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TITLE	GLXMEM  --  Memory Manager for GALAXY Programs
SUBTTL	Chuck O'Toole & Irwin L. Goverman/CDO/ILG/MLB/DC/PJT/DPM/TARL 1-Jan-82

;
;
;        COPYRIGHT (c) 1975,1976,1977,1978,1979,1980,1981,1982
;                    DIGITAL EQUIPMENT CORPORATION
;
;     THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY  BE  USED
;     AND COPIED ONLY IN ACCORDANCE WITH THE TERMS OF SUCH LICENSE
;     AND WITH THE INCLUSION OF THE ABOVE COPYRIGHT NOTICE.   THIS
;     SOFTWARE  OR ANY OTHER COPIES THEREOF MAY NOT BE PROVIDED OR
;     OTHERWISE MADE AVAILABLE TO ANY OTHER PERSON.  NO  TITLE  TO
;     AND OWNERSHIP OF THE SOFTWARE IS HEREBY TRANSFERRED.
;
;     THE INFORMATION  IN  THIS  SOFTWARE  IS  SUBJECT  TO  CHANGE
;     WITHOUT  NOTICE  AND SHOULD NOT BE CONSTRUED AS A COMMITMENT
;     BY DIGITAL EQUIPMENT CORPORATION.
;
;     DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR RELIABILITY
;     OF  ITS  SOFTWARE  ON  EQUIPMENT  WHICH  IS  NOT SUPPLIED BY
;     DIGITAL.

	SEARCH	GLXMAC			;SUBSYSTEMS SYMBOLS
	PROLOG(GLXMEM,MEM)		;PRODUCE PROLOG CODE



	MEMEDT==27			;MODULE EDIT LEVEL

SUBTTL Entry Points found in GLXMEM



ENTRY	M%INIT	;Initialization entry point
ENTRY	M%ACQP	;Acquire a page from the page map (page number is returned)
ENTRY	M%RELP	;Return page to the page map (by page number)
ENTRY	M%GPAG	;Get a free page (address is returned)
ENTRY	M%RPAG	;Return a page to the page map (by address)
ENTRY	M%IPSN	;Notification that IPCF send of page is about to occur
ENTRY	M%NXPG	;Get a non-existant page for an IPCF receive
ENTRY	M%IPRC	;Notification that IPCF receive of a page has occurred
ENTRY	M%IPRM	;Make room for IPCF page we couldn't fit in core
ENTRY	M%AQNP	;Acquire N contiguous pages from the map
ENTRY	M%RLNP	;Release pages acquired from M%AQNP
ENTRY	M%CLNC	;Clean Core For Cusps About To Go Dormant
ENTRY	M%FPGS	;Return free page counter
ENTRY	M%GMEM	;Allocate a chunk of memory
ENTRY	M%RMEM	;De-allocate a chunk of memory

ENTRY	PAGFRE	;Called from I%INIT

SUBTTL Table of contents

;               TABLE OF CONTENTS FOR GLXMEM
;
;
;                        SECTION                                   PAGE
;    1. Entry Points found in GLXMEM..............................   2
;    2. Table of contents.........................................   3
;    3. Revision History..........................................   4
;    4. Global Storage............................................   5
;    5. M%INIT - Initialize the memory system.....................   6
;    6. PAGFRE - Determine if a given page is free or not.........   7
;    7. M%GPAG - Acquire one free page full of zeroes (address)...   8
;    8. M%ACQP - Acquire one free page full of zeroes (page number)   8
;    9. M%AQNP - Acquire several free pages full of zeroes........   9
;   10. FNDPAG - Find first free page.............................   9
;   11. CREPAG - Routine to create a page.........................  10
;   12. M%NXPG - Acquire the number of a free page for IPCF reception  11
;   13. M%RLNP - Release contiquous free pages....................  12
;   14. M%RELP - Release a single page to the free pool (by page number)  12
;   15. M%RPAG - Release a single page to the free pool (by address)  12
;   16. M%FPGS - Return number of free pages......................  12
;   17. M%IPSN - Inform that page is about to be sent via IPCF....  13
;   18. M%IPRC - Inform that page has been created via IPCF.......  13
;   19. M%GMEM - Allocate a chunk of memory.......................  14
;   20. APMEM  - Routine to add one page to the chunk pool........  15
;   21. PGCOLL - Routine to remove whole pages from chunk free pool  16
;   22. M%RMEM - Routine to de-allocate a memory chunk............  17
;   23. Consistency checking routines.............................  18
;   24. M%CLNC - Routines for cleaning up core....................  19
;   25. M%IPRM - Routine to swap out anything possible............  20
;   27. TOPS-20 Dummy routines....................................  22

SUBTTL Revision History

COMMENT \

Edit	SPR/QAR			Explanation
----    -------	   -----------------------------------------------------
0001		   First pass at GLXMEM, remove AP usage, etc.
0002		   Remove TOPS-10 PFH and move it to the GLXINI module
0003		   Convert to new OTS format
0004		   Move creation of data area to INIT module
0005		   Add M%GPAG and M%RPAG
0006	G053	   Fix M%NXPG on the -20 to clear PT.USE and PT.WRK
0007	G054	   Fix GMEM and RMEM to Garbage Collected when asked for
		   more than CNK.PM pages and cleanup core when available
		   pages exceeds PAGAVL
0010		   Make BPN $STOP dump out offending page number
0011		   Remove usage of PJUMPE opdef
0012		   Arrange to zero our own $DATA space, but keep the stuff
		   we need for restart.  Also, comment out the zeroing of any
		   location that gets zeroed on initialization.
0013		   On TOPS20, make M%INIT start scanning for free pages
		   at c(.JBFF), not page zero.

0014		Restructure GLXLIB
		 1) Do PFH initialization here instead of in PFH. This includes
		    mapping core and marking all symbol table pages.
		 2) Create a non-sharable page and BLT the PFH into it.
		 3) As part of PFH setup, add new routine PFHADR to tell the
		    page fault handler where some of the memory manager data
		    base lives.
		 4) Add PFHRET kludge to allow the page fault handler to return
		    to the library when execute-only is in effect.
		 5) Copy NODDT routine here from PFH.

0015		Add new bit IB.NPF in the IB to disable GLXPFH.

0016		Shuffle some variables so GLXPFH can keep its data base in
		core. This is needed to avoid the possibility of getting a
		fault in the PFH itself. Also, force PFHRET whether or not
		GLXLIB is execute only.

0017		Shift some stuff around to preserve which locations get
		zeroed on a re-start. Broken by edit 16.

0020		Fix Stevens QAR on memory management loop. Allow calls to
		M%GMEM of greater then CNK.PM*PAGSIZ words.

0021		Synchronize with edit 15 to GLXPFH. Remove interface from
		GLXPFH to GLXMEM.

0022		Make creating PFH more robust. Don't call CREPAG to create
		page for PFH, do our own PAGE. uuo. If fails because of
		physical limit, swap out page 1, create ours, then swap 1
		back in.

