transmission/libtransmission/inout.cc

292 lines
8.1 KiB
C++

/*
* This file Copyright (C) 2007-2014 Mnemosyne LLC
*
* It may be used under the GNU GPL versions 2 or 3
* or any future license endorsed by Mnemosyne LLC.
*
*/
#include <algorithm>
#include <cerrno>
#include <cstdlib> /* bsearch() */
#include <cstring> /* memcmp() */
#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"
/****
***** 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 fileIndex,
uint64_t fileOffset,
void* buf,
size_t buflen)
{
int err = 0;
bool const doWrite = ioMode >= TR_IO_WRITE;
tr_info const* const info = &tor->info;
tr_file const* const file = &info->files[fileIndex];
TR_ASSERT(fileIndex < info->fileCount);
TR_ASSERT(file->length == 0 || fileOffset < file->length);
TR_ASSERT(fileOffset + buflen <= file->length);
if (file->length == 0)
{
return 0;
}
/***
**** Find the fd
***/
tr_sys_file_t fd = tr_fdFileGetCached(session, tr_torrentId(tor), fileIndex, 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, fileIndex, &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, fileIndex) :
tr_strdup(file->name);
}
if (err == 0)
{
/* open (and maybe create) the file */
auto const filename = tr_strvPath(base, subpath);
tr_preallocation_mode const prealloc = (file->dnd || !doWrite) ? TR_PREALLOCATE_NONE :
tor->session->preallocationMode;
fd = tr_fdFileCheckout(session, tor->uniqueId, fileIndex, filename.c_str(), doWrite, prealloc, file->length);
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, fileOffset, nullptr, &error))
{
err = error->code;
tr_logAddTorErr(tor, "read failed for \"%s\": %s", file->name, error->message);
tr_error_free(error);
}
}
else if (ioMode == TR_IO_WRITE)
{
if (!tr_sys_file_write_at(fd, buf, buflen, fileOffset, nullptr, &error))
{
err = error->code;
tr_logAddTorErr(tor, "write failed for \"%s\": %s", file->name, error->message);
tr_error_free(error);
}
}
else if (ioMode == TR_IO_PREFETCH)
{
tr_sys_file_advise(fd, fileOffset, buflen, TR_SYS_FILE_ADVICE_WILL_NEED, nullptr);
}
else
{
abort();
}
}
return err;
}
static int compareOffsetToFile(void const* a, void const* b)
{
auto const offset = *static_cast<uint64_t const*>(a);
auto const* file = static_cast<tr_file const*>(b);
if (offset < file->offset)
{
return -1;
}
if (offset >= file->offset + file->length)
{
return 1;
}
return 0;
}
void tr_ioFindFileLocation(
tr_torrent const* tor,
tr_piece_index_t pieceIndex,
uint32_t pieceOffset,
tr_file_index_t* fileIndex,
uint64_t* fileOffset)
{
TR_ASSERT(tr_isTorrent(tor));
uint64_t const offset = tr_pieceOffset(tor, pieceIndex, pieceOffset, 0);
TR_ASSERT(offset < tor->info.totalSize);
auto const* file = static_cast<tr_file const*>(
bsearch(&offset, tor->info.files, tor->info.fileCount, sizeof(tr_file), compareOffsetToFile));
TR_ASSERT(file != nullptr);
if (file != nullptr)
{
*fileIndex = file - tor->info.files;
*fileOffset = offset - file->offset;
TR_ASSERT(*fileIndex < tor->info.fileCount);
TR_ASSERT(*fileOffset < file->length);
TR_ASSERT(tor->info.files[*fileIndex].offset + *fileOffset == offset);
}
}
/* returns 0 on success, or an errno on failure */
static int readOrWritePiece(
tr_torrent* tor,
int ioMode,
tr_piece_index_t pieceIndex,
uint32_t pieceOffset,
uint8_t* buf,
size_t buflen)
{
int err = 0;
tr_info const* info = &tor->info;
if (pieceIndex >= tor->info.pieceCount)
{
return EINVAL;
}
auto fileIndex = tr_file_index_t{};
auto fileOffset = uint64_t{};
tr_ioFindFileLocation(tor, pieceIndex, pieceOffset, &fileIndex, &fileOffset);
while (buflen != 0 && err == 0)
{
tr_file const* file = &info->files[fileIndex];
uint64_t const bytesThisPass = std::min(uint64_t{ buflen }, uint64_t{ file->length - fileOffset });
err = readOrWriteBytes(tor->session, tor, ioMode, fileIndex, fileOffset, buf, bytesThisPass);
buf += bytesThisPass;
buflen -= bytesThisPass;
fileIndex++;
fileOffset = 0;
if (err != 0 && ioMode == TR_IO_WRITE && tor->error != TR_STAT_LOCAL_ERROR)
{
auto const path = tr_strvPath(tor->downloadDir, file->name);
tr_torrentSetLocalError(tor, "%s (%s)", tr_strerror(err), path.c_str());
}
}
return err;
}
int tr_ioRead(tr_torrent* tor, tr_piece_index_t pieceIndex, uint32_t begin, uint32_t len, uint8_t* buf)
{
return readOrWritePiece(tor, TR_IO_READ, pieceIndex, begin, buf, len);
}
int tr_ioPrefetch(tr_torrent* tor, tr_piece_index_t pieceIndex, uint32_t begin, uint32_t len)
{
return readOrWritePiece(tor, TR_IO_PREFETCH, pieceIndex, begin, nullptr, len);
}
int tr_ioWrite(tr_torrent* tor, tr_piece_index_t pieceIndex, uint32_t begin, uint32_t len, uint8_t const* buf)
{
return readOrWritePiece(tor, TR_IO_WRITE, pieceIndex, begin, (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->info.pieceCount);
auto bytes_left = size_t{ tr_torPieceCountBytes(tor, piece) };
auto offset = uint32_t{};
tr_ioPrefetch(tor, piece, offset, 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));
auto const success = tr_cacheReadBlock(tor->session->cache, tor, piece, offset, len, std::data(buffer)) == 0;
if (!success)
{
tr_sha1_final(sha, nullptr);
return {};
}
tr_sha1_update(sha, std::data(buffer), len);
offset += 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);
}