ASM 32bit -> 64bit

[grabiller]

Hello,

This is my first message on this forum, so hi to everyone

I'm no ASM coder but I use a little trick from a message posted on this forum to retrieve the String pointer of a string:

Code: Select all

Macro StrToPtr( var, ptr )
EnableASM
  LEA eax, var
  MOV ptr, eax
DisableASM
EndMacro

mystr.s      = ""
*pstr.String = 0
StrToPtr( mystr, *pstr )

*pstr\s + "Hello"

Debug mystr ; "Hello"

However, this only works for 32bit compilation.

Could someone here be kind enough to show me / explain to me the required 64bit version ?

Thanks a lot in advance.
Guy.

[Fred]

You can try to replace 'eax' with 'rax', it should do the trick. 'rax' is the 64 bit equivalent of 'eax'

[grabiller]

You can try to replace 'eax' with 'rax', it should do the trick. 'rax' is the 64 bit equivalent of 'eax'

Yes it works.

Thanks a lot Fred !

Cheers,
Guy.

[SPP]

Hi Guy,

Sorry for my curiosity (and for my english) but i think that you can do the same without ASM:

mystr.s = ""
*stradd = @mystr
*pstr.String = @*stradd
*pstr\s = "hello"
Debug mystr

although may be i'm in error and you don't need it

Best regards

[grabiller]

Hello SPP,

Your exemple works 'as is' but in the context of my application, this make it crash.

I'm passing the *ptr variable as an argument to a procedure wich is modifying the string.

This is the procedure in question :

Code: Select all

Procedure.size_t vnp_raw_unpack_string( *buffer, *pstr.String, max_size.size_t )
  If *buffer = 0 Or *pstr = 0 : ProcedureReturn 0 : EndIf
  Protected str_tmp.s = PeekS( *buffer, max_size, #PB_UTF8 )
  *pstr\s + str_tmp
  ProcedureReturn StringByteLength( str_tmp, #PB_UTF8 ) + 1
EndProcedure

mystr.s = "" : *pstr.String = 0 : StrToPtr( mystr, *pstr) ; ( ASM Macro )

vnp_raw_unpack_string( *buffer, *pstr, 1000 )

; ( *buffer beeing memory allocated with some UTF-8 string. )

I'm not sure why your way is crashing the application, actualy, but with the ASM macro it works perfectly well.

Cheers,
Guy.

[luis]

Uhmmm... I would try this way (32/64 bit)

Code: Select all

Macro StrToPtr(var, ptr)
 ptr = @var
 ptr = @ptr  - SizeOf(Integer)
EndMacro


mystr.s      = ""
*pstr.String = 0

StrToPtr(mystr, *pstr)
*pstr\s + "Hello"

Debug *pstr 
Debug mystr

You need to come back with the pointer inside the structure to point to the structure's base address.

At least that's sound reasonable to me

Does it work in your code ?

[luis]

It seem to work

Code: Select all

Macro StrToPtr(var, ptr)
ptr = @var
ptr = @ptr  - SizeOf(Integer)
EndMacro

Procedure.i vnp_raw_unpack_string(*buffer, *pstr.String, max_size.i )
  If *buffer = 0 Or *pstr = 0 : ProcedureReturn 0 : EndIf
  Protected str_tmp.s = PeekS(*buffer, max_size, #PB_UTF8 )
  *pstr\s + str_tmp
  ProcedureReturn StringByteLength( str_tmp, #PB_UTF8 ) + 1
EndProcedure


buffer$ = "tanto va la gatta al lardo che ci lascia lo zampino"

mystr.s = "" : *pstr.String = 0 : StrToPtr( mystr, *pstr) ; ( ex ASM Macro )

vnp_raw_unpack_string(@buffer$, *pstr, 1000)

Debug mystr

[ts-soft]

@luis
your code is incorrect, you write in none allocate memory!

Enable purifier to see the error.

greetings - Thomas

[luis]

Yup, you are right, the offset was 4 bytes off compared to the asm macro

I don't know why at this point, but changing the macro this way seem to work (at least purifier seems happy)

Code: Select all

Macro StrToPtr(var, ptr)
 ptr = @var
 ptr = @ptr - (4 + SizeOf(Integer))
EndMacro

Code: Select all

Macro StrToPtr(var, ptr)
 ptr = @var
 ptr = @ptr - (4 + SizeOf(Integer))
EndMacro


Procedure.i vnp_raw_unpack_string(*buffer, *pstr.String, max_size.i )
  If *buffer = 0 Or *pstr = 0 : ProcedureReturn 0 : EndIf
  Protected str_tmp.s = PeekS(*buffer, max_size, #PB_UTF8 )
  *pstr\s + str_tmp
  ProcedureReturn StringByteLength( str_tmp, #PB_UTF8 ) + 1
EndProcedure


buffer$ = "tanto va la gatta al lardo che ci lascia lo zampino"

mystr.s = "" : *pstr.String = 0 : StrToPtr( mystr, *pstr) ; ( ex ASM Macro )

vnp_raw_unpack_string(@buffer$, *pstr, 1000)

Debug mystr

[ts-soft]

This example works only with purifier enabled? Without purifier i become a empty string

[luis]

This example works only with purifier enabled? Without purifier i become a empty string

LOL, so that's the reason why I wrote above "I don't know why". After all I believied to have checked the returned pointers were the same... The purifier seem to alter something, and after all considering these are pb internals it can have all the rights to do so.


So, this code (the original one) seems correct after all:

Code: Select all

 
Macro PB_StrToPtr(var, ptr)
 ptr = @var
 ptr = @ptr - SizeOf(Integer)
EndMacro


CompilerIf (#PB_Compiler_Processor = #PB_Processor_x86)
Macro ASM_StrToPtr( var, ptr )
EnableASM
  LEA eax, var
  MOV ptr, eax
DisableASM
EndMacro
 CompilerElse   
Macro ASM_StrToPtr( var, ptr )
EnableASM
  LEA rax, var
  MOV ptr, rax
DisableASM
EndMacro 
CompilerEndIf


mystr.s      = "ASM_"
*pstr.String = 0
ASM_StrToPtr( mystr, *pstr )

Debug *pstr
*pstr\s + "Hello"
Debug mystr ; "Hello"


mystr.s      = "PB_"
*pstr.String = 0
PB_StrToPtr( mystr, *pstr )

Debug *pstr
*pstr\s + "Hello"
Debug mystr ; "Hello"

It works ok and results in the same pointer returned from the assembly macro, but using PB code instead of asm seem to make it "tamper-able" by the purifier.

In the end, considering the purifier it's a nice thing to have, it's better to stick to the asm version.

Interesting nevertheless.

Hey, I could be wrong but it seem that way!