| 1 | /* |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * This source code is licensed under both the BSD-style license (found in the |
| 6 | * LICENSE file in the root directory of this source tree) and the GPLv2 (found |
| 7 | * in the COPYING file in the root directory of this source tree). |
| 8 | */ |
| 9 | #pragma once |
| 10 | |
| 11 | #include "utils/Range.h" |
| 12 | |
| 13 | #include <array> |
| 14 | #include <cstddef> |
| 15 | #include <memory> |
| 16 | |
| 17 | namespace pzstd { |
| 18 | |
| 19 | /** |
| 20 | * A `Buffer` has a pointer to a shared buffer, and a range of the buffer that |
| 21 | * it owns. |
| 22 | * The idea is that you can allocate one buffer, and write chunks into it |
| 23 | * and break off those chunks. |
| 24 | * The underlying buffer is reference counted, and will be destroyed when all |
| 25 | * `Buffer`s that reference it are destroyed. |
| 26 | */ |
| 27 | class Buffer { |
| 28 | std::shared_ptr<unsigned char> buffer_; |
| 29 | MutableByteRange range_; |
| 30 | |
| 31 | static void delete_buffer(unsigned char* buffer) { |
| 32 | delete[] buffer; |
| 33 | } |
| 34 | |
| 35 | public: |
| 36 | /// Construct an empty buffer that owns no data. |
| 37 | explicit Buffer() {} |
| 38 | |
| 39 | /// Construct a `Buffer` that owns a new underlying buffer of size `size`. |
| 40 | explicit Buffer(std::size_t size) |
| 41 | : buffer_(new unsigned char[size], delete_buffer), |
| 42 | range_(buffer_.get(), buffer_.get() + size) {} |
| 43 | |
| 44 | explicit Buffer(std::shared_ptr<unsigned char> buffer, MutableByteRange data) |
| 45 | : buffer_(buffer), range_(data) {} |
| 46 | |
| 47 | Buffer(Buffer&&) = default; |
| 48 | Buffer& operator=(Buffer&&) = default; |
| 49 | |
| 50 | /** |
| 51 | * Splits the data into two pieces: [begin, begin + n), [begin + n, end). |
| 52 | * Their data both points into the same underlying buffer. |
| 53 | * Modifies the original `Buffer` to point to only [begin + n, end). |
| 54 | * |
| 55 | * @param n The offset to split at. |
| 56 | * @returns A buffer that owns the data [begin, begin + n). |
| 57 | */ |
| 58 | Buffer splitAt(std::size_t n) { |
| 59 | auto firstPiece = range_.subpiece(0, n); |
| 60 | range_.advance(n); |
| 61 | return Buffer(buffer_, firstPiece); |
| 62 | } |
| 63 | |
| 64 | /// Modifies the buffer to point to the range [begin + n, end). |
| 65 | void advance(std::size_t n) { |
| 66 | range_.advance(n); |
| 67 | } |
| 68 | |
| 69 | /// Modifies the buffer to point to the range [begin, end - n). |
| 70 | void subtract(std::size_t n) { |
| 71 | range_.subtract(n); |
| 72 | } |
| 73 | |
| 74 | /// Returns a read only `Range` pointing to the `Buffer`s data. |
| 75 | ByteRange range() const { |
| 76 | return range_; |
| 77 | } |
| 78 | /// Returns a mutable `Range` pointing to the `Buffer`s data. |
| 79 | MutableByteRange range() { |
| 80 | return range_; |
| 81 | } |
| 82 | |
| 83 | const unsigned char* data() const { |
| 84 | return range_.data(); |
| 85 | } |
| 86 | |
| 87 | unsigned char* data() { |
| 88 | return range_.data(); |
| 89 | } |
| 90 | |
| 91 | std::size_t size() const { |
| 92 | return range_.size(); |
| 93 | } |
| 94 | |
| 95 | bool empty() const { |
| 96 | return range_.empty(); |
| 97 | } |
| 98 | }; |
| 99 | } |