0023		Remove GLXPFH. Set PHY core limit low and request a timer
		trap to invoke the system PFH.

0024		Clean and simplify M%IPRM. Allow it to give error returns.

0025		Remove reference to obsolete PFH symbols, and fix problem
		with M%CLNC not being called enough to kill pages.

0026		Don't set guigelines since PFH will work without doing that.

0027		Dont reset PT.ADR when restarting so GLXMEM doesnt stopcode.
\

SUBTTL	Global Storage

	$GDATA	VRTPRV		;VIRTUAL PRIVS FLAG (0 = NONE, 1 = YES)
	$GDATA	PAGTBL,MEMSIZ	;PAGE MAP OF ALL PAGES
	$DATA	PAGSTA		;STARTING POINT FOR PAGSRC PAGES

	$DATA	MEMBEG,0	;START OF ZEROABLE DATA FOR GLXMEM

	$DATA	AVBPGS		;COUNT OF RELP'D BUT IN CORE PAGES
	$DATA	FREPGS		;COUNT OF FREE PAGES IN ADR SPACE
	$DATA	FREWDS		;FREINI, EXPRESSED AS WORDS NOT PAGES
	$DATA	DICT,DCT.MX+1	;CHUNK DICTIONARY OF FREQUENTLY USED SIZES
	$DATA	PANFLG		;FLAG FOR CHUNK MANAGER
	$DATA	APCNT		;COUNTER FOR COLLECT OR ADD PAGE TEST
	$DATA	CNT.AP		;COUNTER: PAGES ADDED TO FREE CHUNK POOL
	$DATA	CNT.DD		;COUNTER: TIMES DICT HAD TO BE DUMPED
	$DATA	CNT.PC		;COUNTER: NUMBER OF PAGES GARBAGE COLLECTED
	$DATA	CNT.CL		;COUNTER: TIMES RECLAIMED MEMORY
	$DATA	MEMEND,0	;END OF ZEROABLE DATA FOR GLXMEM
				;HERE COMES NON-ZEROABLE $DATA SPACE
	$DATA	MEMFLG		;-1 WHEN M%INIT HAS BEEN CALLED
	$DATA	FREINI		;INITIAL VALUE OF FREPGS FOR CHECKING

SUBTTL M%INIT - Initialize the memory system

; M%INIT HAS THE TASK OF PUTTING THE PAGE TABLE AND PAGE COUNTERS INTO
; A DETERMINED STATE.

; CALL IS:	NO ARGUMENTS
;
;TRUE RETURN:	ALWAYS

M%INIT:	MOVE	S1,[MEMBEG,,MEMBEG+1]	;SETUP BLT PTR TO ZERO $DATA SPACE
	SETZM	MEMBEG			;ZERO OUT FIRST LOCATION
	BLT	S1,MEMEND-1		;AND DO THE REST
	SKIPGE	MEMFLG			;HAVE WE BEEN HERE BEFORE (RESTART)?
	JRST	INIT.3			;YES, RESTORE INITIAL STATE
	SETOM	MEMFLG			;NO, DETERMINE INITIAL STATE

TOPS10 <MOVEI	S1,0>			;START AT PAGE 0
TOPS20 <HRRZ	S1,.JBFF##>		;START FROM FIRST FREE

	ADR2PG	S1			;CONVERT TO PAGE NUMBER
	SETOM	PAGSTA			;NO PAGE MARKED AS FIRST FREE YET

INIT.1:	PUSHJ	P,PAGFRE		;IS THIS PAGE FREE?
	JUMPN	S2,INIT.2		;IF ITS IN USE, MARK IT AS SUCH
	AOS	FREINI			;INCREMENT COUNT OF FREE PAGES
	SKIPGE	PAGSTA			;HAVE WE ALREADY FOUND ONE FREE PAGE?
	MOVEM	S1,PAGSTA		;NO, SO SET IT UP NOW

INIT.2:	STORE	S2,PAGTBL(S1),PT.INI	;SAVE INITIAL BIT (1=PART OF ORIGINAL)
	STORE	S2,PAGTBL(S1),PT.USE	;SET THE PAGE STATUS UP TOO
	STORE	S2,PAGTBL(S1),PT.ADR	;AND ADDRESSABLE
	CAIE	S1,MEMSIZ-1		;LOOP FOR ALL PAGES
	AOJA	S1,INIT.1		;MARKING FREE AND INUSE
	JRST	INIT.6			;THEN DO COMMON SET UP

INIT.3:	MOVEI	S1,0			;START AT PAGE 0

INIT.4:	LOAD	S2,PAGTBL(S1),PT.INI	;GET INITIAL IN-USE BIT
	STORE	S2,PAGTBL(S1),PT.USE	;RESET 'IN USE' BIT FOR THIS PAGE
	CAIE	S1,MEMSIZ-1		;ARE WE DONE?
	AOJA	S1,INIT.4		;NO, SO DO NEXT PAGE

INIT.6:	MOVE	S1,FREINI		;GET NUMBER OF FREE PAGES
	MOVEM	S1,FREPGS		;STORE CURRENT NUMBER OF FREE PAGES
	PG2ADR	S1			;CONVERT TO WORDS
	MOVEM	S1,FREWDS		;AND STORE THAT TOO
	MOVX	S1,DDCNT		;RE-SET THE DICT DUMP COUNT
	MOVEM	S1,APCNT		;FOR M%GMEM AND M%RMEM
	PUSHJ	P,M%CLNC		;CLEAN UP CORE
	ZERO	AVBPGS			;CLEAR COUNT OF AVAILABLE PAGES
	PUSHJ	P,PFHINI		;SET UP THE PAGE FAULT HANDLER
	$RETT				;ALL DONE, RETURN NOW

SUBTTL	System PFH interface


; System page fault handler (PFH) initialization
;
PFHINI:	SETZM	VRTPRV			;ASSUME NO VIRTUAL PRIVS

TOPS10 <				;TOPS-10 ONLY
	MOVX	TF,IB.NPF		;GET 'DON'T SET UP GLXPFH' BIT
	SKIPN	.JBPFH			;ALREADY SET UP?
	TDNE	TF,IIB##+IB.FLG		;USER WANT PFH ?
	POPJ	P,			;NO - JUST RETURN
	HRROI	TF,.GTMVL		;SET UP AC
	GETTAB	TF,			;READ MAXIMUM CORE LIMITS
	  SETZ	TF,			;CAN'T
	TLNN	TF,-1			;HAVE VM PRIVS ?
	POPJ	P,			;NOPE - JUST RETURN
	AOS	VRTPRV			;YES - REMEMBER IT

