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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/clib/ftell.c

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+/***********************************************************************
+*
+*			f t e l l   F u n c t i o n
+*			---------------------------
+*	Copyright 1982 by Digital Research Inc.  All rights reserved.
+*
+*	"ftell" returns the present value of the read/write pointer
+*	within the stream.  This is a meaningless number for console
+*	and list devices.
+*
+*	Calling sequence:
+*		offset = ftell(sp)
+*	Where:
+*		sp -> (FILE *) stream
+*		offset = (LONG) where stream is reading from/writing to
+*
+******************************************************************************/
+
+#include "stdio.h"
+
+LONG	ftell(sp)				/* CLEAR FUNCTION ***********/
+	REG FILE *sp;				/* stream pointer	    */
+{						/*			    */
+	REG LONG filepos;			/* file position	    */
+	REG BYTE *bp;				/* Buffer ptr		    */
+	LONG nread;				/* Temp var		    */
+	LONG lseek();				/* byte offset into buf	    */
+						/*			    */
+	if( isatty(fileno(sp)) )		/* are we talking to a tty? */
+		return(0L);			/* quit now if so	    */
+	filepos = FAILURE;			/* default return value	    */
+	if( sp->_flag & (_IOREAD|_IOWRT) )	/* if file is open	    */
+	{					/*			    */
+	    if((filepos=lseek(fileno(sp),0L,1))	/* get where next byte read */
+		== FAILURE )			/*  from or written to	    */
+		    return((LONG)FAILURE);	/*  quit if bad lseek	    */
+	    if( sp->_base == NULLPTR )		/* if file hasn't had i/o   */
+	      return(filepos);			/*  return this position    */
+	    nread = sp->_ptr - sp->_base;	/* calc for # read/written  */
+	    filepos += nread;			/* correct for # read/wrtn  */
+	    if( sp->_flag & _IOREAD )		/* if reading from file	    */
+	      if( filepos > 0 )			/*  and we've read from file*/
+		filepos -= nread + sp->_cnt;	/* adjust file position	    */
+						/*  to reflect read ahead   */
+	    if( sp->_flag & _IOASCI )		/* ascii file? **************/
+	    {					/* count the newlines	    */
+	      if( sp->_flag & _IOWRT )		/* add in newline's cr's    */
+	      {					/*			    */
+		for( bp=sp->_base; bp < sp->_ptr; bp++ ) /*		    */
+		    if( *bp == '\n' )		/* count newlines in stuff  */
+			filepos++;		/*   written/read so far    */
+	      } else {				/* we're reading...	    */
+		if( filepos > 0 )		/* check to see we've read  */
+	          for(bp= &(sp->_ptr[sp->_cnt-1]);/* start at end of buffer */
+			bp >= sp->_ptr; bp-- )	/* back up to next read char*/
+		    if( *bp == '\n' )		/* count off for newlines   */
+			filepos--;		/*			    */
+	      }					/*			    */
+	    }					/* fini ascii ***************/
+	}					/****************************/
+	return(filepos);			/*			    */
+}						/****************************/
+