Datum funcname(PG_FUNCTION_ARGS)

PG_FUNCTION_INFO_V1(funcname);

#include "postgres.h"
#include <string.h>
#include "utils/geo_decls.h"
#include "fmgr.h"

/* By Value */

PG_FUNCTION_INFO_V1(add_one);
         
Datum
add_one(PG_FUNCTION_ARGS)
{
    int32   arg = PG_GETARG_INT32(0);

    PG_RETURN_INT32(arg + 1);
}

/* By Reference, Fixed Length */

PG_FUNCTION_INFO_V1(add_one_float8);

Datum
add_one_float8(PG_FUNCTION_ARGS)
{
    /* The macros for FLOAT8 hide 
     * its pass-by-reference nature 
     */
    float8   arg = PG_GETARG_FLOAT8(0);

    PG_RETURN_FLOAT8(arg + 1.0);
}

PG_FUNCTION_INFO_V1(makepoint);

Datum
makepoint(PG_FUNCTION_ARGS)
{
    /* Here, the pass-by-reference nature
     * of Point is not hidden            
     */
    Point  *pointx = PG_GETARG_POINT_P(0);
    Point  *pointy = PG_GETARG_POINT_P(1);
    Point  *new_point = (Point *) palloc(sizeof(Point));

    new_point->x = pointx->x;
    new_point->y = pointy->y;
       
    PG_RETURN_POINT_P(new_point);
}

/* By Reference, Variable Length */

PG_FUNCTION_INFO_V1(copytext);

Datum
copytext(PG_FUNCTION_ARGS)
{
    text *t = PG_GETARG_TEXT_P(0);
    /*
     * VARSIZE is the total size 
     *  of the struct in bytes.
     */
    text *new_t = (text *) palloc(VARSIZE(t));
    VARATT_SIZEP(new_t) = VARSIZE(t);
    /*
     * VARDATA is a pointer to the 
     * data region of the struct.
     */
    memcpy((void *) VARDATA(new_t), /* destination */
           (void *) VARDATA(t),     /* source */
           VARSIZE(t)-VARHDRSZ);    /* how many bytes */
    PG_RETURN_TEXT_P(new_t);
}

PG_FUNCTION_INFO_V1(concat_text);

Datum
concat_text(PG_FUNCTION_ARGS)
{
    text  *arg1 = PG_GETARG_TEXT_P(0);
    text  *arg2 = PG_GETARG_TEXT_P(1);
    int32 new_text_size = VARSIZE(arg1) + 
       VARSIZE(arg2) - VARHDRSZ;
    text *new_text = (text *) palloc(new_text_size);

    VARATT_SIZEP(new_text) = new_text_size;
    memcpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ);
    memcpy(VARDATA(new_text) + (VARSIZE(arg1)-VARHDRSZ),
       VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ);
    PG_RETURN_TEXT_P(new_text);
}

CREATE FUNCTION add_one(int4) RETURNS int4
     AS 'PGROOT/tutorial/funcs_new.so' LANGUAGE 'c'
     WITH (isStrict);

-- note overloading of SQL function name add_one()
CREATE FUNCTION add_one(float8) RETURNS float8
     AS 'PGROOT/tutorial/funcs_new.so',
        'add_one_float8'
     LANGUAGE 'c' WITH (isStrict);

CREATE FUNCTION makepoint(point, point) RETURNS point
     AS 'PGROOT/tutorial/funcs_new.so' LANGUAGE 'c'
     WITH (isStrict);
                         
CREATE FUNCTION copytext(text) RETURNS text
     AS 'PGROOT/tutorial/funcs_new.so' LANGUAGE 'c'
     WITH (isStrict);

CREATE FUNCTION concat_text(text, text) RETURNS text
     AS 'PGROOT/tutorial/funcs_new.so' LANGUAGE 'c'
     WITH (isStrict);