Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 1 | // Copyright 2017 The Chromium Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef COMPONENTS_ZUCCHINI_BUFFER_VIEW_H_ |
| 6 | #define COMPONENTS_ZUCCHINI_BUFFER_VIEW_H_ |
| 7 | |
| 8 | #include <stddef.h> |
| 9 | #include <stdint.h> |
| 10 | |
| 11 | #include <algorithm> |
| 12 | #include <type_traits> |
| 13 | |
Hans Wennborg | d5ccca8 | 2020-06-24 13:46:35 +0000 | [diff] [blame] | 14 | #include "base/check_op.h" |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 15 | #include "components/zucchini/algorithm.h" |
| 16 | |
| 17 | namespace zucchini { |
| 18 | |
| 19 | // Describes a region within a buffer, with starting offset and size. |
| 20 | struct BufferRegion { |
| 21 | // The region data are stored as |offset| and |size|, but often it is useful |
| 22 | // to represent it as an interval [lo(), hi()) = [offset, offset + size). |
| 23 | size_t lo() const { return offset; } |
| 24 | size_t hi() const { return offset + size; } |
| 25 | |
| 26 | // Returns whether the Region fits in |[0, container_size)|. Special case: |
Samuel Huang | d758cb7 | 2018-07-19 14:32:28 +0000 | [diff] [blame] | 27 | // a size-0 region starting at |container_size| fits. |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 28 | bool FitsIn(size_t container_size) const { |
Samuel Huang | d758cb7 | 2018-07-19 14:32:28 +0000 | [diff] [blame] | 29 | return offset <= container_size && container_size - offset >= size; |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 30 | } |
| 31 | |
| 32 | // Returns |v| clipped to the inclusive range |[lo(), hi()]|. |
| 33 | size_t InclusiveClamp(size_t v) const { |
| 34 | return zucchini::InclusiveClamp(v, lo(), hi()); |
| 35 | } |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 36 | |
| 37 | // Region data use size_t to match BufferViewBase::size_type, to make it |
| 38 | // convenient to index into buffer view. |
| 39 | size_t offset; |
| 40 | size_t size; |
| 41 | }; |
| 42 | |
| 43 | namespace internal { |
| 44 | |
| 45 | // TODO(huangs): Rename to BasicBufferView. |
| 46 | // BufferViewBase should not be used directly; it is an implementation used for |
| 47 | // both BufferView and MutableBufferView. |
| 48 | template <class T> |
| 49 | class BufferViewBase { |
| 50 | public: |
| 51 | using value_type = T; |
| 52 | using reference = T&; |
| 53 | using pointer = T*; |
| 54 | using iterator = T*; |
| 55 | using const_iterator = typename std::add_const<T>::type*; |
| 56 | using size_type = std::size_t; |
| 57 | using difference_type = std::ptrdiff_t; |
| 58 | |
| 59 | static BufferViewBase FromRange(iterator first, iterator last) { |
| 60 | DCHECK_GE(last, first); |
| 61 | BufferViewBase ret; |
| 62 | ret.first_ = first; |
| 63 | ret.last_ = last; |
| 64 | return ret; |
| 65 | } |
| 66 | |
| 67 | BufferViewBase() = default; |
| 68 | |
| 69 | BufferViewBase(iterator first, size_type size) |
| 70 | : first_(first), last_(first_ + size) { |
| 71 | DCHECK_GE(last_, first_); |
| 72 | } |
| 73 | |
| 74 | template <class U> |
| 75 | BufferViewBase(const BufferViewBase<U>& that) |
| 76 | : first_(that.begin()), last_(that.end()) {} |
| 77 | |
| 78 | template <class U> |
| 79 | BufferViewBase(BufferViewBase<U>&& that) |
| 80 | : first_(that.begin()), last_(that.end()) {} |
| 81 | |
| 82 | BufferViewBase(const BufferViewBase&) = default; |
| 83 | BufferViewBase& operator=(const BufferViewBase&) = default; |
| 84 | |
| 85 | // Iterators |
| 86 | |
| 87 | iterator begin() const { return first_; } |
| 88 | iterator end() const { return last_; } |
| 89 | const_iterator cbegin() const { return begin(); } |
| 90 | const_iterator cend() const { return end(); } |
| 91 | |
| 92 | // Capacity |
| 93 | |
| 94 | bool empty() const { return first_ == last_; } |
| 95 | size_type size() const { return last_ - first_; } |
| 96 | |
| 97 | // Returns whether the buffer is large enough to cover |region|. |
| 98 | bool covers(const BufferRegion& region) const { |
| 99 | return region.FitsIn(size()); |
| 100 | } |
| 101 | |
Etienne Pierre-Doray | fff1ca3 | 2018-03-29 13:33:46 +0000 | [diff] [blame] | 102 | // Returns whether the buffer is large enough to cover an array starting at |
| 103 | // |offset| with |num| elements, each taking |elt_size| bytes. |
| 104 | bool covers_array(size_t offset, size_t num, size_t elt_size) { |
| 105 | DCHECK_GT(elt_size, 0U); |
| 106 | // Use subtraction and division to avoid overflow. |
Samuel Huang | a09f4e2 | 2018-07-11 19:16:21 +0000 | [diff] [blame] | 107 | return offset <= size() && (size() - offset) / elt_size >= num; |
Etienne Pierre-Doray | fff1ca3 | 2018-03-29 13:33:46 +0000 | [diff] [blame] | 108 | } |
| 109 | |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 110 | // Element access |
| 111 | |
