transmission/libtransmission/inout.cc

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// This file Copyright © 2007-2023 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.
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#include <algorithm>
#include <array>
#include <cerrno>
#include <optional>
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#include <string_view>
#include <utility> // std::move
#include <fmt/core.h>
#include "libtransmission/transmission.h"
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#include "libtransmission/block-info.h" // tr_block_info
#include "libtransmission/crypto-utils.h"
#include "libtransmission/error.h"
#include "libtransmission/file.h"
#include "libtransmission/inout.h"
#include "libtransmission/log.h"
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#include "libtransmission/session.h"
#include "libtransmission/torrent.h"
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#include "libtransmission/torrent-files.h"
#include "libtransmission/tr-assert.h"
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#include "libtransmission/tr-macros.h" // tr_sha1_digest_t
#include "libtransmission/tr-strbuf.h" // tr_pathbuf
#include "libtransmission/utils.h"
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using namespace std::literals;
namespace
{
bool readEntireBuf(tr_sys_file_t fd, uint64_t file_offset, uint8_t* buf, uint64_t buflen, tr_error** error)
{
while (buflen > 0)
{
auto n_read = uint64_t{};
if (!tr_sys_file_read_at(fd, buf, buflen, file_offset, &n_read, error))
{
return false;
}
buf += n_read;
buflen -= n_read;
file_offset += n_read;
}
return true;
}
bool writeEntireBuf(tr_sys_file_t fd, uint64_t file_offset, uint8_t const* buf, uint64_t buflen, tr_error** error)
{
while (buflen > 0)
{
auto n_written = uint64_t{};
if (!tr_sys_file_write_at(fd, buf, buflen, file_offset, &n_written, error))
{
return false;
}
buf += n_written;
buflen -= n_written;
file_offset += n_written;
}
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return true;
}
enum class IoMode
{
Read,
Prefetch,
Write
};
bool getFilename(tr_pathbuf& setme, tr_torrent const* tor, tr_file_index_t file_index, IoMode io_mode)
{
if (auto found = tor->find_file(file_index); found)
{
setme.assign(found->filename());
return true;
}
if (io_mode != IoMode::Write)
{
return false;
}
// We didn't find the file that we want to write to.
// Let's figure out where it goes so that we can create it.
auto const base = tor->current_dir();
auto const suffix = tor->session->isIncompleteFileNamingEnabled() ? tr_torrent_files::PartialFileSuffix : ""sv;
setme.assign(base, '/', tor->file_subpath(file_index), suffix);
return true;
}
void readOrWriteBytes(
tr_session* session,
tr_torrent* tor,
IoMode io_mode,
tr_file_index_t file_index,
uint64_t file_offset,
uint8_t* buf,
size_t buflen,
tr_error** error)
{
TR_ASSERT(file_index < tor->file_count());
bool const do_write = io_mode == IoMode::Write;
auto const file_size = tor->file_size(file_index);
TR_ASSERT(file_size == 0 || file_offset < file_size);
TR_ASSERT(file_offset + buflen <= file_size);
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if (file_size == 0)
{
return;
}
// --- Find the fd
auto fd = session->openFiles().get(tor->id(), file_index, do_write);
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auto filename = tr_pathbuf{};
if (!fd && !getFilename(filename, tor, file_index, io_mode))
{
auto const err = ENOENT;
auto const msg = fmt::format(
_("Couldn't get '{path}': {error} ({error_code})"),
fmt::arg("path", tor->file_subpath(file_index)),
fmt::arg("error", tr_strerror(err)),
fmt::arg("error_code", err));
tr_error_set(error, err, msg);
return;
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}
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if (!fd) // not in the cache, so open or create it now
{
// open (and maybe create) the file
auto const prealloc = (!do_write || !tor->file_is_wanted(file_index)) ? TR_PREALLOCATE_NONE :
tor->session->preallocationMode();
fd = session->openFiles().get(tor->id(), file_index, do_write, filename, prealloc, file_size);
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if (fd && do_write)
{
// make a note that we just created a file
tor->session->add_file_created();
}
}
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if (!fd) // couldn't create/open it either
{
auto const err = errno;
auto msg = fmt::format(
_("Couldn't get '{path}': {error} ({error_code})"),
fmt::arg("path", filename),
fmt::arg("error", tr_strerror(err)),
fmt::arg("error_code", err));
tr_error_set(error, err, msg);
