1 \ *****************************************************************************
2 \ * Copyright (c) 2004, 2008 IBM Corporation
3 \ * All rights reserved.
4 \ * This program and the accompanying materials
5 \ * are made available under the terms of the BSD License
6 \ * which accompanies this distribution, and is available at
7 \ * http://www.opensource.org/licenses/bsd-license.php
10 \ * IBM Corporation - initial implementation
11 \ ****************************************************************************/
14 \ Memory "heap" (de-)allocation.
16 \ Keep a linked list of free blocks per power-of-two size.
17 \ Never coalesce entries when freed; split blocks when needed while allocating.
19 \ 3f CONSTANT (max-heads#)
20 heap-end heap-start - log2 1+ CONSTANT (max-heads#)
22 CREATE heads (max-heads#) cells allot
23 heads (max-heads#) cells erase
26 : size>head ( size -- headptr ) log2 3 max cells heads + ;
29 \ Allocate a memory block
30 : alloc-mem ( len -- a-addr )
32 1 over log2 3 max ( len 1 log_len )
33 dup (max-heads#) >= IF cr ." Out of internal memory." cr 3drop 0 EXIT THEN
34 lshift >r ( len R: 1<<log_len )
36 dup @ dup >r @ swap ! r> r> drop EXIT
37 THEN ( headptr R: 1<<log_len)
38 r@ 2* recurse dup ( headptr a-addr2 a-addr2 R: 1<<log_len)
39 dup 0= IF r> 2drop 2drop 0 EXIT THEN
40 r> + >r 0 over ! swap ! r>
46 : free-mem ( a-addr len -- )
47 dup 0= IF 2drop EXIT THEN size>head 2dup @ swap ! !
52 @ 0 BEGIN over WHILE 1+ swap @ swap REPEAT nip
58 heads i cells + #links dup IF
59 cr dup . ." * " 1 i lshift dup . ." = " * dup .
67 \ Start with just one free block.
68 heap-start heap-end heap-start - free-mem
71 \ : free-mem ( a-addr len -- ) 2drop ;
73 \ Uncomment the following line for debugging:
74 \ #include <alloc-mem-debug.fs>