int.c

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/*-------------------------------------------------------------------------
 *
 * int.c
 *    Functions for the built-in integer types (except int8).
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/int.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * OLD COMMENTS
 *      I/O routines:
 *       int2in, int2out, int2recv, int2send
 *       int4in, int4out, int4recv, int4send
 *       int2vectorin, int2vectorout, int2vectorrecv, int2vectorsend
 *      Boolean operators:
 *       inteq, intne, intlt, intle, intgt, intge
 *      Arithmetic operators:
 *       intpl, intmi, int4mul, intdiv
 *
 *      Arithmetic operators:
 *       intmod
 */
#include "postgres.h"

#include <ctype.h>
#include <limits.h>

#include "catalog/pg_type.h"
#include "funcapi.h"
#include "libpq/pqformat.h"
#include "utils/array.h"
#include "utils/builtins.h"


#define SAMESIGN(a,b)   (((a) < 0) == ((b) < 0))

#define Int2VectorSize(n)   (offsetof(int2vector, values) + (n) * sizeof(int16))

typedef struct
{
    int32       current;
    int32       finish;
    int32       step;
} generate_series_fctx;


/*****************************************************************************
 *   USER I/O ROUTINES                                                       *
 *****************************************************************************/

/*
 *      int2in          - converts "num" to short
 */
Datum
int2in(PG_FUNCTION_ARGS)
{
    char       *num = PG_GETARG_CSTRING(0);

    PG_RETURN_INT16(pg_atoi(num, sizeof(int16), '\0'));
}

/*
 *      int2out         - converts short to "num"
 */
Datum
int2out(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    char       *result = (char *) palloc(7);    /* sign, 5 digits, '\0' */

    pg_itoa(arg1, result);
    PG_RETURN_CSTRING(result);
}

/*
 *      int2recv            - converts external binary format to int2
 */
Datum
int2recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);

    PG_RETURN_INT16((int16) pq_getmsgint(buf, sizeof(int16)));
}

/*
 *      int2send            - converts int2 to binary format
 */
Datum
int2send(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendint(&buf, arg1, sizeof(int16));
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

/*
 * construct int2vector given a raw array of int2s
 *
 * If int2s is NULL then caller must fill values[] afterward
 */
int2vector *
buildint2vector(const int16 *int2s, int n)
{
    int2vector *result;

    result = (int2vector *) palloc0(Int2VectorSize(n));

    if (n > 0 && int2s)
        memcpy(result->values, int2s, n * sizeof(int16));

    /*
     * Attach standard array header.  For historical reasons, we set the index
     * lower bound to 0 not 1.
     */
    SET_VARSIZE(result, Int2VectorSize(n));
    result->ndim = 1;
    result->dataoffset = 0;     /* never any nulls */
    result->elemtype = INT2OID;
    result->dim1 = n;
    result->lbound1 = 0;

    return result;
}

/*
 *      int2vectorin            - converts "num num ..." to internal form
 */
Datum
int2vectorin(PG_FUNCTION_ARGS)
{
    char       *intString = PG_GETARG_CSTRING(0);
    int2vector *result;
    int         n;

    result = (int2vector *) palloc0(Int2VectorSize(FUNC_MAX_ARGS));

    for (n = 0; *intString && n < FUNC_MAX_ARGS; n++)
    {
        while (*intString && isspace((unsigned char) *intString))
            intString++;
        if (*intString == '\0')
            break;
        result->values[n] = pg_atoi(intString, sizeof(int16), ' ');
        while (*intString && !isspace((unsigned char) *intString))
            intString++;
    }
    while (*intString && isspace((unsigned char) *intString))
        intString++;
    if (*intString)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("int2vector has too many elements")));

    SET_VARSIZE(result, Int2VectorSize(n));
    result->ndim = 1;
    result->dataoffset = 0;     /* never any nulls */
    result->elemtype = INT2OID;
    result->dim1 = n;
    result->lbound1 = 0;

    PG_RETURN_POINTER(result);
}

/*
 *      int2vectorout       - converts internal form to "num num ..."
 */
Datum
int2vectorout(PG_FUNCTION_ARGS)
{
    int2vector *int2Array = (int2vector *) PG_GETARG_POINTER(0);
    int         num,
                nnums = int2Array->dim1;
    char       *rp;
    char       *result;

    /* assumes sign, 5 digits, ' ' */
    rp = result = (char *) palloc(nnums * 7 + 1);
    for (num = 0; num < nnums; num++)
    {
        if (num != 0)
            *rp++ = ' ';
        pg_itoa(int2Array->values[num], rp);
        while (*++rp != '\0')
            ;
    }
    *rp = '\0';
    PG_RETURN_CSTRING(result);
}

