transmission/libtransmission/inout.c

318 lines
8.3 KiB
C

/*
* This file Copyright (C) Mnemosyne LLC
*
* This file is licensed by the GPL version 2. Works owned by the
* Transmission project are granted a special exemption to clause 2 (b)
* so that the bulk of its code can remain under the MIT license.
* This exemption does not extend to derived works not owned by
* the Transmission project.
*
* $Id$
*/
#include <assert.h>
#include <errno.h>
#include <stdlib.h> /* bsearch () */
#include <string.h> /* memcmp () */
#include <openssl/sha.h>
#include "transmission.h"
#include "cache.h" /* tr_cacheReadBlock () */
#include "fdlimit.h"
#include "inout.h"
#include "peer-common.h" /* MAX_BLOCK_SIZE */
#include "stats.h" /* tr_statsFileCreated () */
#include "torrent.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 fd;
int err = 0;
const bool doWrite = ioMode >= TR_IO_WRITE;
const tr_info * const info = &tor->info;
const tr_file * const file = &info->files[fileIndex];
assert (fileIndex < info->fileCount);
assert (!file->length || (fileOffset < file->length));
assert (fileOffset + buflen <= file->length);
if (!file->length)
return 0;
/***
**** Find the fd
***/
fd = tr_fdFileGetCached (session, tr_torrentId (tor), fileIndex, doWrite);
if (fd < 0)
{
/* it's not cached, so open/create it now */
char * subpath;
const char * base;
/* see if the file exists... */
if (!tr_torrentFindFile2 (tor, fileIndex, &base, &subpath, NULL))
{
/* 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)
{
/* open (and maybe create) the file */
char * filename = tr_buildPath (base, subpath, NULL);
const int prealloc = file->dnd || !doWrite
? TR_PREALLOCATE_NONE
: tor->session->preallocationMode;
if (((fd = tr_fdFileCheckout (session, tor->uniqueId, fileIndex,
filename, doWrite,
prealloc, file->length))) < 0)
{
err = errno;
tr_torerr (tor, "tr_fdFileCheckout failed for \"%s\": %s",
filename, tr_strerror (err));
}
else if (doWrite)
{
/* make a note that we just created a file */
tr_statsFileCreated (tor->session);
}
tr_free (filename);
}
tr_free (subpath);
}
/***
**** Use the fd
***/
if (!err)
{
if (ioMode == TR_IO_READ)
{
const int rc = tr_pread (fd, buf, buflen, fileOffset);
if (rc < 0)
{
err = errno;
tr_torerr (tor, "read failed for \"%s\": %s", file->name, tr_strerror (err));
}
}
else if (ioMode == TR_IO_WRITE)
{
const int rc = tr_pwrite (fd, buf, buflen, fileOffset);
if (rc < 0)
{
err = errno;
tr_torerr (tor, "write failed for \"%s\": %s", file->name, tr_strerror (err));
}
}
else if (ioMode == TR_IO_PREFETCH)
{
tr_prefetch (fd, fileOffset, buflen);
}
else
{
abort ();
}
}
return err;
}
static int
compareOffsetToFile (const void * a, const void * b)
{
const uint64_t offset = * (const uint64_t*)a;
const tr_file * file = b;
if (offset < file->offset)
return -1;
if (offset >= file->offset + file->length)
return 1;
return 0;
}
void
tr_ioFindFileLocation (const tr_torrent * tor,
tr_piece_index_t pieceIndex,
uint32_t pieceOffset,
tr_file_index_t * fileIndex,
uint64_t * fileOffset)
{
const uint64_t offset = tr_pieceOffset (tor, pieceIndex, pieceOffset, 0);
const tr_file * file;
assert (tr_isTorrent (tor));
assert (offset < tor->info.totalSize);
file = bsearch (&offset,
tor->info.files, tor->info.fileCount, sizeof (tr_file),
compareOffsetToFile);
assert (file != NULL);
*fileIndex = file - tor->info.files;
*fileOffset = offset - file->offset;
assert (*fileIndex < tor->info.fileCount);
assert (*fileOffset < file->length);
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_file_index_t fileIndex;
uint64_t fileOffset;
const tr_info * info = &tor->info;
if (pieceIndex >= tor->info.pieceCount)
return EINVAL;
tr_ioFindFileLocation (tor, pieceIndex, pieceOffset,
&fileIndex, &fileOffset);
while (buflen && !err)
{
const tr_file * file = &info->files[fileIndex];
const uint64_t bytesThisPass = MIN (buflen, 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))
{
char * path = tr_buildPath (tor->downloadDir, file->name, NULL);
tr_torrentSetLocalError (tor, "%s (%s)", tr_strerror (err), path);
tr_free (path);
}
}
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, NULL, len);
}
int
tr_ioWrite (tr_torrent * tor,
tr_piece_index_t pieceIndex,
uint32_t begin,
uint32_t len,
const uint8_t * buf)
{
return readOrWritePiece (tor, TR_IO_WRITE, pieceIndex, begin, (uint8_t*)buf, len);
}
/****
*****
****/
static bool
recalculateHash (tr_torrent * tor, tr_piece_index_t pieceIndex, uint8_t * setme)
{
size_t bytesLeft;
uint32_t offset = 0;
bool success = true;
const size_t buflen = tor->blockSize;
void * buffer = tr_valloc (buflen);
SHA_CTX sha;
assert (tor != NULL);
assert (pieceIndex < tor->info.pieceCount);
assert (buffer != NULL);
assert (buflen > 0);
assert (setme != NULL);
SHA1_Init (&sha);
bytesLeft = tr_torPieceCountBytes (tor, pieceIndex);
tr_ioPrefetch (tor, pieceIndex, offset, bytesLeft);
while (bytesLeft)
{
const int len = MIN (bytesLeft, buflen);
success = !tr_cacheReadBlock (tor->session->cache, tor, pieceIndex, offset, len, buffer);
if (!success)
break;
SHA1_Update (&sha, buffer, len);
offset += len;
bytesLeft -= len;
}
if (success)
SHA1_Final (setme, &sha);
tr_free (buffer);
return success;
}
bool
tr_ioTestPiece (tr_torrent * tor, tr_piece_index_t piece)
{
uint8_t hash[SHA_DIGEST_LENGTH];
return recalculateHash (tor, piece, hash)
&& !memcmp (hash, tor->info.pieces[piece].hash, SHA_DIGEST_LENGTH);
}