Buffer interface issue

[Simon Dumortier]

Hello,

I'm using SWIG (2.0.12) on Raspberry Pi with Python (2.7.9).
The buffer interface as described in the Doc2.0 section 34.12.2 doesn't seem to work for me:
http://www.swig.org/Doc2.0/SWIGDocumentation.html#Python_nn75

I get the following:
>>> from example import *
>>> p=bytearray(10)
>>> get_path(p)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: in method 'get_path', argument 1 of type 'char *'



Here are my c/i files:
# test.c ------------------------------------------------------
#include <stdio.h>
#include <string.h>
#include "test.h"

int print_stuff(void) {
        printf("More stuff\n");
        return 14;
}

void get_path(char *s) {
        char hString[10] = "Hello";

        strncpy(s, hString, 10);
}

int main (int argc, char** argv) {
        char zString[10];

        get_path(zString);
        printf("%s\n", zString);
        return 0;
}

# test.i ------------------------------------------------------
/* File: test.i */
%module example
%include "pybuffer.i"

%{
    #include "test.h"
%}

%pybuffer_mutable_string(char *str);
void get_path(char *s);
int print_stuff(void);

---------------------------------------------------------------


Am I doing something wrong?
Thank you,
Simon



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[Ervin Hegedüs]

Hi Simon,

On Wed, Feb 15, 2017 at 03:33:16PM +0000, Simon Dumortier wrote:

> Hello,
>
> # test.i ------------------------------------------------------
> /* File: test.i */
> %module example
> %include "pybuffer.i"
>
> %{
>     #include "test.h"
> %}
>
> %pybuffer_mutable_string(char *str);
> void get_path(char *s);
> int print_stuff(void);
>
> ---------------------------------------------------------------

the right form of the lines above:

%pybuffer_mutable_string(char *s);

%{
    #include "test.h"
%}
void get_path(char *s);


* may be that's not important, but I've placed the
  pybuffer_mutable_string macro _before_ the header
* but that's important, that the argument name _must_be_ same
  as you're using in your method; I mean, "char *str" in
  your macro is not equal with "char *s" in your method.


Regards,

a.

--
I � UTF-8

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[Simon Dumortier]

Hi Ervin,

Thank you for your answer, my issue was indeed to have a different argument name (*s Vs. *str).
The SWIG 2.0 documentation might need to be updated though, because I took the example from there:

-----------------------------------------------------
34.12.2 Buffer interface

%include <pybuffer.i>
%pybuffer_mutable_string(char *str);
void get_path(char *s);
-----------------------------------------------------

Regards,
Simon





-----Original Message-----
From: Ervin Hegedüs [mailto:[hidden email]]
Sent: Wednesday, February 15, 2017 2:02 PM
To: Simon Dumortier
Cc: [hidden email]
Subject: Re: [Swig-user] Buffer interface issue

EXTERNAL EMAIL


Hi Simon,

On Wed, Feb 15, 2017 at 03:33:16PM +0000, Simon Dumortier wrote:

> Hello,
>
> # test.i ------------------------------------------------------
> /* File: test.i */
> %module example
> %include "pybuffer.i"
>
> %{
>     #include "test.h"
> %}
>
> %pybuffer_mutable_string(char *str);
> void get_path(char *s);
> int print_stuff(void);
>
> ---------------------------------------------------------------

the right form of the lines above:

%pybuffer_mutable_string(char *s);

%{
    #include "test.h"
%}
void get_path(char *s);


* may be that's not important, but I've placed the
  pybuffer_mutable_string macro _before_ the header
* but that's important, that the argument name _must_be_ same
  as you're using in your method; I mean, "char *str" in
  your macro is not equal with "char *s" in your method.


Regards,

a.

--
I � UTF-8
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[William S Fulton]

On 15 February 2017 at 20:51, Simon Dumortier <[hidden email]> wrote:

Hi Ervin,

Thank you for your answer, my issue was indeed to have a different argument name (*s Vs. *str).
The SWIG 2.0 documentation might need to be updated though, because I took the example from there:

-----------------------------------------------------
34.12.2 Buffer interface

%include <pybuffer.i>
%pybuffer_mutable_string(char *str);
void get_path(char *s);
-----------------------------------------------------

Thanks for pointing this out, I've updated it for the next release.

William

 

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