282 lines
9.5 KiB
C
282 lines
9.5 KiB
C
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/***
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*ftell.c - get current file position
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*
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* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines ftell() - find current current position of file pointer
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*
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*Revision History:
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* 09-02-83 RN initial version
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* ??-??-?? TC added code to allow variable buffer sizes
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* 05-22-86 TC added code to seek to send if last operation was a
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* write and append mode specified
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* 11-20-86 SKS do not seek to end of file in append mode
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* 12-01-86 SKS fix off-by-1 problem in text mode when last byte in
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* buffer was a '\r', and it was followed by a '\n'. Since
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* the \n was pushed back and the \r was discarded, we
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* must adjust the computed position for the \r.
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* 02-09-87 JCR Added errno set code (if flag (_IORW not set)
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* 09-09-87 JCR Optimized to eliminate two lseek() calls in binary mode.
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* 09-28-87 JCR Corrected _iob2 indexing (now uses _iob_index() macro).
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* 11-04-87 JCR Multi-thread version
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* 12-11-87 JCR Added "_LOAD_DS" to declaration
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* 01-13-88 JCR Removed unnecessary calls to mthread fileno/feof/ferror
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* 05-27-88 PHG Merged DLL and normal versions
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* 06-06-88 JCR Use _iob2_ macro instead of _iob_index
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* 06-15-88 JCR Near reference to _iob[] entries; improve REG variables
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* 07-27-88 JCR Changed some variables from int to unsigned (bug fix)
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* 08-25-88 GJF Don't use FP_OFF() macro for the 386
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* 12-05-88 JCR Added _IOCTRLZ support (fixes bug pertaining to ^Z at
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* eof)
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* 08-17-89 GJF Cleanup, now specific to OS/2 2.0 (i.e., 386 flat
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* model), also fixed copyright
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* 02-15-90 GJF _iob[], _iob2[] merge. Also, fixed copyright and
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* indents.
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* 03-19-90 GJF Made calling type _CALLTYPE1, added #include
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* <cruntime.h> and removed #include <register.h>.
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* 07-23-90 SBM Replaced <assertm.h> by <assert.h>
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* 10-02-90 GJF New-style function declarators.
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* 01-21-91 GJF ANSI naming.
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* 03-27-92 DJM POSIX support.
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* 08-26-92 GJF Include unistd.h for POSIX build.
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* 09-01-92 GJF Fixed POSIX support (was returning -1 for all except
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* read-write streams).
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* 04-06-93 SKS Replace _CRTAPI* with __cdecl
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* 06-29-93 GJF Fixed bug related to variable buffer sizing (Cuda
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* #5456).
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 02-06-94 CFW assert -> _ASSERTE.
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* 02-20-95 GJF Merged in Mac version.
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* 03-07-95 GJF _[un]lock_str macros now take FILE * arg.
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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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* 02-27-98 RKP Add 64 bit support.
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* 03-02-98 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 <stdio.h>
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#include <file2.h>
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#include <dbgint.h>
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#include <errno.h>
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#ifdef _POSIX_
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#include <unistd.h>
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#else
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#include <msdos.h>
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#endif
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#include <stddef.h>
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#include <io.h>
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#include <internal.h>
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#ifndef _POSIX_
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#include <mtdll.h>
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#endif
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/***
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*long ftell(stream) - query stream file pointer
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*
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*Purpose:
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* Find out what stream's position is. coordinate with buffering; adjust
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* backward for read-ahead and forward for write-behind. This is NOT
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* equivalent to fseek(stream,0L,1), because fseek will remove an ungetc,
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* may flush buffers, etc.
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*
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*Entry:
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* FILE *stream - stream to query for position
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*
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*Exit:
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* return present file position if succeeds
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* returns -1L and sets errno if fails
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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 ftell() and _lk_ftell() */
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long __cdecl ftell (
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FILE *stream
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)
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{
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long 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 = _ftell_lk (stream);
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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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*_ftell_lk() - Ftell() core routine (assumes stream is locked).
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*
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*Purpose:
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* Core ftell() routine; assumes caller has aquired stream lock).
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*
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* [See ftell() above for more info.]
