191 lines
5.2 KiB
C
191 lines
5.2 KiB
C
/***
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*lseeki64.c - change file position
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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 _lseeki64() - move the file pointer
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*
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*Revision History:
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* 11-16-94 GJF Created. Adapted from lseek.c
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* 03-13-95 CFW Verify handles before passing to OS.
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* 06-12-95 GJF Replaced _osfile[] with _osfile() (macro referencing
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* field in ioinfo struct).
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* 06-26-95 GJF Added check that the file handle is open.
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* 12-19-97 GJF Exception-safe locking.
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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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* Convenient union for accessing the upper and lower 32-bits of a 64-bit
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* integer.
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*/
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typedef union doubleint {
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__int64 bigint;
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struct {
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unsigned long lowerhalf;
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long upperhalf;
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} twoints;
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} DINT;
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/***
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*__int64 _lseeki64( 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. The new
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* position is pos bytes (pos may be negative) away from the origin
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* 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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* _lseeki64() = locks/unlocks the file
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* _lseeki64_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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* __int64 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 -1i64 (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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__int64 __cdecl _lseeki64 (
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int fh,
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__int64 pos,
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int mthd
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)
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{
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__int64 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 OS error */
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return( -1i64 );
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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 = _lseeki64_lk( fh, pos, mthd ); /* seek */
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else {
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errno = EBADF;
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_doserrno = 0; /* not OS error */
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r = -1i64;
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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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/***
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*__int64 _lseeki64_lk( fh, pos, mthd ) - move the file pointer
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*
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*Purpose:
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* Non-locking version of _lseeki64 for internal use only.
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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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__int64 __cdecl _lseeki64_lk (
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int fh,
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__int64 pos,
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int mthd
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)
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{
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DINT newpos; /* new file position */
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unsigned long errcode; /* error code from API call */
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HANDLE osHandle; /* o.s. handle value */
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#else /* ndef _MT */
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__int64 __cdecl _lseeki64 (
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int fh,
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__int64 pos,
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int mthd
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)
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{
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DINT newpos; /* new file position */
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unsigned long errcode; /* error code from API call */
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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 OS error */
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return( -1i64 );
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}
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#endif /* _MT */
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newpos.bigint = pos;
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/* tell OS 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( -1i64 );
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}
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if ( ((newpos.twoints.lowerhalf =
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SetFilePointer( osHandle,
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newpos.twoints.lowerhalf,
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&(newpos.twoints.upperhalf),
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mthd )) == -1L) &&
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((errcode = GetLastError()) != NO_ERROR) )
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{
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_dosmaperr( errcode );
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return( -1i64 );
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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.bigint ); /* return */
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}
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