varbit.c

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/*-------------------------------------------------------------------------
 *
 * varbit.c
 *    Functions for the SQL datatypes BIT() and BIT VARYING().
 *
 * The data structure contains the following elements:
 *   header  -- length of the whole data structure (incl header)
 *              in bytes (as with all varying length datatypes)
 *   data section -- private data section for the bits data structures
 *     bitlength -- length of the bit string in bits
 *     bitdata   -- bit string, most significant byte first
 *
 * The length of the bitdata vector should always be exactly as many
 * bytes as are needed for the given bitlength.  If the bitlength is
 * not a multiple of 8, the extra low-order padding bits of the last
 * byte must be zeroes.
 *
 * attypmod is defined as the length of the bit string in bits, or for
 * varying bits the maximum length.
 *
 * Code originally contributed by Adriaan Joubert.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/varbit.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/htup_details.h"
#include "common/int.h"
#include "libpq/pqformat.h"
#include "nodes/nodeFuncs.h"
#include "nodes/supportnodes.h"
#include "port/pg_bitutils.h"
#include "utils/array.h"
#include "utils/fmgrprotos.h"
#include "utils/varbit.h"
 
#define HEXDIG(z)    ((z)<10 ? ((z)+'0') : ((z)-10+'A'))
 
/* Mask off any bits that should be zero in the last byte of a bitstring */
#define VARBIT_PAD(vb) \
    do { \
        int32   pad_ = VARBITPAD(vb); \
        Assert(pad_ >= 0 && pad_ < BITS_PER_BYTE); \
        if (pad_ > 0) \
            *(VARBITS(vb) + VARBITBYTES(vb) - 1) &= BITMASK << pad_; \
    } while (0)
 
/*
 * Many functions work byte-by-byte, so they have a pointer handy to the
 * last-plus-one byte, which saves a cycle or two.
 */
#define VARBIT_PAD_LAST(vb, ptr) \
    do { \
        int32   pad_ = VARBITPAD(vb); \
        Assert(pad_ >= 0 && pad_ < BITS_PER_BYTE); \
        if (pad_ > 0) \
            *((ptr) - 1) &= BITMASK << pad_; \
    } while (0)
 
/* Assert proper padding of a bitstring */
#ifdef USE_ASSERT_CHECKING
#define VARBIT_CORRECTLY_PADDED(vb) \
    do { \
        int32   pad_ = VARBITPAD(vb); \
        Assert(pad_ >= 0 && pad_ < BITS_PER_BYTE); \
        Assert(pad_ == 0 || \
               (*(VARBITS(vb) + VARBITBYTES(vb) - 1) & ~(BITMASK << pad_)) == 0); \
    } while (0)
#else
#define VARBIT_CORRECTLY_PADDED(vb) ((void) 0)
#endif
 
static VarBit *bit_catenate(VarBit *arg1, VarBit *arg2);
static VarBit *bitsubstring(VarBit *arg, int32 s, int32 l,
                            bool length_not_specified);
static VarBit *bit_overlay(VarBit *t1, VarBit *t2, int sp, int sl);
 
 
/*
 * common code for bittypmodin and varbittypmodin
 */
static int32
anybit_typmodin(ArrayType *ta, const char *typename)
{
    int32       typmod;
    int32      *tl;
    int         n;
 
    tl = ArrayGetIntegerTypmods(ta, &n);
 
    /*
     * we're not too tense about good error message here because grammar
     * shouldn't allow wrong number of modifiers for BIT
     */
    if (n != 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("invalid type modifier")));
 
    if (*tl < 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("length for type %s must be at least 1",
                        typename)));
    if (*tl > (MaxAttrSize * BITS_PER_BYTE))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("length for type %s cannot exceed %d",
                        typename, MaxAttrSize * BITS_PER_BYTE)));
 
    typmod = *tl;
 
    return typmod;
}
 
/*
 * common code for bittypmodout and varbittypmodout
 */
static char *
anybit_typmodout(int32 typmod)
{
    char       *res = (char *) palloc(64);
 
    if (typmod >= 0)
        snprintf(res, 64, "(%d)", typmod);
    else
        *res = '\0';
 
    return res;
}
 
 
/*
 * bit_in -
 *    converts a char string to the internal representation of a bitstring.
 *        The length is determined by the number of bits required plus
 *        VARHDRSZ bytes or from atttypmod.
 */
Datum
bit_in(PG_FUNCTION_ARGS)
{
    char       *input_string = PG_GETARG_CSTRING(0);
#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       atttypmod = PG_GETARG_INT32(2);
    Node       *escontext = fcinfo->context;
    VarBit     *result;         /* The resulting bit string           */
    char       *sp;             /* pointer into the character string  */
    bits8      *r;              /* pointer into the result */
    int         len,            /* Length of the whole data structure */
                bitlen,         /* Number of bits in the bit string   */
                slen;           /* Length of the input string         */
    bool        bit_not_hex;    /* false = hex string  true = bit string */
    int         bc;
    bits8       x = 0;
 
    /* Check that the first character is a b or an x */
    if (input_string[0] == 'b' || input_string[0] == 'B')
    {
        bit_not_hex = true;
        sp = input_string + 1;
    }
    else if (input_string[0] == 'x' || input_string[0] == 'X')
    {
        bit_not_hex = false;
        sp = input_string + 1;
    }
    else
    {
        /*
         * Otherwise it's binary.  This allows things like cast('1001' as bit)
         * to work transparently.
         */
        bit_not_hex = true;
        sp = input_string;
    }
 
    /*
     * Determine bitlength from input string.  MaxAllocSize ensures a regular
     * input is small enough, but we must check hex input.
     */
    slen = strlen(sp);
    if (bit_not_hex)
        bitlen = slen;
    else
    {
        if (slen > VARBITMAXLEN / 4)
            ereturn(escontext, (Datum) 0,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("bit string length exceeds the maximum allowed (%d)",
                            VARBITMAXLEN)));
        bitlen = slen * 4;
    }
 
