156 lines
3.9 KiB
C
156 lines
3.9 KiB
C
/***
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*fseeki64.c - reposition file pointer on a stream
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*
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* Copyright (c) 1994-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines _fseeki64() - move the file pointer to new place in file
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*
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*Revision History:
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* 12-15-94 GJF Module created. Derived from fseek.c.
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* 02-06-94 CFW assert -> _ASSERTE.
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* 03-07-95 GJF _[un]lock_str macros now take FILE * arg.
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* 03-02-98 GJF Exception-safe locking.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <stdio.h>
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#include <file2.h>
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#include <dbgint.h>
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#include <msdos.h>
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#include <errno.h>
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#include <malloc.h>
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#include <io.h>
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#include <stddef.h>
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#include <internal.h>
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#include <mtdll.h>
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/***
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*int _fseeki64(stream, offset, whence) - reposition file pointer
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*
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*Purpose:
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*
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* Reposition file pointer to the desired location. The new location
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* is calculated as follows:
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* { whence=0, beginning of file }
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* <offset> bytes + { whence=1, current position }
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* { whence=2, end of file }
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*
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* Be careful to coordinate with buffering.
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*
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*Entry:
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* FILE *stream - file to reposition file pointer on
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* _int64 offset - offset to seek to
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* int whence - origin offset is measured from (0=beg, 1=current pos,
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* 2=end)
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*
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*Exit:
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* returns 0 if succeeds
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* returns -1 and sets errno if fails
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* fields of FILE struct will be changed
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*
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*Exceptions:
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*
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*******************************************************************************/
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#ifdef _MT /* multi-thread; define both fseek() and _lk_fseek() */
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int __cdecl _fseeki64 (
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FILE *stream,
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__int64 offset,
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int whence
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)
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{
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int retval;
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_ASSERTE(stream != NULL);
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_lock_str(stream);
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__try {
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retval = _fseeki64_lk (stream, offset, whence);
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}
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__finally {
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_unlock_str(stream);
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}
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return(retval);
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}
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/***
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*_fseeki64_lk() - Core _fseeki64() routine (stream is locked)
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*
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*Purpose:
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* Core _fseeki64() routine; assumes that caller has the stream locked.
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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int __cdecl _fseeki64_lk (
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#else /* non multi-thread; just define fseek() */
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int __cdecl _fseeki64 (
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#endif /* rejoin common code */
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FILE *str,
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__int64 offset,
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int whence
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)
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{
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REG1 FILE *stream;
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_ASSERTE(str != NULL);
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/* Init stream pointer */
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stream = str;
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if ( !inuse(stream) || ((whence != SEEK_SET) && (whence != SEEK_CUR) &&
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(whence != SEEK_END)) ) {
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errno=EINVAL;
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return(-1);
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}
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/* Clear EOF flag */
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stream->_flag &= ~_IOEOF;
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/* If seeking relative to current location, then convert to
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a seek relative to beginning of file. This accounts for
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buffering, etc. by letting fseek() tell us where we are. */
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if (whence == SEEK_CUR) {
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offset += _ftelli64_lk(stream);
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whence = SEEK_SET;
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}
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/* Flush buffer as necessary */
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_flush(stream);
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/* If file opened for read/write, clear flags since we don't know
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what the user is going to do next. If the file was opened for
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read access only, decrease _bufsiz so that the next _filbuf
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won't cost quite so much */
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if (stream->_flag & _IORW)
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stream->_flag &= ~(_IOWRT|_IOREAD);
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else if ( (stream->_flag & _IOREAD) && (stream->_flag & _IOMYBUF) &&
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!(stream->_flag & _IOSETVBUF) )
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stream->_bufsiz = _SMALL_BUFSIZ;
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/* Seek to the desired locale and return. */
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return(_lseeki64(_fileno(stream), offset, whence) == -1i64 ? -1 : 0);
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}
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