PFHI.1:	MOVE	S2,[.STTVM,,^D1000]	;REQUEST A VIRTUAL TIMER TRAP
	SETUUO	S2,			;AFTER 1000 MILLISECONDS
	  JFCL				;LOSER
	POPJ	P,			;RETURN
>					;END OF TOPS10 CONDITIONAL

TOPS20	<				;TOPS-20 ONLY
	AOS	VRTPRV			;ALWAYS HAVE VIRTUAL PRIVS ON THE -20
	POPJ	P,			;RETURN
>					;END OF TOPS-20 CONDITIONAL

SUBTTL	NODDT - Remove DDT.VMX routine for TOPS10


TOPS10	<				;TOPS-10 ONLY

;This routine is intended to be used as an emergency tool
; in case a library gets saved with DDT in its high segment.
; In this case, any lowseg program which also has DDT.VMX in page 700
; will get page overlap errors when getting the library.
; It is not the intention that the library be saved in this state,
; however, if it happens, then this routine will be useful.
; The procedure is as follows:
; .GET GLXLIB	;The bad one, with DDT.VMX in it
; .DDT		;get into DDT.VMX
; NODDT$G	;Start it at this routine
; .SAVE		;Save the library without the symbols
;
;This routine is also useful to remove VMDDT after a component
;has been attached to, and DDTed. It will remove VMDDT and continue
;the program at .JBOPC (the interrupted PC)
;
; NODDT$G	;Remove VMDDT and restart @.JBOPC

NODDT::	SKIPN	S1,DDTADR		;Get the end,,start adr of DDT
	JRST	NODD.2			;No DDT to begin with!
	HRRZ	T2,S1			;Get start adr of DDT
	HLRZ	P1,S1			;And ending adr
	ADR2PG	T2			;Make starting page number
	ADR2PG	P1			;Make ending page number
	SUB	P1,T2			;Get number of pages in DDT
	TXO	T2,1B0			;Light the destroy page bit
	MOVEI	T1,1			;Count the args to PAGE. UUO
	MOVE	S2,[XWD .PAGCD,T1]	;Create/Destroy,, adr of arg list
NODD.1:	PAGE.	S2,			;Get rid of a page
	 JRST	NODDFA			;Complain!
	AOS	T2			;Bump to next page
	SOJGE	P1,NODD.1		;And try the rest of the pages
	SETZ	S1,			;Store 0 in protected DDT loc
	SETDDT	S1,			;And tell the monitor
NODDTE:	SKIPN	.JBOPC			;Old PC around?
	 EXIT				;No--Just exit
	JRSTF	@.JBOPC			;Yes--Resume program

;Here is trying to destroy DDT, and it isn't here at all!
NODD.2:	OUTSTR	[ASCIZ/
% DDT not loaded
/]					;Inform the dumb user
	JRST	NODDTE				;And leave 'em alone


;Here if the PAGE. UUO fails
NODDFA:	OUTSTR	[ASCIZ/
?Can't destroy DDT page
/]
	JRST	NODDTE				;And die

> ;End of TOPS-10 conditional

SUBTTL PAGFRE - Determine if a given page is free or not

;CALL		S1/PAGE NUMBER OF PAGE IN QUESTION
;
;TRUE RETURN:	S2/0			;IF PAGE IS FREE
;  OR
;		S2/1			;IF PAGE IS IN USE


TOPS10 <
PAGFRE:	MOVE	S2,S1			;GET ARGUMENT (PAGE NR.)
	HRLI	S2,.PAGCA		;GET PAGE ACCESS
	PAGE.	S2,			;LOOK UP PAGE ACESS CODE
	  $STOP(PEF,Page existence check failed)
	TXNE	S2,PA.GNE		;DOES PAGE EXIST?
	TDZA	S2,S2			;NO, RETURN 0, I.E. PAGE IS FREE
	MOVX	S2,1			;YES, MARK IT AS IN USE
	$RETT				;IN EITHER CASE, RETURN
> ;END TOPS10 CONDITIONAL


TOPS20 <
PAGFRE:	HRLI	S1,.FHSLF		;CHECK FOR THIS PROCESS
	RPACS				;THE PAGE ACCESSABLITY
	  ERCAL	[$STOP(PEF,Page existence check failed)]
	TXNN	S2,PA%PEX		;DOES PAGE EXIST?
	TDZA	S2,S2			;NO, RETURN THAT PAGE IS FREE
	MOVX	S2,1			;OTHERWISE MARK ITS USE
	ANDI	S1,-1			;PUT JUST PAGE NUMBER BACK INTO S1
	$RETT				;AND RETURN
> ;END TOPS20 CONDITIONAL

SUBTTL	M%GPAG - Acquire one free page full of zeroes (address)

;This routine is called to acquire one free page (zeroed).
;
;Call:	no arguments
;
;T Ret:	S1/  address of first word of page acquired

M%GPAG:	PUSHJ	P,M%ACQP		;GET A PAGE
	PG2ADR	S1			;CONVERT PAGE NUMBER TO ADDRESS
	$RETT				;AND RETURN


SUBTTL M%ACQP - Acquire one free page full of zeroes (page number)

;THIS ROUTINE IS CALLED TO ACQUIRE A SINGLE FREE PAGE
;
;TRUE RETURN:	S1/PAGE NUMBER OF ACQUIRED PAGE
;
;FALSE RETURN:	NEVER, STOP CODE "ASE" INSTEAD
;

M%ACQP:	MOVEI	S1,1			;WILL ASK FOR 1 PAGE
	SKIPG	AVBPGS			;ANY "GOOD" PAGES AVAILABLE?
	JRST	M%AQNP			;NO, TAKE ANY AVAILABLE PAGE
	MOVE	S1,PAGSTA		;GET STARTING POINT FOR SEARCH
ACQP.1:	CAIL	S1,MEMSIZ		;OFF THE TOP OF MEMORY
	$STOP(CAC,Count of Available Pages Confused)
	MOVE	S2,PAGTBL(S1)		;GET PAGE FLAGS
	TXC	S2,PT.ADR		;WANT TO TEST FOR ON
	TXNE	S2,PT.USE!PT.ADR	;IS IT FREE AND IN-CORE NOW
	AOJA	S1,ACQP.1		;NOT THE BEST, TRY THE NEXT
	PJRST	CREPAG			;EXIT, CREATING AND ZEROING PAGE "S1"

SUBTTL M%AQNP - Acquire several free pages full of zeroes

;CALL IS:	S1/NUMBER OF PAGES DESIRED (MAYBE 1 TO MEMSIZ, BUT NOT 0)
;
;TRUE RETURN:	S1/PAGE NUMBER OF FIRST PAGE ACQUIRED
;
;FALSE RETURN:	NEVER, STOP CODE "ASE" INSTEAD