    /*
     * Sometimes atttypmod is not supplied. If it is supplied we need to make
     * sure that the bitstring fits.
     */
    if (atttypmod <= 0)
        atttypmod = bitlen;
    else if (bitlen != atttypmod)
        ereturn(escontext, (Datum) 0,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("bit string length %d does not match type bit(%d)",
                        bitlen, atttypmod)));
 
    len = VARBITTOTALLEN(atttypmod);
    /* set to 0 so that *r is always initialised and string is zero-padded */
    result = (VarBit *) palloc0(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = atttypmod;
 
    r = VARBITS(result);
    if (bit_not_hex)
    {
        /* Parse the bit representation of the string */
        /* We know it fits, as bitlen was compared to atttypmod */
        x = HIGHBIT;
        for (; *sp; sp++)
        {
            if (*sp == '1')
                *r |= x;
            else if (*sp != '0')
                ereturn(escontext, (Datum) 0,
                        (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                         errmsg("\"%.*s\" is not a valid binary digit",
                                pg_mblen(sp), sp)));
 
            x >>= 1;
            if (x == 0)
            {
                x = HIGHBIT;
                r++;
            }
        }
    }
    else
    {
        /* Parse the hex representation of the string */
        for (bc = 0; *sp; sp++)
        {
            if (*sp >= '0' && *sp <= '9')
                x = (bits8) (*sp - '0');
            else if (*sp >= 'A' && *sp <= 'F')
                x = (bits8) (*sp - 'A') + 10;
            else if (*sp >= 'a' && *sp <= 'f')
                x = (bits8) (*sp - 'a') + 10;
            else
                ereturn(escontext, (Datum) 0,
                        (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                         errmsg("\"%.*s\" is not a valid hexadecimal digit",
                                pg_mblen(sp), sp)));
 
            if (bc)
            {
                *r++ |= x;
                bc = 0;
            }
            else
            {
                *r = x << 4;
                bc = 1;
            }
        }
    }
 
    PG_RETURN_VARBIT_P(result);
}
 
 
Datum
bit_out(PG_FUNCTION_ARGS)
{
#if 1
    /* same as varbit output */
    return varbit_out(fcinfo);
#else
 
    /*
     * This is how one would print a hex string, in case someone wants to
     * write a formatting function.
     */
    VarBit     *s = PG_GETARG_VARBIT_P(0);
    char       *result,
               *r;
    bits8      *sp;
    int         i,
                len,
                bitlen;
 
    /* Assertion to help catch any bit functions that don't pad correctly */
    VARBIT_CORRECTLY_PADDED(s);
 
    bitlen = VARBITLEN(s);
    len = (bitlen + 3) / 4;
    result = (char *) palloc(len + 2);
    sp = VARBITS(s);
    r = result;
    *r++ = 'X';
    /* we cheat by knowing that we store full bytes zero padded */
    for (i = 0; i < len; i += 2, sp++)
    {
        *r++ = HEXDIG((*sp) >> 4);
        *r++ = HEXDIG((*sp) & 0xF);
    }
 
    /*
     * Go back one step if we printed a hex number that was not part of the
     * bitstring anymore
     */
    if (i > len)
        r--;
    *r = '\0';
 
    PG_RETURN_CSTRING(result);
#endif
}
 
/*
 *      bit_recv            - converts external binary format to bit
 */
Datum
bit_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
 
#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       atttypmod = PG_GETARG_INT32(2);
    VarBit     *result;
    int         len,
                bitlen;
 
    bitlen = pq_getmsgint(buf, sizeof(int32));
    if (bitlen < 0 || bitlen > VARBITMAXLEN)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                 errmsg("invalid length in external bit string")));
 
    /*
     * Sometimes atttypmod is not supplied. If it is supplied we need to make
     * sure that the bitstring fits.
     */
    if (atttypmod > 0 && bitlen != atttypmod)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("bit string length %d does not match type bit(%d)",
                        bitlen, atttypmod)));
 
    len = VARBITTOTALLEN(bitlen);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen;
 
    pq_copymsgbytes(buf, VARBITS(result), VARBITBYTES(result));
 
    /* Make sure last byte is correctly zero-padded */
    VARBIT_PAD(result);
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 *      bit_send            - converts bit to binary format
 */
Datum
bit_send(PG_FUNCTION_ARGS)
{
    /* Exactly the same as varbit_send, so share code */
    return varbit_send(fcinfo);
}
 
/*
 * bit()
 * Converts a bit() type to a specific internal length.
 * len is the bitlength specified in the column definition.
 *
 * If doing implicit cast, raise error when source data is wrong length.
 * If doing explicit cast, silently truncate or zero-pad to specified length.
 */
Datum
bit(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    int32       len = PG_GETARG_INT32(1);
    bool        isExplicit = PG_GETARG_BOOL(2);
    VarBit     *result;
    int         rlen;
 
    /* No work if typmod is invalid or supplied data matches it already */
    if (len <= 0 || len > VARBITMAXLEN || len == VARBITLEN(arg))
        PG_RETURN_VARBIT_P(arg);
 
    if (!isExplicit)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("bit string length %d does not match type bit(%d)",
                        VARBITLEN(arg), len)));
 
    rlen = VARBITTOTALLEN(len);
    /* set to 0 so that string is zero-padded */
    result = (VarBit *) palloc0(rlen);
    SET_VARSIZE(result, rlen);
    VARBITLEN(result) = len;
 
    memcpy(VARBITS(result), VARBITS(arg),
           Min(VARBITBYTES(result), VARBITBYTES(arg)));
 
    /*
     * Make sure last byte is zero-padded if needed.  This is useless but safe
     * if source data was shorter than target length (we assume the last byte
     * of the source data was itself correctly zero-padded).
     */
    VARBIT_PAD(result);
 
    PG_RETURN_VARBIT_P(result);
}
 
Datum
bittypmodin(PG_FUNCTION_ARGS)
{
    ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
 
    PG_RETURN_INT32(anybit_typmodin(ta, "bit"));
}
 
Datum
bittypmodout(PG_FUNCTION_ARGS)
{
    int32       typmod = PG_GETARG_INT32(0);
 
