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// 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>
namespace leveldb {
class 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 int 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_
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