M%AQNP:	SKIPG	S1			;WANTS 1 OR MORE PAGES, RIGHT?
	$STOP(RZP,Request for zero pages) ; NO, SO STOP NOW
	PUSHJ	P,.SAVE3		;SAVE A COUPLE FIRST
	MOVE	P1,S1			;GET THE NUMBER REQUESTED
AQNP.0:	MOVE	S1,PAGSTA		;FIRST PAGE TO TRY FOR
	MOVEI	P2,-1(P1)		;COPY THE COUNT FOR THE LOOP BELOW
	PUSHJ	P,FNDPAG		;GET A PAGE
	JUMPF	AQNP.3			;IF NO PAGES, TRY TO ROB CHUNK POOL
	JUMPE	P2,AQNP.2		;DONE IF ONLY WANTS ONE
AQNP.1:	MOVE	P3,S1			;SAVE THAT NUMBER
	PUSHJ	P,[ AOJA S1,FNDPAG]	;TRY NEXT PAGE NOW
	JUMPF	AQNP.3			;IF FAILS, TRY COLLECTING
	CAIE	S1,1(P3)		;ARE THEY CONTIGUOUS?
	  MOVEI	P2,(P1)			;NO, RESET LOOP COUNT
	SOJG	P2,AQNP.1		;GET MORE IF REQUIRED
AQNP.2:	PUSHJ	P,CREPAG		;CREATE PAGE "S1"
	SOJLE	P1,.RETT		;RETURN IF ALL DONE
	SOJA	S1,AQNP.2		;ELSE BACK DOWN TO THE NEXT ONE

AQNP.3:	SKIPE	PANFLG			;CALL FROM M%GMEM?
	JRST	S..ASE			;YES, ITS ALL OVER
	PUSHJ	P,PGCOLL		;COLLECT PAGES FROM CHUNK ODD SIZE POOL
	JUMPT	AQNP.0			;IF WE GOT A PAGE, TRY ALL OVER
	$STOP(ASE,Addressing space exhausted) ;ELSE, REALLY NO CORE LEFT




SUBTTL FNDPAG - Find first free page

;CALL IS:	S1/ STARTING POINT FOR THE SEARCH
;TRUE RETURN:	S1/ FIRST FREE PAGE
;FALSE RETURN:	COULD NOT FIND A FREE PAGE

FNDPAG:	CAIL	S1,MEMSIZ		;ONLY WANT PAGES THAT ARE UNUSED
	  $RETF				;IF CAN'T FIND ONE, FAIL RETURN
	LOAD	S2,PAGTBL(S1),PT.USE	;THIS ONE USED
	JUMPE	S2,.RETT		;NO, TAKE THIS ONE
	AOJA	S1,FNDPAG		;TRY ANOTHER

SUBTTL CREPAG - Routine to create a page

TOPS20 <

CREPAG:	MOVE	S2,PAGTBL(S1)		;GET OLD SETTINGS
	TXNE	S2,PT.ADR		;ADDRESSABLE
	 SOS	AVBPGS			;DECREMENT COUNT OF "GOOD" PAGES
	MOVX	S2,PT.USE!PT.ADR	;GET ALL THE BITS
	IORM	S2,PAGTBL(S1)		;INCLUDE THEM
	PUSHJ	P,REDUCE		;REDUCE COUNT OF FREE CORE 
	PJRST	.ZPAGN			;RETURN, ZEROING THE PAGE

>  ;END TOPS20 CONDITIONAL

TOPS10 <

CREPAG:	PUSHJ	P,REDUCE		;REDUCE COUNT OF FREE PAGES
	MOVX	S2,PT.USE		;GET THE INUSE BIT
	IORB	S2,PAGTBL(S1)		;SET IN USE, GET THE OTHERS
	TXNE	S2,PT.ADR		;IS IT ADDRESSABLE
	 JRST	[SOS	AVBPGS		;YES--DECREMENT "GOOD" PAGES
		 PJRST	.ZPAGN]		;AND RETURN ZEROING PAGE

	PUSHJ	P,.SAVE4		;SAVE P1-P4
CREP.1:	MOVE	P3,S1			;ARGUMENT FOR CREATE A PAGE
	MOVEI	P2,1			;ONLY 1 ARGUMENT
	MOVE	P1,[.PAGCD,,P2]		;FUNCTION CREATE/DESTROY,,ARGUMENTS
	PAGE.	P1,			;TRY THE CREATE
	  JRST	CREP.2			;ANALYZE THE ERROR
	MOVX	S2,PT.ADR		;ADDRESSABLE
	IORM	S2,PAGTBL(S1)		;INCLUDE THE FLAG
	PJRST	.ZPAGN			;RETURN, ZEROING THE PAGE

CREP.2:	PUSH	P,S1			;SAVE THE PAGE WE'RE TRYING TO CREATE
	CAIE	P1,PAGNS%		;OUT OF SWAPPING SPACE
	  JRST	CREP.3			;NO, LOOK AGAIN
	MOVEI	S1,5			;TAKE A QUICK NAP FIRST
	SLEEP	S1,			;IN CASE SOME FREES UP
	PUSHJ	P,M%CLNC		;FREE SOME SWAPPING SPACE
	POP	P,S1			;RESTORE PAGE NUMBER
	JRST	CREP.1			;AND RETRY THE CREATE

CREP.3:	CAIE	P1,PAGLE%		;MY LIMIT EXCEEDED
	  $STOP(CCP,Cannot create page)	;
	PUSHJ	P,M%IPRM		;SWAP OUT ANYTHING
	SKIPT				;CHECK FOR ERRORS
	  $STOP	(NFP,<No free pages>)
	POP	P,S1			;RESTORE PAGE NUMBER
	JRST	CREP.1			;RETRY THE CREATE

>  ;END TOPS10 CONDITIONAL

SUBTTL M%NXPG - Acquire the number of a free page for IPCF reception

;CALL		NO ARGUMENTS
;
;TRUE RETURN:	S1/THE PAGE NUMBER AVAILABLE FOR IPCF RECEIVE
;FALSE RETURN:	S1/?, NO PAGES AVAILABLE AT THIS TIME, TRY LATER
;
;		AFTER THE RECEIVE, A CALL TO M%IPRC IS REQUIRED.

