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perf: in Buffer::Iterator, defer evbuffer API calls (#5420)

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Charles Kerr 2023-04-19 16:00:30 -05:00 committed by GitHub
parent f2aa3e197b
commit 3044c14b10
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 71 additions and 43 deletions
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114
libtransmission/tr-buffer.h
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@ -112,28 +112,30 @@ public:
using reference = value_type&;
using iterator_category = std::random_access_iterator_tag;
Iterator(evbuffer* buf, size_t offset)
constexpr Iterator(evbuffer* buf, size_t offset)
: buf_{ buf }
, buf_offset_{ offset }
{
set_offset(offset);
}
[[nodiscard]] constexpr value_type& operator*() noexcept
[[nodiscard]] value_type& operator*() noexcept
{
return static_cast<value_type*>(iov_.iov_base)[iov_offset_];
auto& info = iov();
return static_cast<value_type*>(info.iov.iov_base)[info.offset];
}
[[nodiscard]] constexpr value_type operator*() const noexcept
[[nodiscard]] value_type operator*() const noexcept
{
return static_cast<value_type*>(iov_.iov_base)[iov_offset_];
auto const& info = iov();
return static_cast<value_type*>(info.iov.iov_base)[info.offset];
}
[[nodiscard]] Iterator operator+(size_t n_bytes)
[[nodiscard]] constexpr Iterator operator+(size_t n_bytes)
{
return Iterator{ buf_, offset() + n_bytes };
}
[[nodiscard]] Iterator operator-(size_t n_bytes)
[[nodiscard]] constexpr Iterator operator-(size_t n_bytes)
{
return Iterator{ buf_, offset() - n_bytes };
}
@ -143,73 +145,99 @@ public:
return offset() - that.offset();
}
Iterator& operator++() noexcept
constexpr Iterator& operator++() noexcept
{
*this += 1U;
inc_offset(1U);
return *this;
}
Iterator& operator+=(size_t n_bytes)
constexpr Iterator& operator+=(size_t n_bytes)
{
if (iov_offset_ + n_bytes < iov_.iov_len)
{
iov_offset_ += n_bytes;
}
else
{
inc_offset(n_bytes);
}
inc_offset(n_bytes);
return *this;
}
Iterator& operator--() noexcept
constexpr Iterator& operator--() noexcept
{
if (iov_offset_ > 0)
{
--iov_offset_;
}
else
{
set_offset(offset() - 1);
}
dec_offset(1);
return *this;
}
[[nodiscard]] constexpr bool operator==(Iterator const& that) const noexcept
{
return offset() == that.offset();
return this->buf_ == that.buf_ && this->offset() == that.offset();
}
[[nodiscard]] constexpr bool operator!=(Iterator const& that) const noexcept
{
return offset() != that.offset();
return !(*this == that);
}
private:
struct IovInfo
{
evbuffer_iovec iov = {};
size_t offset = 0;
};
[[nodiscard]] constexpr size_t offset() const noexcept
{
return ptr_.pos + iov_offset_;
return buf_offset_;
}
void inc_offset(size_t increment)
constexpr void dec_offset(size_t increment)
{
evbuffer_ptr_set(buf_, &ptr_, iov_offset_ + increment, EVBUFFER_PTR_ADD);
evbuffer_peek(buf_, std::numeric_limits<ev_ssize_t>::max(), &ptr_, &iov_, 1);
iov_offset_ = 0;
buf_offset_ -= increment;
if (iov_)
{
if (iov_->offset >= increment)
{
iov_->offset -= increment;
}
else
{
iov_.reset();
}
}
}
void set_offset(size_t offset)
constexpr void inc_offset(size_t increment)
{
evbuffer_ptr_set(buf_, &ptr_, offset, EVBUFFER_PTR_SET);
evbuffer_peek(buf_, std::numeric_limits<ev_ssize_t>::max(), &ptr_, &iov_, 1);
iov_offset_ = 0;
buf_offset_ += increment;
if (iov_)
{
if (iov_->offset + increment < iov_->iov.iov_len)
{
iov_->offset += increment;
}
else
{
iov_.reset();
}
}
}
[[nodiscard]] IovInfo& iov() const noexcept
{
if (!iov_)
{
auto ptr = evbuffer_ptr{};
auto iov = IovInfo{};
evbuffer_ptr_set(buf_, &ptr, buf_offset_, EVBUFFER_PTR_SET);
evbuffer_peek(buf_, std::numeric_limits<ev_ssize_t>::max(), &ptr, &iov.iov, 1);
iov.offset = 0;
iov_ = iov;
}
return *iov_;
}
mutable std::optional<IovInfo> iov_;
evbuffer* buf_;
evbuffer_ptr ptr_ = {};
evbuffer_iovec iov_ = {};
size_t iov_offset_ = 0;
size_t buf_offset_ = 0;
};
Buffer(Buffer&&) = default;