complex.c

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/*
 * src/tutorial/complex.c
 *
 ******************************************************************************
  This file contains routines that can be bound to a Postgres backend and
  called by the backend in the process of processing queries.  The calling
  format for these routines is dictated by Postgres architecture.
******************************************************************************/

#include "postgres.h"

#include "fmgr.h"
#include "libpq/pqformat.h"     /* needed for send/recv functions */


PG_MODULE_MAGIC;

typedef struct Complex
{
    double      x;
    double      y;
}   Complex;

/*
 * Since we use V1 function calling convention, all these functions have
 * the same signature as far as C is concerned.  We provide these prototypes
 * just to forestall warnings when compiled with gcc -Wmissing-prototypes.
 */
Datum       complex_in(PG_FUNCTION_ARGS);
Datum       complex_out(PG_FUNCTION_ARGS);
Datum       complex_recv(PG_FUNCTION_ARGS);
Datum       complex_send(PG_FUNCTION_ARGS);
Datum       complex_add(PG_FUNCTION_ARGS);
Datum       complex_abs_lt(PG_FUNCTION_ARGS);
Datum       complex_abs_le(PG_FUNCTION_ARGS);
Datum       complex_abs_eq(PG_FUNCTION_ARGS);
Datum       complex_abs_ge(PG_FUNCTION_ARGS);
Datum       complex_abs_gt(PG_FUNCTION_ARGS);
Datum       complex_abs_cmp(PG_FUNCTION_ARGS);


/*****************************************************************************
 * Input/Output functions
 *****************************************************************************/

PG_FUNCTION_INFO_V1(complex_in);

Datum
complex_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);
    double      x,
                y;
    Complex    *result;

    if (sscanf(str, " ( %lf , %lf )", &x, &y) != 2)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                 errmsg("invalid input syntax for complex: \"%s\"",
                        str)));

    result = (Complex *) palloc(sizeof(Complex));
    result->x = x;
    result->y = y;
    PG_RETURN_POINTER(result);
}

PG_FUNCTION_INFO_V1(complex_out);

Datum
complex_out(PG_FUNCTION_ARGS)
{
    Complex    *complex = (Complex *) PG_GETARG_POINTER(0);
    char       *result;

    result = (char *) palloc(100);
    snprintf(result, 100, "(%g,%g)", complex->x, complex->y);
    PG_RETURN_CSTRING(result);
}

/*****************************************************************************
 * Binary Input/Output functions
 *
 * These are optional.
 *****************************************************************************/

PG_FUNCTION_INFO_V1(complex_recv);

Datum
complex_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    Complex    *result;

    result = (Complex *) palloc(sizeof(Complex));
    result->x = pq_getmsgfloat8(buf);
    result->y = pq_getmsgfloat8(buf);
    PG_RETURN_POINTER(result);
}

PG_FUNCTION_INFO_V1(complex_send);

Datum
complex_send(PG_FUNCTION_ARGS)
{
    Complex    *complex = (Complex *) PG_GETARG_POINTER(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendfloat8(&buf, complex->x);
    pq_sendfloat8(&buf, complex->y);
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

/*****************************************************************************
 * New Operators
 *
 * A practical Complex datatype would provide much more than this, of course.
 *****************************************************************************/

PG_FUNCTION_INFO_V1(complex_add);

Datum
complex_add(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);
    Complex    *result;

    result = (Complex *) palloc(sizeof(Complex));
    result->x = a->x + b->x;
    result->y = a->y + b->y;
    PG_RETURN_POINTER(result);
}


/*****************************************************************************
 * Operator class for defining B-tree index
 *
 * It's essential that the comparison operators and support function for a
 * B-tree index opclass always agree on the relative ordering of any two
 * data values.  Experience has shown that it's depressingly easy to write
 * unintentionally inconsistent functions.  One way to reduce the odds of
 * making a mistake is to make all the functions simple wrappers around
 * an internal three-way-comparison function, as we do here.
 *****************************************************************************/

#define Mag(c)  ((c)->x*(c)->x + (c)->y*(c)->y)

static int
complex_abs_cmp_internal(Complex * a, Complex * b)
{
    double      amag = Mag(a),
                bmag = Mag(b);

    if (amag < bmag)
        return -1;
    if (amag > bmag)
        return 1;
    return 0;
}


PG_FUNCTION_INFO_V1(complex_abs_lt);

Datum
complex_abs_lt(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) < 0);
}

PG_FUNCTION_INFO_V1(complex_abs_le);

Datum
complex_abs_le(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) <= 0);
}

PG_FUNCTION_INFO_V1(complex_abs_eq);

Datum
complex_abs_eq(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) == 0);
}

PG_FUNCTION_INFO_V1(complex_abs_ge);

Datum
complex_abs_ge(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) >= 0);
}

PG_FUNCTION_INFO_V1(complex_abs_gt);

Datum
complex_abs_gt(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) > 0);
}

PG_FUNCTION_INFO_V1(complex_abs_cmp);

Datum
complex_abs_cmp(PG_FUNCTION_ARGS)
{
    Complex    *a = (Complex *) PG_GETARG_POINTER(0);
    Complex    *b = (Complex *) PG_GETARG_POINTER(1);

    PG_RETURN_INT32(complex_abs_cmp_internal(a, b));
}