/*
 *      int2vectorrecv          - converts external binary format to int2vector
 */
Datum
int2vectorrecv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    FunctionCallInfoData locfcinfo;
    int2vector *result;

    /*
     * Normally one would call array_recv() using DirectFunctionCall3, but
     * that does not work since array_recv wants to cache some data using
     * fcinfo->flinfo->fn_extra.  So we need to pass it our own flinfo
     * parameter.
     */
    InitFunctionCallInfoData(locfcinfo, fcinfo->flinfo, 3,
                             InvalidOid, NULL, NULL);

    locfcinfo.arg[0] = PointerGetDatum(buf);
    locfcinfo.arg[1] = ObjectIdGetDatum(INT2OID);
    locfcinfo.arg[2] = Int32GetDatum(-1);
    locfcinfo.argnull[0] = false;
    locfcinfo.argnull[1] = false;
    locfcinfo.argnull[2] = false;

    result = (int2vector *) DatumGetPointer(array_recv(&locfcinfo));

    Assert(!locfcinfo.isnull);

    /* sanity checks: int2vector must be 1-D, 0-based, no nulls */
    if (ARR_NDIM(result) != 1 ||
        ARR_HASNULL(result) ||
        ARR_ELEMTYPE(result) != INT2OID ||
        ARR_LBOUND(result)[0] != 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                 errmsg("invalid int2vector data")));

    /* check length for consistency with int2vectorin() */
    if (ARR_DIMS(result)[0] > FUNC_MAX_ARGS)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("oidvector has too many elements")));

    PG_RETURN_POINTER(result);
}

/*
 *      int2vectorsend          - converts int2vector to binary format
 */
Datum
int2vectorsend(PG_FUNCTION_ARGS)
{
    return array_send(fcinfo);
}


/*****************************************************************************
 *   PUBLIC ROUTINES                                                         *
 *****************************************************************************/

/*
 *      int4in          - converts "num" to int4
 */
Datum
int4in(PG_FUNCTION_ARGS)
{
    char       *num = PG_GETARG_CSTRING(0);

    PG_RETURN_INT32(pg_atoi(num, sizeof(int32), '\0'));
}

/*
 *      int4out         - converts int4 to "num"
 */
Datum
int4out(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    char       *result = (char *) palloc(12);   /* sign, 10 digits, '\0' */

    pg_ltoa(arg1, result);
    PG_RETURN_CSTRING(result);
}

/*
 *      int4recv            - converts external binary format to int4
 */
Datum
int4recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);

    PG_RETURN_INT32((int32) pq_getmsgint(buf, sizeof(int32)));
}

/*
 *      int4send            - converts int4 to binary format
 */
Datum
int4send(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendint(&buf, arg1, sizeof(int32));
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}


/*
 *      ===================
 *      CONVERSION ROUTINES
 *      ===================
 */

Datum
i2toi4(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);

    PG_RETURN_INT32((int32) arg1);
}

Datum
i4toi2(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);

    if (arg1 < SHRT_MIN || arg1 > SHRT_MAX)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));

    PG_RETURN_INT16((int16) arg1);
}

/* Cast int4 -> bool */
Datum
int4_bool(PG_FUNCTION_ARGS)
{
    if (PG_GETARG_INT32(0) == 0)
        PG_RETURN_BOOL(false);
    else
        PG_RETURN_BOOL(true);
}

/* Cast bool -> int4 */
Datum
bool_int4(PG_FUNCTION_ARGS)
{
    if (PG_GETARG_BOOL(0) == false)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(1);
}

/*
 *      ============================
 *      COMPARISON OPERATOR ROUTINES
 *      ============================
 */

/*
 *      inteq           - returns 1 iff arg1 == arg2
 *      intne           - returns 1 iff arg1 != arg2
 *      intlt           - returns 1 iff arg1 < arg2
 *      intle           - returns 1 iff arg1 <= arg2
 *      intgt           - returns 1 iff arg1 > arg2
 *      intge           - returns 1 iff arg1 >= arg2
 */

Datum
int4eq(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 == arg2);
}

Datum
int4ne(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 != arg2);
}

Datum
int4lt(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 < arg2);
}

Datum
int4le(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 <= arg2);
}

Datum
int4gt(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 > arg2);
}

Datum
int4ge(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 >= arg2);
}

Datum
int2eq(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 == arg2);
}

Datum
int2ne(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 != arg2);
}

Datum
int2lt(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 < arg2);
}

Datum
int2le(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 <= arg2);
}

Datum
int2gt(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 > arg2);
}

Datum
int2ge(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 >= arg2);
}

Datum
int24eq(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 == arg2);
}

Datum
int24ne(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 != arg2);
}

Datum
int24lt(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 < arg2);
}

Datum
int24le(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 <= arg2);
}

Datum
int24gt(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 > arg2);
}

Datum
int24ge(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_BOOL(arg1 >= arg2);
}

