Hackers,
Currently, `bytea` does not have any bitwise logical operations yet.
This issue came up in an old thread from 2006 [1], but nobody seemed to
have picked this issue so far.
Being in the need for this myself, I copied the bit vector's bitwise
logical operations and converted them to bytea. I'm using this as a
PostgreSQL extension right now, but would be very happy to see this
integrated into mainstream as default bytea operations in the future.
Find attached the implementation, plus a SQL file, for:
* bytea_xor
* bytea_and
* bytea_or
* bytea_not
* bytea_bitsset (returns number of set bits in a bytea; feel free to
drop this one if you don't see utility)
Tested on PG 9.6. I hope you find this useful.
Cheers,
Christian
[1]: https://www.postgresql.org/message-id/5171.1146927915%40sss.pgh.pa.us
DROP FUNCTION IF EXISTS bytea_xor(bytea, bytea);
CREATE FUNCTION bytea_xor(bytea, bytea) RETURNS bytea
AS 'bytea_bitops.so', 'bytea_xor'
LANGUAGE C STRICT;
DROP FUNCTION IF EXISTS bytea_and(bytea, bytea);
CREATE FUNCTION bytea_and(bytea, bytea) RETURNS bytea
AS 'bytea_bitops.so', 'bytea_and'
LANGUAGE C STRICT;
DROP FUNCTION IF EXISTS bytea_or(bytea, bytea);
CREATE FUNCTION bytea_or(bytea, bytea) RETURNS bytea
AS 'bytea_bitops.so', 'bytea_or'
LANGUAGE C STRICT;
DROP FUNCTION IF EXISTS bytea_not(bytea);
CREATE FUNCTION bytea_not(bytea) RETURNS bytea
AS 'bytea_bitops.so', 'bytea_not'
LANGUAGE C STRICT;
DROP FUNCTION IF EXISTS bytea_bitsset(bytea);
CREATE FUNCTION bytea_bitsset(bytea) RETURNS integer
AS 'bytea_bitops.so', 'bytea_bitsset'
LANGUAGE C STRICT;
/* bytea_bitops.c
*
* Adding bytea bit operation functions similar to varbit's bit operations.
* Written by Christian Rossow
* License: Do whatever you want with this code.
* To build:
* gcc -I`pg_config --includedir` -fpic -c bytea_bitops.c
* gcc -shared -o bytea_bitops.so bytea_bitops.o
* sudo cp bytea_bitops.so /usr/lib/postgresql/9.1/lib/
* cd /usr/lib/postgresql/9.1/lib/
* sudo chmod +r bytea_bitops.so
*/
#include <postgres.h>
#include <fmgr.h>
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
PG_FUNCTION_INFO_V1(bytea_xor);
Datum bytea_xor(PG_FUNCTION_ARGS)
{
bytea* ba1 = PG_GETARG_BYTEA_P(0);
bytea* ba2 = PG_GETARG_BYTEA_P(1);
bytea* result;
char* str1 = VARDATA(ba1);
char* str2 = VARDATA(ba2);
char* resstr;
int32 len;
int32 i;
if (VARSIZE(ba1) != VARSIZE(ba2))
{
ereport(ERROR,
(errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
errmsg("cannot XOR bytea of different
sizes")));
}
len = VARSIZE(ba1);
result = (bytea *) palloc(len);
SET_VARSIZE(result, len);
resstr = VARDATA(result);
for (i=0; i < len - VARHDRSZ; ++i)
{
resstr[i] = str1[i] ^ str2[i];
}
PG_RETURN_BYTEA_P(result);
}
PG_FUNCTION_INFO_V1(bytea_and);
Datum bytea_and(PG_FUNCTION_ARGS)
{
bytea* ba1 = PG_GETARG_BYTEA_P(0);
bytea* ba2 = PG_GETARG_BYTEA_P(1);
bytea* result;
char* str1 = VARDATA(ba1);
char* str2 = VARDATA(ba2);
char* resstr;
int32 len;
int32 i;
if (VARSIZE(ba1) != VARSIZE(ba2))
{
ereport(ERROR,
(errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
errmsg("cannot AND bytea of different
sizes")));
}
len = VARSIZE(ba1);
result = (bytea *) palloc(len);
SET_VARSIZE(result, len);
resstr = VARDATA(result);
for (i=0; i < len - VARHDRSZ; ++i)
{
resstr[i] = str1[i] & str2[i];
}
PG_RETURN_BYTEA_P(result);
}
PG_FUNCTION_INFO_V1(bytea_or);
Datum bytea_or(PG_FUNCTION_ARGS)
{
bytea* ba1 = PG_GETARG_BYTEA_P(0);
bytea* ba2 = PG_GETARG_BYTEA_P(1);
bytea* result;
char* str1 = VARDATA(ba1);
char* str2 = VARDATA(ba2);
char* resstr;
int32 len;
int32 i;
if (VARSIZE(ba1) != VARSIZE(ba2))
{
ereport(ERROR,
(errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
errmsg("cannot AND bytea of different
sizes")));
}
len = VARSIZE(ba1);
result = (bytea *) palloc(len);
SET_VARSIZE(result, len);
resstr = VARDATA(result);
for (i=0; i < len - VARHDRSZ; ++i)
{
resstr[i] = str1[i] | str2[i];
}
PG_RETURN_BYTEA_P(result);
}
PG_FUNCTION_INFO_V1(bytea_not);
Datum bytea_not(PG_FUNCTION_ARGS)
{
bytea* ba1 = PG_GETARG_BYTEA_P(0);
bytea* result;
char* str1 = VARDATA(ba1);
char* resstr;
int32 len = VARSIZE(ba1);
int32 i;
result = (bytea *) palloc(len);
SET_VARSIZE(result, len);
resstr = VARDATA(result);
for (i=0; i < len - VARHDRSZ; ++i)
{
resstr[i] = ~str1[i];
}
PG_RETURN_BYTEA_P(result);
}
PG_FUNCTION_INFO_V1(bytea_bitsset);
Datum bytea_bitsset(PG_FUNCTION_ARGS)
{
bytea* ba1 = PG_GETARG_BYTEA_P(0);
int32 result = 0;
char* str1 = VARDATA(ba1);
int32 len = VARSIZE(ba1) - VARHDRSZ;
int32 i;
for (i=0; i < len; ++i)
{
uint8_t c = (uint8_t) str1[i];
//elog(WARNING, "processing char 0x%02x before %d", c, result);
result += (c & 0x01); c = c >> 1; // 1
result += (c & 0x01); c = c >> 1; // 2
result += (c & 0x01); c = c >> 1; // 3
result += (c & 0x01); c = c >> 1; // 4
result += (c & 0x01); c = c >> 1; // 5
result += (c & 0x01); c = c >> 1; // 6
result += (c & 0x01); c = c >> 1; // 7
result += (c & 0x01); // 8
}
PG_RETURN_INT32(result);
}
