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  1. global _start
  2.  
  3. section .data
  4.     ten 	dq	10.0
  5.     one 	dq	1.0
  6.     zero 	dq	0.0
  7.     negate	dq  8000000000000000h
  8.     result 	dd	0.0
  9.     hex 	db	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
  10.     length 	dd	0
  11.     buffer 	db	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
  12.  
  13. section .text
  14.  
  15. _start:
  16.     ;;
  17.     ;; read the fp number from stdin
  18.     ;;
  19.     mov		ecx, buffer
  20.     mov		edx, 32
  21.     call	read
  22.     mov		dword [length], eax
  23.     movq	xmm0, qword [zero]
  24.     movq	xmm1, qword [zero]
  25.     movq	xmm2, qword [ten]
  26.     movq	xmm4, qword [ten]
  27.     ;;
  28.     ;; loop through 1 character at a time
  29.     ;;
  30.     mov		ebx, dword [length]
  31.     test	ebx, ebx
  32.     jz		quit		;; there's no input
  33.     mov		ecx, 0		;; offset counter
  34.     mov		edx, 0 		;; 0 for before decimal, 1 for after decimal
  35.     mov 	edi, 0 		;; 0 for positive, 1 for negative
  36.     mov		esi, buffer
  37.     cmp		byte [esi], '-'
  38.     jne		process
  39.     mov		edi, 1		;; the number is negative
  40.     inc		ecx
  41. process:
  42.     movzx	eax, byte [esi + ecx]
  43.     cmp		al, '.'		;; does al contain a decimal point '.'
  44.     jne		next_check
  45.     test	edx, edx	;; more than 1 decimal error
  46.     jnz		quit
  47.     mov		edx, 1
  48.     jmp		continue_process
  49. next_check:
  50.     sub		eax, '0'	;; ascii digit to binary
  51.     js		end_process ;; not a digit since eax is negative
  52.     cmp		eax, 10
  53.     jge		end_process ;; not a digit since eax is >= 10
  54.     test	edx, edx	;; before or after decimal
  55.     jnz		mantissa_process
  56.     mulsd	xmm0, xmm2	;; result characteristic * 10
  57.    cvtsi2sd	xmm3, eax
  58.     addsd	xmm0, xmm3 	;; result characteristic + next digit
  59.     jmp		continue_process
  60. mantissa_process:
  61.     cvtsi2sd	xmm3, eax
  62.     divsd	xmm3, xmm2	;; next digit / current mantissa power of 10
  63.     addsd	xmm1, xmm3	;; result mantissa + next fraction
  64.     mulsd	xmm2, xmm4	;; mantissa power * 10
  65. continue_process:
  66.     inc		ecx
  67.     cmp		ecx, ebx
  68.     jl		process
  69. end_process:
  70.     addsd	xmm0, xmm1	;; characteristic + mantissa
  71.     test	edi, edi	;; is the number supposed to be negative ?
  72.     jz		store_result
  73.     movq	xmm3, qword [negate]
  74.     por		xmm0, xmm3	;; toggle the sign bit
  75.  store_result:
  76.    cvtsd2ss	xmm0, xmm0	;; double (64bit) to single (32) fp
  77.     movd	eax, xmm0
  78.     mov		dword[result], eax
  79.     ;;
  80.     ;; convert result to hex
  81.     ;;
  82. to_hex:
  83.     mov	edi, buffer
  84.     mov	esi, hex
  85.     mov	ebx, 0
  86.     mov	eax, dword [result]
  87.     mov	bl, al
  88.     and	bl, 0fh
  89.     mov	bl, byte [esi + ebx]
  90.     mov	byte [edi + 7], bl
  91.     shr	eax, 4
  92.     mov	bl, al
  93.     and	bl, 0fh
  94.     mov	bl, byte [esi + ebx]
  95.     mov	byte [edi + 6], bl
  96.     shr	eax, 4
  97.     mov	bl, al
  98.     and	bl, 0fh
  99.     mov	bl, byte [esi + ebx]
  100.     mov	byte [edi + 5], bl
  101.     shr	eax, 4
  102.     mov	bl, al
  103.     and	bl, 0fh
  104.     mov	bl, byte [esi + ebx]
  105.     mov	byte [edi + 4], bl
  106.     shr	eax, 4
  107.     mov	bl, al
  108.     and	bl, 0fh
  109.     mov	bl, byte [esi + ebx]
  110.     mov	byte [edi + 3], bl
  111.     shr	eax, 4
  112.     mov	bl, al
  113.     and	bl, 0fh
  114.     mov	bl, byte [esi + ebx]
  115.     mov	byte [edi + 2], bl
  116.     shr	eax, 4
  117.     mov	bl, al
  118.     and	bl, 0fh
  119.     mov	bl, byte [esi + ebx]
  120.     mov	byte [edi + 1], bl
  121.     shr	eax, 4
  122.     mov	bl, al
  123.     and	bl, 0fh
  124.     mov	bl, byte [esi + ebx]
  125.     mov	byte [edi + 0], bl
  126.     ;;
  127.     ;; print result
  128.     ;;
  129. print_dword:
  130.     mov		ecx, buffer
  131.     mov		edx, 8
  132.     call	write
  133.     ;;
  134.     ;; quit
  135.     ;;
  136. quit:
  137.     call	exit
  138.  
  139. exit:
  140.     mov		eax, 01h	; exit()
  141.     xor		ebx, ebx	; errno
  142.     int		80h
  143. read:
  144.     mov		eax, 03h	; read()
  145.     mov		ebx, 00h	; stdin
  146.     int		80h
  147.     ret
  148. write:
  149.     mov		eax, 04h	; write()
  150.     mov		ebx, 01h	; stdout
  151.     int		80h
  152.     ret
Success #stdin #stdout 0s 144KB
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stdin
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-1.5
stdout
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bfc00000
https://ideone.com/Q3naVN
language:
Assembler 32bit (nasm 2.14)
created:
10 years ago
visibility:
public

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