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; flat assembler interface for DOS
; Copyright (c) 1999-2022, Tomasz Grysztar.
; All rights reserved.
init_dpmi_memory:
mov ax,500h ; get free memory information
mov edi,[buffer_address]
int 31h
mov ebx,[edi]
allocate_dpmi_memory:
mov edx,[memory_setting]
shl edx,10
jz dpmi_memory_size_ok
cmp ebx,edx
jbe dpmi_memory_size_ok
mov ebx,edx
dpmi_memory_size_ok:
mov [memory_end],ebx
mov ecx,ebx
shr ebx,16
mov ax,501h
int 31h
jnc dpmi_memory_ok
mov ebx,[memory_end]
shr ebx,1
cmp ebx,4000h
jb out_of_memory
jmp allocate_dpmi_memory
dpmi_memory_ok:
shl ebx,16
mov bx,cx
sub ebx,[program_base]
jc out_of_memory
mov [memory_start],ebx
add [memory_end],ebx
mov ax,100h ; get free conventional memory size
mov bx,-1
int 31h
movzx ecx,bx
shl ecx,4
jecxz no_conventional_memory
mov ax,100h ; allocate all conventional memory
int 31h
movzx edi,ax
shl edi,4
sub edi,[program_base]
jc no_conventional_memory
mov [additional_memory],edi
mov [additional_memory_end],edi
add [additional_memory_end],ecx
mov eax,[memory_end]
sub eax,[memory_start]
shr eax,2
cmp eax,ecx
ja no_conventional_memory
ret
no_conventional_memory:
mov eax,[memory_end]
mov ebx,[memory_start]
sub eax,ebx
shr eax,2
mov [additional_memory],ebx
add ebx,eax
mov [additional_memory_end],ebx
mov [memory_start],ebx
ret
dpmi_dos_int:
mov [real_mode_segment],main
simulate_real_mode:
push 0 ; SS:SP (DPMI will allocate stack)
push 0 ; CS:IP (ignored)
push 0
push [real_mode_segment] ; DS
push [real_mode_segment] ; ES
stc
pushfw
push eax
push ecx
push edx
push ebx
push 0
push ebp
push esi
push edi
mov ax,300h
mov bx,21h
xor cx,cx
mov edi,esp
push es ss
pop es
int 31h
pop es
mov edi,[esp]
mov esi,[esp+4]
mov ebp,[esp+8]
mov ebx,[esp+10h]
mov edx,[esp+14h]
mov ecx,[esp+18h]
mov ah,[esp+20h]
sahf
mov eax,[esp+1Ch]
lea esp,[esp+32h]
ret
dpmi_dos_int_with_buffer:
mov [real_mode_segment],buffer
jmp simulate_real_mode
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