Datum
int42eq(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 == arg2);
}

Datum
int42ne(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 != arg2);
}

Datum
int42lt(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 < arg2);
}

Datum
int42le(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 <= arg2);
}

Datum
int42gt(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 > arg2);
}

Datum
int42ge(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_BOOL(arg1 >= arg2);
}

/*
 *      int[24]pl       - returns arg1 + arg2
 *      int[24]mi       - returns arg1 - arg2
 *      int[24]mul      - returns arg1 * arg2
 *      int[24]div      - returns arg1 / arg2
 */

Datum
int4um(PG_FUNCTION_ARGS)
{
    int32       arg = PG_GETARG_INT32(0);
    int32       result;

    result = -arg;
    /* overflow check (needed for INT_MIN) */
    if (arg != 0 && SAMESIGN(result, arg))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int4up(PG_FUNCTION_ARGS)
{
    int32       arg = PG_GETARG_INT32(0);

    PG_RETURN_INT32(arg);
}

Datum
int4pl(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 + arg2;

    /*
     * Overflow check.  If the inputs are of different signs then their sum
     * cannot overflow.  If the inputs are of the same sign, their sum had
     * better be that sign too.
     */
    if (SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int4mi(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 - arg2;

    /*
     * Overflow check.  If the inputs are of the same sign then their
     * difference cannot overflow.  If they are of different signs then the
     * result should be of the same sign as the first input.
     */
    if (!SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int4mul(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 * arg2;

    /*
     * Overflow check.  We basically check to see if result / arg2 gives arg1
     * again.  There are two cases where this fails: arg2 = 0 (which cannot
     * overflow) and arg1 = INT_MIN, arg2 = -1 (where the division itself will
     * overflow and thus incorrectly match).
     *
     * Since the division is likely much more expensive than the actual
     * multiplication, we'd like to skip it where possible.  The best bang for
     * the buck seems to be to check whether both inputs are in the int16
     * range; if so, no overflow is possible.
     */
    if (!(arg1 >= (int32) SHRT_MIN && arg1 <= (int32) SHRT_MAX &&
          arg2 >= (int32) SHRT_MIN && arg2 <= (int32) SHRT_MAX) &&
        arg2 != 0 &&
        ((arg2 == -1 && arg1 < 0 && result < 0) ||
         result / arg2 != arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int4div(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /*
     * INT_MIN / -1 is problematic, since the result can't be represented on a
     * two's-complement machine.  Some machines produce INT_MIN, some produce
     * zero, some throw an exception.  We can dodge the problem by recognizing
     * that division by -1 is the same as negation.
     */
    if (arg2 == -1)
    {
        result = -arg1;
        /* overflow check (needed for INT_MIN) */
        if (arg1 != 0 && SAMESIGN(result, arg1))
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("integer out of range")));
        PG_RETURN_INT32(result);
    }

    /* No overflow is possible */

    result = arg1 / arg2;

    PG_RETURN_INT32(result);
}

Datum
int4inc(PG_FUNCTION_ARGS)
{
    int32       arg = PG_GETARG_INT32(0);
    int32       result;

    result = arg + 1;
    /* Overflow check */
    if (arg > 0 && result < 0)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));

    PG_RETURN_INT32(result);
}

Datum
int2um(PG_FUNCTION_ARGS)
{
    int16       arg = PG_GETARG_INT16(0);
    int16       result;

    result = -arg;
    /* overflow check (needed for SHRT_MIN) */
    if (arg != 0 && SAMESIGN(result, arg))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));
    PG_RETURN_INT16(result);
}

Datum
int2up(PG_FUNCTION_ARGS)
{
    int16       arg = PG_GETARG_INT16(0);

    PG_RETURN_INT16(arg);
}

Datum
int2pl(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int16       result;

    result = arg1 + arg2;

    /*
     * Overflow check.  If the inputs are of different signs then their sum
     * cannot overflow.  If the inputs are of the same sign, their sum had
     * better be that sign too.
     */
    if (SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));
    PG_RETURN_INT16(result);
}

Datum
int2mi(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int16       result;

    result = arg1 - arg2;

    /*
     * Overflow check.  If the inputs are of the same sign then their
     * difference cannot overflow.  If they are of different signs then the
     * result should be of the same sign as the first input.
     */
    if (!SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));
    PG_RETURN_INT16(result);
}

