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https://github.com/facebookincubator/mvfst.git
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cf783ae678
Summary: `IOBufQueue` has some facilities for fast appending to the tail. This is not useful for us in the retransmission buffer usecase, and probably not at all. Flushing the tail cache from the `IOBufQueue` is expensive when we have to shuffle around the retransmission buffer queue on removal. This diff replaces `IOBufQueue` with a bespoke version that only has some of the functionality. This also changes the dependent peek APIs to use `IOBuf`s directly. Reviewed By: siyengar, yangchi Differential Revision: D18126437 fbshipit-source-id: a2fec0f45a72459855700c605bfd0d863a9067b7
78 lines
1.8 KiB
C++
78 lines
1.8 KiB
C++
// Copyright 2004-present Facebook. All Rights Reserved.
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#include "quic/common/BufUtil.h"
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namespace quic {
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Buf BufQueue::split(size_t n) {
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Buf result;
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while (n != 0) {
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if (chain_ == nullptr) {
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throw std::underflow_error(
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"Attempt to remove more bytes than are present in BufQueue");
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} else if (chain_->length() <= n) {
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n -= chain_->length();
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chainLength_ -= chain_->length();
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Buf remainder = chain_->pop();
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appendToChain(result, std::move(chain_));
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chain_ = std::move(remainder);
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} else {
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Buf clone = chain_->cloneOne();
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clone->trimEnd(clone->length() - n);
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appendToChain(result, std::move(clone));
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chain_->trimStart(n);
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chainLength_ -= n;
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break;
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}
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}
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if (UNLIKELY(result == nullptr)) {
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return folly::IOBuf::create(0);
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}
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return result;
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}
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size_t BufQueue::trimStartAtMost(size_t amount) {
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auto original = amount;
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while (amount > 0) {
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if (!chain_) {
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break;
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}
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if (chain_->length() > amount) {
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chain_->trimStart(amount);
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chainLength_ -= amount;
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amount = 0;
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break;
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}
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amount -= chain_->length();
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chainLength_ -= chain_->length();
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chain_ = chain_->pop();
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}
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return original - amount;
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}
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// TODO replace users with trimStartAtMost
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void BufQueue::trimStart(size_t amount) {
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auto trimmed = trimStartAtMost(amount);
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if (trimmed != amount) {
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throw std::underflow_error(
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"Attempt to trim more bytes than are present in BufQueue");
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}
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}
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void BufQueue::append(Buf&& buf) {
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if (!buf || buf->empty()) {
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return;
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}
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chainLength_ += buf->computeChainDataLength();
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appendToChain(chain_, std::move(buf));
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}
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void BufQueue::appendToChain(Buf& dst, Buf&& src) {
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if (dst == nullptr) {
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dst = std::move(src);
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} else {
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dst->prependChain(std::move(src));
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}
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}
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} // namespace quic
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