I'm working on FP IEEE-754 to StrDec on MASM Assembly. It works fine, and despite the fact I spent some time figuring out this, I'm not sure how to add more numbers after comma - now there are two, like 123.46, but I need 123.456789. I guess I do need a counter to process my extra-bit, but I get access violation while adding extra numbers after comma and increasing bytes number.
.data
CaptionOut BYTE "Result: ", 0
temp_bcd dt ?
szdecimal db 32 dup(0)
MyNum REAL10 123.456789
.code
main PROC
; FPU to DecStr
fld MyNum
pushd 100 ;use the stack as storage for this value
fimul dword ptr[esp] ;converts 2 decimal places as 2 more integer digits
fbstp temp_bcd ;store the packed BCD integer value
pop eax ;clean the stack of the pushed 100
; ESI will be used for pointing to the packed BCD
; EDI will be used for pointing to the decimal string
push esi
push edi
lea esi,temp_bcd+9 ;point to the most significant byte
lea edi,szdecimal ;point to the start of the decimal string buffer
xor eax,eax
fwait ;to ascertain that the transfer of the
;packed BCD is completed
mov al,[esi] ;get the byte with the sign code
dec esi ;decrement to next most significant byte
or al,al ;for checking the sign bit
jns @F ;jump if no sign bit
mov al,"-" ;the value is negative
stosb ;insert the negative sign
@@:
; The next 8 bytes (in this example) will contain the integer digits
; and the least significant byte will then contain the 2 decimal digits.
; No leading 0 will be included in the integer portion
; unless it would be the only integer digit.
mov ecx,8 ;number of bytes to process for integer digits
@@:
mov al,[esi] ;get the next byte
dec esi ;adjust the pointer to the next one
or al,al ;for checking if it is 0
jnz @F ;the starting integer digit is now in AL
dec ecx ;adjust the counter of integer bytes
jnz @B ;continue searching for the first integer digit
; If the loop terminates with ECX=0, the integer portion would be 0.
; A "0" character must be inserted before processing the decimal digits
mov al,"0" ;the ASCII 0
stosb ;insert it
mov al,[esi] ;get the byte containing the decimal digits
jmp decimal_digits
@@:
; The first integer byte must be checked to determine
; if it contains 1 or 2 integer digits
test al,0f0h ;test if the H.O. nibble contains a digit
jz int_digit2 ;if not, process only the L.O. nibble
int_digit1:
ror ax,4 ;puts the H.O. nibble in the L.O. nibble position
;and saves the L.O. nibble in AH
add al,30h ;convert it to ASCII character
stosb ;store this character
shr ax,12 ;restores the L.O. nibble in AL
;and also resets the other bits of AX
int_digit2:
add al,30h ;convert it to ASCII character
stosb ;store this character
mov al,[esi] ;get next byte
dec esi ;adjust the pointer to the next one
dec ecx ;adjust the counter of integer bytes
jnz int_digit1 ;continue processing the integer bytes
decimal_digits:
mov byte ptr [edi],"." ;insert the preferred decimal delimiter
inc edi
; Also, if the number of required decimal digits is not even, the code
; would have to be altered to insert the decimal delimiter at the
; proper location.
ror ax,4 ;puts the H.O. nibble in the L.O. nibble position
;and saves the L.O. nibble in AH
add al,30h ;convert it to ASCII character
stosb ;store this character
shr ax,12 ;restores the L.O. nibble in AL
;and also resets the other bits of AX
add al,30h ;convert it to ASCII character
stosw ;store this character + the terminating 0
INVOKE MessageBoxA, 0, ADDR szdecimal, ADDR CaptionOut, 0
INVOKE ExitProcess,0
main ENDP
END main
Thanks for any help or ideas!
You don't need to introduce a new counter. You're parsing temp_bcd from bottom to top by decrementing ESI. If ESI is at an address before temp_bcd begins, the parsing has ended. A little problem is that you decrement ESI after loading AL. So the last (correct) AL implies an (incorrect) ESI beyound the boarder. So ESI must be 2 bytes too small to break the loop.
For six numbers after comma you have to multiply MyNum by 1.000.000 and to change ECX to 6 (currently 8).
