String Generation

[Citric]

Just something i have been thinking about recently,

i know you cant do this,

Code Select Expand


mov [stringVar], "This is my String"


but you would have to move the correct ascii codes into memory, to generate the string you want.

how would you easily generate Strings on the fly.

just a thought.

[mnemonic]

I don't know what you mean by saying "generate"... but it looks like you want to copy a string.
There is some proc called "szCopy" in the masm32 library. There are also some more procs and macros that handle strings. Have a look at it.

[pbrennick]

Citric,
There is a macro that does this for you.  Take a look at macro.asm (make sure you have the latest one.  The sas macro does exactly what you are discribing, I think, take a look at it.

EDIT:  Hi mnemonic, looks like we cross-posted, sorry, but I think the sas macro is a better fit as it works at the assembly level.  Anyway, sorry.

hth:
Paul

[Mark Jones]

An easy way to generate strings on the fly is by including macros.asm and using its szText macro.

Code Select Expand


sztext HelloWorld, "Hello world!!!"
sztext Title, "Window Title"
invoke MessageBox, hWnd,addr HelloWorld, addr title, MB_OK

(untested code, from memory)

[pbrennick]

Wow, busy topic...  :clap:

Nice example Mark.

Paul

[Mark Jones]

Indeed Paul, I think we all chimed in at exactly the same time. :bg

[mnemonic]

@Paul:
No issue.
In here it´s like: the more replies the more info. It all assembles to a sharper picture. :wink

@Citric:
I recommend having a look at the "MASMLIB.HLP" file in the "help" folder (if it is up-to-date i don´t know...).

Regards, Jens

[pbrennick]

Ctric,
In that help file if you look under Psuedo Mnemonics, you will see:

sas This macro assigns a quoted string to a DWORD variable.
sas var,"This is a string"

As you can see it does a nice job of creating the code 'on the fly' necessary to assemble as you requested.  It doesn't get much press but I like it...

hth:
Paul

[Citric]

Ctric,
In that help file if you look under Psuedo Mnemonics, you will see:

sas This macro assigns a quoted string to a DWORD variable.
sas var,"This is a string"

As you can see it does a nice job of creating the code 'on the fly' necessary to assemble as you requested. It doesn't get much press but I like it...

hth:
Paul

Hi Paul

So let me get this straight it puts the address of the String in the variable assigned.

ie from above var containts the address of "This is a string".

cool that is exactly what i was looking for.

Hi All

Thanks for the replies.

[AeroASM]

This is hardly string generation on-the-fly. This is:

Code Select Expand


.data
buffer db 512 dup(0)
.code
start:
mov edi,offset buffer
mov al,"H"
stosb
mov al,"e"
stosb
mov al,"l"
stosb
mov al,"l"
stosb
mov al,"o"
stosb
mov al,0
stosb
end start


[Citric]

this is more i ment by

but you would have to move the correct ascii codes into memory, to generate the string you want.

This is hardly string generation on-the-fly. This is:

Code Select Expand


.data
buffer db 512 dup(0)
.code
start:
mov edi,offset buffer
mov al,"H"
stosb
mov al,"e"
stosb
mov al,"l"
stosb
mov al,"l"
stosb
mov al,"o"
stosb
mov al,0
stosb
end start


But that gets messy and very hard to read!

[AeroASM]

It is also slower and larger, but is the only way to make strings on-the-fly. Therefore, don't!

[Citric]

It is also slower and larger, but is the only way to make strings on-the-fly. Therefore, don't!

Thats because its run time generation and not compile time generation like the other suggestions.

[Rifleman]

Hi Citric,
As you saw, the sas macro does create 'on the fly' strings.  Aero gets funny at times but he is a helpful guy ordinarily.  His code actually is a very close expansion to how the macro works.  I don't think he even looked at it!!  :bdg

Paul

[hutch--]

Citric,

Its an OK way of embedding string data directly into code but you will be more efficient doing it on the stack 4 bytes at a time.

Code Select Expand


"masm is great"

becomes

push 00000074h    ; 74h = "t"
push "grea"
push " is "
push "masm"


use the string a ESP then rebalance the stack.