint64(Slice* input, uint64_t* value);
      32             : extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
      33             : 
      34             : // Pointer-based variants of GetVarint...  These either store a value
      35             : // in *v and return a pointer just past the parsed value, or return
      36             : // NULL on error.  These routines only look at bytes in the range
      37             : // [p..limit-1]
      38             : extern const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v);
      39             : extern const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v);
      40             : 
      41             : // Returns the length of the varint32 or varint64 encoding of "v"
      42             : extern int VarintLength(uint64_t v);
      43             : 
      44             : // Lower-level versions of Put... that write directly into a character buffer
      45             : // REQUIRES: dst has enough space for the value being written
      46             : extern void EncodeFixed32(char* dst, uint32_t value);
      47             : extern void EncodeFixed64(char* dst, uint64_t value);
      48             : 
      49             : // Lower-level versions of Put... that write directly into a character buffer
      50             : // and return a pointer just past the last byte written.
      51             : // REQUIRES: dst has enough space for the value being written
      52             : extern char* EncodeVarint32(char* dst, uint32_t value);
      53             : extern char* EncodeVarint64(char* dst, uint64_t value);
      54             : 
      55             : // Lower-level versions of Get... that read directly from a character buffer
      56             : // without any bounds checking.
      57             : 
      58             : inline uint32_t DecodeFixed32(const char* ptr) {
      59             :   if (port::kLittleEndian) {
      60             :     // Load the raw bytes
      61             :     uint32_t result;
      62             :     memcpy(&result, ptr, sizeof(result));  // gcc optimizes this to a plain load
      63             :     return result;
      64             :   } else {
      65             :     return ((static_cast<uint32_t>(static_cast<unsigned char>(ptr[0])))
      66             :         | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[1])) << 8)
      67             :         | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[2])) << 16)
      68             :         | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[3])) << 24));
      69             :   }
      70             : }
      71             : 
      72             : inline uint64_t DecodeFixed64(const char* ptr) {
      73             :   if (port::kLittleEndian) {
      74             :     // Load the raw bytes
      75             :     uint64_t result;
      76             :     memcpy(&result, ptr, sizeof(result));  // gcc optimizes this to a plain load
      77             :     return result;
      78             :   } else {
      79             :     uint64_t lo = DecodeFixed32(ptr);
      80             :     uint64_t hi = DecodeFixed32(ptr + 4);
      81             :     return (hi << 32) | lo;
      82             :   }
      83             : }
      84             : 
      85             : // Internal routine for use by fallback path of GetVarint32Ptr
      86             : extern const char* GetVarint32PtrFallback(const char* p,
      87             :                                           const char* limit,
      88             :                                           uint32_t* value);
      89      825938 : inline const char* GetVarint32Ptr(const char* p,
      90             :                                   const char* limit,
      91             :                                   uint32_t* value) {
      92      825938 :   if (p < limit) {
      93      825579 :     uint32_t result = *(reinterpret_cast<const unsigned char*>(p));
      94      825579 :     if ((result & 128) == 0) {
      95      825429 :       *value = result;
      96      825429 :       return p + 1;
      97             :     }
      98             :   }
      99         509 :   return GetVarint32PtrFallback(p, limit, value);
     100             : }
     101             : 
     102             : }  // namespace leveldb
     103             : 
     104             : #endif  // STORAGE_LEVELDB_UTIL_CODING_H_