path: root/other/burneye/src/stub/utils/lde32.asm

; LDE32 -- Length-Disassembler Engine
; FREEWARE
;
; programmed by Z0MBiE, http://z0mbie.cjb.net
;
; release 1.00          8-12-99
; release 1.01          9-12-99
; release 1.02         17-03-00  0xF6/0xF7 'test' opcode bugfixed
; release 1.03         21-04-00  bugfix: some prefixes before 0F were cleared
;                                bugfix: error in MODRM analysis
;                                CD 20 now is 6 bytes length
; release 1.04          1-05-00  AAM & AAD bugfixed (was 1-byte len)
; release 1.05         xx-xx-xx  special edition, flags changed
; release 1.06          3-01-01  partially rewritten, __cdecl


C_ERROR		equ	-1              ; never change it

C_MEM1		equ	0x0001       ; |
C_MEM2		equ	0x0002       ; |may be used simultaneously
C_MEM4		equ	0x0004       ; |
C_DATA1		equ	0x0100       ; |
C_DATA2		equ	0x0200       ; |may be used simultaneously
C_DATA4		equ	0x0400       ; |
C_67		equ	0x0010       ; used with C_PREFIX
C_MEM67		equ	0x0020       ; C_67 ? C_MEM2 : C_MEM4
C_66		equ	0x1000       ; used with C_PREFIX
C_DATA66	equ	0x2000       ; C_66 ? C_DATA2 : C_DATA4
C_PREFIX	equ	0x0008       ; prefix. take opcode again
C_MODRM		equ	0x4000       ; MODxxxR/M
C_DATAW0	equ	0x8000       ; opc&1 ? C_DATA66 : C_DATA1


; void __cdecl disasm_init(void* tableptr);


disasm_init:
_disasm_init:
DISASM_INIT:
                        pusha
                        mov     edi, [esp+32+4]
                        cld

                        ; Huffman-compressed 2048-byte table
                        xor     eax, eax
                        push    eax
                        push    eax
                        push    eax
                        push    dword 0x002AAA800
                        push    dword 0x03FFF687F
                        push    dword 0x0FFE6DEA0
                        push    dword 0x0DBD5FFFF
                        push    dword 0x0FFFEAAAA
                        push    dword 0x0AAAAAAAA
                        push    dword 0x0AAAA0000
                        push    eax
                        push    eax
                        push    eax
                        push    eax
                        push    eax
                        push    eax
                        push    dword 0x000000154
                        push    dword 0x041FFF555
                        push    dword 0x055DEDDAA
                        push    dword 0x019955111
                        push    dword 0x011111FFF
                        push    dword 0x0FA11FFAA
                        push    dword 0x08E60CF96
                        push    dword 0x0FC72D6AA
                        push    dword 0x0AAAAAA88
                        push    dword 0x0888888D5
                        push    dword 0x0528D559B
                        push    dword 0x0366CD553
                        push    dword 0x0355555FF
                        push    dword 0x0FFFED6F9
                        push    dword 0x068888888
                        push    dword 0x088888888
                        push    dword 0x08D5347CA
                        push    dword 0x0DCC67BDF
                        push    dword 0x0AAAAAAAA
                        push    dword 0x0AAAAAAAA
                        push    dword 0x0ABA94FFD
                        push    dword 0x0D4A7FEEA
                        push    dword 0x053FF7529
                        push    dword 0x0FFA4A7FE
                        push    dword 0x0929FFA4A
                        push    dword 0x07FE929FF

                        mov     ecx, 512
                        xor     ebx, ebx
cycle:                xor     eax, eax
                        call    tree
                        stosd
                        loop    cycle

                        popa
                        retn

getbit:               or      ebx, ebx
                        jnz     skip
                        pop     ebp
                        pop     esi
                        pop     edx
                        push    esi
                        push    ebp
                        mov     bl, 32
skip:                 dec     ebx
                        shr     edx, 1
                        retn

