Upload

Digital Research

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

@@ -0,0 +1,45 @@
+/*****************************************************************************
+*
+*		I G E T C   /   F R E E C   R O U T I N E S
+*		-------------------------------------------
+*
+*	Routines "igetc" and "freec" are used to allocate / deallocate a 
+*	channel number so that the user may do I/O directly without the OTS
+*	getting in the way.
+*
+*	Calling Sequence:
+*
+*		i = getc();
+*		freec(i);
+*
+*****************************************************************************/
+#include	"stdio.h"			/* Include std definitions  */
+#include	"cpm.h"				/* Also CP/M ones	    */
+WORD		chmask	= 0;			/* Allocate storage	    */
+WORD	igetc()					/****************************/
+{						/*			    */
+	REG	i,j;				/* Define 2 temporaries	    */
+						/*			    */
+	j = 1;					/* Start with channel 0	    */
+	for(i=0;i<MAXFILE;i++)			/* Look at all 16 bits	    */
+	{					/*			    */
+	  if((j & chmask) == 0)			/* If 0, then channel free  */
+	  {					/*			    */
+		chmask |= j;			/* set allocated bit	    */
+		return(i);			/* and return the channel # */
+	  }					/*			    */
+	  j = j << 1;				/* Up to next bit	    */
+	}					/* End FOR loop		    */
+	return(FAILURE);			/* All channels in use!	    */
+}						/****************************/
+
+WORD	freec(ch)				/****************************/
+{						/*			    */
+	REG	i,j;				/* Define 2 temporaries	    */
+						/*			    */
+	j = 1;					/* Start with channel 0	    */
+	for (i=0; i<ch; i++)			/* Compute		    */
+		j = j << 1;			/*	    bit mask	    */
+	chmask &= (~j);				/* clear allocation bit	    */
+	return(SUCCESS);			/* Return OK		    */
+}						/****************************/