transmission/libtransmission/inout.cc

235 lines
6.8 KiB
C++

// This file Copyright © 2007-2022 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.
#include <algorithm>
#include <cerrno>
#include <cstdlib> /* abort() */
#include <optional>
#include <vector>
#include "transmission.h"
#include "cache.h" /* tr_cacheReadBlock() */
#include "crypto-utils.h"
#include "error.h"
#include "fdlimit.h"
#include "file.h"
#include "inout.h"
#include "log.h"
#include "peer-common.h" /* MAX_BLOCK_SIZE */
#include "stats.h" /* tr_statsFileCreated() */
#include "torrent.h"
#include "tr-assert.h"
#include "utils.h"
using namespace std::literals;
/****
***** Low-level IO functions
****/
enum
{
TR_IO_READ,
TR_IO_PREFETCH,
/* Any operations that require write access must follow TR_IO_WRITE. */
TR_IO_WRITE
};
/* returns 0 on success, or an errno on failure */
static int readOrWriteBytes(
tr_session* session,
tr_torrent* tor,
int ioMode,
tr_file_index_t file_index,
uint64_t file_offset,
void* buf,
size_t buflen)
{
TR_ASSERT(file_index < tor->fileCount());
int err = 0;
bool const doWrite = ioMode >= TR_IO_WRITE;
auto const file_size = tor->fileSize(file_index);
TR_ASSERT(file_size == 0 || file_offset < file_size);
TR_ASSERT(file_offset + buflen <= file_size);
if (file_size == 0)
{
return 0;
}
/***
**** Find the fd
***/
auto fd = tr_fdFileGetCached(session, tr_torrentId(tor), file_index, doWrite);
if (fd == TR_BAD_SYS_FILE) /* it's not cached, so open/create it now */
{
/* see if the file exists... */
char const* base = nullptr;
char* subpath = nullptr;
if (!tr_torrentFindFile2(tor, file_index, &base, &subpath, nullptr))
{
/* we can't read a file that doesn't exist... */
if (!doWrite)
{
err = ENOENT;
}
/* figure out where the file should go, so we can create it */
base = tr_torrentGetCurrentDir(tor);
subpath = tr_sessionIsIncompleteFileNamingEnabled(tor->session) ? tr_torrentBuildPartial(tor, file_index) :
tr_strvDup(tor->fileSubpath(file_index));
}
if (err == 0)
{
/* open (and maybe create) the file */
auto const filename = tr_strvPath(base, subpath);
auto const prealloc = (!doWrite || !tor->fileIsWanted(file_index)) ? TR_PREALLOCATE_NONE :
tor->session->preallocationMode;
fd = tr_fdFileCheckout(session, tor->uniqueId, file_index, filename.c_str(), doWrite, prealloc, file_size);
if (fd == TR_BAD_SYS_FILE)
{
err = errno;
tr_logAddTorErr(tor, "tr_fdFileCheckout failed for \"%s\": %s", filename.c_str(), tr_strerror(err));
}
else if (doWrite)
{
/* make a note that we just created a file */
tr_statsFileCreated(tor->session);
}
}
tr_free(subpath);
}
/***
**** Use the fd
***/
if (err == 0)
{
tr_error* error = nullptr;
if (ioMode == TR_IO_READ)
{
if (!tr_sys_file_read_at(fd, buf, buflen, file_offset, nullptr, &error))
{
err = error->code;
tr_logAddTorErr(tor, "read failed for \"%s\": %s", tor->fileSubpath(file_index).c_str(), error->message);
tr_error_free(error);
}
}
else if (ioMode == TR_IO_WRITE)
{
if (!tr_sys_file_write_at(fd, buf, buflen, file_offset, nullptr, &error))
{
err = error->code;
tr_logAddTorErr(tor, "write failed for \"%s\": %s", tor->fileSubpath(file_index).c_str(), error->message);
tr_error_free(error);
}
}
else if (ioMode == TR_IO_PREFETCH)
{
tr_sys_file_advise(fd, file_offset, buflen, TR_SYS_FILE_ADVICE_WILL_NEED, nullptr);
}
else
{
abort();
}
}
return err;
}
/* returns 0 on success, or an errno on failure */
static int readOrWritePiece(tr_torrent* tor, int ioMode, tr_block_info::Location loc, uint8_t* buf, size_t buflen)
{
int err = 0;
if (loc.piece >= tor->pieceCount())
{
return EINVAL;
}
auto [file_index, file_offset] = tor->fileOffset(loc);
while (buflen != 0 && err == 0)
{
uint64_t const bytes_this_pass = std::min(uint64_t{ buflen }, uint64_t{ tor->fileSize(file_index) - file_offset });
err = readOrWriteBytes(tor->session, tor, ioMode, file_index, file_offset, buf, bytes_this_pass);
buf += bytes_this_pass;
buflen -= bytes_this_pass;
if (err != 0 && ioMode == TR_IO_WRITE && tor->error != TR_STAT_LOCAL_ERROR)
{
auto const path = tr_strvPath(tor->downloadDir().sv(), tor->fileSubpath(file_index));
tor->setLocalError(tr_strvJoin(tr_strerror(err), " ("sv, path, ")"sv));
}
++file_index;
file_offset = 0;
}
return err;
}
int tr_ioRead(tr_torrent* tor, tr_block_info::Location loc, uint32_t len, uint8_t* buf)
{
return readOrWritePiece(tor, TR_IO_READ, loc, buf, len);
}
int tr_ioPrefetch(tr_torrent* tor, tr_block_info::Location loc, uint32_t len)
{
return readOrWritePiece(tor, TR_IO_PREFETCH, loc, nullptr, len);
}
int tr_ioWrite(tr_torrent* tor, tr_block_info::Location loc, uint32_t len, uint8_t const* buf)
{
return readOrWritePiece(tor, TR_IO_WRITE, loc, (uint8_t*)buf, len);
}
/****
*****
****/
static std::optional<tr_sha1_digest_t> recalculateHash(tr_torrent* tor, tr_piece_index_t piece)
{
TR_ASSERT(tor != nullptr);
TR_ASSERT(piece < tor->pieceCount());
auto bytes_left = size_t(tor->pieceSize(piece));
auto loc = tor->pieceLoc(piece);
tr_ioPrefetch(tor, loc, bytes_left);
auto sha = tr_sha1_init();
auto buffer = std::vector<uint8_t>(tor->blockSize());
while (bytes_left != 0)
{
size_t const len = std::min(bytes_left, std::size(buffer));
if (auto const success = tr_cacheReadBlock(tor->session->cache, tor, loc, len, std::data(buffer)) == 0; !success)
{
tr_sha1_final(sha);
return {};
}
tr_sha1_update(sha, std::data(buffer), len);
loc = tor->byteLoc(loc.byte + len);
bytes_left -= len;
}
return tr_sha1_final(sha);
}
bool tr_ioTestPiece(tr_torrent* tor, tr_piece_index_t piece)
{
auto const hash = recalculateHash(tor, piece);
return hash && *hash == tor->pieceHash(piece);
}