M%NXPG:
NXPG.0:	MOVE	S1,FREPGS		;GET COUNT OF FREE PAGES
	CAILE	S1,IPCPAD		;ENOUGH TO HANDLE AN INCOMING MESSAGE
	  JRST	NXPG.1			;YES, GO TAKE ONE
	PUSHJ	P,PGCOLL		;NO, TAKE ONE FROM THE FREE SPACE
	JUMPF	.RETF			;CAN'T GET ONE, RETURN FALSE
	JRST	NXPG.0			;TRY UNTIL ENOUGH FREE

TOPS20 <		;TOPS20 WILL REPLACE ANY EXISTING PAGE WITH THE MESSAGE

NXPG.1:	MOVE	S1,PAGSTA		;WHERE TO START LOOKING
	PUSHJ	P,FNDPAG		;GRAB AN AVAILABLE PAGE
	SKIPT				;GREAT IF WE GOT ONE
	  $STOP(CFC,Count of Free Pages Confused)
	MOVX	S2,PT.USE		;SET THE TEMP STATE
	IORB	S2,PAGTBL(S1)		;OF INUSE BUT NOT ADDRESSABLE
	TXNE	S2,PT.ADR		;TAKE ONE OF THE "NICE" PAGES?
	 SOS	AVBPGS			;YES, REDUCE COUNT OF THEM NOW
	MOVX	S2,PT.ADR		;GET THESE FLAGS
	ANDCAM	S2,PAGTBL(S1)		;CLEAR THE FLAGS TO BE SAFE
	$RETT				;AND TAKE A GOOD RETURN

>  ;END TOPS20 CONDITIONAL

TOPS10 <			;TOPS10 REQUIRES A NON-EXISTANT PAGE

NXPG.1:	PUSHJ	P,NXPG.3		;FIND A COMPLETELY MISSING PAGE
	JUMPT	NXPG.2			;TAKE THIS ONE IF WE CAN
	PUSHJ	P,M%CLNC		;DESTROY ANY PAGES I CAN
	PUSHJ	P,NXPG.3		;NOW TRY TO FIND ONE
	SKIPT				;GREAT IF WE GOT ONE
	  $STOP(CFC,Count of Free Pages Confused)
NXPG.2:	MOVX	S2,PT.USE		;SET THE TEMP STATE
	IORM	S2,PAGTBL(S1)		;OF INUSE BUT NOT ADDRESSABLE
	$RETT				;RETURN OUR SUCCESS

NXPG.3:	MOVE	S1,PAGSTA		;START AT THE FIRST AVAILABLE PAGE
NXPG.4:	CAIL	S1,MEMSIZ		;END OF THE ADDRESSING SPACE
	  $RETF				;YES, RETURN A FAILURE
	MOVE	S2,PAGTBL(S1)		;GET THE TABLE ENTRY
	TXNN	S2,PT.USE!PT.ADR	;IS THIS PAGE THERE
	  $RETT				;NO BITS MEANS OK TO USE IT
	AOJA	S1,NXPG.4		;WELL, TRY THE NEXT

>  ;END TOPS10 CONDITIONAL

SUBTTL M%RLNP - Release contiquous free pages

;CALL IS:	S1 / NUMBER TO RELEASE
;		S2 / THE FIRST PAGE
;
;TRUE RETURN:	ALWAYS

M%RLNP:	PUSHJ	P,.SAVE2		;SAVE P1 AND P2
	DMOVE	P1,S1			;COPY THE ARGS OVER
RLNP.1:	SOJL	P1,.RETT		;DECR THE COUNT AND RTN ON 0
	MOVE	S1,P2			;GET THE PAGE NUMBER
	PUSHJ	P,M%RELP		;RELEASE IT
	AOJA	P2,RLNP.1		;AND LOOP



SUBTTL M%RELP - Release a single page to the free pool (by page number)
SUBTTL M%RPAG - Release a single page to the free pool (by address)

;CALL IS:	S1/ PAGE NUMBER TO RELEASE
;
;TRUE RETURN:	ALWAYS


M%RPAG:	ADR2PG	S1			;CONVERT ADR TO PAGE
					;  AND FALL INTO M%RELP

M%RELP:	PUSHJ	P,VALPAG		;CONSISTENCY CHECK PAGE NUMBER
	MOVE	S2,PAGTBL(S1)		;GET THE FLAGS
	TXNE	S2,PT.ADR		;IS THIS THE ONE IPCF'ED AWAY
	  JRST	RELP.1			;NO, GO FIX THE COUNTS
	ZERO	PAGTBL(S1)		;CLEAR THE ENTRY
	$RETT				;AND RETURN

RELP.1:	PUSHJ	P,.SAVE1		;SAVE AN AC
	MOVEI	P1,PAGTBL(S1)		;SAVE ADDRESS OF PAGTBL ENTRY
	PUSHJ	P,INCLUD		;BUMP FREE PAGE COUNT
	AOS	S1,AVBPGS		;BUMP COUNT OF AVAILABLE PAGES
	CAILE	S1,PAGAVL		;EXCEED WORKING SET SIZE
	PUSHJ	P,M%CLNC		;YES..CLEANUP MEMORY
RELP.2:	TXZ	S2,PT.USE		;CLEAR IN USE
	MOVEM	S2,(P1)			;SAVE THE ENTRY IN PAGE TABLE
	$RETT				;NOW RETURN..
					;THIS WILL ALWAYS LEAVE ONE PAGE
					;FOR AVBPGS



SUBTTL M%FPGS - Return number of free pages

;CALL		NO ARGUMENTS
;
;TRUE RETURN:	ALWAYS, S1/THE NUMBER OF PAGES FREE

M%FPGS:	MOVE	S1,FREPGS		;PICK UP THE NUMBER
	$RETT				;AND RETURN

SUBTTL M%IPSN - Inform that page is about to be sent via IPCF

; CALL IS:	S1/ PAGE NUMBER OF IPCF'ED PAGE
;
;TRUE RETURN:	ALWAYS

M%IPSN:	PUSHJ	P,VALPAG		;CONSISTENCY CHECK PAGE NUMBER
	MOVX	S2,PT.ADR		;CLEAR ADDRESSABLE
	ANDCAM	S2,PAGTBL(S1)		;SO THAT WE DON'T GET CONFUSED
	PJRST	INCLUD			;BUMP FREE PAGE COUNT AND RETURN



SUBTTL M%IPRC - Inform that page has been created via IPCF

;CALL IS:	S1/PAGE NUMBER THAT RECEIVE CREATED
;
;TRUE RETURN:	ALWAYS

TOPS10 <	;NOW NEED TO KNOW IF THE PAGE IS IN THE WORKING SET

M%IPRC:	PUSHJ	P,VALPAG		;CONSISTENCY CHECK PAGE NUMBER
	PUSH	P,S1			;SAVE THE PAGE NUMBER
	HRLI	S1,.PAGCA		;CHECK ITS ACCESS BITS
	PAGE.	S1,			;SEE IF THE PAGE IS SWAPPED OUT
	  $STOP(PAF,Page access check failed)
	MOVX	S2,PT.ADR		;ADDRESSABLE
	TXNE	S1,PA.GNE		;PAGE DOESN'T EXIST
	  $STOP(RNF,Received non-existent page)
	POP	P,S1			;RESTORE PAGE NUMBER
	IORM	S2,PAGTBL(S1)		;INCLUDE THE FLAG(S)
	PJRST	REDUCE			;REDUCE COUNT OF FREE PAGES AND RETURN

