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The procedures p_getheap and p_rtnheap
are intrinsics in the Pascal run-time library. Any program that
runs on the operating system can call them, regardless of the language
in which it is written. (For more information on intrinsics, Chapter 10 “Intrinsics ”). The procedure p_getheap tries to allocate
a region of heap space of a specified size and alignment. If it
succeeds, it "points" its VAR pointer parameter at the first element
of the region and assigns its VAR Boolean parameter the value true.
If it fails, it assigns its VAR Boolean parameter the value false. Syntax p_getheap (VAR regptr : localanyptr;
regsize : integer;
alignment : integer;
VAR ok : Boolean); |
Parameters - regptr
If p_getheap can allocate
the region of heap space, it "points" regptr
at the first element of the region (that is, p_getheap
assigns the address of the first element of the region to regptr). - regsize
The size of the region of heap space, in bytes. - alignment
Title not available (P_getheap and P_rtnheap Procedures ) - Integer:
Specifies the region of heap space to
be: - 1
Byte-aligned - 2
Halfword-aligned - 4
Word-aligned - 8
Double-word-aligned - 16
16-byte aligned - 32
32-byte aligned - 64
64-byte aligned - 2048
Page-aligned
- ok
If p_getheap can allocate
the region of heap space, it assigns ok
the value true; if not, it assigns ok
the value false.
The procedure p_rtnheap tries to
deallocate a region of heap space that the p_getheap
procedure allocated. If it succeeds, it assigns its VAR Boolean
parameter the value true. If it fails,
it assigns its VAR Boolean parameter the value false.
P_rtnheap does not close files residing
in the region allocated by p_getheap. Syntax p_rtnheap (VAR regptr : localanyptr;
regsize : integer;
alignment : integer;
VAR ok : Boolean); |
Parameters - regptr
A pointer whose current value was assigned to it
by the procedure p_getheap. - regsize
The size in bytes of the region of heap space that
p_getheap assigned to regptr. - alignment
The number that specified the alignment of the region
of heap space that p_getheap assigned
to regptr. - ok
If p_rtnheap can deallocate
the region of heap space, it assigns ok
the value true; if not, it assigns ok
the value false.
Example 1 $STANDARD_LEVEL 'HP_MODCAL'$
PROGRAM prog;
TYPE
intpointer = ^integer;
VAR
b : Boolean;
i : integer;
ptr1,
ptr2 : intpointer;
PROCEDURE p_getheap (VAR regptr : intpointer;
regsize : integer;
alignment : integer;
VAR ok : Boolean); EXTERNAL;
PROCEDURE p_rtnheap (VAR regptr : intpointer;
regsize : integer;
alignment : integer;
VAR ok : Boolean); EXTERNAL;
BEGIN
p_getheap(ptr1,40,4,b); {allocate a 40-byte region}
ptr2 := ptr1; {save ptr1 for later call to p_rtnheap}
FOR i := 1 TO 10 DO BEGIN
ptr2^ := i;
ptr2 := addtopointer(ptr2,4);
END;
p_rtnheap(ptr1,40,4,b); {deallocate the 40-byte region}
p_getheap(ptr1,50,2,b);
p_rtnheap(ptr1,20,2,b); {illegal 20 must be 50}
p_getheap(ptr1,16,8,b);
p_rtnheap(ptr1,16,1,b); {illegal 1 must be 8}
END. |
The procedures p_getheap and p_rtnheap
are independent from the procedures mark, release, new,
and dispose. Example 2 $STANDARD_LEVEL 'HP_MODCAL'$
PROGRAM prog;
VAR
i : integer;
b : Boolean;
p1,p2,p3,
ptr1, ptr2, ptr3 : ^integer;
PROCEDURE p_getheap; INTRINSIC;
PROCEDURE p_rtnheap; INTRINSIC;
BEGIN
p_getheap(ptr1,28,4,b); {allocate a 28-byte region}
ptr3 := ptr1; {assign values in the 28-byte region}
FOR i := 1 TO 7 DO BEGIN
ptr3^ := i;
ptr3 := addtopointer(ptr3,4);
END;
ptr3 := ptr1;
mark(ptr2); {mark the heap}
new(p1); {allocate p1, p2, and p3}
new(p2);
new(p3);
p_rtnheap(ptr1,28,4,b); {deallocate the 28-byte region}
ptr3^ := 0; {illegal p_rtnheap deallocated ptr3^}
p1^ := 1; {p_rtnheap did not deallocate p1, p2, or p3;}
p2^ := 2; {they are still accessible}
p3^ := 3;
p_getheap(ptr1,4,4,b); {allocate a 4-byte region} |
release(ptr2);
ptr1^ := 0; {The 4-byte region was not
deallocated, and the values
in it are still accessible}
p1^ := p2^ + p3^; {illegal p1, p2, and p3 were deallocated}
END. |
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