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rocksdb/util/coding.h

374 lines
12 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// 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
#pragma once
#include <algorithm>
#include <stdint.h>
#include <string.h>
#include <string>
#include "rocksdb/write_batch.h"
#include "port/port.h"
// Some processors does not allow unaligned access to memory
#if defined(__sparc)
#define PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED
#endif
namespace rocksdb {
// The maximum length of a varint in bytes for 64-bit.
const unsigned int kMaxVarint64Length = 10;
// 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 PutVarint32Varint32(std::string* dst, uint32_t value1,
uint32_t value2);
extern void PutVarint32Varint32Varint32(std::string* dst, uint32_t value1,
uint32_t value2, uint32_t value3);
extern void PutVarint64(std::string* dst, uint64_t value);
extern void PutVarint64Varint64(std::string* dst, uint64_t value1,
uint64_t value2);
extern void PutVarint32Varint64(std::string* dst, uint32_t value1,
uint64_t value2);
extern void PutVarint32Varint32Varint64(std::string* dst, uint32_t value1,
uint32_t value2, uint64_t value3);
extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
extern void PutLengthPrefixedSliceParts(std::string* dst,
const SliceParts& slice_parts);
// Standard Get... routines parse a value from the beginning of a Slice
// and advance the slice past the parsed value.
extern bool GetFixed64(Slice* input, uint64_t* value);
extern bool GetFixed32(Slice* input, uint32_t* value);
extern bool GetVarint32(Slice* input, uint32_t* value);
extern bool GetVarint64(Slice* input, uint64_t* value);
extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
// This function assumes data is well-formed.
extern Slice GetLengthPrefixedSlice(const char* data);
extern Slice GetSliceUntil(Slice* slice, char delimiter);
// 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]
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);
}
// -- Implementation of the functions declared above
inline void EncodeFixed32(char* buf, uint32_t value) {
if (port::kLittleEndian) {
memcpy(buf, &value, sizeof(value));
} else {
buf[0] = value & 0xff;
buf[1] = (value >> 8) & 0xff;
buf[2] = (value >> 16) & 0xff;
buf[3] = (value >> 24) & 0xff;
}
}
inline void EncodeFixed64(char* buf, uint64_t value) {
if (port::kLittleEndian) {
memcpy(buf, &value, sizeof(value));
} else {
buf[0] = value & 0xff;
buf[1] = (value >> 8) & 0xff;
buf[2] = (value >> 16) & 0xff;
buf[3] = (value >> 24) & 0xff;
buf[4] = (value >> 32) & 0xff;
buf[5] = (value >> 40) & 0xff;
buf[6] = (value >> 48) & 0xff;
buf[7] = (value >> 56) & 0xff;
}
}
// Pull the last 8 bits and cast it to a character
inline void PutFixed32(std::string* dst, uint32_t value) {
if (port::kLittleEndian) {
dst->append(const_cast<const char*>(reinterpret_cast<char*>(&value)),
sizeof(value));
} else {
char buf[sizeof(value)];
EncodeFixed32(buf, value);
dst->append(buf, sizeof(buf));
}
}
inline void PutFixed64(std::string* dst, uint64_t value) {
if (port::kLittleEndian) {
dst->append(const_cast<const char*>(reinterpret_cast<char*>(&value)),
sizeof(value));
} else {
char buf[sizeof(value)];
EncodeFixed64(buf, value);
dst->append(buf, sizeof(buf));
}
}
inline void PutVarint32(std::string* dst, uint32_t v) {
char buf[5];
char* ptr = EncodeVarint32(buf, v);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutVarint32Varint32(std::string* dst, uint32_t v1, uint32_t v2) {
char buf[10];
char* ptr = EncodeVarint32(buf, v1);
ptr = EncodeVarint32(ptr, v2);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutVarint32Varint32Varint32(std::string* dst, uint32_t v1,
uint32_t v2, uint32_t v3) {
char buf[15];
char* ptr = EncodeVarint32(buf, v1);
ptr = EncodeVarint32(ptr, v2);
ptr = EncodeVarint32(ptr, v3);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline char* EncodeVarint64(char* dst, uint64_t v) {
static const unsigned int B = 128;
unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
while (v >= B) {
*(ptr++) = (v & (B - 1)) | B;
v >>= 7;
}
*(ptr++) = static_cast<unsigned char>(v);
return reinterpret_cast<char*>(ptr);
}
inline void PutVarint64(std::string* dst, uint64_t v) {
