Category : Files from Magazines
Archive   : PJ91.ZIP
Filename : MALLOC.ASM

title malloc
include asm.inc

public calloc
public free
public malloc

.const
ertx_malloc_range db 'malloc out of range',0

.code
extn ms_dos_strerror,set_strerror


;; calloc
;
; entry CX requested byte count (1..FFF0)
; exit ES:DI storage pointer
; AX actual byte count
; Cf if no storage
;
calloc proc
call malloc ; allocate storage
jc cal1

pushm ax,cx,di ; zero storage
mov cx,ax
movx ax,0
shr cx,1
rep stosw
popm di,cx,ax
cal1: ret
calloc endp


;; free
;
; entry ES:DI storage pointer (OK if NULL)
; exit ES:DI NULL
; Cf if bad pointer
; uses AX
;
free proc
mov ax,es
or ax,di
jz fee1 ;\ if NULL pointer - ignore call

mov ah,49h
call ms_dos_strerror

mov di,NULL_POINTER ; return NULL (don't modify flags)
mov es,di

fee1: ret
free endp


;; malloc
;
; entry CX requested byte count (1..FFF0)
; exit ES:DI storage pointer
; AX actual byte count
; Cf if no storage
;
malloc proc
jcxz mal2 ; if byte count out of range
mov ax,cx
add ax,15
jc mal2 ; if byte count out of range
and al,0F0h

pushm ax,bx ; convert byte count to paragraph cnt
shr ax,1
shr ax,1
shr ax,1
shr ax,1
mov bx,ax

mov ah,48h ; request memory from dos
call ms_dos_strerror
jc mal1 ; if not enough memory
mov es,ax
movx di,NULL_POINTER

mal1: popm bx,ax
ret

mal2: lea ax,ertx_malloc_range
jmp set_strerror
malloc endp

end