Não pode escolher mais do que 25 tópicos
Os tópicos devem começar com uma letra ou um número, podem incluir traços ('-') e podem ter até 35 caracteres.
110 linhas
3.1 KiB
110 linhas
3.1 KiB
// 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.
|
|
//
|
|
// Slice is a simple structure containing a pointer into some external
|
|
// storage and a size. The user of a Slice must ensure that the slice
|
|
// is not used after the corresponding external storage has been
|
|
// deallocated.
|
|
//
|
|
// Multiple threads can invoke const methods on a Slice without
|
|
// external synchronization, but if any of the threads may call a
|
|
// non-const method, all threads accessing the same Slice must use
|
|
// external synchronization.
|
|
|
|
#ifndef STORAGE_LEVELDB_INCLUDE_SLICE_H_
|
|
#define STORAGE_LEVELDB_INCLUDE_SLICE_H_
|
|
|
|
#include <assert.h>
|
|
#include <stddef.h>
|
|
#include <string.h>
|
|
#include <string>
|
|
#include "leveldb/export.h"
|
|
|
|
namespace leveldb {
|
|
|
|
class LEVELDB_EXPORT Slice {
|
|
public:
|
|
// Create an empty slice.
|
|
Slice() : data_(""), size_(0) { }
|
|
|
|
// Create a slice that refers to d[0,n-1].
|
|
Slice(const char* d, size_t n) : data_(d), size_(n) { }
|
|
|
|
// Create a slice that refers to the contents of "s"
|
|
Slice(const std::string& s) : data_(s.data()), size_(s.size()) { }
|
|
|
|
// Create a slice that refers to s[0,strlen(s)-1]
|
|
Slice(const char* s) : data_(s), size_(strlen(s)) { }
|
|
|
|
// Return a pointer to the beginning of the referenced data
|
|
const char* data() const { return data_; }
|
|
|
|
// Return the length (in bytes) of the referenced data
|
|
size_t size() const { return size_; }
|
|
|
|
// Return true iff the length of the referenced data is zero
|
|
bool empty() const { return size_ == 0; }
|
|
|
|
// Return the ith byte in the referenced data.
|
|
// REQUIRES: n < size()
|
|
char operator[](size_t n) const {
|
|
assert(n < size());
|
|
return data_[n];
|
|
}
|
|
|
|
// Change this slice to refer to an empty array
|
|
void clear() { data_ = ""; size_ = 0; }
|
|
|
|
// Drop the first "n" bytes from this slice.
|
|
void remove_prefix(size_t n) {
|
|
assert(n <= size());
|
|
data_ += n;
|
|
size_ -= n;
|
|
}
|
|
|
|
// Return a string that contains the copy of the referenced data.
|
|
std::string ToString() const { return std::string(data_, size_); }
|
|
|
|
// Three-way comparison. Returns value:
|
|
// < 0 iff "*this" < "b",
|
|
// == 0 iff "*this" == "b",
|
|
// > 0 iff "*this" > "b"
|
|
int compare(const Slice& b) const;
|
|
|
|
// Return true iff "x" is a prefix of "*this"
|
|
bool starts_with(const Slice& x) const {
|
|
return ((size_ >= x.size_) &&
|
|
(memcmp(data_, x.data_, x.size_) == 0));
|
|
}
|
|
|
|
private:
|
|
const char* data_;
|
|
size_t size_;
|
|
|
|
// Intentionally copyable
|
|
};
|
|
|
|
inline bool operator==(const Slice& x, const Slice& y) {
|
|
return ((x.size() == y.size()) &&
|
|
(memcmp(x.data(), y.data(), x.size()) == 0));
|
|
}
|
|
|
|
inline bool operator!=(const Slice& x, const Slice& y) {
|
|
return !(x == y);
|
|
}
|
|
|
|
inline int Slice::compare(const Slice& b) const {
|
|
const size_t min_len = (size_ < b.size_) ? size_ : b.size_;
|
|
int r = memcmp(data_, b.data_, min_len);
|
|
if (r == 0) {
|
|
if (size_ < b.size_) r = -1;
|
|
else if (size_ > b.size_) r = +1;
|
|
}
|
|
return r;
|
|
}
|
|
|
|
} // namespace leveldb
|
|
|
|
|
|
#endif // STORAGE_LEVELDB_INCLUDE_SLICE_H_
|