190 lines
6.2 KiB
C
190 lines
6.2 KiB
C
/***
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*lseek.c - change file position
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*
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* Copyright (c) 1989-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines _lseek() - move the file pointer
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*
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*Revision History:
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* 06-20-89 PHG Module created, based on asm version
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* 03-12-90 GJF Made calling type _CALLTYPE2 (for now), added #include
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* <cruntime.h> and fixed the copyright. Also, cleaned up
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* the formatting a bit.
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* 04-03-90 GJF Now _CALLTYPE1.
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* 07-24-90 SBM Removed '32' from API names
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* 08-14-90 SBM Compiles cleanly with -W3
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* 09-28-90 GJF New-style function declarators.
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* 12-04-90 GJF Appended Win32 version with #ifdef-s. It's probably
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* worth coming back and doing a more complete merge later
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* (much later).
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* 12-04-90 SRW Changed to include <oscalls.h> instead of <doscalls.h>
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* 12-06-90 SRW Changed to use _osfile and _osfhnd instead of _osfinfo
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* 01-16-91 GJF ANSI naming.
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* 02-07-91 SRW Changed to call _get_osfhandle [_WIN32_]
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* 04-09-91 PNT Added _MAC_ conditional
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* 02-13-92 GJF Replaced _nfile by _nhandle for Win32.
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* 04-06-93 SKS Replace _CRTAPI* with __cdecl
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* 09-06-94 CFW Remove Cruiser support.
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 12-03-94 SKS Clean up OS/2 references
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* 01-04-95 GJF _WIN32_ -> _WIN32
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* 02-15-95 GJF Appended Mac version of source file (somewhat cleaned
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* up), with appropriate #ifdef-s.
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* 03-13-95 CFW Verify handles before passing to OS.
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* 06-06-95 GJF Replaced _osfile[] with _osfile() (macro referencing
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* field in ioinfo struct).
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* 06-27-95 GJF Added check that the file handle is open.
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* 07-08-96 GJF Replaced defined(_WIN32) with !defined(_MAC), and
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* defined(_M_M68K) || defined(_M_MPPC) with
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* defined(_MAC). Also, detab-ed and cleaned up the
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* format a bit.
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* 12-30-97 GJF Exception-safe locking.
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* 05-17-99 PML Remove all Macintosh support.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <oscalls.h>
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#include <mtdll.h>
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#include <io.h>
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#include <internal.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <msdos.h>
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#include <stdio.h>
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/***
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*long _lseek(fh,pos,mthd) - move the file pointer
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*
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*Purpose:
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* Moves the file pointer associated with fh to a new position.
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* The new position is pos bytes (pos may be negative) away
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* from the origin specified by mthd.
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*
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* If mthd == SEEK_SET, the origin in the beginning of file
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* If mthd == SEEK_CUR, the origin is the current file pointer position
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* If mthd == SEEK_END, the origin is the end of the file
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*
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* Multi-thread:
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* _lseek() = locks/unlocks the file
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* _lseek_lk() = does NOT lock/unlock the file (it is assumed that
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* the caller has the aquired the file lock,if needed).
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*
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*Entry:
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* int fh - file handle to move file pointer on
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* long pos - position to move to, relative to origin
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* int mthd - specifies the origin pos is relative to (see above)
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*
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*Exit:
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* returns the offset, in bytes, of the new position from the beginning
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* of the file.
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* returns -1L (and sets errno) if fails.
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* Note that seeking beyond the end of the file is not an error.
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* (although seeking before the beginning is.)
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*
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*Exceptions:
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*
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*******************************************************************************/
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#ifdef _MT
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/* define locking/validating lseek */
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long __cdecl _lseek (
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int fh,
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long pos,
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int mthd
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)
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{
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int r;
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/* validate fh */
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if ( ((unsigned)fh >= (unsigned)_nhandle) ||
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!(_osfile(fh) & FOPEN) )
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{
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/* bad file handle */
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errno = EBADF;
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_doserrno = 0; /* not o.s. error */
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return -1;
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}
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_lock_fh(fh); /* lock file handle */
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__try {
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if ( _osfile(fh) & FOPEN )
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r = _lseek_lk(fh, pos, mthd); /* seek */
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else {
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errno = EBADF;
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_doserrno = 0;
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r = -1;
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}
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}
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__finally {
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_unlock_fh(fh); /* unlock file handle */
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}
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return r;
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}
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/* define core _lseek -- doesn't lock or validate fh */
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long __cdecl _lseek_lk (
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int fh,
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long pos,
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int mthd
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)
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{
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ULONG newpos; /* new file position */
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ULONG dosretval; /* o.s. return value */
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HANDLE osHandle; /* o.s. handle value */
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#else
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/* define normal _lseek */
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long __cdecl _lseek (
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int fh,
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long pos,
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int mthd
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)
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{
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ULONG newpos; /* new file position */
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ULONG dosretval; /* o.s. return value */
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HANDLE osHandle; /* o.s. handle value */
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/* validate fh */
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if ( ((unsigned)fh >= (unsigned)_nhandle) ||
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!(_osfile(fh) & FOPEN) )
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{
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/* bad file handle */
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errno = EBADF;
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_doserrno = 0; /* not o.s. error */
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return -1;
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}
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#endif
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/* tell o.s. to seek */
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#if SEEK_SET != FILE_BEGIN || SEEK_CUR != FILE_CURRENT || SEEK_END != FILE_END /*IFSTRIP=IGN*/
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#error Xenix and Win32 seek constants not compatible
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#endif
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if ((osHandle = (HANDLE)_get_osfhandle(fh)) == (HANDLE)-1)
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{
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errno = EBADF;
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return -1;
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}
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if ((newpos = SetFilePointer(osHandle, pos, NULL, mthd)) == -1)
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dosretval = GetLastError();
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else
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dosretval = 0;
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if (dosretval) {
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/* o.s. error */
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_dosmaperr(dosretval);
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return -1;
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}
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_osfile(fh) &= ~FEOFLAG; /* clear the ctrl-z flag on the file */
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return newpos; /* return */
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}
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