how to call this dll in python

[Shark]

I have a windows dll1.dll with a export function:

int f1(char filename,char **buf,int *bufLen)
{
int len;
//got the length of file anyway,such as 100
len = 100;//len = getLen(filename );
*buf = (char*)calloc(1 00);
*bufLen = len;
return 0;
}

then how can I call the f1 function with python.
thanks for your response.

[Diez B. Roggisch]

Re: how to call this dll in python

Shark schrieb:

I have a windows dll1.dll with a export function:
>
int f1(char filename,char **buf,int *bufLen)
{
int len;
//got the length of file anyway,such as 100
len = 100;//len = getLen(filename );
*buf = (char*)calloc(1 00);
*bufLen = len;
return 0;
}
>
then how can I call the f1 function with python.
thanks for your response.

If the above is *really* what you want to access from python, you
shouldn't bother & write it new in python itself. You could either use

bufLen = len(open(filena me).read())

or make a os.stat-call.

If it serves only as a rather ugly illustrative example, then you should
investigate the ctypes-module of python, which is made for accessing
arbitrary dlls from python.

Diez

[Shark]

Re: how to call this dll in python

On Nov 3, 4:22 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Shark schrieb:
>

I have a windows dll1.dll with a export function:

>

int f1(char filename,char **buf,int *bufLen)
{
int len;
//got the length of file anyway,such as 100
len = 100;//len = getLen(filename );
*buf = (char*)calloc(1 00);
*bufLen = len;
return 0;
}

>

then how can I call the f1 function with python.
thanks for your response.

>
If the above is *really* what you want to access from python, you
shouldn't bother & write it new in python itself. You could either use
>
bufLen = len(open(filena me).read())
>
or make a os.stat-call.
>
If it serves only as a rather ugly illustrative example, then you should
investigate the ctypes-module of python, which is made for accessing
arbitrary dlls from python.
>
Diez

Yes,the function is rather ugly, but how can python get the memory
alloced by a dll through the dll function's parameter.
I am facing the problem in my project, I try ctypes all over, but can
not get the correct solution.

[Mark Tolonen]

Re: how to call this dll in python


"Shark" <ysystudio@gmai l.comwrote in message
news:eb620337-0a9e-4d50-ab66-cfeeaba18dc4@v3 9g2000pro.googl egroups.com...

>I have a windows dll1.dll with a export function:
>
int f1(char filename,char **buf,int *bufLen)
{
int len;
//got the length of file anyway,such as 100
len = 100;//len = getLen(filename );
*buf = (char*)calloc(1 00);
*bufLen = len;
return 0;
}
>
then how can I call the f1 function with python.
thanks for your response.

Here's a quick, tested example. It's not pretty but demonstrates what you
want:

===== begin C DLL code =======
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

__declspec(dlle xport)
int get(const char* filename,char **buf,int *bufLen)
{
int i,len;
printf("*buf before malloc=%p\n",*b uf);
len = strlen(filename );
*buf = (char*)malloc(l en);
*bufLen = len;
for(i=0;i<len-1;i++)
(*buf)[i]='a';
(*buf)[i]=0;
printf("*buf after malloc=%p\n",*b uf);
return 5;
}

__declspec(dlle xport)
void release(char* buf)
{
printf("buf[0]=%d\n",buf[0]);
printf("buf=%p\ n",buf);
free(buf);
}
===== end C DLL code =======

===== begin Python code =======
from ctypes import *
x = CDLL('x.dll')
x.get.argtypes=[c_char_p,POINTE R(POINTER(c_byt e)),POINTER(c_i nt)]
buf = POINTER(c_byte) ()
length = c_int()
print x.get("hello.tx t",byref(buf),b yref(length))
print repr(string_at( buf,length))
buf[0]=55 # change first byte
x.release.argty pes=[POINTER(c_byte)]
x.release(buf)
===== end Python code =======

sample output:

*buf before malloc=00000000
*buf after malloc=00C92940
5
'aaaaaaaa\x00'
buf[0]=55
buf=00C92940

-Mark

[Diez B. Roggisch]

Re: how to call this dll in python

Shark schrieb:

On Nov 3, 4:22 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

>Shark schrieb:
>>

>>I have a windows dll1.dll with a export function:
>>int f1(char filename,char **buf,int *bufLen)
>>{
>>int len;
>>//got the length of file anyway,such as 100
>>len = 100;//len = getLen(filename );
>>*buf = (char*)calloc(1 00);
>>*bufLen = len;
>>return 0;
>>}
>>then how can I call the f1 function with python.
>>thanks for your response.

>If the above is *really* what you want to access from python, you
>shouldn't bother & write it new in python itself. You could either use
>>
>bufLen = len(open(filena me).read())
>>
>or make a os.stat-call.
>>
>If it serves only as a rather ugly illustrative example, then you should
>investigate the ctypes-module of python, which is made for accessing
>arbitrary dlls from python.
>>
>Diez

>
Yes,the function is rather ugly, but how can python get the memory
alloced by a dll through the dll function's parameter.
I am facing the problem in my project, I try ctypes all over, but can
not get the correct solution.

But it *will* work with ctypes. However, without you disclosing your
actual attempts, how do you think we can help you? Mind-reading is on my
list to learn next, but until then you will need to provide code &
tracebacks.

Diez

[Shark]

Re: how to call this dll in python

On Nov 4, 2:16 pm, "Mark Tolonen" <M8R-yft...@mailinat or.comwrote:

"Shark" <ysystu...@gmai l.comwrote in message
>
news:eb620337-0a9e-4d50-ab66-cfeeaba18dc4@v3 9g2000pro.googl egroups.com...
>

I have a windows dll1.dll with a export function:

>

int f1(char filename,char **buf,int *bufLen)
{
int len;
//got the length of file anyway,such as 100
len = 100;//len = getLen(filename );
*buf = (char*)calloc(1 00);
*bufLen = len;
return 0;
}

>

then how can I call the f1 function with python.
thanks for your response.

>
Here's a quick, tested example.  It's not pretty but demonstrates what you
want:
>
===== begin C DLL code =======
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
>
__declspec(dlle xport)
int get(const char* filename,char **buf,int *bufLen)
{
 int i,len;
 printf("*buf before malloc=%p\n",*b uf);
 len = strlen(filename );
 *buf = (char*)malloc(l en);
 *bufLen = len;
 for(i=0;i<len-1;i++)
      (*buf)[i]='a';
 (*buf)[i]=0;
 printf("*buf after malloc=%p\n",*b uf);
 return 5;
>
}
>
__declspec(dlle xport)
void release(char* buf)
{
 printf("buf[0]=%d\n",buf[0]);
 printf("buf=%p\ n",buf);
 free(buf);}
>
===== end C DLL code =======
>
===== begin Python code =======
from ctypes import *
x = CDLL('x.dll')
x.get.argtypes=[c_char_p,POINTE R(POINTER(c_byt e)),POINTER(c_i nt)]
buf = POINTER(c_byte) ()
length = c_int()
print x.get("hello.tx t",byref(buf),b yref(length))
print repr(string_at( buf,length))
buf[0]=55 # change first byte
x.release.argty pes=[POINTER(c_byte)]
x.release(buf)
===== end Python code =======
>
sample output:
>
*buf before malloc=00000000
*buf after malloc=00C92940
5
'aaaaaaaa\x00'
buf[0]=55
buf=00C92940
>
-Mark

thank you, Mark. I got it.