HCCU Buffer pool

{
	BufPool - static allocated buffers
	-----------------------------------------------------
	As method for avoiding Copying of the data through
	mailboxes, the static buffer concept has these
	advantages:
	-a minimum of copying is required
	-as a resource, access is protected by a semaphore
	-the protection is internal to the access
	-----------------------------------------------------
	concept of use :
	 a task allocates the buffer, and fills it,
	 it then passes the index to the next task,
	 the final task releases the buffer.
	note :
	 the allocating task waits until it gets the buffer,
	 should there be none available
	-----------------------------------------------------
	Use:
	 k:=GetFreeMMUBuffer;		/ allocate
	 ..
	 ..
	 MMUBufferPool[k].s:=size;	/ use
	 MMUBufferPool[k].v:=data;
	 ..
	 ..
	 ReleaseMMUBuffer(k);		/ release
	-----------------------------------------------------
	changes
	 24.6.94 :add MMUBufFree,NetBufFree
	  4.8.94 :remove net part
         19.feb97:increse BufSize from $80 to 140
         9.okt97:increse BufSize from 140 to 160

	-----------------------------------------------------
	Created		:15/apr/94
	Last Update	:24.6.94,4.8.94,9.10.97
	-----------------------------------------------------
	Is updated version of :
}
{$D-,L-}
UNIT BufPool;

INTERFACE

CONST
{$IFDEF EV}
 BufSize=160; { see also Globdef.bufsize for network buffer size }
{$ELSE}
 BufSize=160; { $80; }
{$ENDIF}
 MMUBufCount=20;

TYPE
 BufType=RECORD
  InUse:BOOLEAN;
  s:BYTE;
  V:ARRAY[0..BufSize-1]OF BYTE;
 END;


FUNCTION GetFreeMMUBuffer:BYTE;
PROCEDURE ReleaseMMUBuffer(z:BYTE);

VAR
 MMUBufferPool:ARRAY[1..MMUBufCount]OF BufType;
 MMUBufFree:BYTE;

IMPLEMENTATION
{-----------------------------------------------------}
USES RTKernel;
VAR MMUBufSema:RTKERNEL.Semaphore;
{-----------------------------------------------------}
FUNCTION GetFreeMMUBuffer:BYTE;
VAR i:BYTE;
 f:BOOLEAN;
BEGIN
 f:=FALSE;
 REPEAT
  Wait(MMUBufSema);
  IF (MMUBufFree<>0) THEN BEGIN
    i:=0;
    REPEAT
     inc(i);
     IF (Not MMUBufferPool[i].InUse) THEN BEGIN
       f:=TRUE;
       Dec(MMUBufFree);
       MMUBufferPool[i].InUse:=TRUE;
      END;
    UNTIL (f)OR(i>=MMUBufCount);
   END;
  Signal(MMUBufSema);
  IF (Not f) THEN RTKERNEL.Delay(1);
 UNTIL f;
 GetFreeMMUBuffer:=i;
END;
{-----------------------------------------------------}
PROCEDURE ReleaseMMUBuffer(z:BYTE);
BEGIN
 Wait(MMUBufSema);
 MMUBufferPool[z].InUse:=FALSE;
 Inc(MMUBufFree);
 Signal(MMUBufSema);
END;
{-----------------------------------------------------}
VAR i:BYTE;
BEGIN	{ autoinit of this unit}
 FOR i:=1 TO MMUBufCount DO MMUBufferPool[i].Inuse:=FALSE;
 MMUBufFree:=MMUBufCount;
 InitSemaphore(MMUBufSema,resource,1,'MMUBuf');
END.	{ unit }