    PG_RETURN_CSTRING(anybit_typmodout(typmod));
}
 
 
/*
 * varbit_in -
 *    converts a string to the internal representation of a bitstring.
 *      This is the same as bit_in except that atttypmod is taken as
 *      the maximum length, not the exact length to force the bitstring to.
 */
Datum
varbit_in(PG_FUNCTION_ARGS)
{
    char       *input_string = PG_GETARG_CSTRING(0);
#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       atttypmod = PG_GETARG_INT32(2);
    Node       *escontext = fcinfo->context;
    VarBit     *result;         /* The resulting bit string           */
    char       *sp;             /* pointer into the character string  */
    bits8      *r;              /* pointer into the result */
    int         len,            /* Length of the whole data structure */
                bitlen,         /* Number of bits in the bit string   */
                slen;           /* Length of the input string         */
    bool        bit_not_hex;    /* false = hex string  true = bit string */
    int         bc;
    bits8       x = 0;
 
    /* Check that the first character is a b or an x */
    if (input_string[0] == 'b' || input_string[0] == 'B')
    {
        bit_not_hex = true;
        sp = input_string + 1;
    }
    else if (input_string[0] == 'x' || input_string[0] == 'X')
    {
        bit_not_hex = false;
        sp = input_string + 1;
    }
    else
    {
        bit_not_hex = true;
        sp = input_string;
    }
 
    /*
     * Determine bitlength from input string.  MaxAllocSize ensures a regular
     * input is small enough, but we must check hex input.
     */
    slen = strlen(sp);
    if (bit_not_hex)
        bitlen = slen;
    else
    {
        if (slen > VARBITMAXLEN / 4)
            ereturn(escontext, (Datum) 0,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("bit string length exceeds the maximum allowed (%d)",
                            VARBITMAXLEN)));
        bitlen = slen * 4;
    }
 
    /*
     * Sometimes atttypmod is not supplied. If it is supplied we need to make
     * sure that the bitstring fits.
     */
    if (atttypmod <= 0)
        atttypmod = bitlen;
    else if (bitlen > atttypmod)
        ereturn(escontext, (Datum) 0,
                (errcode(ERRCODE_STRING_DATA_RIGHT_TRUNCATION),
                 errmsg("bit string too long for type bit varying(%d)",
                        atttypmod)));
 
    len = VARBITTOTALLEN(bitlen);
    /* set to 0 so that *r is always initialised and string is zero-padded */
    result = (VarBit *) palloc0(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = Min(bitlen, atttypmod);
 
    r = VARBITS(result);
    if (bit_not_hex)
    {
        /* Parse the bit representation of the string */
        /* We know it fits, as bitlen was compared to atttypmod */
        x = HIGHBIT;
        for (; *sp; sp++)
        {
            if (*sp == '1')
                *r |= x;
            else if (*sp != '0')
                ereturn(escontext, (Datum) 0,
                        (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                         errmsg("\"%.*s\" is not a valid binary digit",
                                pg_mblen(sp), sp)));
 
            x >>= 1;
            if (x == 0)
            {
                x = HIGHBIT;
                r++;
            }
        }
    }
    else
    {
        /* Parse the hex representation of the string */
        for (bc = 0; *sp; sp++)
        {
            if (*sp >= '0' && *sp <= '9')
                x = (bits8) (*sp - '0');
            else if (*sp >= 'A' && *sp <= 'F')
                x = (bits8) (*sp - 'A') + 10;
            else if (*sp >= 'a' && *sp <= 'f')
                x = (bits8) (*sp - 'a') + 10;
            else
                ereturn(escontext, (Datum) 0,
                        (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                         errmsg("\"%.*s\" is not a valid hexadecimal digit",
                                pg_mblen(sp), sp)));
 
            if (bc)
            {
                *r++ |= x;
                bc = 0;
            }
            else
            {
                *r = x << 4;
                bc = 1;
            }
        }
    }
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * varbit_out -
 *    Prints the string as bits to preserve length accurately
 *
 * XXX varbit_recv() and hex input to varbit_in() can load a value that this
 * cannot emit.  Consider using hex output for such values.
 */
Datum
varbit_out(PG_FUNCTION_ARGS)
{
    VarBit     *s = PG_GETARG_VARBIT_P(0);
    char       *result,
               *r;
    bits8      *sp;
    bits8       x;
    int         i,
                k,
                len;
 
    /* Assertion to help catch any bit functions that don't pad correctly */
    VARBIT_CORRECTLY_PADDED(s);
 
    len = VARBITLEN(s);
    result = (char *) palloc(len + 1);
    sp = VARBITS(s);
    r = result;
    for (i = 0; i <= len - BITS_PER_BYTE; i += BITS_PER_BYTE, sp++)
    {
        /* print full bytes */
        x = *sp;
        for (k = 0; k < BITS_PER_BYTE; k++)
        {
            *r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
            x <<= 1;
        }
    }
    if (i < len)
    {
        /* print the last partial byte */
        x = *sp;
        for (k = i; k < len; k++)
        {
            *r++ = IS_HIGHBIT_SET(x) ? '1' : '0';
            x <<= 1;
        }
    }
    *r = '\0';
 
    PG_RETURN_CSTRING(result);
}
 
/*
 *      varbit_recv         - converts external binary format to varbit
 *
 * External format is the bitlen as an int32, then the byte array.
 */
Datum
varbit_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
 
#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       atttypmod = PG_GETARG_INT32(2);
    VarBit     *result;
    int         len,
                bitlen;
 
    bitlen = pq_getmsgint(buf, sizeof(int32));
    if (bitlen < 0 || bitlen > VARBITMAXLEN)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                 errmsg("invalid length in external bit string")));
 
    /*
     * Sometimes atttypmod is not supplied. If it is supplied we need to make
     * sure that the bitstring fits.
     */
    if (atttypmod > 0 && bitlen > atttypmod)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_RIGHT_TRUNCATION),
                 errmsg("bit string too long for type bit varying(%d)",
                        atttypmod)));
 
    len = VARBITTOTALLEN(bitlen);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen;
 
    pq_copymsgbytes(buf, VARBITS(result), VARBITBYTES(result));
 
