126 lines
1.6 KiB
NASM
126 lines
1.6 KiB
NASM
; IN DS:SI remaining unparsed string
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; CS:DI error message
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parse_error:
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push si
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mov si, .str1
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call putcs
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mov si, di
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call putcs
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mov si, .str2
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call putcs
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pop si
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call putds
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jmp crlf
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.str1: db "Not a ", 0
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.str2: db ": ", 0
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; Advance over whitespace
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; IN DS:SI
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eat_whitespace:
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; peek on next char
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mov al, [si]
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; ES := CS
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push es
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push cs
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pop es
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; string search
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mov di, .chars
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mov cx, 4
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scasb
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; restore bss segment
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pop es
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jne .ret
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inc si
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jmp eat_whitespace
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.chars: db 0x09, 0x0A, 0x0D, 0x20
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.ret: ret
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; Parse a register name
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; IN DS:SI string to read
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; OUT CF set if no match
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; BX register number * 2 if CF clear
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eat_register:
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push si
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push es
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lodsw
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and ax, 0xDFDF
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; ES := CS
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push cs
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pop es
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mov di, rnames
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mov cx, 14
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repne scasw
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pop es
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jne .fail
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pop bx
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mov bx, di
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sub bx, (rnames+2)
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clc
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ret
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.fail: pop si
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stc
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ret
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.emsg: db "register name", 0
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; Parse hex digit
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; IN DS:SI
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; OUT AL
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eat_hex_digit:
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push si
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lodsb
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sub al, '0'
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jc .err
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cmp al, 9
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jna .ret
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sub al, 7
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cmp al, 0xF
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ja .err
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.ret: add sp, 2
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ret
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.err: pop si
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stc
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ret
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.emsg: db "hex digit", 0
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; Parse hexadecimal byte
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; IN DS:SI
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; OUT DL or carry set
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eat_hex_byte:
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push si
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mov cl, 4
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xor dl, dl
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call eat_hex_digit
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jc .err
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or dl, al
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shl dl, cl
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call eat_hex_digit
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jc .err
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or dl, al
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add sp, 2
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ret
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.err: pop si
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stc
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ret
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.emsg: db "hex byte", 0
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; Parse hexadecimal word
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; OUT DX or carry set
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eat_hex_word:
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push si
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xor dx, dx
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call eat_hex_byte
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jc .err
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mov dh, dl
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call eat_hex_byte
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jc .err
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add sp, 2
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ret
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.err: pop si
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stc
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ret
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.emsg: db "hex word", 0
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