transmission/libtransmission/tr-buffer.h

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// This file Copyright © 2022-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#pragma once
#include <cstddef>
#include <iterator>
#include <limits>
#include <memory>
#include <string>
#include <string_view>
#include <event2/buffer.h>
#include "error.h"
#include "net.h" // tr_socket_t
#include "utils-ev.h"
#include "utils.h" // for tr_htonll(), tr_ntohll()
namespace libtransmission
{
class Buffer
{
public:
class Iterator
{
public:
using difference_type = long;
using value_type = std::byte;
using pointer = value_type*;
using reference = value_type&;
using iterator_category = std::random_access_iterator_tag;
Iterator(evbuffer* buf, size_t offset)
: buf_{ buf }
{
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set_offset(offset);
}
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[[nodiscard]] constexpr value_type& operator*() noexcept
{
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return static_cast<value_type*>(iov_.iov_base)[iov_offset_];
}
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[[nodiscard]] constexpr value_type operator*() const noexcept
{
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return static_cast<value_type*>(iov_.iov_base)[iov_offset_];
}
[[nodiscard]] Iterator operator+(size_t n_bytes)
{
return Iterator{ buf_, offset() + n_bytes };
}
[[nodiscard]] Iterator operator-(size_t n_bytes)
{
return Iterator{ buf_, offset() - n_bytes };
}
[[nodiscard]] constexpr auto operator-(Iterator const& that) const noexcept
{
return offset() - that.offset();
}
Iterator& operator++() noexcept
{
*this += 1U;
return *this;
}
Iterator& operator+=(size_t n_bytes)
{
if (iov_offset_ + n_bytes < iov_.iov_len)
{
iov_offset_ += n_bytes;
}
else
{
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inc_offset(n_bytes);
}
return *this;
}
Iterator& operator--() noexcept
{
if (iov_offset_ > 0)
{
--iov_offset_;
}
else
{
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set_offset(offset() - 1);
}
return *this;
}
[[nodiscard]] constexpr bool operator==(Iterator const& that) const noexcept
{
return offset() == that.offset();
}
[[nodiscard]] constexpr bool operator!=(Iterator const& that) const noexcept
{
return offset() != that.offset();
}
private:
[[nodiscard]] constexpr size_t offset() const noexcept
{
return ptr_.pos + iov_offset_;
}
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void inc_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;
}
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void set_offset(size_t offset)
{
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;
}
evbuffer* buf_;
evbuffer_ptr ptr_ = {};
evbuffer_iovec iov_ = {};
size_t iov_offset_ = 0;
};
Buffer() = default;
Buffer(Buffer&&) = default;
Buffer(Buffer const&) = delete;
Buffer& operator=(Buffer const&) = delete;
Buffer& operator=(Buffer&&) = default;
template<typename T>
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explicit Buffer(T const& data)
{
add(std::data(data), std::size(data));
}
[[nodiscard]] auto size() const noexcept
{
return evbuffer_get_length(buf_.get());
}
[[nodiscard]] auto empty() const noexcept
{
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return evbuffer_get_length(buf_.get()) == 0;
}
[[nodiscard]] auto begin() noexcept
{
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return Iterator{ buf_.get(), 0U };
}
[[nodiscard]] auto end() noexcept
{
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return Iterator{ buf_.get(), size() };
}
[[nodiscard]] auto begin() const noexcept
{
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return Iterator{ buf_.get(), 0U };
}
[[nodiscard]] auto end() const noexcept
{
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return Iterator{ buf_.get(), size() };
}
template<typename T>
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[[nodiscard]] TR_CONSTEXPR20 bool starts_with(T const& needle) const
{
auto const n_bytes = std::size(needle);
auto const needle_begin = reinterpret_cast<std::byte const*>(std::data(needle));
auto const needle_end = needle_begin + n_bytes;
return n_bytes <= size() && std::equal(needle_begin, needle_end, cbegin());
}
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[[nodiscard]] std::string to_string() const
{
auto str = std::string{};
str.resize(size());
evbuffer_copyout(buf_.get(), std::data(str), std::size(str));
return str;
}
auto to_buf(void* tgt, size_t n_bytes)
{
return evbuffer_remove(buf_.get(), tgt, n_bytes);
}
[[nodiscard]] auto to_uint8()
{
auto tmp = uint8_t{};
to_buf(&tmp, sizeof(tmp));
return tmp;
}
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[[nodiscard]] uint16_t to_uint16()
{
auto tmp = uint16_t{};
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to_buf(&tmp, sizeof(tmp));
return ntohs(tmp);
}
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[[nodiscard]] uint32_t to_uint32()
{
auto tmp = uint32_t{};
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to_buf(&tmp, sizeof(tmp));
return ntohl(tmp);
}
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[[nodiscard]] uint64_t to_uint64()
{
auto tmp = uint64_t{};
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to_buf(&tmp, sizeof(tmp));
return tr_ntohll(tmp);
}
void drain(size_t n_bytes)
{
evbuffer_drain(buf_.get(), n_bytes);
}
void clear()
{
drain(size());
}
// Returns the number of bytes written. Check `error` for error.