    /* Make sure last byte is correctly zero-padded */
    VARBIT_PAD(result);
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 *      varbit_send         - converts varbit to binary format
 */
Datum
varbit_send(PG_FUNCTION_ARGS)
{
    VarBit     *s = PG_GETARG_VARBIT_P(0);
    StringInfoData buf;
 
    pq_begintypsend(&buf);
    pq_sendint32(&buf, VARBITLEN(s));
    pq_sendbytes(&buf, VARBITS(s), VARBITBYTES(s));
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}
 
/*
 * varbit_support()
 *
 * Planner support function for the varbit() length coercion function.
 *
 * Currently, the only interesting thing we can do is flatten calls that set
 * the new maximum length >= the previous maximum length.  We can ignore the
 * isExplicit argument, since that only affects truncation cases.
 */
Datum
varbit_support(PG_FUNCTION_ARGS)
{
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
    Node       *ret = NULL;
 
    if (IsA(rawreq, SupportRequestSimplify))
    {
        SupportRequestSimplify *req = (SupportRequestSimplify *) rawreq;
        FuncExpr   *expr = req->fcall;
        Node       *typmod;
 
        Assert(list_length(expr->args) >= 2);
 
        typmod = (Node *) lsecond(expr->args);
 
        if (IsA(typmod, Const) && !((Const *) typmod)->constisnull)
        {
            Node       *source = (Node *) linitial(expr->args);
            int32       new_typmod = DatumGetInt32(((Const *) typmod)->constvalue);
            int32       old_max = exprTypmod(source);
            int32       new_max = new_typmod;
 
            /* Note: varbit() treats typmod 0 as invalid, so we do too */
            if (new_max <= 0 || (old_max > 0 && old_max <= new_max))
                ret = relabel_to_typmod(source, new_typmod);
        }
    }
 
    PG_RETURN_POINTER(ret);
}
 
/*
 * varbit()
 * Converts a varbit() type to a specific internal length.
 * len is the maximum bitlength specified in the column definition.
 *
 * If doing implicit cast, raise error when source data is too long.
 * If doing explicit cast, silently truncate to max length.
 */
Datum
varbit(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    int32       len = PG_GETARG_INT32(1);
    bool        isExplicit = PG_GETARG_BOOL(2);
    VarBit     *result;
    int         rlen;
 
    /* No work if typmod is invalid or supplied data matches it already */
    if (len <= 0 || len >= VARBITLEN(arg))
        PG_RETURN_VARBIT_P(arg);
 
    if (!isExplicit)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_RIGHT_TRUNCATION),
                 errmsg("bit string too long for type bit varying(%d)",
                        len)));
 
    rlen = VARBITTOTALLEN(len);
    result = (VarBit *) palloc(rlen);
    SET_VARSIZE(result, rlen);
    VARBITLEN(result) = len;
 
    memcpy(VARBITS(result), VARBITS(arg), VARBITBYTES(result));
 
    /* Make sure last byte is correctly zero-padded */
    VARBIT_PAD(result);
 
    PG_RETURN_VARBIT_P(result);
}
 
Datum
varbittypmodin(PG_FUNCTION_ARGS)
{
    ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
 
    PG_RETURN_INT32(anybit_typmodin(ta, "varbit"));
}
 
Datum
varbittypmodout(PG_FUNCTION_ARGS)
{
    int32       typmod = PG_GETARG_INT32(0);
 
    PG_RETURN_CSTRING(anybit_typmodout(typmod));
}
 
 
/*
 * Comparison operators
 *
 * We only need one set of comparison operators for bitstrings, as the lengths
 * are stored in the same way for zero-padded and varying bit strings.
 *
 * Note that the standard is not unambiguous about the comparison between
 * zero-padded bit strings and varying bitstrings. If the same value is written
 * into a zero padded bitstring as into a varying bitstring, but the zero
 * padded bitstring has greater length, it will be bigger.
 *
 * Zeros from the beginning of a bitstring cannot simply be ignored, as they
 * may be part of a bit string and may be significant.
 *
 * Note: btree indexes need these routines not to leak memory; therefore,
 * be careful to free working copies of toasted datums.  Most places don't
 * need to be so careful.
 */
 
/*
 * bit_cmp
 *
 * Compares two bitstrings and returns <0, 0, >0 depending on whether the first
 * string is smaller, equal, or bigger than the second. All bits are considered
 * and additional zero bits may make one string smaller/larger than the other,
 * even if their zero-padded values would be the same.
 */
static int32
bit_cmp(VarBit *arg1, VarBit *arg2)
{
    int         bitlen1,
                bytelen1,
                bitlen2,
                bytelen2;
    int32       cmp;
 
    bytelen1 = VARBITBYTES(arg1);
    bytelen2 = VARBITBYTES(arg2);
 
    cmp = memcmp(VARBITS(arg1), VARBITS(arg2), Min(bytelen1, bytelen2));
    if (cmp == 0)
    {
        bitlen1 = VARBITLEN(arg1);
        bitlen2 = VARBITLEN(arg2);
        if (bitlen1 != bitlen2)
            cmp = (bitlen1 < bitlen2) ? -1 : 1;
    }
    return cmp;
}
 
Datum
biteq(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
    int         bitlen1,
                bitlen2;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
 
    /* fast path for different-length inputs */
    if (bitlen1 != bitlen2)
        result = false;
    else
        result = (bit_cmp(arg1, arg2) == 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitne(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
    int         bitlen1,
                bitlen2;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
 
    /* fast path for different-length inputs */
    if (bitlen1 != bitlen2)
        result = true;
    else
        result = (bit_cmp(arg1, arg2) != 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitlt(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
 
    result = (bit_cmp(arg1, arg2) < 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitle(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
 
    result = (bit_cmp(arg1, arg2) <= 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitgt(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
 
    result = (bit_cmp(arg1, arg2) > 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitge(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    bool        result;
 
    result = (bit_cmp(arg1, arg2) >= 0);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_BOOL(result);
}
 
Datum
bitcmp(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    int32       result;
 
    result = bit_cmp(arg1, arg2);
 