Datum
int2mul(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int32       result32;

    /*
     * The most practical way to detect overflow is to do the arithmetic in
     * int32 (so that the result can't overflow) and then do a range check.
     */
    result32 = (int32) arg1 * (int32) arg2;

    if (result32 < SHRT_MIN || result32 > SHRT_MAX)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));

    PG_RETURN_INT16((int16) result32);
}

Datum
int2div(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int16       result;

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /*
     * SHRT_MIN / -1 is problematic, since the result can't be represented on
     * a two's-complement machine.  Some machines produce SHRT_MIN, some
     * produce zero, some throw an exception.  We can dodge the problem by
     * recognizing that division by -1 is the same as negation.
     */
    if (arg2 == -1)
    {
        result = -arg1;
        /* overflow check (needed for SHRT_MIN) */
        if (arg1 != 0 && SAMESIGN(result, arg1))
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("smallint out of range")));
        PG_RETURN_INT16(result);
    }

    /* No overflow is possible */

    result = arg1 / arg2;

    PG_RETURN_INT16(result);
}

Datum
int24pl(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 + arg2;

    /*
     * Overflow check.  If the inputs are of different signs then their sum
     * cannot overflow.  If the inputs are of the same sign, their sum had
     * better be that sign too.
     */
    if (SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int24mi(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 - arg2;

    /*
     * Overflow check.  If the inputs are of the same sign then their
     * difference cannot overflow.  If they are of different signs then the
     * result should be of the same sign as the first input.
     */
    if (!SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int24mul(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);
    int32       result;

    result = arg1 * arg2;

    /*
     * Overflow check.  We basically check to see if result / arg2 gives arg1
     * again.  There is one case where this fails: arg2 = 0 (which cannot
     * overflow).
     *
     * Since the division is likely much more expensive than the actual
     * multiplication, we'd like to skip it where possible.  The best bang for
     * the buck seems to be to check whether both inputs are in the int16
     * range; if so, no overflow is possible.
     */
    if (!(arg2 >= (int32) SHRT_MIN && arg2 <= (int32) SHRT_MAX) &&
        result / arg2 != arg1)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int24div(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /* No overflow is possible */
    PG_RETURN_INT32((int32) arg1 / arg2);
}

Datum
int42pl(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int32       result;

    result = arg1 + arg2;

    /*
     * Overflow check.  If the inputs are of different signs then their sum
     * cannot overflow.  If the inputs are of the same sign, their sum had
     * better be that sign too.
     */
    if (SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int42mi(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int32       result;

    result = arg1 - arg2;

    /*
     * Overflow check.  If the inputs are of the same sign then their
     * difference cannot overflow.  If they are of different signs then the
     * result should be of the same sign as the first input.
     */
    if (!SAMESIGN(arg1, arg2) && !SAMESIGN(result, arg1))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int42mul(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int32       result;

    result = arg1 * arg2;

    /*
     * Overflow check.  We basically check to see if result / arg1 gives arg2
     * again.  There is one case where this fails: arg1 = 0 (which cannot
     * overflow).
     *
     * Since the division is likely much more expensive than the actual
     * multiplication, we'd like to skip it where possible.  The best bang for
     * the buck seems to be to check whether both inputs are in the int16
     * range; if so, no overflow is possible.
     */
    if (!(arg1 >= (int32) SHRT_MIN && arg1 <= (int32) SHRT_MAX) &&
        result / arg1 != arg2)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int42div(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int16       arg2 = PG_GETARG_INT16(1);
    int32       result;

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /*
     * INT_MIN / -1 is problematic, since the result can't be represented on a
     * two's-complement machine.  Some machines produce INT_MIN, some produce
     * zero, some throw an exception.  We can dodge the problem by recognizing
     * that division by -1 is the same as negation.
     */
    if (arg2 == -1)
    {
        result = -arg1;
        /* overflow check (needed for INT_MIN) */
        if (arg1 != 0 && SAMESIGN(result, arg1))
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("integer out of range")));
        PG_RETURN_INT32(result);
    }

    /* No overflow is possible */

    result = arg1 / arg2;

    PG_RETURN_INT32(result);
}

Datum
int4mod(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /*
     * Some machines throw a floating-point exception for INT_MIN % -1, which
     * is a bit silly since the correct answer is perfectly well-defined,
     * namely zero.
     */
    if (arg2 == -1)
        PG_RETURN_INT32(0);

    /* No overflow is possible */

    PG_RETURN_INT32(arg1 % arg2);
}

Datum
int2mod(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    if (arg2 == 0)
    {
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));
        /* ensure compiler realizes we mustn't reach the division (gcc bug) */
        PG_RETURN_NULL();
    }

