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