    PG_FREE_IF_COPY(arg1, 0);
    PG_FREE_IF_COPY(arg2, 1);
 
    PG_RETURN_INT32(result);
}
 
/*
 * bitcat
 * Concatenation of bit strings
 */
Datum
bitcat(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
 
    PG_RETURN_VARBIT_P(bit_catenate(arg1, arg2));
}
 
static VarBit *
bit_catenate(VarBit *arg1, VarBit *arg2)
{
    VarBit     *result;
    int         bitlen1,
                bitlen2,
                bytelen,
                bit1pad,
                bit2shift;
    bits8      *pr,
               *pa;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
 
    if (bitlen1 > VARBITMAXLEN - bitlen2)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("bit string length exceeds the maximum allowed (%d)",
                        VARBITMAXLEN)));
    bytelen = VARBITTOTALLEN(bitlen1 + bitlen2);
 
    result = (VarBit *) palloc(bytelen);
    SET_VARSIZE(result, bytelen);
    VARBITLEN(result) = bitlen1 + bitlen2;
 
    /* Copy the first bitstring in */
    memcpy(VARBITS(result), VARBITS(arg1), VARBITBYTES(arg1));
 
    /* Copy the second bit string */
    bit1pad = VARBITPAD(arg1);
    if (bit1pad == 0)
    {
        memcpy(VARBITS(result) + VARBITBYTES(arg1), VARBITS(arg2),
               VARBITBYTES(arg2));
    }
    else if (bitlen2 > 0)
    {
        /* We need to shift all the bits to fit */
        bit2shift = BITS_PER_BYTE - bit1pad;
        pr = VARBITS(result) + VARBITBYTES(arg1) - 1;
        for (pa = VARBITS(arg2); pa < VARBITEND(arg2); pa++)
        {
            *pr |= ((*pa >> bit2shift) & BITMASK);
            pr++;
            if (pr < VARBITEND(result))
                *pr = (*pa << bit1pad) & BITMASK;
        }
    }
 
    /* The pad bits should be already zero at this point */
 
    return result;
}
 
/*
 * bitsubstr
 * retrieve a substring from the bit string.
 * Note, s is 1-based.
 * SQL draft 6.10 9)
 */
Datum
bitsubstr(PG_FUNCTION_ARGS)
{
    PG_RETURN_VARBIT_P(bitsubstring(PG_GETARG_VARBIT_P(0),
                                    PG_GETARG_INT32(1),
                                    PG_GETARG_INT32(2),
                                    false));
}
 
Datum
bitsubstr_no_len(PG_FUNCTION_ARGS)
{
    PG_RETURN_VARBIT_P(bitsubstring(PG_GETARG_VARBIT_P(0),
                                    PG_GETARG_INT32(1),
                                    -1, true));
}
 
static VarBit *
bitsubstring(VarBit *arg, int32 s, int32 l, bool length_not_specified)
{
    VarBit     *result;
    int         bitlen,
                rbitlen,
                len,
                ishift,
                i;
    int32       e,
                s1,
                e1;
    bits8      *r,
               *ps;
 
    bitlen = VARBITLEN(arg);
    s1 = Max(s, 1);
    /* If we do not have an upper bound, use end of string */
    if (length_not_specified)
    {
        e1 = bitlen + 1;
    }
    else if (l < 0)
    {
        /* SQL99 says to throw an error for E < S, i.e., negative length */
        ereport(ERROR,
                (errcode(ERRCODE_SUBSTRING_ERROR),
                 errmsg("negative substring length not allowed")));
        e1 = -1;                /* silence stupider compilers */
    }
    else if (pg_add_s32_overflow(s, l, &e))
    {
        /*
         * L could be large enough for S + L to overflow, in which case the
         * substring must run to end of string.
         */
        e1 = bitlen + 1;
    }
    else
    {
        e1 = Min(e, bitlen + 1);
    }
    if (s1 > bitlen || e1 <= s1)
    {
        /* Need to return a zero-length bitstring */
        len = VARBITTOTALLEN(0);
        result = (VarBit *) palloc(len);
        SET_VARSIZE(result, len);
        VARBITLEN(result) = 0;
    }
    else
    {
        /*
         * OK, we've got a true substring starting at position s1-1 and ending
         * at position e1-1
         */
        rbitlen = e1 - s1;
        len = VARBITTOTALLEN(rbitlen);
        result = (VarBit *) palloc(len);
        SET_VARSIZE(result, len);
        VARBITLEN(result) = rbitlen;
        len -= VARHDRSZ + VARBITHDRSZ;
        /* Are we copying from a byte boundary? */
        if ((s1 - 1) % BITS_PER_BYTE == 0)
        {
            /* Yep, we are copying bytes */
            memcpy(VARBITS(result), VARBITS(arg) + (s1 - 1) / BITS_PER_BYTE,
                   len);
        }
        else
        {
            /* Figure out how much we need to shift the sequence by */
            ishift = (s1 - 1) % BITS_PER_BYTE;
            r = VARBITS(result);
            ps = VARBITS(arg) + (s1 - 1) / BITS_PER_BYTE;
            for (i = 0; i < len; i++)
            {
                *r = (*ps << ishift) & BITMASK;
                if ((++ps) < VARBITEND(arg))
                    *r |= *ps >> (BITS_PER_BYTE - ishift);
                r++;
            }
        }
 
        /* Make sure last byte is correctly zero-padded */
        VARBIT_PAD(result);
    }
 
    return result;
}
 
/*
 * bitoverlay
 *  Replace specified substring of first string with second
 *
 * The SQL standard defines OVERLAY() in terms of substring and concatenation.
 * This code is a direct implementation of what the standard says.
 */
Datum
bitoverlay(PG_FUNCTION_ARGS)
{
    VarBit     *t1 = PG_GETARG_VARBIT_P(0);
    VarBit     *t2 = PG_GETARG_VARBIT_P(1);
    int         sp = PG_GETARG_INT32(2);    /* substring start position */
    int         sl = PG_GETARG_INT32(3);    /* substring length */
 