| 112 | // Returns the raw value at specified location |pos|. |
| 113 | // If |pos| is not within the range of the buffer, the process is terminated. |
| 114 | reference operator[](size_type pos) const { |
| 115 | CHECK_LT(pos, size()); |
| 116 | return first_[pos]; |
| 117 | } |
| 118 | |
| 119 | // Returns a sub-buffer described by |region|. |
| 120 | BufferViewBase operator[](BufferRegion region) const { |
| 121 | DCHECK_LE(region.offset, size()); |
| 122 | DCHECK_LE(region.size, size() - region.offset); |
| 123 | return {begin() + region.offset, region.size}; |
| 124 | } |
| 125 | |
| 126 | template <class U> |
| 127 | const U& read(size_type pos) const { |
Etienne Pierre-Doray | a88cad0 | 2018-07-25 20:16:02 +0000 | [diff] [blame] | 128 | // TODO(huangs): Use can_access<U>(pos) after fixing can_access(). |
| 129 | CHECK_LE(sizeof(U), size()); |
| 130 | CHECK_LE(pos, size() - sizeof(U)); |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 131 | return *reinterpret_cast<const U*>(begin() + pos); |
| 132 | } |
| 133 | |
| 134 | template <class U> |
| 135 | void write(size_type pos, const U& value) { |
Etienne Pierre-Doray | a88cad0 | 2018-07-25 20:16:02 +0000 | [diff] [blame] | 136 | // TODO(huangs): Use can_access<U>(pos) after fixing can_access(). |
| 137 | CHECK_LE(sizeof(U), size()); |
| 138 | CHECK_LE(pos, size() - sizeof(U)); |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 139 | *reinterpret_cast<U*>(begin() + pos) = value; |
| 140 | } |
| 141 | |
Etienne Pierre-Doray | a88cad0 | 2018-07-25 20:16:02 +0000 | [diff] [blame] | 142 | // Returns a mutable reference to an object type U whose raw storage starts |
| 143 | // at location |pos|. |
| 144 | template <class U> |
| 145 | U& modify(size_type pos) { |
| 146 | // TODO(huangs): Use can_access<U>(pos) after fixing can_access(). |
| 147 | CHECK_LE(sizeof(U), size()); |
| 148 | CHECK_LE(pos, size() - sizeof(U)); |
| 149 | return *reinterpret_cast<U*>(begin() + pos); |
| 150 | } |
| 151 | |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 152 | template <class U> |
| 153 | bool can_access(size_type pos) const { |
| 154 | return pos < size() && size() - pos >= sizeof(U); |
| 155 | } |
| 156 | |
| 157 | // Returns a BufferRegion describing the full view, with offset = 0. If the |
| 158 | // BufferViewBase is derived from another, this does *not* return the |
| 159 | // original region used for its definition (hence "local"). |
| 160 | BufferRegion local_region() const { return BufferRegion{0, size()}; } |
| 161 | |
| 162 | bool equals(BufferViewBase other) const { |
| 163 | return size() == other.size() && std::equal(begin(), end(), other.begin()); |
| 164 | } |
| 165 | |
| 166 | // Modifiers |
| 167 | |
| 168 | void shrink(size_type new_size) { |
| 169 | DCHECK_LE(first_ + new_size, last_); |
| 170 | last_ = first_ + new_size; |
| 171 | } |
| 172 | |
| 173 | // Moves the start of the view forward by n bytes. |
| 174 | void remove_prefix(size_type n) { |
| 175 | DCHECK_LE(n, size()); |
| 176 | first_ += n; |
| 177 | } |
| 178 | |
| 179 | // Moves the start of the view to |it|, which is in range [begin(), end()). |
| 180 | void seek(iterator it) { |
| 181 | DCHECK_GE(it, begin()); |
| 182 | DCHECK_LE(it, end()); |
| 183 | first_ = it; |
| 184 | } |
| 185 | |
| 186 | // Given |origin| that contains |*this|, minimally increase |first_| (possibly |
| 187 | // by 0) so that |first_ <= last_|, and |first_ - origin.first_| is a multiple |
| 188 | // of |alignment|. On success, updates |first_| and returns true. Otherwise |
| 189 | // returns false. |
| 190 | bool AlignOn(BufferViewBase origin, size_type alignment) { |
| 191 | DCHECK_GT(alignment, 0U); |
| 192 | DCHECK_LE(origin.first_, first_); |
| 193 | DCHECK_GE(origin.last_, last_); |
| 194 | size_type aligned_size = |
Samuel Huang | 607ce60 | 2018-06-13 17:47:39 +0000 | [diff] [blame] | 195 | AlignCeil(static_cast<size_type>(first_ - origin.first_), alignment); |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 196 | if (aligned_size > static_cast<size_type>(last_ - origin.first_)) |
| 197 | return false; |
| 198 | first_ = origin.first_ + aligned_size; |
| 199 | return true; |
| 200 | } |
| 201 | |
| 202 | private: |
| 203 | iterator first_ = nullptr; |
| 204 | iterator last_ = nullptr; |
| 205 | }; |
| 206 | |
| 207 | } // namespace internal |
| 208 | |
| 209 | // Classes to encapsulate a contiguous sequence of raw data, without owning the |
| 210 | // encapsulated memory regions. These are intended to be used as value types. |
| 211 | |
| 212 | using ConstBufferView = internal::BufferViewBase<const uint8_t>; |
| 213 | using MutableBufferView = internal::BufferViewBase<uint8_t>; |
| 214 | |
| 215 | } // namespace zucchini |
| 216 | |
| 217 | #endif // COMPONENTS_ZUCCHINI_BUFFER_VIEW_H_ |