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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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src
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fseeki64.c
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1998-06-17
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/***
*fseeki64.c - reposition file pointer on a stream
*
* Copyright (c) 1994-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines _fseeki64() - move the file pointer to new place in file
*
*******************************************************************************/
#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <dbgint.h>
#include <msdos.h>
#include <errno.h>
#include <malloc.h>
#include <io.h>
#include <stddef.h>
#include <internal.h>
#include <mtdll.h>
/***
*int _fseeki64(stream, offset, whence) - reposition file pointer
*
*Purpose:
*
* Reposition file pointer to the desired location. The new location
* is calculated as follows:
* { whence=0, beginning of file }
* <offset> bytes + { whence=1, current position }
* { whence=2, end of file }
*
* Be careful to coordinate with buffering.
*
*Entry:
* FILE *stream - file to reposition file pointer on
* _int64 offset - offset to seek to
* int whence - origin offset is measured from (0=beg, 1=current pos,
* 2=end)
*
*Exit:
* returns 0 if succeeds
* returns -1 and sets errno if fails
* fields of FILE struct will be changed
*
*Exceptions:
*
*******************************************************************************/
#ifdef _MT
int __cdecl _fseeki64 (
FILE *stream,
__int64 offset,
int whence
)
{
int retval;
_ASSERTE(stream != NULL);
_lock_str(stream);
retval = _fseeki64_lk (stream, offset, whence);
_unlock_str(stream);
return(retval);
}
/***
*_fseeki64_lk() - Core _fseeki64() routine (stream is locked)
*
*Purpose:
* Core _fseeki64() routine; assumes that caller has the stream locked.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
int __cdecl _fseeki64_lk (
#else /* _MT */
int __cdecl _fseeki64 (
#endif /* _MT */
FILE *str,
__int64 offset,
int whence
)
{
REG1 FILE *stream;
_ASSERTE(str != NULL);
/* Init stream pointer */
stream = str;
if ( !inuse(stream) || ((whence != SEEK_SET) && (whence != SEEK_CUR) &&
(whence != SEEK_END)) ) {
errno=EINVAL;
return(-1);
}
/* Clear EOF flag */
stream->_flag &= ~_IOEOF;
/* If seeking relative to current location, then convert to
a seek relative to beginning of file. This accounts for
buffering, etc. by letting fseek() tell us where we are. */
if (whence == SEEK_CUR) {
offset += _ftelli64_lk(stream);
whence = SEEK_SET;
}
/* Flush buffer as necessary */
_flush(stream);
/* If file opened for read/write, clear flags since we don't know
what the user is going to do next. If the file was opened for
read access only, decrease _bufsiz so that the next _filbuf
won't cost quite so much */
if (stream->_flag & _IORW)
stream->_flag &= ~(_IOWRT|_IOREAD);
else if ( (stream->_flag & _IOREAD) && (stream->_flag & _IOMYBUF) &&
!(stream->_flag & _IOSETVBUF) )
stream->_bufsiz = _SMALL_BUFSIZ;
/* Seek to the desired locale and return. */
return(_lseeki64(_fileno(stream), offset, whence) == -1i64 ? -1 : 0);
}