tr_logAddErrorTor(tor, std::move(msg));
return;
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}
switch (io_mode)
{
case IoMode::Read:
if (tr_error* my_error = nullptr; !readEntireBuf(*fd, file_offset, buf, buflen, &my_error) && my_error != nullptr)
{
tr_logAddErrorTor(
tor,
fmt::format(
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_("Couldn't read '{path}': {error} ({error_code})"),
fmt::arg("path", tor->file_subpath(file_index)),
fmt::arg("error", my_error->message),
fmt::arg("error_code", my_error->code)));
tr_error_propagate(error, &my_error);
return;
}
break;
case IoMode::Write:
if (tr_error* my_error = nullptr; !writeEntireBuf(*fd, file_offset, buf, buflen, &my_error) && my_error != nullptr)
{
tr_logAddErrorTor(
tor,
fmt::format(
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_("Couldn't save '{path}': {error} ({error_code})"),
fmt::arg("path", tor->file_subpath(file_index)),
fmt::arg("error", my_error->message),
fmt::arg("error_code", my_error->code)));
tr_error_propagate(error, &my_error);
return;
}
break;
case IoMode::Prefetch:
tr_sys_file_advise(*fd, file_offset, buflen, TR_SYS_FILE_ADVICE_WILL_NEED);
break;
}
}
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/* returns 0 on success, or an errno on failure */
int readOrWritePiece(tr_torrent* tor, IoMode io_mode, tr_block_info::Location loc, uint8_t* buf, size_t buflen)
{
if (loc.piece >= tor->piece_count())
{
return EINVAL;
}
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auto [file_index, file_offset] = tor->file_offset(loc);
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while (buflen != 0)
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{
uint64_t const bytes_this_pass = std::min(uint64_t{ buflen }, uint64_t{ tor->file_size(file_index) - file_offset });
tr_error* error = nullptr;
readOrWriteBytes(tor->session, tor, io_mode, file_index, file_offset, buf, bytes_this_pass, &error);
if (error != nullptr)
{
if (io_mode == IoMode::Write && tor->error != TR_STAT_LOCAL_ERROR)
{
tor->set_local_error(error->message);
tr_torrentStop(tor);
}
auto const error_code = error->code;
tr_error_clear(&error);
return error_code;
}
if (buf != nullptr)
{
buf += bytes_this_pass;
}
buflen -= bytes_this_pass;
++file_index;
file_offset = 0;
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}
return 0;
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}
std::optional<tr_sha1_digest_t> recalculateHash(tr_torrent* tor, tr_piece_index_t piece)
{
TR_ASSERT(tor != nullptr);
TR_ASSERT(piece < tor->piece_count());
auto sha = tr_sha1::create();
auto buffer = std::array<uint8_t, tr_block_info::BlockSize>{};
auto& cache = tor->session->cache;
auto const [begin_byte, end_byte] = tor->block_info().byte_span_for_piece(piece);
auto const [begin_block, end_block] = tor->block_span_for_piece(piece);
[[maybe_unused]] auto n_bytes_checked = size_t{};
for (auto block = begin_block; block < end_block; ++block)
{
auto const block_loc = tor->block_loc(block);
auto const block_len = tor->block_size(block);
if (auto const success = cache->read_block(tor, block_loc, block_len, std::data(buffer)) == 0; !success)
{
return {};
}
auto begin = std::data(buffer);
auto end = begin + block_len;
// handle edge case where blocks aren't on piece boundaries:
if (block == begin_block) // `block` may begin before `piece` does
{
begin += (begin_byte - block_loc.byte);
}
if (block + 1 == end_block) // `block` may end after `piece` does
{
end -= (block_loc.byte + block_len - end_byte);
}
sha->add(begin, end - begin);
n_bytes_checked += (end - begin);
}
TR_ASSERT(tor->piece_size(piece) == n_bytes_checked);
return sha->finish();
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}
} // namespace
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int tr_ioRead(tr_torrent* tor, tr_block_info::Location const& loc, size_t len, uint8_t* setme)
{
return readOrWritePiece(tor, IoMode::Read, loc, setme, len);
}
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int tr_ioPrefetch(tr_torrent* tor, tr_block_info::Location const& loc, size_t len)
{
return readOrWritePiece(tor, IoMode::Prefetch, loc, nullptr, len);
}
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int tr_ioWrite(tr_torrent* tor, tr_block_info::Location const& loc, size_t len, uint8_t const* writeme)
{
return readOrWritePiece(tor, IoMode::Write, loc, const_cast<uint8_t*>(writeme), len);
}
bool tr_ioTestPiece(tr_torrent* tor, tr_piece_index_t piece)
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{
auto const hash = recalculateHash(tor, piece);
return hash && *hash == tor->piece_hash(piece);
}