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size_t to_socket(tr_socket_t sockfd, size_t n_bytes, tr_error** error = nullptr)
{
EVUTIL_SET_SOCKET_ERROR(0);
auto const res = evbuffer_write_atmost(buf_.get(), sockfd, n_bytes);
auto const err = EVUTIL_SOCKET_ERROR();
if (res >= 0)
{
return static_cast<size_t>(res);
}
tr_error_set(error, err, tr_net_strerror(err));
return 0;
}
[[nodiscard]] std::pair<std::byte*, size_t> pullup()
{
return { reinterpret_cast<std::byte*>(evbuffer_pullup(buf_.get(), -1)), size() };
}
[[nodiscard]] auto pullup_sv()
{
auto const [buf, buflen] = pullup();
return std::string_view{ reinterpret_cast<char const*>(buf), buflen };
}
void reserve(size_t n_bytes)
{
evbuffer_expand(buf_.get(), n_bytes - size());
}
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size_t add_socket(tr_socket_t sockfd, size_t n_bytes, tr_error** error = nullptr)
{
EVUTIL_SET_SOCKET_ERROR(0);
auto const res = evbuffer_read(buf_.get(), sockfd, static_cast<int>(n_bytes));
auto const err = EVUTIL_SOCKET_ERROR();
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if (res > 0)
{
return static_cast<size_t>(res);
}
if (res == 0)
{
tr_error_set_from_errno(error, ENOTCONN);
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}
else
{
tr_error_set(error, err, tr_net_strerror(err));
}
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return {};
}
// Move all data from one buffer into another.
// This is a destructive add: the source buffer is empty after this call.
void add(Buffer& that)
{
evbuffer_add_buffer(buf_.get(), that.buf_.get());
}
void add(Buffer&& that)
{
evbuffer_add_buffer(buf_.get(), that.buf_.get());
}
void add(void const* bytes, size_t n_bytes)
{
evbuffer_add(buf_.get(), bytes, n_bytes);
}
template<typename T>
void add(T const& data)
{
add(std::data(data), std::size(data));
}
template<
typename T,
typename std::enable_if_t<
std::is_same_v<T, char> || std::is_same_v<T, unsigned char> || std::is_same_v<T, std::byte>>* = nullptr>
void push_back(T ch)
{
add(&ch, 1);
}
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void add_port(tr_port const& port)
{
auto nport = port.network();
add(&nport, sizeof(nport));
}
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void add_uint8(uint8_t uch)
{
add(&uch, 1);
}
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void add_uint16(uint16_t hs)
{
uint16_t const ns = htons(hs);
add(&ns, sizeof(ns));
}
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void add_hton16(uint16_t hs)
{
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add_uint16(hs);
}
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void add_uint32(uint32_t hl)
{
uint32_t const nl = htonl(hl);
add(&nl, sizeof(nl));
}
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void eadd_hton32(uint32_t hl)
{
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add_uint32(hl);
}
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void add_uint64(uint64_t hll)
{
uint64_t const nll = tr_htonll(hll);
add(&nll, sizeof(nll));
}
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void add_hton64(uint64_t hll)
{
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add_uint64(hll);
}
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private:
evhelpers::evbuffer_unique_ptr buf_{ evbuffer_new() };
[[nodiscard]] Iterator cbegin() const noexcept
{
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return Iterator{ buf_.get(), 0U };
}
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[[nodiscard]] Iterator cend() const noexcept
{
return Iterator{ buf_.get(), size() };
}
};
} // namespace libtransmission