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 <algorithm> // for std::copy_n
#include <cstddef>
#include <iterator>
#include <limits>
#include <memory>
#include <optional>
#include <string>
#include <string_view>
#include <event2/buffer.h>
#include "error.h"
#include "net.h" // tr_socket_t
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#include "tr-assert.h"
#include "utils-ev.h"
#include "utils.h" // for tr_htonll(), tr_ntohll()
namespace libtransmission
{
template<typename value_type>
class BufferReader
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{
public:
virtual ~BufferReader() = default;
virtual void drain(size_t n_bytes) = 0;
[[nodiscard]] virtual size_t size() const noexcept = 0;
[[nodiscard]] virtual value_type const* data() const = 0;
[[nodiscard]] auto empty() const noexcept
{
return size() == 0;
}
[[nodiscard]] auto const* begin() const noexcept
{
return data();
}
[[nodiscard]] auto const* end() const noexcept
{
return begin() + size();
}
template<typename T>
[[nodiscard]] TR_CONSTEXPR20 bool starts_with(T const& needle) const
{
auto const n_bytes = std::size(needle);
auto const needle_begin = reinterpret_cast<value_type const*>(std::data(needle));
auto const needle_end = needle_begin + n_bytes;
return n_bytes <= size() && std::equal(needle_begin, needle_end, data());
}
[[nodiscard]] auto to_string_view() const
{
return std::string_view{ reinterpret_cast<char const*>(data()), size() };
}
[[nodiscard]] auto to_string() const
{
return std::string{ to_string_view() };
}
void to_buf(void* tgt, size_t n_bytes)
{
n_bytes = std::min(n_bytes, size());
std::copy_n(data(), n_bytes, static_cast<value_type*>(tgt));
drain(n_bytes);
}
[[nodiscard]] auto to_uint8()
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{
auto tmp = uint8_t{};
to_buf(&tmp, sizeof(tmp));
return tmp;
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}
[[nodiscard]] uint16_t to_uint16()
{
auto tmp = uint16_t{};
to_buf(&tmp, sizeof(tmp));
return ntohs(tmp);
}
[[nodiscard]] uint32_t to_uint32()
{
auto tmp = uint32_t{};
to_buf(&tmp, sizeof(tmp));
return ntohl(tmp);
}
[[nodiscard]] uint64_t to_uint64()
{
auto tmp = uint64_t{};
to_buf(&tmp, sizeof(tmp));
return tr_ntohll(tmp);
}
// Returns the number of bytes written. Check `error` for error.
size_t to_socket(tr_socket_t sockfd, size_t n_bytes, tr_error** error = nullptr)
{
n_bytes = std::min(n_bytes, size());
if (n_bytes == 0U)
{
return {};
}
if (auto const n_sent = send(sockfd, reinterpret_cast<char const*>(data()), n_bytes, 0); n_sent >= 0U)
{
drain(n_sent);
return n_sent;
}
auto const err = sockerrno;
tr_error_set(error, err, tr_net_strerror(err));
return {};
}
};
template<typename value_type>
class BufferWriter
{
public:
virtual ~BufferWriter() = default;
virtual std::pair<value_type*, size_t> reserve_space(size_t n_bytes) = 0;
virtual void commit_space(size_t n_bytes) = 0;
void add(void const* span_begin, size_t span_len)
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{
auto [buf, buflen] = reserve_space(span_len);
std::copy_n(reinterpret_cast<value_type const*>(span_begin), span_len, buf);
commit_space(span_len);
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}
template<typename ContiguousContainer>
void add(ContiguousContainer const& container)
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{
add(std::data(container), std::size(container));
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}
template<typename OneByteType>
void push_back(OneByteType ch)
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{
add(&ch, 1);
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}
void add_uint8(uint8_t uch)
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{
add(&uch, 1);
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}
void add_uint16(uint16_t hs)
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{
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)
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{
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)
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{
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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}
void add_port(tr_port port)
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{
auto nport = port.network();
add(&nport, sizeof(nport));
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}
size_t add_socket(tr_socket_t sockfd, size_t n_bytes, tr_error** error = nullptr)
{
auto const [buf, buflen] = reserve_space(n_bytes);
auto const n_read = recv(sockfd, reinterpret_cast<char*>(buf), std::min(n_bytes, buflen), 0);
auto const err = sockerrno;
if (n_read > 0)
{
commit_space(n_read);
return static_cast<size_t>(n_read);
}
// When a stream socket peer has performed an orderly shutdown,
// the return value will be 0 (the traditional "end-of-file" return).
if (n_read == 0)
{
tr_error_set_from_errno(error, ENOTCONN);
}
else
{
tr_error_set(error, err, tr_net_strerror(err));
}
return {};
}
};
class Buffer final
: public BufferReader<std::byte>
, public BufferWriter<std::byte>
{
public:
using value_type = std::byte;
Buffer() = default;
Buffer(Buffer&&) = default;
Buffer(Buffer const&) = delete;
Buffer& operator=(Buffer&&) = default;
Buffer& operator=(Buffer const&) = delete;
template<typename T>
explicit Buffer(T const& data)
{
add(data);
}
[[nodiscard]] size_t size() const noexcept override
{
return evbuffer_get_length(buf_.get());
}
[[nodiscard]] value_type const* data() const override
{
return reinterpret_cast<value_type const*>(evbuffer_pullup(buf_.get(), -1));
}
void drain(size_t n_bytes) override
{
evbuffer_drain(buf_.get(), n_bytes);
}
[[nodiscard]] std::pair<value_type*, size_t> reserve_space(size_t n_bytes) override
{
auto iov = evbuffer_iovec{};
evbuffer_reserve_space(buf_.get(), n_bytes, &iov, 1);
TR_ASSERT(iov.iov_len >= n_bytes);
reserved_space_ = iov;
return { static_cast<value_type*>(iov.iov_base), static_cast<size_t>(iov.iov_len) };
}
void commit_space(size_t n_bytes) override
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{
TR_ASSERT(reserved_space_);
TR_ASSERT(reserved_space_->iov_len >= n_bytes);
reserved_space_->iov_len = n_bytes;
evbuffer_commit_space(buf_.get(), &*reserved_space_, 1);
reserved_space_.reset();
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}
private:
evhelpers::evbuffer_unique_ptr buf_{ evbuffer_new() };
std::optional<evbuffer_iovec> reserved_space_;
};
} // namespace libtransmission