Thread: Text function problem

Hi,

I've been adding some bit functions to postgres and this works fine,
until I tried to construct a function that returns 8 bits as a string,
e.g. 4 as 00000100. I constructed the function with the help of the
programmer manual.

Now I have the following problem on Friday's snapshot: the first time I
select an integer as bitstring it works fine, but the second time I get
a segflt. So I'm evidently missing something somewhere. I'd appreciate
it if somebody could tell me what I'm doing wrong.

I'm getting (from the backend)

=================================================================================
darkstar$ postgres tt

POSTGRES backend interactive interface
$Revision: 1.117 $ $Date: 1999/05/26 12:55:55 $

backend> select bout(4);
blank
         1: bout        (typeid = 25, len = -1, typmod = -1, byval = f)
        ----
         1: bout = "00000100"   (typeid = 25, len = -1, typmod = -1,
byval = f)
        ----
backend> select bout(4);
blank
         1: bout        (typeid = 25, len = -1, typmod = -1, byval = f)
        ----
Segmentation fault
=================================================================================

This is on a DEC Alpha running DU 4.0D.

Thanks

Adriaan

Here is the C file:

=================================================================================
#include "bit.h"
#include "postgres.h"

int bor (int a, int b) {
  return a|b;
}

int band (int a, int b) {
  return a&b;
}

int bxor (int a, int b) {
  return a^b;
}

int bnot (int a) {
  return ~a;
}

int bshift (int a, int s) {
  return s>0 ? a << s : a >> -s;
}

int bbool (int a) {
  return a!=0 ? 1 : 0;
}

text * bout (int a) {
  int32 new_text_size = VARHDRSZ + sizeof(char)*8;
  text *new_text = (text *) palloc(new_text_size);
  int i;
  for (i=0; i<8; i++)
    VARDATA(new_text)[i] = (a>>(7-i))%2 ? '1' : '0';
  return new_text;
}
=================================================================================

And here is the SQL

=================================================================================
drop function bor(int4,int4);
create function bor(int4,int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function band(int4,int4);
create function band(int4,int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function bxor(int4,int4);
create function bxor(int4,int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function bnot(int4);
create function bnot(int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function bshift(int4,int4);
create function bshift(int4,int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function bbool(int4);
create function bbool(int4) returns int4
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop function bout(int4);
create function bout(int4) returns text
  as 'PGLIB/contrib/bit.so'
  language 'C';

drop aggregate bor_agg int4;
create aggregate bor_agg(
  sfunc1 = bor,
  basetype = int4,
  stype1 = int4,
  initcond1 = '0'
);

drop aggregate band_agg int4;
create aggregate band_agg(
  sfunc1 = band,
  basetype = int4,
  stype1 = int4,
  initcond1 = '-1'
);
=================================================================================

>>>>> "AJ" == Adriaan Joubert <a.joubert@albourne.com> writes:

 AJ> Hi,
 AJ> I've been adding some bit functions to postgres and this works fine,
 AJ> until I tried to construct a function that returns 8 bits as a string,
 AJ> e.g. 4 as 00000100. I constructed the function with the help of the
 AJ> programmer manual.

 AJ> Now I have the following problem on Friday's snapshot: the first time I
 AJ> select an integer as bitstring it works fine, but the second time I get
 AJ> a segflt. So I'm evidently missing something somewhere. I'd appreciate
 AJ> it if somebody could tell me what I'm doing wrong.

 AJ> I'm getting (from the backend)

. . .

skip

. . .
 AJ> text * bout (int a) {
 AJ> int32 new_text_size = VARHDRSZ + sizeof(char)*8;
 AJ> text *new_text = (text *) palloc(new_text_size);
 AJ> int i;
 AJ> for (i=0; i<8; i++)
 AJ> VARDATA(new_text)[i] = (a>>(7-i))%2 ? '1' : '0';
 AJ> return new_text;
 AJ> }

You do not set length of data in *new_text. You must write about this:


 ---------------------------------
text * bout (int a) {
int32 new_text_size = VARHDRSZ + sizeof(char)*8;
text *new_text = (text *) palloc(new_text_size);
int i;

VARSIZE(new_text) = new_text_size; /* !!!!! */

for (i=0; i<8; i++)
VARDATA(new_text)[i] = (a>>(7-i))%2 ? '1' : '0';
return new_text;
}
 ---------------------------------

 More: it'll be better if you change 'int' to 'int4' data type in your
nexts.

--
Anatoly K. Lasareff              Email:       tolik@icomm.ru
Senior programmer