>  ;END TOPS10 CONDITIONAL

TOPS20 <

M%IPRC:	PUSHJ	P,VALPAG		;CONSISTENCY CHECK PAGE NUMBER
	MOVX	S2,PT.ADR		;ADDRESSABLE
	IORM	S2,PAGTBL(S1)		;INCLUDE THE FLAGS
	PJRST	REDUCE			;REDUCE COUNT OF FREE PAGES AND RETURN

>  ;END TOPS20 CONDITIONAL

SUBTTL M%GMEM - Allocate a chunk of memory

;CALL IS:	S1/ NUMBER OF WORDS WANTED
;
;TRUE RETURN:	S1/ NUMBER OF WORDS OBTAINED
;		S2/ ADDRESS OF FIRST WORD


M%GMEM:	PUSHJ	P,.SAVE2		;GET TWO WORK REGISTERS
	CAMG	S1,FREWDS		;IN RANGE OF AVAILABLE SPACE?
	SKIPG	S1			;OR SILLY NUMBER?
	$STOP(RNW,Ridiculous number of words requested)
	CAIG	S1,DCT.MX		;IF REQUIRED SIZE .GT. DICTIONARY
	SKIPN	S2,DICT(S1)		;OR IF DICTIONARY ENTRY IS 0
	JRST	GMEM.0			;GO TRY THE ODD SIZE POOL
	MOVE	P1,0(S2)		;GET FORWARD LINK OF CHOSEN BLOCK
	MOVEM	P1,DICT(S1)		;STORE INTO HEAD AS NEXT TO CHOSE
	PJRST	.ZCHNK			;RETURN ZEROING CHUNK

GMEM.0:	MOVE	P1,S1			;SAVE THE REQUIRED BLOCK LENGTH
	MOVE	S1,CNT.AP		;GET FREE POOL ALLOCATED PAGE COUNT
	CAIL	S1,CNK.PM		;WITHIN BOUNDS OF PAGES
	PUSHJ	P,[PUSHJ P,PGCOLL	;NO,,GARBAGE COLLECT
		   SETZM CNT.AP		;CLEAR ADDED PAGE COUNT
		   POPJ  P,   ]		;RETURN
	MOVE	S1,P1			;RESTORE REQUIRED BLOCK LENGTH

GMEM.1:	MOVEI	S2,DICT			;START WITH HEADER OF ODD LIST
GMEM.2:	MOVE	P1,S2			;REMEMBER WHO POINTS TO CURRENT
	HRRZ	S2,0(P1)		;S2 IS NOW CURRENT BLOCK
	JUMPE	S2,GMEM.4		;IF 0, WE HAVE REACHED END OF THE ROAD
	HLRZ	P2,0(S2)		;GET SIZE OF CURRENT BLOCK
	CAMGE	P2,S1			;IS IT SUFFICIENT FOR REQUEST?
	JRST	GMEM.2			;NO, SO TRY NEXT BLOCK
GMEM.3:	HRL	S2,0(S2)		;GET LINK OF CURRENT BLOCK
	HLRM	S2,0(P1)		;MAKE PREV LINK BE WHAT WAS OUR LINK
	HRRZS	S2			;ISOLATE CURRENT BLOCKS ADDRESS
	CAMN	P2,S1			;IS THIS AN EXACT MATCH ON SIZE?
	PJRST	.ZCHNK			;YES, RETURN, ZEROING CHUNK
	PUSH	P,S1			;SAVE NUMBER OF WORDS
	PUSH	P,S2			;SAVE ADDRESS
	ADD	S2,S1			;GET FIRST WORD TO RETURN
	SUBM	P2,S1			;NUMBER OF WORDS TO RETURN
	PUSHJ	P,M%RMEM		;RETURN THE EXTRA WORDS
	POP	P,S2			;RESTORE ADDRESS OF BLOCK
	POP	P,S1			;RESTORE NUMBER OF WORDS
	PJRST	.ZCHNK			;YES, RETURN, ZEROING CHUNK

GMEM.4:	MOVEI	P2,1(S1)		;START WITH NEXT DICT SLOT
GMEM.5:	CAILE	P2,DCT.MX		;IS THIS STILL INSIDE DICTIONARY?
	JRST	GMEM.6			;TIME FOR MORE MEMORY
	SKIPN	S2,DICT(P2)		;ANYTHING IN THIS DICTIONARY SLOT ???
	AOJA	P2,GMEM.5		;NO, TRY NEXT LARGEST
	MOVEI	P1,DICT(P2)		;P1 IS CELL POINTING TO CHOSEN
	JRST	GMEM.3			;EXIT RETURNING EXTRA MEMORY

GMEM.6:	PUSH	P,S1			;SAVE SIZE WANTED
	PUSHJ	P,APMEM			;TRY TO FIX UP FREE CHUNK POOL
	POP	P,S1			;RESTORE THE SIZE
	JRST	GMEM.1			;AND TRY AGAIN

SUBTTL APMEM  - Routine to add one page to the chunk pool

;CALL IS:	No arguments
;TRUE RETURN:	Always


APMEM:	PUSHJ	P,.SAVE2		;GET SOME INDICES
	SETOM	PANFLG			;DON'T WANT ANYTHING TO GO TO DICT
	SOSL	APCNT			;TIME TO DUMP THE DICTIONARY?
	JRST	APME.4			;NO, JUST GET A PAGE
	MOVEI	P1,DCT.MX		;GET MAXIMUM DICTIONARY ENTRY
APME.1:	MOVE	P2,DICT(P1)		;GET START OF LINKED LIST FOR SIZE
	SETZM	DICT(P1)		;CLEAR IT OUT
APME.2:	SKIPN	S2,P2			;DO WE HAVE A VALID ADDRESS?
	JRST	APME.3			;NO, PROCESS NEXT SIZE
	MOVE	S1,P1			;SET SIZE OF CHUNK UP
	MOVE	P2,0(P2)		;GET LINK TO NEXT BLOCK
	PUSHJ	P,M%RMEM		;AND RETURN IT
	JRST	APME.2			;REPEAT FOR POSSIBLE NEXT BLOCK

APME.3:	SOJG	P1,APME.1		;DO FOR ENTIRE DICTIONARY
	MOVEI	P1,DDCNT		;SET COUNTER AGAIN
	MOVEM	P1,APCNT		;RESET IT
	SETZM	PANFLG			;CLEAR PANIC LEVEL FLAG
	INCR	CNT.DD			;DUMPED DICTIONARY AGAIN
	$RETT				;AND RETURN

APME.4:	AOS	CNT.AP			;BUMP THE ADDED PAGE COUNT
	PUSHJ	P,M%ACQP		;ACQUIRE A PAGE
	SETZM	PANFLG			;CLEAR PANIC LEVEL FLAG
	MOVE	S2,S1			;GET PAGE NUMBER
	PG2ADR	S2			;CONVERT TO AN ADDRESS
	MOVEI	S1,PAGSIZ		;AND THE SIZE
	PJRST	M%RMEM			;RETURN, RETURNING TO FREE POOL

SUBTTL PGCOLL - Routine to remove whole pages from chunk free pool

;This routine is called to remove, from the odd-size pool of the chunk
;manager, whole pages so that they are available to routines needing
;whole, page-aligned areas of memory.