    PG_RETURN_VARBIT_P(bit_overlay(t1, t2, sp, sl));
}
 
Datum
bitoverlay_no_len(PG_FUNCTION_ARGS)
{
    VarBit     *t1 = PG_GETARG_VARBIT_P(0);
    VarBit     *t2 = PG_GETARG_VARBIT_P(1);
    int         sp = PG_GETARG_INT32(2);    /* substring start position */
    int         sl;
 
    sl = VARBITLEN(t2);         /* defaults to length(t2) */
    PG_RETURN_VARBIT_P(bit_overlay(t1, t2, sp, sl));
}
 
static VarBit *
bit_overlay(VarBit *t1, VarBit *t2, int sp, int sl)
{
    VarBit     *result;
    VarBit     *s1;
    VarBit     *s2;
    int         sp_pl_sl;
 
    /*
     * Check for possible integer-overflow cases.  For negative sp, throw a
     * "substring length" error because that's what should be expected
     * according to the spec's definition of OVERLAY().
     */
    if (sp <= 0)
        ereport(ERROR,
                (errcode(ERRCODE_SUBSTRING_ERROR),
                 errmsg("negative substring length not allowed")));
    if (pg_add_s32_overflow(sp, sl, &sp_pl_sl))
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
 
    s1 = bitsubstring(t1, 1, sp - 1, false);
    s2 = bitsubstring(t1, sp_pl_sl, -1, true);
    result = bit_catenate(s1, t2);
    result = bit_catenate(result, s2);
 
    return result;
}
 
/*
 * bit_count
 *
 * Returns the number of bits set in a bit string.
 */
Datum
bit_bit_count(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
 
    PG_RETURN_INT64(pg_popcount((char *) VARBITS(arg), VARBITBYTES(arg)));
}
 
/*
 * bitlength, bitoctetlength
 * Return the length of a bit string
 */
Datum
bitlength(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
 
    PG_RETURN_INT32(VARBITLEN(arg));
}
 
Datum
bitoctetlength(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
 
    PG_RETURN_INT32(VARBITBYTES(arg));
}
 
/*
 * bit_and
 * perform a logical AND on two bit strings.
 */
Datum
bit_and(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    VarBit     *result;
    int         len,
                bitlen1,
                bitlen2,
                i;
    bits8      *p1,
               *p2,
               *r;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
    if (bitlen1 != bitlen2)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("cannot AND bit strings of different sizes")));
 
    len = VARSIZE(arg1);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen1;
 
    p1 = VARBITS(arg1);
    p2 = VARBITS(arg2);
    r = VARBITS(result);
    for (i = 0; i < VARBITBYTES(arg1); i++)
        *r++ = *p1++ & *p2++;
 
    /* Padding is not needed as & of 0 pads is 0 */
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bit_or
 * perform a logical OR on two bit strings.
 */
Datum
bit_or(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    VarBit     *result;
    int         len,
                bitlen1,
                bitlen2,
                i;
    bits8      *p1,
               *p2,
               *r;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
    if (bitlen1 != bitlen2)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("cannot OR bit strings of different sizes")));
    len = VARSIZE(arg1);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen1;
 
    p1 = VARBITS(arg1);
    p2 = VARBITS(arg2);
    r = VARBITS(result);
    for (i = 0; i < VARBITBYTES(arg1); i++)
        *r++ = *p1++ | *p2++;
 
    /* Padding is not needed as | of 0 pads is 0 */
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bitxor
 * perform a logical XOR on two bit strings.
 */
Datum
bitxor(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    VarBit     *arg2 = PG_GETARG_VARBIT_P(1);
    VarBit     *result;
    int         len,
                bitlen1,
                bitlen2,
                i;
    bits8      *p1,
               *p2,
               *r;
 
    bitlen1 = VARBITLEN(arg1);
    bitlen2 = VARBITLEN(arg2);
    if (bitlen1 != bitlen2)
        ereport(ERROR,
                (errcode(ERRCODE_STRING_DATA_LENGTH_MISMATCH),
                 errmsg("cannot XOR bit strings of different sizes")));
 
    len = VARSIZE(arg1);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen1;
 
    p1 = VARBITS(arg1);
    p2 = VARBITS(arg2);
    r = VARBITS(result);
    for (i = 0; i < VARBITBYTES(arg1); i++)
        *r++ = *p1++ ^ *p2++;
 
    /* Padding is not needed as ^ of 0 pads is 0 */
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bitnot
 * perform a logical NOT on a bit string.
 */
Datum
bitnot(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    VarBit     *result;
    bits8      *p,
               *r;
 
    result = (VarBit *) palloc(VARSIZE(arg));
    SET_VARSIZE(result, VARSIZE(arg));
    VARBITLEN(result) = VARBITLEN(arg);
 
    p = VARBITS(arg);
    r = VARBITS(result);
    for (; p < VARBITEND(arg); p++)
        *r++ = ~*p;
 
    /* Must zero-pad the result, because extra bits are surely 1's here */
    VARBIT_PAD_LAST(result, r);
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bitshiftleft
 * do a left shift (i.e. towards the beginning of the string)
 */
Datum
bitshiftleft(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    int32       shft = PG_GETARG_INT32(1);
    VarBit     *result;
    int         byte_shift,
                ishift,
                len;
    bits8      *p,
               *r;
 
    /* Negative shift is a shift to the right */
    if (shft < 0)
    {
        /* Prevent integer overflow in negation */
        if (shft < -VARBITMAXLEN)
            shft = -VARBITMAXLEN;
        PG_RETURN_DATUM(DirectFunctionCall2(bitshiftright,
                                            VarBitPGetDatum(arg),
                                            Int32GetDatum(-shft)));
    }
 
    result = (VarBit *) palloc(VARSIZE(arg));
    SET_VARSIZE(result, VARSIZE(arg));
    VARBITLEN(result) = VARBITLEN(arg);
    r = VARBITS(result);
 
