iAPX 286 Operating System Writers Guide 1983

REAL MEMORY MANAGEMENTPL/M-286 COMPILER 960-501 date PAGE 3NEXT LINK BASED SLOT_C STRUCTURE (MEM_LINK);293031323334353637383940414243444546474849505152535455222333222333212222222233322IF THIS LINK. PRIOR = NULL PHYS ADDR/* ThIs is the beginning of the list. */THEN FIRST AVLBL = THIS LINK. NEXT ;ELSE DO; /* Update link-from prior segment. */CALL POINT AT(SLOT C, DWRIGHTS,- -@THIS LINK.PRIOR, LINK_LIMIT);PRIOR_LINK.NEXT = THIS_LINK. NEXT; .END;IF THIS LINK. NEXT = NULL PHYS ADDR/* This is the end of the list. */THEN LAST AVLBL = THIS_LINK. PRIOR;ELSE DO; /* Update link from next segment. */CALL POINT AT(SLOT C, DWRIGHTS,-@THIS LINK.NEXT, LINK_LIMIT);NEXT_LINK. PRIOR THIS_LINK. PRIOR;END;END DELINK;1*******************************************************/FIND FIRST FIT: PROCEDURE (SIZE,BASE ADDR PTR)- - WORD REENTRANT;DECLARE SIZE WORD,BASE ADDR PTR POINTER,BASE-ADDR-BASED BASE ADDR_PTR DWORD;DECLARE CURR LINK BASED SLOT_A STRUCTURE (MEM_LINK),PHYS-SIZE DWORD,SIZE-DIFF DWORD,/* Boundary tag items */BOUND ADDR DWORD,BOUND-MID BASED SLOT B STRUCTURE (MEM LINK) ,BOUND-HI BASED SLOT B STRUCTURE (MEM:=LINK);DECLARE TOP LOOP LABEL;PHYS SIZE = SIZE;CALL-ROUND SIZE(@PHYS SIZE);CALL POINT-AT(SLOT A,-DWRIGHTS,- @CURR_AVLBL, LINK_LIMIT);TOP LOOP:IF-SLOT A SELECTOR$OF(NIL) /* Check for end of list */THEN DO;IF FIRST AVLBL = NULL PHYS ADDR/* The list is empty~ */ -THEN RETURN FAILED;END;ELSE CALL POINT AT(SLOT A, DWRIGHTS,- @FIRST AVLBL, LINK LIMIT);/* Continue from beginning of list. */ -IF CURR LINK. SIZE < PHYS SIZETHEN /* This segment is-too small, so •.. */Figure 3-9. Code for Memory-Management Example (Cont'd.)3-17 121960-001