;CALL IS:	No arguments
;TRUE RETURN:	A page has been freed
;FALSE RETURN:	No page could be removed

PGCOLL:	AOS	CNT.CL			;BUMP NUMBER OF TIMES COLLECTED
	SETZM	APCNT			;FORCE DICTIONARY DUMP
	PUSHJ	P,APMEM			;TO INSURE FREE POOL IS ALL IN ODD SIZE
	PUSHJ	P,.SAVE4		;NEED LOTS OF SCRATCH SPACE
	SETZM	CNT.PC			;CLEAR COUNT OF PAGES GOTTEN
	MOVEI	P1,DICT			;SEED HEAD OF LIST AS PREVIOUS
PGCO.1:	HRRZ	P2,0(P1)		;GET ADDR OF NEXT CHUNK
	JUMPE	P2,PGCO.2		;IF 0 LINK, WE ARE AT END
	HLRZ	P3,0(P2)		;GET LENGTH OF THIS CHUNK
	MOVE	S1,P2			;GET ADDRESS OF CHUNK
	ADDI	S1,PAGSIZ-1		;AND ROUND UP TO
	TRZ	S1,PAGSIZ-1		; PAGE BOUNDARY
	MOVE	P4,P2			;COPY ADDRESS OF THIS CHUNK
	ADD	P4,P3			;COMPUTE FIRST ADDR NOT IN THIS CHUNK
	MOVE	S2,S1			;GET START OF CHUNK
	ADDI	S2,PAGSIZ		;ADDR OF PAGE STARTING HERE
	CAMGE	P4,S2			;IS SIZE OF PAGE WITH BOUNDS OF CHUNK?
	  JRST	[ MOVE P1,P2		;NO, SO STEP TO NEXT CHUNK
		  JRST PGCO.1 ]		;AND TRY AGAIN
	MOVE	P4,S2			;REMEMBER END ADDRESS OF PAGE SIZE CHUNK
	HRRZ	S2,0(P2)		;GET ADDR OF NEXT CHUNK IN CHAIN
	HRRM	S2,0(P1)		;DE-LINK THIS CHUNK
	SUB	S1,P2			;COMPUTE LN. OF LEFT HAND OVERFLOW
	MOVE	S2,P2			;AND ADDRESS LH OVERFLOW STARTS AT
	SUBI	P3,PAGSIZ(S1)		;ADJUST COUNT TO REFLECT 1 PAGE+LH
	SKIPE	S1			;IF THERE IS ANY LEFT HAND TO RETURN
	PUSHJ	P,M%RMEM		;DO SO NOW
	DMOVE	S1,P3			;GET SIZE, ADDR OF RH OVERFLOW
	SKIPE	S1			;IF THERE IS ANY RH OVERFLOW,
	PUSHJ	P,M%RMEM		;RETURN IT NOW
	INCR	CNT.PC			;COUNT PAGES COLLECTED IN THIS MANNER
	MOVE	S1,P4			;GET END ADDRESS OF PAGE SIZE CHUNK
	SUBI	S1,PAGSIZ		;IT STARTS HERE
	PUSHJ	P,M%RPAG		;RETURN THE PAGE
	JRST	PGCO.1			;TRY TO GET SOME MORE
PGCO.2:	SKIPG	CNT.PC			;DID WE GET ANY
	$RETF				;NO..RETURN FALSE
	$RETT				;YES..RETURN TRUE

SUBTTL M%RMEM - Routine to de-allocate a memory chunk
;CALL IS:	S1/ SIZE OF CHUNK BEING RETURNED
;		S2/ ADDRESS OF CHUNK BEING RETURNED
;
;TRUE RETURN:	ALWAYS

M%RMEM:	PUSHJ	P,.SAVE2		;GET SOME WORK SPACE
	PUSHJ	P,VALADR		;VALIDATE THE ADDRESS
	SKIPG	S1			;REASONABLE AMOUNT BEING RETURNED?
	$STOP(ZWR,Zero words of memory returned)
	SKIPE	PANFLG			;ARE WE IN PANIC MODE?
	JRST	RMEM.1			;YES, DON'T RETURN TO DICTIONARY
	CAIL	S1,DCT.MN		;LESS THAN SMALLEST OR
	CAILE	S1,DCT.MX		;GREATER THAN MAXIMUM IN DICT?
	JRST	RMEM.1			;YES, RETURN TO ODD-SIZE POOL
	MOVE	P1,DICT(S1)		;GET LINK OF HEADER
	HRRZM	P1,0(S2)		;MAKE IT CURRENT BLOCK'S HEADER
	HRRZM	S2,DICT(S1)		;AND MAKE HEADER POINT TO CURRENT
	$RETT				;RETURN NOW

RMEM.1:	MOVEI	P1,DICT			;GET PREV SET UP
RMEM.2:	HRRZ	P2,0(P1)		;GET PREV'S LINK
	SKIPE	P2			;IF CURRENT IS 0 OR
	CAIL	P2,0(S2)		;  ITS ADDRESS IS PAST ADDR OF RETURN BLK
	JRST	RMEM.3			; THEN RETURN BLOCK HERE
	MOVE	P1,P2			;MAKE PREV=CURRENT
	JRST	RMEM.2			;CONTINUE

RMEM.3:	HLRZ	P2,0(P1)		;GET SIZE OF PREVIOUS
	ADD	P2,P1			;ADD SIZE PLUS ADDRESS
	CAIE	P2,0(S2)		;DOES THIS PUT IT AT CURRENT BLOCK?
	JRST	RMEM.4			;NO, CANNOT COMBINE
	MOVE	S2,P1			;CONCATENATE PREV AND CURRENT
	HLRZ	P2,0(P1)		;GET SIZE OF PREVIOUS AGAIN
	ADD	S1,P2			;MAKE A COMBINED SIZE
RMEM.4:	HRLM	S1,0(S2)		;STORE SIZE OF CURRENT BLOCK
	HRRZ	P2,0(P1)		;GET PREV'S FORWARD LINK
	HRRM	P2,0(S2)		;MAKE IT CURRENT'S FORWARD LINK
	CAME	S2,P1			;UNLESS PREV=CURRENT (FROM CONCATENATION)
	HRRM	S2,0(P1)		;MAKE PREV'S FORWARD LINK POINT TO CURR.
	MOVE	P1,S2			;GET ADDRESS OF CURRENT BLOCK
	ADD	P1,S1			;ADD SIZE TO THAT
	CAIE	P1,0(P2)		;DO WE BUTT UP AGAINST NEXT?
	$RETT				;NO, CANNOT COMBINE, RETURN NOW
	HRLZS	S1			;YES, POSITION SIZE OF CURRENT
	ADD	S1,0(P2)		;MAKE COMBINED SIZE,,LINK TO NEW NEXT
	MOVEM	S1,0(S2)		;STORE NEW SIZE AND LINK
	$RETT				;RETURN

