transmission/libtransmission/inout.c

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/*
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* This file Copyright (C) 2007-2008 Charles Kerr <charles@transmissionbt.com>
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*
* 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.
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*
* $Id$
*/
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#include <assert.h>
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#include <errno.h>
#include <stdlib.h> /* realloc */
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#include <string.h> /* memcmp */
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#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <openssl/sha.h>
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#include "transmission.h"
#include "crypto.h"
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#include "fdlimit.h"
#include "inout.h"
#include "platform.h"
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#include "stats.h"
#include "torrent.h"
#include "utils.h"
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/****
***** Low-level IO functions
****/
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#ifdef WIN32
#if defined(read)
#undef read
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#endif
#define read _read
#if defined(write)
#undef write
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#endif
#define write _write
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#endif
enum { TR_IO_READ, TR_IO_WRITE };
static int64_t
tr_lseek( int fd, int64_t offset, int whence )
{
#if defined(_LARGEFILE_SOURCE)
return lseek64( fd, (off64_t)offset, whence );
#elif defined(WIN32)
return _lseeki64( fd, offset, whence );
#else
return lseek( fd, (off_t)offset, whence );
#endif
}
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/* returns 0 on success, or an errno on failure */
static int
readOrWriteBytes( const tr_torrent * tor,
int ioMode,
tr_file_index_t fileIndex,
uint64_t fileOffset,
void * buf,
size_t buflen )
{
const tr_info * info = &tor->info;
const tr_file * file = &info->files[fileIndex];
typedef size_t ( *iofunc )( int, void *, size_t );
iofunc func = ioMode == TR_IO_READ ? (iofunc)read : (iofunc)write;
struct stat sb;
int fd = -1;
int err;
int fileExists;
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assert( tor->downloadDir && *tor->downloadDir );
assert( fileIndex < info->fileCount );
assert( !file->length || ( fileOffset < file->length ) );
assert( fileOffset + buflen <= file->length );
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{
char path[MAX_PATH_LENGTH];
tr_snprintf( path, sizeof( path ), "%s%c%s", tor->downloadDir, TR_PATH_DELIMITER, file->name );
fileExists = !stat( path, &sb );
}
if( !file->length )
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return 0;
if( ( ioMode == TR_IO_READ ) && !fileExists ) /* does file exist? */
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err = errno;
else if( ( fd = tr_fdFileCheckout ( tor->downloadDir, file->name, ioMode == TR_IO_WRITE, !file->dnd, file->length ) ) < 0 )
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err = errno;
else if( tr_lseek( fd, (int64_t)fileOffset, SEEK_SET ) == -1 )
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err = errno;
else if( func( fd, buf, buflen ) != buflen )
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err = errno;
else
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err = 0;
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if( ( !err ) && ( !fileExists ) && ( ioMode == TR_IO_WRITE ) )
tr_statsFileCreated( tor->session );
if( fd >= 0 )
tr_fdFileReturn( fd );
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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;
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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 )
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{
const uint64_t offset = tr_pieceOffset( tor, pieceIndex, pieceOffset, 0 );
const tr_file * file;
file = bsearch( &offset,
tor->info.files, tor->info.fileCount, sizeof( tr_file ),
compareOffsetToFile );
*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 );
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}
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/* returns 0 on success, or an errno on failure */
static int
readOrWritePiece( const tr_torrent * tor,
int ioMode,
tr_piece_index_t pieceIndex,
uint32_t pieceOffset,
uint8_t * buf,
size_t buflen )
{
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int err = 0;
tr_file_index_t fileIndex;
uint64_t fileOffset;
const tr_info * info = &tor->info;
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if( pieceIndex >= tor->info.pieceCount )
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return EINVAL;
if( pieceOffset + buflen > tr_torPieceCountBytes( tor, pieceIndex ) )
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return EINVAL;
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tr_ioFindFileLocation( tor, pieceIndex, pieceOffset,
&fileIndex, &fileOffset );
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while( buflen && !err )
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{
const tr_file * file = &info->files[fileIndex];
const uint64_t bytesThisPass = MIN( buflen, file->length - fileOffset );
err = readOrWriteBytes( tor, ioMode, fileIndex, fileOffset, buf, bytesThisPass );
buf += bytesThisPass;
buflen -= bytesThisPass;
++fileIndex;
fileOffset = 0;
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}
return err;
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}
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int
tr_ioRead( const tr_torrent * tor,
tr_piece_index_t pieceIndex,
uint32_t begin,
uint32_t len,
uint8_t * buf )
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{
return readOrWritePiece( tor, TR_IO_READ, pieceIndex, begin, buf, len );
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}
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int
tr_ioWrite( const tr_torrent * tor,
tr_piece_index_t pieceIndex,
uint32_t begin,
uint32_t len,
const uint8_t * buf )
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{
return readOrWritePiece( tor, TR_IO_WRITE, pieceIndex, begin,
(uint8_t*)buf,
len );
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}
/****
*****
****/
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static tr_bool
recalculateHash( const tr_torrent * tor,
tr_piece_index_t pieceIndex,
void * buffer,
size_t buflen,
uint8_t * setme )
{
size_t bytesLeft;
uint32_t offset = 0;
tr_bool success = TRUE;
uint8_t stackbuf[MAX_STACK_ARRAY_SIZE];
SHA_CTX sha;
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/* fallback buffer */
if( ( buffer == NULL ) || ( buflen < 1 ) )
{
buffer = stackbuf;
buflen = sizeof( stackbuf );
}
assert( tor != NULL );
assert( pieceIndex < tor->info.pieceCount );
assert( buffer != NULL );
assert( buflen > 0 );
assert( setme != NULL );
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SHA1_Init( &sha );
bytesLeft = tr_torPieceCountBytes( tor, pieceIndex );
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while( bytesLeft )
{
const int len = MIN( bytesLeft, buflen );
success = !tr_ioRead( tor, pieceIndex, offset, len, buffer );
if( !success )
break;
SHA1_Update( &sha, buffer, len );
offset += len;
bytesLeft -= len;
}
if( success )
SHA1_Final( setme, &sha );
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return success;
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}
tr_bool
tr_ioTestPiece( const tr_torrent * tor,
tr_piece_index_t pieceIndex,
void * buffer,
size_t buflen )
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{
uint8_t hash[SHA_DIGEST_LENGTH];
return recalculateHash( tor, pieceIndex, buffer, buflen, hash )
&& !memcmp( hash, tor->info.pieces[pieceIndex].hash, SHA_DIGEST_LENGTH );
}