                        ; Huffman-tree, compiled into decompressor code
tree:                 call    getbit
                        jnc     tree0
tree1:                call    getbit
                        jnc     tree10
tree11:               mov     ah, (C_MODRM >> 8)
                        retn
tree10:               call    getbit
                        jc      tree101
tree100:              call    getbit
                        jnc     tree1000
tree1001:             call    getbit
                        jnc     tree10010
tree10011:            call    getbit
                        jc      tree100111
tree100110:           call    getbit
                        jnc     tree1001100
tree1001101:          mov     al, C_MEM67
                        retn
tree1001100:          call    getbit
                        jnc     tree10011000
tree10011001:         mov     ax, C_DATA66+C_MEM2
                        retn
tree10011000:         call    getbit
                        jnc     tree100110000
tree100110001:        mov     ax, C_PREFIX+C_66
                        retn
tree100110000:        mov     ah, ((C_DATA2+C_DATA1) >> 8)
                        retn
tree100111:           call    getbit
                        jnc     tree1001110
tree1001111:          mov     ah, ((C_MODRM+C_DATA66) >> 8)
                        retn
tree1001110:          call    getbit
                        jnc     tree10011100
tree10011101:         mov     al, C_PREFIX+C_67
                        retn
tree10011100:         mov     ah, (C_DATA2 >> 8)
                        retn
tree10010:            mov     ah, (C_DATAW0 >> 8)
                        retn
tree1000:             mov     ah, (C_DATA1 >> 8)
                        retn
tree101:              call    getbit
                        jnc     tree1010
tree1011:             call    getbit
                        jnc     tree10110
tree10111:            mov     al, C_PREFIX
                        retn
tree10110:            mov     ah, ((C_MODRM+C_DATA1) >> 8)
                        retn
tree1010:             mov     ah, (C_DATA66 >> 8)
                        retn
tree0:                call    getbit
;                       jc      tree01
                        adc     al, 0
tree00:               dec     eax
tree01:               retn


; int __cdecl disasm_main(void* opcodeptr, void* tableptr)
; {

; returns opcode length in EAX or -1 if error

disasm_main:
DISASM_MAIN:            pusha

                        mov     esi, [esp+32+4]    ; tableptr
                        mov     ecx, [esp+32+8]    ; param = opcode ptr

                        xor     edx, edx        ; flags
                        xor     eax, eax

prefix:               and     dl, ~C_PREFIX

                        mov     al, [ecx]
                        inc     ecx

                        or      edx, [esi+eax*4]

                        test    dl, C_PREFIX
                        jnz     prefix

                        cmp     al, 0xf6
                        je      btest
                        cmp     al, 0xf7
                        je      btest

                        cmp     al, 0xcd
                        je      bint

                        cmp     al, 0x0f
                        je      b0F
cont:
                        test    dh, (C_DATAW0 >> 8)
                        jnz     dataw0
dataw0done:
                        test    dh, (C_MODRM >> 8)
                        jnz     near modrm
exitmodrm:
                        test    dl, C_MEM67
                        jnz     mem67
mem67done:
                        test    dh, (C_DATA66 >> 8)
                        jnz     data66
data66done:
                        mov     eax, ecx
                        sub     eax, [esp+32+8]

                        and     edx, C_MEM1+C_MEM2+C_MEM4 + C_DATA1+C_DATA2+C_DATA4
                        add     al, dl
                        add     al, dh

exit:                 mov     [esp+7*4], eax

                        popa
                        retn

btest:                 or      dh, (C_MODRM >> 8)
                        test    byte [ecx], 00111000b  ; F6/F7 -- test
                        jnz     cont
                        or      dh, (C_DATAW0 >> 8)
                        jmp     cont

bint:                  or      dh, (C_DATA1 >> 8)
                        cmp     byte [ecx], 0x20
                        jne     cont
                        or      dh, (C_DATA4 >> 8)
                        jmp     cont

b0F:                   mov     al, [ecx]
                        inc     ecx
                        or      edx, [esi+eax*4+1024]      ; 2nd half

                        cmp     edx, -1
                        jne     cont

error:                mov     eax, edx
                        jmp     exit

dataw0:               xor     dh, (C_DATA66 >> 8)
                        test    al, 00000001b
                        jnz     dataw0done
                        xor     dh, ((C_DATA66+C_DATA1) >> 8)
                        jmp     dataw0done

mem67:                xor     dl, C_MEM2
                        test    dl, C_67
                        jnz     mem67done
                        xor     dl, C_MEM4+C_MEM2
                        jmp     mem67done

data66:               xor     dh, (C_DATA2 >> 8)
                        test    dh, (C_66 >> 8)
                        jnz     data66done
                        xor     dh, ((C_DATA4+C_DATA2) >> 8)
                        jmp     data66done

modrm:                mov     al, [ecx]
                        inc     ecx

                        mov     ah, al  ; ah=mod, al=rm

                        and     ax, 0xc007
                        cmp     ah, 0xc0
                        je      near exitmodrm

                        test    dl, C_67
                        jnz     modrm16

modrm32:              cmp     al, 0x04
                        jne     a

                        mov     al, [ecx]       ; sib
                        inc     ecx
                        and     al, 0x07

a:                    cmp     ah, 0x40
                        je      mem1
                        cmp     ah, 0x80
                        je      mem4

                        cmp     ax, 0x0005
                        jne     near exitmodrm

mem4:                 or      dl, C_MEM4
                        jmp     exitmodrm

mem1:                 or      dl, C_MEM1
                        jmp     exitmodrm

modrm16:              cmp     ax, 0x0006
                        je      mem2
                        cmp     ah, 0x40
                        je      mem1
                        cmp     ah, 0x80
                        jne     near exitmodrm

mem2:                 or      dl, C_MEM2
                        jmp     exitmodrm

                        endp