INCLUDE masm32rt.inc
.data
CaptionOut BYTE "Result: ", 0
temp_bcd dt ?
szdecimal db 32 dup(0)
MyNum REAL10 123.456789
.code
main PROC
; FPU to DecStr
fld MyNum
; pushd 100 ;use the stack as storage for this value
pushd 1000000 ;use the stack as storage for this value
fimul dword ptr[esp] ;converts 2 decimal places as 2 more integer digits
fbstp temp_bcd ;store the packed BCD integer value
pop eax ;clean the stack of the pushed 100
; ESI will be used for pointing to the packed BCD
; EDI will be used for pointing to the decimal string
push esi
push edi
lea esi,temp_bcd+9 ;point to the most significant byte
lea edi,szdecimal ;point to the start of the decimal string buffer
xor eax,eax
fwait ;to ascertain that the transfer of the
;packed BCD is completed
mov al,[esi] ;get the byte with the sign code
dec esi ;decrement to next most significant byte
or al,al ;for checking the sign bit
jns @F ;jump if no sign bit
mov al,"-" ;the value is negative
stosb ;insert the negative sign
@@:
; The next 8 bytes (in this example) will contain the integer digits
; and the least significant byte will then contain the 2 decimal digits.
; No leading 0 will be included in the integer portion
; unless it would be the only integer digit.
; mov ecx,8 ;number of bytes to process for integer digits
mov ecx,6 ;number of bytes to process for integer digits
@@:
mov al,[esi] ;get the next byte
dec esi ;adjust the pointer to the next one
or al,al ;for checking if it is 0
jnz @F ;the starting integer digit is now in AL
dec ecx ;adjust the counter of integer bytes
jnz @B ;continue searching for the first integer digit
; If the loop terminates with ECX=0, the integer portion would be 0.
; A "0" character must be inserted before processing the decimal digits
mov al,"0" ;the ASCII 0
stosb ;insert it
mov al,[esi] ;get the byte containing the decimal digits
jmp decimal_digits
@@:
; The first integer byte must be checked to determine
; if it contains 1 or 2 integer digits
test al,0f0h ;test if the H.O. nibble contains a digit
jz int_digit2 ;if not, process only the L.O. nibble
int_digit1:
ror ax,4 ;puts the H.O. nibble in the L.O. nibble position
;and saves the L.O. nibble in AH
add al,30h ;convert it to ASCII character
stosb ;store this character
shr ax,12 ;restores the L.O. nibble in AL
;and also resets the other bits of AX
int_digit2:
add al,30h ;convert it to ASCII character
stosb ;store this character
mov al,[esi] ;get next byte
dec esi ;adjust the pointer to the next one
dec ecx ;adjust the counter of integer bytes
jnz int_digit1 ;continue processing the integer bytes
decimal_digits:
mov byte ptr [edi],"." ;insert the preferred decimal delimiter
inc edi
; Also, if the number of required decimal digits is not even, the code
; would have to be altered to insert the decimal delimiter at the
; proper location.
; ror ax,4 ;puts the H.O. nibble in the L.O. nibble position
;and saves the L.O. nibble in AH
; add al,30h ;convert it to ASCII character
; stosb ;store this character
; shr ax,12 ;restores the L.O. nibble in AL
;and also resets the other bits of AX
; add al,30h ;convert it to ASCII character
; stosw ;store this character + the terminating 0
@@:
ror ax,4 ;puts the H.O. nibble in the L.O. nibble position
;and saves the L.O. nibble in AH
add al,30h ;convert it to ASCII character
stosb ;store this character
shr ax,12 ;restores the L.O. nibble in AL
;and also resets the other bits of AX
add al,30h ;convert it to ASCII character
stosb ;store this character + the terminating 0
mov al,[esi] ;get next byte
dec esi ;adjust the pointer to the next one
cmp esi, OFFSET temp_bcd - 1
jae @B
@@:
mov BYTE PTR [edi], 0
INVOKE MessageBoxA, 0, ADDR szdecimal, ADDR CaptionOut, 0
INVOKE ExitProcess,0
main ENDP
END main
And - of course - I would do it quite different: https://stackoverflow.com/a/30133492/3512216 :-)