100 lines
2.6 KiB
C++
100 lines
2.6 KiB
C++
/**
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* Copyright (c) 2016-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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#pragma once
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#include "utils/Range.h"
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#include <array>
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#include <cstddef>
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#include <memory>
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namespace pzstd {
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/**
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* A `Buffer` has a pointer to a shared buffer, and a range of the buffer that
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* it owns.
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* The idea is that you can allocate one buffer, and write chunks into it
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* and break off those chunks.
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* The underlying buffer is reference counted, and will be destroyed when all
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* `Buffer`s that reference it are destroyed.
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*/
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class Buffer {
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std::shared_ptr<unsigned char> buffer_;
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MutableByteRange range_;
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static void delete_buffer(unsigned char* buffer) {
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delete[] buffer;
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}
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public:
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/// Construct an empty buffer that owns no data.
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explicit Buffer() {}
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/// Construct a `Buffer` that owns a new underlying buffer of size `size`.
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explicit Buffer(std::size_t size)
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: buffer_(new unsigned char[size], delete_buffer),
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range_(buffer_.get(), buffer_.get() + size) {}
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explicit Buffer(std::shared_ptr<unsigned char> buffer, MutableByteRange data)
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: buffer_(buffer), range_(data) {}
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Buffer(Buffer&&) = default;
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Buffer& operator=(Buffer&&) & = default;
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/**
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* Splits the data into two pieces: [begin, begin + n), [begin + n, end).
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* Their data both points into the same underlying buffer.
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* Modifies the original `Buffer` to point to only [begin + n, end).
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*
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* @param n The offset to split at.
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* @returns A buffer that owns the data [begin, begin + n).
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*/
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Buffer splitAt(std::size_t n) {
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auto firstPiece = range_.subpiece(0, n);
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range_.advance(n);
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return Buffer(buffer_, firstPiece);
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}
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/// Modifies the buffer to point to the range [begin + n, end).
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void advance(std::size_t n) {
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range_.advance(n);
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}
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/// Modifies the buffer to point to the range [begin, end - n).
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void subtract(std::size_t n) {
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range_.subtract(n);
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}
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/// Returns a read only `Range` pointing to the `Buffer`s data.
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ByteRange range() const {
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return range_;
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}
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/// Returns a mutable `Range` pointing to the `Buffer`s data.
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MutableByteRange range() {
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return range_;
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}
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const unsigned char* data() const {
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return range_.data();
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}
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unsigned char* data() {
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return range_.data();
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}
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std::size_t size() const {
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return range_.size();
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}
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bool empty() const {
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return range_.empty();
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}
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};
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}
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