65 lines
731 B
NASM
65 lines
731 B
NASM
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extern libz_strlen
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global libz_hextoi
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section .text
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libz_hextoi:
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; mov r11, rdi ;saveing it for later
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push rdi
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call libz_strlen
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mov r9, rax
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pop rdi
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xor r10, r10
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mov rcx, 1
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add r9, rdi
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dec r9
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_loop:
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xor rax, rax
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mov al, [r9]
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cmp rax, 48
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jb _nan
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cmp rax, 70 ;if its not a number then return 0 then exit
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ja _nan ;this actually as a bug if you put a : it will be allowed
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; push rax
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cmp rax, 58 ;if(char < 58){sub char, 48}else{sub char, 55}
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jb _charbelow
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sub rax, 55
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jmp _hexitif
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_charbelow:
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sub rax, 48
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_hexitif:
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mul rcx
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add r10, rax
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; pop rax
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cmp r9, rdi
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je _end
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dec r9
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; push rax
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mov rax, 16
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mul rcx
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mov rcx, rax
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; pop rax
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jmp _loop
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_nan:
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xor r10, r10
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_end:
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mov rax, r10
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ret
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