    /* If we shifted all the bits out, return an all-zero string */
    if (shft >= VARBITLEN(arg))
    {
        MemSet(r, 0, VARBITBYTES(arg));
        PG_RETURN_VARBIT_P(result);
    }
 
    byte_shift = shft / BITS_PER_BYTE;
    ishift = shft % BITS_PER_BYTE;
    p = VARBITS(arg) + byte_shift;
 
    if (ishift == 0)
    {
        /* Special case: we can do a memcpy */
        len = VARBITBYTES(arg) - byte_shift;
        memcpy(r, p, len);
        MemSet(r + len, 0, byte_shift);
    }
    else
    {
        for (; p < VARBITEND(arg); r++)
        {
            *r = *p << ishift;
            if ((++p) < VARBITEND(arg))
                *r |= *p >> (BITS_PER_BYTE - ishift);
        }
        for (; r < VARBITEND(result); r++)
            *r = 0;
    }
 
    /* The pad bits should be already zero at this point */
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bitshiftright
 * do a right shift (i.e. towards the end of the string)
 */
Datum
bitshiftright(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    int32       shft = PG_GETARG_INT32(1);
    VarBit     *result;
    int         byte_shift,
                ishift,
                len;
    bits8      *p,
               *r;
 
    /* Negative shift is a shift to the left */
    if (shft < 0)
    {
        /* Prevent integer overflow in negation */
        if (shft < -VARBITMAXLEN)
            shft = -VARBITMAXLEN;
        PG_RETURN_DATUM(DirectFunctionCall2(bitshiftleft,
                                            VarBitPGetDatum(arg),
                                            Int32GetDatum(-shft)));
    }
 
    result = (VarBit *) palloc(VARSIZE(arg));
    SET_VARSIZE(result, VARSIZE(arg));
    VARBITLEN(result) = VARBITLEN(arg);
    r = VARBITS(result);
 
    /* If we shifted all the bits out, return an all-zero string */
    if (shft >= VARBITLEN(arg))
    {
        MemSet(r, 0, VARBITBYTES(arg));
        PG_RETURN_VARBIT_P(result);
    }
 
    byte_shift = shft / BITS_PER_BYTE;
    ishift = shft % BITS_PER_BYTE;
    p = VARBITS(arg);
 
    /* Set the first part of the result to 0 */
    MemSet(r, 0, byte_shift);
    r += byte_shift;
 
    if (ishift == 0)
    {
        /* Special case: we can do a memcpy */
        len = VARBITBYTES(arg) - byte_shift;
        memcpy(r, p, len);
        r += len;
    }
    else
    {
        if (r < VARBITEND(result))
            *r = 0;             /* initialize first byte */
        for (; r < VARBITEND(result); p++)
        {
            *r |= *p >> ishift;
            if ((++r) < VARBITEND(result))
                *r = (*p << (BITS_PER_BYTE - ishift)) & BITMASK;
        }
    }
 
    /* We may have shifted 1's into the pad bits, so fix that */
    VARBIT_PAD_LAST(result, r);
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * This is not defined in any standard. We retain the natural ordering of
 * bits here, as it just seems more intuitive.
 */
Datum
bitfromint4(PG_FUNCTION_ARGS)
{
    int32       a = PG_GETARG_INT32(0);
    int32       typmod = PG_GETARG_INT32(1);
    VarBit     *result;
    bits8      *r;
    int         rlen;
    int         destbitsleft,
                srcbitsleft;
 
    if (typmod <= 0 || typmod > VARBITMAXLEN)
        typmod = 1;             /* default bit length */
 
    rlen = VARBITTOTALLEN(typmod);
    result = (VarBit *) palloc(rlen);
    SET_VARSIZE(result, rlen);
    VARBITLEN(result) = typmod;
 
    r = VARBITS(result);
    destbitsleft = typmod;
    srcbitsleft = 32;
    /* drop any input bits that don't fit */
    srcbitsleft = Min(srcbitsleft, destbitsleft);
    /* sign-fill any excess bytes in output */
    while (destbitsleft >= srcbitsleft + 8)
    {
        *r++ = (bits8) ((a < 0) ? BITMASK : 0);
        destbitsleft -= 8;
    }
    /* store first fractional byte */
    if (destbitsleft > srcbitsleft)
    {
        unsigned int val = (unsigned int) (a >> (destbitsleft - 8));
 
        /* Force sign-fill in case the compiler implements >> as zero-fill */
        if (a < 0)
            val |= ((unsigned int) -1) << (srcbitsleft + 8 - destbitsleft);
        *r++ = (bits8) (val & BITMASK);
        destbitsleft -= 8;
    }
    /* Now srcbitsleft and destbitsleft are the same, need not track both */
    /* store whole bytes */
    while (destbitsleft >= 8)
    {
        *r++ = (bits8) ((a >> (destbitsleft - 8)) & BITMASK);
        destbitsleft -= 8;
    }
    /* store last fractional byte */
    if (destbitsleft > 0)
        *r = (bits8) ((a << (8 - destbitsleft)) & BITMASK);
 
    PG_RETURN_VARBIT_P(result);
}
 
Datum
bittoint4(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    uint32      result;
    bits8      *r;
 
    /* Check that the bit string is not too long */
    if (VARBITLEN(arg) > sizeof(result) * BITS_PER_BYTE)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("integer out of range")));
 
    result = 0;
    for (r = VARBITS(arg); r < VARBITEND(arg); r++)
    {
        result <<= BITS_PER_BYTE;
        result |= *r;
    }
    /* Now shift the result to take account of the padding at the end */
    result >>= VARBITPAD(arg);
 
    PG_RETURN_INT32(result);
}
 
Datum
bitfromint8(PG_FUNCTION_ARGS)
{
    int64       a = PG_GETARG_INT64(0);
    int32       typmod = PG_GETARG_INT32(1);
    VarBit     *result;
    bits8      *r;
    int         rlen;
    int         destbitsleft,
                srcbitsleft;
 
    if (typmod <= 0 || typmod > VARBITMAXLEN)
        typmod = 1;             /* default bit length */
 
    rlen = VARBITTOTALLEN(typmod);
    result = (VarBit *) palloc(rlen);
    SET_VARSIZE(result, rlen);
    VARBITLEN(result) = typmod;
 
    r = VARBITS(result);
    destbitsleft = typmod;
    srcbitsleft = 64;
    /* drop any input bits that don't fit */
    srcbitsleft = Min(srcbitsleft, destbitsleft);
    /* sign-fill any excess bytes in output */
    while (destbitsleft >= srcbitsleft + 8)
    {
        *r++ = (bits8) ((a < 0) ? BITMASK : 0);
        destbitsleft -= 8;
    }
    /* store first fractional byte */
    if (destbitsleft > srcbitsleft)
    {
        unsigned int val = (unsigned int) (a >> (destbitsleft - 8));
 
