99 lines
1.7 KiB
NASM
99 lines
1.7 KiB
NASM
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format ELF
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public _add as 'heap.add'
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public del as 'heap.del'
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include '../include/macros.inc'
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extrn exit
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section '.bss' writeable
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_heap:
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db 0xB ; flag
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dd 4 ; size
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dd 4096 ; available memory
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rd 4096
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section '.text' executable
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_add:
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prelude
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mov ecx, [ebp+2*4] ; size
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mov eax, _heap
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xor edx, edx
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.loop:
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cmp [eax], byte 0
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je .empty
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mov bl, [eax]
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bt bx, 0
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jc .busy
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inc eax
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cmp edx, 0
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jne @f
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mov edx, eax
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@@:
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cmp ecx, [eax]
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jl .more
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je .equal
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; less
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sub ecx, [eax]
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add eax, [eax]
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add eax, 4
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jmp .loop
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.equal:
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mov [edx], byte 9
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mov ebx, [ebp+2*4]
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mov [edx+1], ebx
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add edx, 5
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mov [ebp+2*4], edx
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postlude
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ret
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.more:
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mov ebx, edx
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add ebx, [ebp+2*4]
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mov [ebx], byte 9
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inc ebx
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mov eax, [eax]
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sub eax, ecx
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mov [ebx], eax
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add ebx, [ebp+2*4]
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mov [edx-1], byte 9
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mov edx, ebx
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add edx, 5
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mov [ebp+2*4], edx
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postlude
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ret
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.empty:
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cmp edx, 0
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jne @f
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mov edx, eax
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@@:
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je @f
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dec edx
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@@:
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jmp .equal
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.busy:
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xor edx, edx
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inc eax
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add eax, [eax]
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add eax, 4
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jmp .loop
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del:
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push eax
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mov eax, [esp+4*2]
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sub eax, 5
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and byte [eax], 254
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mov eax, [esp+4]
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mov [esp+4*2], eax
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pop eax
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add esp, 4
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ret
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