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*
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*Entry: [See ftell()]
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*
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*Exit: [See ftell()]
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*
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*Exceptions:
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*
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*******************************************************************************/
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long __cdecl _ftell_lk (
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#else /* non multi-thread; define only ftell() */
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long __cdecl ftell (
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#endif /* rejoin common code */
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FILE *str
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)
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{
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REG1 FILE *stream;
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unsigned int offset;
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long filepos;
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#if !defined(_POSIX_)
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REG2 char *p;
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char *max;
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#endif
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int fd;
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unsigned int rdcnt;
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_ASSERTE(str != NULL);
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/* Init stream pointer and file descriptor */
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stream = str;
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#ifdef _POSIX_
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fd = fileno(stream);
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#else
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fd = _fileno(stream);
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#endif
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if (stream->_cnt < 0)
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stream->_cnt = 0;
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#ifdef _POSIX_
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if ((filepos = lseek(fd, 0L, SEEK_CUR)) < 0L)
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#else
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if ((filepos = _lseek(fd, 0L, SEEK_CUR)) < 0L)
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#endif
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return(-1L);
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if (!bigbuf(stream)) /* _IONBF or no buffering designated */
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return(filepos - stream->_cnt);
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offset = (unsigned)(stream->_ptr - stream->_base);
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#ifndef _POSIX_
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if (stream->_flag & (_IOWRT|_IOREAD)) {
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if (_osfile(fd) & FTEXT)
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for (p = stream->_base; p < stream->_ptr; p++)
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if (*p == '\n') /* adjust for '\r' */
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offset++;
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}
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else if (!(stream->_flag & _IORW)) {
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errno=EINVAL;
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return(-1L);
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}
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#endif
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if (filepos == 0L)
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return((long)offset);
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if (stream->_flag & _IOREAD) /* go to preceding sector */
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if (stream->_cnt == 0) /* filepos holds correct location */
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offset = 0;
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else {
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/* Subtract out the number of unread bytes left in the buffer.
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[We can't simply use _iob[]._bufsiz because the last read
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may have hit EOF and, thus, the buffer was not completely
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filled.] */
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rdcnt = stream->_cnt + (unsigned)(stream->_ptr - stream->_base);
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#if !defined(_POSIX_)
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/* If text mode, adjust for the cr/lf substitution. If binary
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mode, we're outta here. */
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if (_osfile(fd) & FTEXT) {
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/* (1) If we're not at eof, simply copy _bufsiz onto rdcnt
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to get the # of untranslated chars read. (2) If we're at
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eof, we must look through the buffer expanding the '\n'
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chars one at a time. */
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/* [NOTE: Performance issue -- it is faster to do the two
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_lseek() calls than to blindly go through and expand the
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'\n' chars regardless of whether we're at eof or not.] */
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if (_lseek(fd, 0L, 2) == filepos) {
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max = stream->_base + rdcnt;
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for (p = stream->_base; p < max; p++)
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if (*p == '\n')
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/* adjust for '\r' */
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rdcnt++;
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/* If last byte was ^Z, the lowio read didn't tell us
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about it. Check flag and bump count, if necessary. */
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if (stream->_flag & _IOCTRLZ)
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++rdcnt;
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}
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else {
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_lseek(fd, filepos, 0);
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/* We want to set rdcnt to the number of bytes
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originally read into the stream buffer (before
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crlf->lf translation). In most cases, this will
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just be _bufsiz. However, the buffer size may have
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been changed, due to fseek optimization, at the
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END of the last _filbuf call. */
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if ( (rdcnt <= _SMALL_BUFSIZ) &&
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(stream->_flag & _IOMYBUF) &&
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!(stream->_flag & _IOSETVBUF) )
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{
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/* The translated contents of the buffer is small
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and we are not at eof. The buffer size must have
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been set to _SMALL_BUFSIZ during the last
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_filbuf call. */
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rdcnt = _SMALL_BUFSIZ;
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}
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else
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rdcnt = stream->_bufsiz;
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/* If first byte in untranslated buffer was a '\n',
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assume it was preceeded by a '\r' which was
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discarded by the previous read operation and count
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the '\n'. */
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if (_osfile(fd) & FCRLF)
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++rdcnt;
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}
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} /* end if FTEXT */
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#endif
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filepos -= (long)rdcnt;
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} /* end else stream->_cnt != 0 */
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return(filepos + (long)offset);
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}
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