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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v101/klib/lseek.c

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+/****************************************************************************/
+/*									    */
+/*			    L s e e k   F u n c t i o n			    */
+/*			    ---------------------------			    */
+/*									    */
+/*	The lseek function simulates the UNIX lseek system call.	    */
+/*									    */
+/*	Calling sequence:						    */
+/*									    */
+/*		ret = lseek(fd,offset,sense);				    */
+/*									    */
+/*	Where:								    */
+/*									    */
+/*		fd	Is an open file descriptor			    */
+/*		offset	Is the (long) file offset			    */
+/*		sense	Is the meaning of offset			    */
+/*			0 => From the beginning of the file		    */
+/*			1 => From the present file position		    */
+/*			2 => From the end of the file			    */
+/*									    */
+/*		ret	Is the resulting absolute file offset		    */
+/*			-1 indicates failure				    */
+/*									    */
+/****************************************************************************/
+#include "stdio.h"
+#include "cpm.h"
+LONG	lseek(fd,offs,sense)			/****************************/
+						/*			    */
+	WORD	fd;				/* Open file descriptor	    */
+	LONG	offs;				/* File offset		    */
+	WORD	sense;				/* Sense of offset	    */
+						/*			    */
+						/****************************/
+{
+						/****************************/
+REG	FILE	*fp;				/* File pointer		    */
+EXTERN	LONG	_chkc();			/* fd to fp translation	    */
+						/*			    */
+	if((LONG)(fp = _chkc(fd)) == FAILURE)	/* Convert to pointer	    */
+		return(FAILURE);		/*   Can't		    */
+						/*			    */
+	switch(sense)				/****************************/
+	{					/*			    */
+	case	0:				/* From beginning of file   */
+		fp->offset = offs;		/* Just set to offset	    */
+		break;				/* Then quit		    */
+						/****************************/
+	case	1:				/* From present position    */
+		fp->offset += offs;		/*			    */
+		break;				/*			    */
+						/****************************/
+	case	2:				/* From end of file	    */
+		fp->offset = fp->hiwater + offs;/* compute end of file	    */
+		break;				/*			    */
+						/****************************/
+	default:				/* All others NFG	    */
+		return(FAILURE);		/*			    */
+	}					/****************************/
+	fp->flags &= ~ATEOF;			/* any seek clears EOF	    */
+	return(fp->offset);			/* Return resultant offset  */
+}						/****************************/