char buf[10];
char* ptr = EncodeVarint64(buf, v);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutVarint64Varint64(std::string* dst, uint64_t v1, uint64_t v2) {
char buf[20];
char* ptr = EncodeVarint64(buf, v1);
ptr = EncodeVarint64(ptr, v2);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutVarint32Varint64(std::string* dst, uint32_t v1, uint64_t v2) {
char buf[15];
char* ptr = EncodeVarint32(buf, v1);
ptr = EncodeVarint64(ptr, v2);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutVarint32Varint32Varint64(std::string* dst, uint32_t v1,
uint32_t v2, uint64_t v3) {
char buf[20];
char* ptr = EncodeVarint32(buf, v1);
ptr = EncodeVarint32(ptr, v2);
ptr = EncodeVarint64(ptr, v3);
dst->append(buf, static_cast<size_t>(ptr - buf));
}
inline void PutLengthPrefixedSlice(std::string* dst, const Slice& value) {
PutVarint32(dst, static_cast<uint32_t>(value.size()));
dst->append(value.data(), value.size());
}
inline void PutLengthPrefixedSliceParts(std::string* dst,
const SliceParts& slice_parts) {
size_t total_bytes = 0;
for (int i = 0; i < slice_parts.num_parts; ++i) {
total_bytes += slice_parts.parts[i].size();
}
PutVarint32(dst, static_cast<uint32_t>(total_bytes));
for (int i = 0; i < slice_parts.num_parts; ++i) {
dst->append(slice_parts.parts[i].data(), slice_parts.parts[i].size());
}
}
inline int VarintLength(uint64_t v) {
int len = 1;
while (v >= 128) {
v >>= 7;
len++;
}
return len;
}
inline bool GetFixed64(Slice* input, uint64_t* value) {
if (input->size() < sizeof(uint64_t)) {
return false;
}
*value = DecodeFixed64(input->data());
input->remove_prefix(sizeof(uint64_t));
return true;
}
inline bool GetFixed32(Slice* input, uint32_t* value) {
if (input->size() < sizeof(uint32_t)) {
return false;
}
*value = DecodeFixed32(input->data());
input->remove_prefix(sizeof(uint32_t));
return true;
}
inline bool GetVarint32(Slice* input, uint32_t* value) {
const char* p = input->data();
const char* limit = p + input->size();
const char* q = GetVarint32Ptr(p, limit, value);
if (q == nullptr) {
return false;
} else {
*input = Slice(q, static_cast<size_t>(limit - q));
return true;
}
}
inline bool GetVarint64(Slice* input, uint64_t* value) {
const char* p = input->data();
const char* limit = p + input->size();
const char* q = GetVarint64Ptr(p, limit, value);
if (q == nullptr) {
return false;
} else {
*input = Slice(q, static_cast<size_t>(limit - q));
return true;
}
}
// Provide an interface for platform independent endianness transformation
inline uint64_t EndianTransform(uint64_t input, size_t size) {
char* pos = reinterpret_cast<char*>(&input);
uint64_t ret_val = 0;
for (size_t i = 0; i < size; ++i) {
ret_val |= (static_cast<uint64_t>(static_cast<unsigned char>(pos[i]))
<< ((size - i - 1) << 3));
}
return ret_val;
}
inline bool GetLengthPrefixedSlice(Slice* input, Slice* result) {
uint32_t len = 0;
if (GetVarint32(input, &len) && input->size() >= len) {
*result = Slice(input->data(), len);
input->remove_prefix(len);
return true;
} else {
return false;
}
}
inline Slice GetLengthPrefixedSlice(const char* data) {
uint32_t len = 0;
// +5: we assume "data" is not corrupted
// unsigned char is 7 bits, uint32_t is 32 bits, need 5 unsigned char
auto p = GetVarint32Ptr(data, data + 5 /* limit */, &len);
return Slice(p, len);
}
inline Slice GetSliceUntil(Slice* slice, char delimiter) {
uint32_t len = 0;
for (len = 0; len < slice->size() && slice->data()[len] != delimiter; ++len) {
// nothing
}
Slice ret(slice->data(), len);
slice->remove_prefix(len + ((len < slice->size()) ? 1 : 0));
return ret;
}
template<class T>
inline void PutUnaligned(T *memory, const T &value) {
#if defined(PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED)
char *nonAlignedMemory = reinterpret_cast<char*>(memory);
memcpy(nonAlignedMemory, reinterpret_cast<const char*>(&value), sizeof(T));
#else
*memory = value;
#endif
}
template<class T>
inline void GetUnaligned(const T *memory, T *value) {
#if defined(PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED)
char *nonAlignedMemory = reinterpret_cast<char*>(value);
memcpy(nonAlignedMemory, reinterpret_cast<const char*>(memory), sizeof(T));
#else
*value = *memory;
#endif
}
} // namespace rocksdb