648db22b |
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 | } |