string and asm

[Emil_halim]

Hi all,

i have a function that return a string variable type and i call it by call asm instruction , then i want to save the returned string in file so i used putfile. but it did not wrok as expected , any help please.

Code: [Select]


function name() as string
     string s = "i am string variable"
     return s
end function


sub Main

     call  name
     mov eax,[eax]
     putfile "t.txt",eax

 

[Peter]

Hi Emil,

Code: [Select]

function name() as string
     string s = "i am string variable"
     return s
end function


sub Main

     call  name
     mov eax,[eax]
     putfile "t.txt",eax
     
End Sub     

Main


[Emil_halim]

thanks Peter ,

but open the t.txt file it contains not the "i am string variable" string and that is wrong.

[Peter]

I wonder me, how can the eax register store  a string ?
you just store the address of the string !

[Emil_halim]

Peter this line should get the address of string.

Code: [Select]

    call  name
    mov eax,[eax]  ' this line should get the address of string


[Emil_halim]

Charles , does string variable has a string descriptor , and if  so how is it work ?   

[Peter]

Hi Emil,

Code: [Select]

indexbase 0

function name() as string
     string s = "i am string variable"
     return s
end function


sub Main
     char s[22], dword x
     name
     lea esi,s
     mov edx,x 
     .m1 mov cl,[eax+edx]
mov [esi+edx],cl
         inc edx
         cmp edx,20
         jnz m1     
putfile "t.txt",s
End Sub     

Main


[Emil_halim]

Ok thanks Peter ,

but why you copy the returned string in char array then pass this copy to Putfile?

BTW name is a dummy function here , in real code you did not know the length of returned string?

[Peter]

Hi Emil

Code: [Select]

indexbase 0
sys length

function name() as string
     string s = "i am string variable"
     length = Len(s)
     return s
end function


sub Main
     char s[22], dword x
     name
     lea esi,s
     xor edx,edx 
     .m1 mov cl,[eax+edx]
mov [esi+edx],cl
         inc edx
         cmp edx,length
         jnz m1     
putfile "t.txt",s
End Sub     

Main


[Charles Pegge]

A string function returns a bstring, which points to an array of characters.

With low level handling you must free the string after.

function name() as string
     string s = "i am string variable"
     return s
end function

'low level handling
sys a
call  name
mov a,eax
putfile "t.txt", cast bstring a
freememory a


But basic will do it all for you

putfile "t.txt",name

[Peter]

Why do I love Assembler and not Basic.

[Charles Pegge]

I felt the same about Basic too, which is why I started this project. Would you like to create your own language Peter?

[Emil_halim]

Hi Charles ,

thanks for demonstration ,

'low level handling
sys a
call  name
mov a,eax
putfile "t.txt", cast bstring a
freememory a

using a variable for moving the address of string into it then casting it so that it works with putfile ,
is not good.
can Oxygen allow casting directly from register , something like this ?

Code: [Select]

call  name
putfile "t.txt", cast bstring  Eax


[Emil_halim]

hi Peter

Why do I love Assembler and not Basic.

the best thing in Oxygen basic is that you have a variety of ways to achieve a certain things.

for example see the example of iteration. the for statement can be in pure basic and can be in mix between
basic & C and can be in pure C.

this make Oxygen a very good tool for programming.

I do like to mix my coding in basic , C , asm to get the best thing that i need , so the point here is not to love asm and not basic.       

[Charles Pegge]

Yes, I agree about the variable. I forgot all about the stack

function name() as string
     string s = "i am string variable"
     return s
end function

'low level handling
name
push eax
putfile "t.txt",cast bstring eax
pop eax
freememory eax