Yurii Zubrytskyi | e5e6b0d | 2019-07-12 14:11:54 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2019 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include "types.h" |
| 18 | |
| 19 | IOVector& IOVector::operator=(IOVector&& move) noexcept { |
| 20 | chain_ = std::move(move.chain_); |
| 21 | chain_length_ = move.chain_length_; |
| 22 | begin_offset_ = move.begin_offset_; |
| 23 | start_index_ = move.start_index_; |
| 24 | |
| 25 | move.clear(); |
| 26 | return *this; |
| 27 | } |
| 28 | |
| 29 | IOVector::block_type IOVector::clear() { |
| 30 | chain_length_ = 0; |
| 31 | begin_offset_ = 0; |
| 32 | start_index_ = 0; |
| 33 | block_type res; |
| 34 | if (!chain_.empty()) { |
| 35 | res = std::move(chain_.back()); |
| 36 | } |
| 37 | chain_.clear(); |
| 38 | return res; |
| 39 | } |
| 40 | |
| 41 | void IOVector::drop_front(IOVector::size_type len) { |
| 42 | if (len == 0) { |
| 43 | return; |
| 44 | } |
| 45 | if (len == size()) { |
| 46 | clear(); |
| 47 | return; |
| 48 | } |
| 49 | CHECK_LT(len, size()); |
| 50 | |
| 51 | auto dropped = 0u; |
| 52 | while (dropped < len) { |
| 53 | const auto next = chain_[start_index_].size() - begin_offset_; |
Josh Gao | d11b509 | 2020-03-31 01:53:01 -0700 | [diff] [blame] | 54 | if (dropped + next <= len) { |
Yurii Zubrytskyi | e5e6b0d | 2019-07-12 14:11:54 -0700 | [diff] [blame] | 55 | pop_front_block(); |
| 56 | dropped += next; |
| 57 | } else { |
| 58 | const auto taken = len - dropped; |
| 59 | begin_offset_ += taken; |
| 60 | break; |
| 61 | } |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | IOVector IOVector::take_front(IOVector::size_type len) { |
| 66 | if (len == 0) { |
| 67 | return {}; |
| 68 | } |
| 69 | if (len == size()) { |
| 70 | return std::move(*this); |
| 71 | } |
| 72 | |
| 73 | CHECK_GE(size(), len); |
| 74 | IOVector res; |
| 75 | // first iterate over the blocks that completely go into the other vector |
| 76 | while (chain_[start_index_].size() - begin_offset_ <= len) { |
| 77 | chain_length_ -= chain_[start_index_].size(); |
| 78 | len -= chain_[start_index_].size() - begin_offset_; |
| 79 | if (chain_[start_index_].size() > begin_offset_) { |
| 80 | res.append(std::move(chain_[start_index_])); |
| 81 | if (begin_offset_) { |
| 82 | res.begin_offset_ = std::exchange(begin_offset_, 0); |
| 83 | } |
| 84 | } else { |
| 85 | begin_offset_ = 0; |
| 86 | } |
| 87 | ++start_index_; |
| 88 | } |
| 89 | |
| 90 | if (len > 0) { |
| 91 | // what's left is a single buffer that needs to be split between the |res| and |this| |
| 92 | // we know that it has to be split - there was a check for the case when it has to |
| 93 | // go away as a whole. |
| 94 | if (begin_offset_ != 0 || len < chain_[start_index_].size() / 2) { |
| 95 | // let's memcpy the data out |
| 96 | block_type block(chain_[start_index_].begin() + begin_offset_, |
| 97 | chain_[start_index_].begin() + begin_offset_ + len); |
| 98 | res.append(std::move(block)); |
| 99 | begin_offset_ += len; |
| 100 | } else { |
| 101 | CHECK_EQ(begin_offset_, 0u); |
| 102 | // move out the internal buffer out and copy only the tail of it back in |
| 103 | block_type block(chain_[start_index_].begin() + len, chain_[start_index_].end()); |
| 104 | chain_length_ -= chain_[start_index_].size(); |
| 105 | chain_[start_index_].resize(len); |
| 106 | res.append(std::move(chain_[start_index_])); |
| 107 | chain_length_ += block.size(); |
| 108 | chain_[start_index_] = std::move(block); |
| 109 | } |
| 110 | } |
| 111 | return res; |
| 112 | } |
