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74 lines
1.6 KiB
74 lines
1.6 KiB
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; Puts the stringified version of eax on the stack
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; IN: eax = number to write
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; IN: edi = base of where to write string
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; OUT: ecx = number of characters written to buffer
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IntToString: ; (eax = number, edi = buffer base) -> ecx = number of characters
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push eax
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push edi
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;push ecx
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push edx
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push esi
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push ebp
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mov ecx, edi ; store negative original buffer base
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neg ecx ; (used for counting amount of characters)
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test eax, eax
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jns .not_negative
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mov BYTE [edi], '-'
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neg eax
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add edi, 1
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.not_negative:
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mov esi, edi ; store pointer after potential negative sign character
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mov ebp, 0xcccccccd ; ebp = 32 bit multiplicative reciprocal of 10
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.divide_loop:
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mov ebx, eax ; save number in ebx
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mul ebp
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shr edx, 3 ; edx = quotient
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lea eax, [edx + edx*4] ; eax = quotient * 10 = (number - remainder)
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add eax, eax ; |
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sub ebx, eax ; ebx = number - (number - remainder) = remainder
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add ebx, '0' ; remainder is our digit, turn it ASCII
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mov BYTE [edi], bl ; store ASCII digit to buffer
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lea edi, [edi+1]
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mov eax, edx ; We need quotient in eax for 'mul'
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test eax, eax
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jne .divide_loop
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add ecx, edi ; Update amount of characters
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mov byte [edi], 0 ; Null terminator
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lea edi, [edi-1] ; We incremented the buffer pointer once too much
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.swap_loop:
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cmp esi, edi
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jae .done_swapping
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movzx eax, BYTE [edi]
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movzx edx, BYTE [esi]
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mov BYTE [edi], dl
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mov BYTE [esi], al
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sub edi, 1
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add esi, 1
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jmp .swap_loop
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.done_swapping:
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pop ebp
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pop esi
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pop edx
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;pop ecx
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pop edi
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pop eax
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ret
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