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transmission/libtransmission/inout.c

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/*
* 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 ) )
{
/* 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,
base, 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_PREFETCH ) {
const int rc = tr_prefetch( fd, fileOffset, buflen );
if( rc < 0 ) {
/* (don't set "err" here... it's okay for prefetch to fail) */
tr_tordbg( tor, "prefetch failed for \"%s\": %s",
file->name, tr_strerror( errno ) );
}
} 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 {
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 );
}
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