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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v101/clib/allocc.c

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+/*****************************************************************************
+*
+*		A L L O C C   /   F R E E C   R O U T I N E S
+*		---------------------------------------------
+*	Copyright 1982 by Digital Research Inc.  All rights reserved.
+*
+*	Routines "allocc" 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.
+*	Note that this scheme preserves compatibility with OS's that really
+*	truly use channels, and allows users to inform the C Run Time Library
+*	routines that they are using the channel.
+*	It's not important to use these routines under CP/M, since CP/M
+*	allows you to have as many FCBs as you wish.
+*
+*	Calling Sequence:
+*
+*		i = allocc();
+*		freec(i);
+*
+*****************************************************************************/
+#include	<portab.h>			/* Include std definitions  */
+#include	<cpm.h>				/* Also CP/M ones	    */
+#include	<errno.h>			/* for error returns	    */
+LONG		_chvec	={0};			/* Allocate storage	    */
+WORD	allocc()				/****************************/
+{						/*			    */
+	REG WORD i;				/* Define 2 temporaries	    */
+	REG LONG j;				/*			    */
+						/*			    */
+	j = 1;					/* Start with channel 0	    */
+	for(i=0;i<MAXCCBS;i++)			/* Look at the bits	    */
+	{					/*			    */
+	  if((j & _chvec) == 0)			/* If 0, then channel free  */
+	  {					/*			    */
+		_chvec |= j;			/* set allocated bit	    */
+		return(i);			/* and return the channel # */
+	  }					/*			    */
+	  j = j << 1;				/* Up to next bit	    */
+	}					/* End FOR loop		    */
+	RETERR(FAILURE,EMFILE);			/* All channels in use!	    */
+}						/****************************/
+
+WORD	freec(ch)				/****************************/
+REG	WORD	ch;				/* Channel number to free   */
+{						/*			    */
+	_chvec &= ~(1 << ch);			/* Clear appropriate bit    */
+	return(SUCCESS);			/* Return OK		    */
+}						/****************************/