2 * Copyright 2013 Facebook, Inc.
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #include "folly/io/IOBufQueue.h"
25 using std::unique_ptr;
31 const size_t MIN_ALLOC_SIZE = 2000;
32 const size_t MAX_ALLOC_SIZE = 8000; // Must fit within a uint32_t
33 const size_t MAX_PACK_COPY = 4096;
36 * Convenience function to append chain src to chain dst.
39 appendToChain(unique_ptr<IOBuf>& dst, unique_ptr<IOBuf>&& src, bool pack) {
43 IOBuf* tail = dst->prev();
45 // Copy up to MAX_PACK_COPY bytes if we can free buffers; this helps
46 // reduce wastage (the tail's tailroom and the head's headroom) when
47 // joining two IOBufQueues together.
48 size_t copyRemaining = MAX_PACK_COPY;
51 (n = src->length()) < copyRemaining &&
52 n < tail->tailroom()) {
53 memcpy(tail->writableTail(), src->data(), n);
60 tail->appendChain(std::move(src));
65 } // anonymous namespace
69 IOBufQueue::IOBufQueue(const Options& options)
74 IOBufQueue::IOBufQueue(IOBufQueue&& other)
75 : options_(other.options_),
76 chainLength_(other.chainLength_),
77 head_(std::move(other.head_)) {
78 other.chainLength_ = 0;
81 IOBufQueue& IOBufQueue::operator=(IOBufQueue&& other) {
83 options_ = other.options_;
84 chainLength_ = other.chainLength_;
85 head_ = std::move(other.head_);
86 other.chainLength_ = 0;
91 std::pair<void*, uint32_t>
92 IOBufQueue::headroom() {
94 return std::make_pair(head_->writableBuffer(), head_->headroom());
96 return std::make_pair(nullptr, 0);
101 IOBufQueue::markPrepended(uint32_t n) {
107 if (options_.cacheChainLength) {
113 IOBufQueue::prepend(const void* buf, uint32_t n) {
116 throw std::overflow_error("Not enough room to prepend");
118 memcpy(static_cast<char*>(p.first) + p.second - n, buf, n);
123 IOBufQueue::append(unique_ptr<IOBuf>&& buf, bool pack) {
127 if (options_.cacheChainLength) {
128 chainLength_ += buf->computeChainDataLength();
130 appendToChain(head_, std::move(buf), pack);
134 IOBufQueue::append(IOBufQueue& other, bool pack) {
138 if (options_.cacheChainLength) {
139 if (other.options_.cacheChainLength) {
140 chainLength_ += other.chainLength_;
142 chainLength_ += other.head_->computeChainDataLength();
145 appendToChain(head_, std::move(other.head_), pack);
146 other.chainLength_ = 0;
150 IOBufQueue::append(const void* buf, size_t len) {
151 auto src = static_cast<const uint8_t*>(buf);
153 if ((head_ == nullptr) || head_->prev()->isSharedOne() ||
154 (head_->prev()->tailroom() == 0)) {
155 appendToChain(head_, std::move(
156 IOBuf::create(std::max(MIN_ALLOC_SIZE,
157 std::min(len, MAX_ALLOC_SIZE)))),
160 IOBuf* last = head_->prev();
161 uint32_t copyLen = std::min(len, (size_t)last->tailroom());
162 memcpy(last->writableTail(), src, copyLen);
164 last->append(copyLen);
165 if (options_.cacheChainLength) {
166 chainLength_ += copyLen;
173 IOBufQueue::wrapBuffer(const void* buf, size_t len, uint32_t blockSize) {
174 auto src = static_cast<const uint8_t*>(buf);
176 size_t n = std::min(len, size_t(blockSize));
177 append(IOBuf::wrapBuffer(src, n));
184 IOBufQueue::preallocate(uint32_t min, uint32_t newAllocationSize,
186 if (head_ != nullptr) {
187 // If there's enough space left over at the end of the queue, use that.
188 IOBuf* last = head_->prev();
189 if (!last->isSharedOne()) {
190 uint32_t avail = last->tailroom();
192 return make_pair(last->writableTail(), std::min(max, avail));
196 // Allocate a new buffer of the requested max size.
197 unique_ptr<IOBuf> newBuf(IOBuf::create(std::max(min, newAllocationSize)));
198 appendToChain(head_, std::move(newBuf), false);
199 IOBuf* last = head_->prev();
200 return make_pair(last->writableTail(),
201 std::min(max, last->tailroom()));
205 IOBufQueue::postallocate(uint32_t n) {
206 head_->prev()->append(n);
207 if (options_.cacheChainLength) {
213 IOBufQueue::split(size_t n) {
214 unique_ptr<IOBuf> result;
216 if (head_ == nullptr) {
217 throw std::underflow_error(
218 "Attempt to remove more bytes than are present in IOBufQueue");
219 } else if (head_->length() <= n) {
220 n -= head_->length();
221 if (options_.cacheChainLength) {
222 chainLength_ -= head_->length();
224 unique_ptr<IOBuf> remainder = head_->pop();
225 appendToChain(result, std::move(head_), false);
226 head_ = std::move(remainder);
228 unique_ptr<IOBuf> clone = head_->cloneOne();
229 clone->trimEnd(clone->length() - n);
230 appendToChain(result, std::move(clone), false);
232 if (options_.cacheChainLength) {
238 return std::move(result);
241 void IOBufQueue::trimStart(size_t amount) {
244 throw std::underflow_error(
245 "Attempt to trim more bytes than are present in IOBufQueue");
247 if (head_->length() > amount) {
248 head_->trimStart(amount);
249 if (options_.cacheChainLength) {
250 chainLength_ -= amount;
254 amount -= head_->length();
255 if (options_.cacheChainLength) {
256 chainLength_ -= head_->length();
258 head_ = head_->pop();
262 void IOBufQueue::trimEnd(size_t amount) {
265 throw std::underflow_error(
266 "Attempt to trim more bytes than are present in IOBufQueue");
268 if (head_->prev()->length() > amount) {
269 head_->prev()->trimEnd(amount);
270 if (options_.cacheChainLength) {
271 chainLength_ -= amount;
275 amount -= head_->prev()->length();
276 if (options_.cacheChainLength) {
277 chainLength_ -= head_->prev()->length();
280 if (head_->isChained()) {
281 head_->prev()->unlink();
288 std::unique_ptr<folly::IOBuf> IOBufQueue::pop_front() {
292 if (options_.cacheChainLength) {
293 chainLength_ -= head_->length();
295 std::unique_ptr<folly::IOBuf> retBuf = std::move(head_);
296 head_ = retBuf->pop();
300 void IOBufQueue::clear() {
304 IOBuf* buf = head_.get();
308 } while (buf != head_.get());
309 if (options_.cacheChainLength) {