Re: reading array[text] in C extension function

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От Rémi Cura
Тема Re: reading array[text] in C extension function
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Msg-id CAJvUf_vy1wRpO8t9j3NxA0pZO-m6X04PGohV0UU-9369FwEyjA@mail.gmail.com
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Ответ на reading array[text] in C extension function  (Rémi Cura <remi.cura@gmail.com>)
Список pgsql-general
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I'll auto-answer ;-)

Based on the function "btoptions" from postgres source, which takes aas a first arg a text[] :

ArrayType  *array;
Datum      *dimdatums;
int         ndim;
array = DatumGetArrayTypeP(dimensions);
Assert(ARR_ELEMTYPE(array) == TEXTOID);
pcinfo("after assert \n");
deconstruct_array(array, TEXTOID, -1, false, 'i',
 &dimdatums, NULL, &ndim);
 
//construct the array to hold the result :
char ** final_dimension_array = (char **) pcalloc(ndim * sizeof(char * ) ); 
for (i = 0; i < ndim; i++)
{
 text       *dimensiontext = DatumGetTextP(dimdatums[i]);
char       *text_str = VARDATA(dimensiontext);
int         text_len = VARSIZE(dimensiontext) - VARHDRSZ;
char       *s;
char       *p;
s = TextDatumGetCString(dimdatums[i]);
final_dimension_array[i] = s;
}
//pcinfo("end of the text retrieval\n");  

Cheers,

Rémi-C



2014/1/15 Rémi Cura <remi.cura@gmail.com>
Hey,
I'm trying to use an array of text as input in a C function in a custom extension.

the prototype of the sql function is  :
CREATE OR REPLACE FUNCTION pc_subset(  dimensions TEXT[])
 

it is called like :
pc_subset(  ARRAY['X'::text,'Y'::text])

and the C function trying to read the text array (converting it to cstring ) :

text ** vals;
char ** cstring_array;
nelems = ARR_DIMS(arrptr)[0];
vals = (text**) ARR_DATA_PTR(arrptr);
cstring_array = (char **) pcalloc(nelems * sizeof(char * ) );
for (i3=0;i3<nelems;i3++)
{ 
cstring_array[i3] = text_to_cstring( vals[i3]);
elog(INFO, "elem %d of dim_array : %s\n",i3,cstring_array[i3]);
}

I crashes postgres because of a segfault.


Any help appreciated =)

Cheers,
Rémi-C

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