    /*
     * Some machines throw a floating-point exception for INT_MIN % -1, which
     * is a bit silly since the correct answer is perfectly well-defined,
     * namely zero.  (It's not clear this ever happens when dealing with
     * int16, but we might as well have the test for safety.)
     */
    if (arg2 == -1)
        PG_RETURN_INT16(0);

    /* No overflow is possible */

    PG_RETURN_INT16(arg1 % arg2);
}


/* int[24]abs()
 * Absolute value
 */
Datum
int4abs(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       result;

    result = (arg1 < 0) ? -arg1 : arg1;
    /* overflow check (needed for INT_MIN) */
    if (result < 0)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
    PG_RETURN_INT32(result);
}

Datum
int2abs(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       result;

    result = (arg1 < 0) ? -arg1 : arg1;
    /* overflow check (needed for SHRT_MIN) */
    if (result < 0)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("smallint out of range")));
    PG_RETURN_INT16(result);
}

Datum
int2larger(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_INT16((arg1 > arg2) ? arg1 : arg2);
}

Datum
int2smaller(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_INT16((arg1 < arg2) ? arg1 : arg2);
}

Datum
int4larger(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32((arg1 > arg2) ? arg1 : arg2);
}

Datum
int4smaller(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32((arg1 < arg2) ? arg1 : arg2);
}

/*
 * Bit-pushing operators
 *
 *      int[24]and      - returns arg1 & arg2
 *      int[24]or       - returns arg1 | arg2
 *      int[24]xor      - returns arg1 # arg2
 *      int[24]not      - returns ~arg1
 *      int[24]shl      - returns arg1 << arg2
 *      int[24]shr      - returns arg1 >> arg2
 */

Datum
int4and(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg1 & arg2);
}

Datum
int4or(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg1 | arg2);
}

Datum
int4xor(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg1 ^ arg2);
}

Datum
int4shl(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg1 << arg2);
}

Datum
int4shr(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg1 >> arg2);
}

Datum
int4not(PG_FUNCTION_ARGS)
{
    int32       arg1 = PG_GETARG_INT32(0);

    PG_RETURN_INT32(~arg1);
}

Datum
int2and(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_INT16(arg1 & arg2);
}

Datum
int2or(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_INT16(arg1 | arg2);
}

Datum
int2xor(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int16       arg2 = PG_GETARG_INT16(1);

    PG_RETURN_INT16(arg1 ^ arg2);
}

Datum
int2not(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);

    PG_RETURN_INT16(~arg1);
}


Datum
int2shl(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT16(arg1 << arg2);
}

Datum
int2shr(PG_FUNCTION_ARGS)
{
    int16       arg1 = PG_GETARG_INT16(0);
    int32       arg2 = PG_GETARG_INT32(1);

    PG_RETURN_INT16(arg1 >> arg2);
}

/*
 * non-persistent numeric series generator
 */
Datum
generate_series_int4(PG_FUNCTION_ARGS)
{
    return generate_series_step_int4(fcinfo);
}

Datum
generate_series_step_int4(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    generate_series_fctx *fctx;
    int32       result;
    MemoryContext oldcontext;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        int32       start = PG_GETARG_INT32(0);
        int32       finish = PG_GETARG_INT32(1);
        int32       step = 1;

        /* see if we were given an explicit step size */
        if (PG_NARGS() == 3)
            step = PG_GETARG_INT32(2);
        if (step == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("step size cannot equal zero")));

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* allocate memory for user context */
        fctx = (generate_series_fctx *) palloc(sizeof(generate_series_fctx));

        /*
         * Use fctx to keep state from call to call. Seed current with the
         * original start value
         */
        fctx->current = start;
        fctx->finish = finish;
        fctx->step = step;

        funcctx->user_fctx = fctx;
        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();

    /*
     * get the saved state and use current as the result for this iteration
     */
    fctx = funcctx->user_fctx;
    result = fctx->current;

    if ((fctx->step > 0 && fctx->current <= fctx->finish) ||
        (fctx->step < 0 && fctx->current >= fctx->finish))
    {
        /* increment current in preparation for next iteration */
        fctx->current += fctx->step;

        /* if next-value computation overflows, this is the final result */
        if (SAMESIGN(result, fctx->step) && !SAMESIGN(result, fctx->current))
            fctx->step = 0;

        /* do when there is more left to send */
        SRF_RETURN_NEXT(funcctx, Int32GetDatum(result));
    }
    else
        /* do when there is no more left */
        SRF_RETURN_DONE(funcctx);
}