59 lines
947 B
NASM
59 lines
947 B
NASM
org 0x100
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mov ax, 0x3D00
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mov dx, infile
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int 0x21
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jc err
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mov [fd], ax
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loop: call getc
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jc end
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cmp dl, 26
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je end
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mov ah, 2
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int 0x21
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jmp loop
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end: ret
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err: mov dx, ax
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dumpdx: ; setup bx and ah for int 10h call
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xor bx, bx
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mov ah, 0x0e
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mov cl, 4
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; this double-call is essentially a 4 times repeating loop
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call dmpdx1
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dmpdx1: call dmpdx2
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dmpdx2: ; grab highest nibble from dx
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mov al, dh
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; remove highest nibble from dx
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shl dx, cl
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; shift away second-highest nibble that we accidentally copied
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shr al, cl
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; map 0-9 to ascii codes for '0' to '9'
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add al, 0x30
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; if result is larger than '9', ...
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cmp al, 0x3a
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jl dmpdx3
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; ... add 7 so we continue at 'A'
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add al, 7
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dmpdx3: int 0x10
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ret
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; read a character from the input file into DL
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getc: mov dl, 26
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push dx
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mov ah, 0x3f
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mov bx, [fd]
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mov cx, 1
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mov dx, sp
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int 0x21
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pop dx
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ret
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infile: db "com/a86.asm", 0
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fd: dw 0
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