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