| 113 | |
| 114 | void IOVector::trim_front() { |
| 115 | if ((begin_offset_ == 0 && start_index_ == 0) || chain_.empty()) { |
| 116 | return; |
| 117 | } |
| 118 | block_type& first_block = chain_[start_index_]; |
| 119 | if (begin_offset_ == first_block.size()) { |
| 120 | ++start_index_; |
| 121 | } else { |
| 122 | memmove(first_block.data(), first_block.data() + begin_offset_, |
| 123 | first_block.size() - begin_offset_); |
| 124 | first_block.resize(first_block.size() - begin_offset_); |
| 125 | } |
| 126 | chain_length_ -= begin_offset_; |
| 127 | begin_offset_ = 0; |
| 128 | trim_chain_front(); |
| 129 | } |
| 130 | |
| 131 | void IOVector::trim_chain_front() { |
| 132 | if (start_index_) { |
| 133 | chain_.erase(chain_.begin(), chain_.begin() + start_index_); |
| 134 | start_index_ = 0; |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | void IOVector::pop_front_block() { |
| 139 | chain_length_ -= chain_[start_index_].size(); |
| 140 | begin_offset_ = 0; |
| 141 | chain_[start_index_].clear(); |
| 142 | ++start_index_; |
| 143 | if (start_index_ > std::max<size_t>(4, chain_.size() / 2)) { |
| 144 | trim_chain_front(); |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | IOVector::block_type IOVector::coalesce() && { |
| 149 | // Destructive coalesce() may optimize for several cases when it doesn't need to allocate |
| 150 | // new buffer, or even return one of the existing blocks as is. The only guarantee is that |
| 151 | // after this call the IOVector is in some valid state. Nothing is guaranteed about the |
| 152 | // specifics. |
| 153 | if (size() == 0) { |
| 154 | return {}; |
| 155 | } |
| 156 | if (begin_offset_ == chain_[start_index_].size() && chain_.size() == start_index_ + 2) { |
| 157 | chain_length_ -= chain_.back().size(); |
| 158 | auto res = std::move(chain_.back()); |
| 159 | chain_.pop_back(); |
| 160 | return res; |
| 161 | } |
| 162 | if (chain_.size() == start_index_ + 1) { |
| 163 | chain_length_ -= chain_.back().size(); |
| 164 | auto res = std::move(chain_.back()); |
| 165 | chain_.pop_back(); |
| 166 | if (begin_offset_ != 0) { |
| 167 | memmove(res.data(), res.data() + begin_offset_, res.size() - begin_offset_); |
| 168 | res.resize(res.size() - begin_offset_); |
| 169 | begin_offset_ = 0; |
| 170 | } |
| 171 | return res; |
| 172 | } |
| 173 | if (auto& firstBuffer = chain_[start_index_]; firstBuffer.capacity() >= size()) { |
| 174 | auto res = std::move(chain_[start_index_]); |
| 175 | auto size = res.size(); |
| 176 | chain_length_ -= size; |
| 177 | if (begin_offset_ != 0) { |
| 178 | memmove(res.data(), res.data() + begin_offset_, res.size() - begin_offset_); |
| 179 | size -= begin_offset_; |
| 180 | begin_offset_ = 0; |
| 181 | } |
| 182 | for (auto i = start_index_ + 1; i < chain_.size(); ++i) { |
| 183 | memcpy(res.data() + size, chain_[i].data(), chain_[i].size()); |
| 184 | size += chain_[i].size(); |
| 185 | } |
| 186 | res.resize(size); |
| 187 | ++start_index_; |
| 188 | return res; |
| 189 | } |
| 190 | return const_cast<const IOVector*>(this)->coalesce<>(); |
| 191 | } |
| 192 | |
| 193 | std::vector<adb_iovec> IOVector::iovecs() const { |
| 194 | std::vector<adb_iovec> result; |
| 195 | result.reserve(chain_.size() - start_index_); |
| 196 | iterate_blocks([&result](const char* data, size_t len) { |
| 197 | adb_iovec iov; |
| 198 | iov.iov_base = const_cast<char*>(data); |
| 199 | iov.iov_len = len; |
| 200 | result.emplace_back(iov); |
| 201 | }); |
| 202 | |
| 203 | return result; |
| 204 | } |