SUBTTL Consistency checking routines

;"REDUCE" DECREMENTS THE FREE PAGE COUNT , "INCLUD" ADDS A FREE PAGE
;


REDUCE:	SOSGE	FREPGS			;DECREMENT COUNT OF FREE PAGES
	  $STOP(FCN,Free count negative)
	$RETT				;RETURN IF OK

INCLUD:	AOS	S1,FREPGS		;ADD A FREE PAGE
	CAMLE	S1,FREINI		;MORE THAN WE STARTED OUT WITH
	  $STOP(FCE,Free count exceeds FREINI)
	$RETT				;RETURN IF OK

;VALADR VALIDATES THE RANGE OF MEMORY THAT STARTS AT ADDR IN S2
;	AND CONTINUES FOR THE NUMBER OF WORDS IN S1

VALADR:	PUSH	P,S1			;SAVE INPUT ARGUMENTS
	PUSH	P,S2			;FROM M%RMEM
	EXCH	S1,S2			;GET ADDRESS IN S1, SIZE IN S2
	ADR2PG	S1			;CONVERT TO A PAGE NUMBER
VALA.1:	PUSHJ	P,VALPAG		;VALIDATE IT
	SUBI	S2,PAGSIZ		;HAVE ACCOUNTED FOR ONE PAGE
	SKIPLE	S2			;DONE ENTIRE CHUNK?
	AOJA	S1,VALA.1		;NO, DO THE NEXT PAGE
	POP	P,S2			;RESTORE S2 (ADDRESS)
	POP	P,S1			;RESTORE S1 (SIZE)
	$RETT				;AND RETURN

;VALPAG VALIDATES THE PAGE NUMBER IN AC S1

VALPAG:	CAIL	S1,MEMSIZ		;RANGE CHECK THE PAGE NUMBER
	  JRST	S..BPN			;OUT OF RANGE OF PAGE TABLE
	PUSH	P,S2			;SAVE CALLER'S AC
	MOVE	S2,PAGTBL(S1)		;GET THE PAGE TABLE ENTRY FOR PAGE
	TXNN	S2,PT.INI		;PART OF INITIAL CORE IMAGE?
	TXNN	S2,PT.USE		;OR NOT IN USE?
	$STOP(BPN,Bad page number ^O/S1/)	;YES, STOP NOW
	POP	P,S2			;RESTORE CALLER'S S2
	$RETT				;RETURN IF OK

SUBTTL M%CLNC - Routines for cleaning up core

;CALL IS:	NO ARGUMENTS
;
;TRUE RETURN:	ALWAYS

M%CLNC:
TOPS10	<				;TOPS-10 ONLY
	PUSHJ	P,.SAVE4		;SAVE P1-P4
	MOVE	P4,PAGSTA		;THE FIRST AVAILABLE PAGE
CLNC.1:	CAIL	P4,MEMSIZ		;OFF THE END OF THE WORLD
	  $RETT				;YES, RETURN
	MOVE	P1,PAGTBL(P4)		;GET THE TABLE ENTRY
	TXC	P1,PT.ADR		;NEED CHECK FOR BOTH SO FLIP
	TXNN	P1,PT.USE!PT.ADR	;USED OR NOT ADDRESSABEL
	  PUSHJ	P,KILPAG		;DESTROY THE PAGE (COULD BE PAGED OUT)
	AOJA	P4,CLNC.1		;AND CONTINUE LOOPING

KILPAG:	MOVEI	P3,(P4)			;WANT IT IN P3
	TXO	P3,1B0			;SET TO DESTROY
	MOVEI	P2,1			;1 ARGUMENT
	MOVE	P1,[.PAGCD,,P2]		;CREATE/DESTROY,,ARGUMENT
	PAGE.	P1,			;TRY TO DESTROY IT
	  $STOP(PKF,Page kill failed)
	ZERO	P1			;CLEAR A REG
	EXCH	P1,PAGTBL(P4)		;CLEAR PAGE TABLE ENTRY, GET OLD FLAGS
	SOS	AVBPGS			;ONE LESS "GOOD" PAGE
	$RETT				;RETURN
>					;END OF TOPS-10 CONDITIONAL

TOPS20	<$RETT>				;TOPS-20 ONLY

SUBTTL M%IPRM -  Routine to find a free page for an IPCF receive


; M%IPRM will find a free page for an IPCF receive. To do this
; correctly in all cases, we create a page on disk, fault it into
; core, and destroy it. This leaves us a slot in our working set
; to receive an IPCF packet.
; Call:	$CALL	M%IPRM
;
; TRUE return:	a page free in the working set
; FALSE return:	can't find a free page
;
M%IPRM:
TOPS10	<				;TOPS-10 ONLY
	SKIPN	VRTPRV			;HAVE VIRTUAL PRIVS?
	JRST	IPRM.E			;NOPE - THEN WE CAN'T FIND A FREE PAGE
	PUSHJ	P,.SAVE3##		;SAVE SOME ACS
	PUSHJ	P,M%NXPG		;GET A NON-EXISTANT PAGE NUMBER
	  JUMPF	IPRM.E			;CAN'T
	MOVE	P1,[.PAGCD,,P2]		;SET UP UUO
	MOVEI	P2,1			;ONE WORD ARGUMENT
	MOVE	P3,S1			;GET THE PAGE NUMBER
	TXO	P3,PA.GCD		;CREATE THE PAGE ON DISK
	PAGE.	P1,			;CREATE THE PAGE
	  JRST	IPRM.E			;CAN'T
	MOVE	P1,S1			;GET THE PAGE NUMBER
	PG2ADR	P1			;CONVERT TO AN ADDRESS
	MOVE	S2,(P1)			;PAGE FAULT IT INTO CORE
	MOVE	P1,[.PAGCD,,P2]		;SET UP UUO
	MOVEI	P2,1			;ONE WORD ARGUMENT
	MOVE	P3,S1			;GET THE PAGE NUMBER
	TXO	P3,PA.GAF		;LITE THE DESTROY BIT
	PAGE.	P1,			;DESTROY THE PAGE
	  SKIPA				;CAN'T
	$RETT				;RETURN

IPRM.E:	$RETE	(NFP)			;?NO FREE PAGES
>					;END OF TOPS-10 CONDITIONAL

TOPS20	<$RETT>				;TOPS-20 ONLY

SUBTTL	End


MEM%L:

	END