        /* Force sign-fill in case the compiler implements >> as zero-fill */
        if (a < 0)
            val |= ((unsigned int) -1) << (srcbitsleft + 8 - destbitsleft);
        *r++ = (bits8) (val & BITMASK);
        destbitsleft -= 8;
    }
    /* Now srcbitsleft and destbitsleft are the same, need not track both */
    /* store whole bytes */
    while (destbitsleft >= 8)
    {
        *r++ = (bits8) ((a >> (destbitsleft - 8)) & BITMASK);
        destbitsleft -= 8;
    }
    /* store last fractional byte */
    if (destbitsleft > 0)
        *r = (bits8) ((a << (8 - destbitsleft)) & BITMASK);
 
    PG_RETURN_VARBIT_P(result);
}
 
Datum
bittoint8(PG_FUNCTION_ARGS)
{
    VarBit     *arg = PG_GETARG_VARBIT_P(0);
    uint64      result;
    bits8      *r;
 
    /* Check that the bit string is not too long */
    if (VARBITLEN(arg) > sizeof(result) * BITS_PER_BYTE)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("bigint out of range")));
 
    result = 0;
    for (r = VARBITS(arg); r < VARBITEND(arg); r++)
    {
        result <<= BITS_PER_BYTE;
        result |= *r;
    }
    /* Now shift the result to take account of the padding at the end */
    result >>= VARBITPAD(arg);
 
    PG_RETURN_INT64(result);
}
 
 
/*
 * Determines the position of S2 in the bitstring S1 (1-based string).
 * If S2 does not appear in S1 this function returns 0.
 * If S2 is of length 0 this function returns 1.
 * Compatible in usage with POSITION() functions for other data types.
 */
Datum
bitposition(PG_FUNCTION_ARGS)
{
    VarBit     *str = PG_GETARG_VARBIT_P(0);
    VarBit     *substr = PG_GETARG_VARBIT_P(1);
    int         substr_length,
                str_length,
                i,
                is;
    bits8      *s,              /* pointer into substring */
               *p;              /* pointer into str */
    bits8       cmp,            /* shifted substring byte to compare */
                mask1,          /* mask for substring byte shifted right */
                mask2,          /* mask for substring byte shifted left */
                end_mask,       /* pad mask for last substring byte */
                str_mask;       /* pad mask for last string byte */
    bool        is_match;
 
    /* Get the substring length */
    substr_length = VARBITLEN(substr);
    str_length = VARBITLEN(str);
 
    /* String has zero length or substring longer than string, return 0 */
    if ((str_length == 0) || (substr_length > str_length))
        PG_RETURN_INT32(0);
 
    /* zero-length substring means return 1 */
    if (substr_length == 0)
        PG_RETURN_INT32(1);
 
    /* Initialise the padding masks */
    end_mask = BITMASK << VARBITPAD(substr);
    str_mask = BITMASK << VARBITPAD(str);
    for (i = 0; i < VARBITBYTES(str) - VARBITBYTES(substr) + 1; i++)
    {
        for (is = 0; is < BITS_PER_BYTE; is++)
        {
            is_match = true;
            p = VARBITS(str) + i;
            mask1 = BITMASK >> is;
            mask2 = ~mask1;
            for (s = VARBITS(substr);
                 is_match && s < VARBITEND(substr); s++)
            {
                cmp = *s >> is;
                if (s == VARBITEND(substr) - 1)
                {
                    mask1 &= end_mask >> is;
                    if (p == VARBITEND(str) - 1)
                    {
                        /* Check that there is enough of str left */
                        if (mask1 & ~str_mask)
                        {
                            is_match = false;
                            break;
                        }
                        mask1 &= str_mask;
                    }
                }
                is_match = ((cmp ^ *p) & mask1) == 0;
                if (!is_match)
                    break;
                /* Move on to the next byte */
                p++;
                if (p == VARBITEND(str))
                {
                    mask2 = end_mask << (BITS_PER_BYTE - is);
                    is_match = mask2 == 0;
#if 0
                    elog(DEBUG4, "S. %d %d em=%2x sm=%2x r=%d",
                         i, is, end_mask, mask2, is_match);
#endif
                    break;
                }
                cmp = *s << (BITS_PER_BYTE - is);
                if (s == VARBITEND(substr) - 1)
                {
                    mask2 &= end_mask << (BITS_PER_BYTE - is);
                    if (p == VARBITEND(str) - 1)
                    {
                        if (mask2 & ~str_mask)
                        {
                            is_match = false;
                            break;
                        }
                        mask2 &= str_mask;
                    }
                }
                is_match = ((cmp ^ *p) & mask2) == 0;
            }
            /* Have we found a match? */
            if (is_match)
                PG_RETURN_INT32(i * BITS_PER_BYTE + is + 1);
        }
    }
    PG_RETURN_INT32(0);
}
 
 
/*
 * bitsetbit
 *
 * Given an instance of type 'bit' creates a new one with
 * the Nth bit set to the given value.
 *
 * The bit location is specified left-to-right in a zero-based fashion
 * consistent with the other get_bit and set_bit functions, but
 * inconsistent with the standard substring, position, overlay functions
 */
Datum
bitsetbit(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    int32       n = PG_GETARG_INT32(1);
    int32       newBit = PG_GETARG_INT32(2);
    VarBit     *result;
    int         len,
                bitlen;
    bits8      *r,
               *p;
    int         byteNo,
                bitNo;
 
    bitlen = VARBITLEN(arg1);
    if (n < 0 || n >= bitlen)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("bit index %d out of valid range (0..%d)",
                        n, bitlen - 1)));
 
    /*
     * sanity check!
     */
    if (newBit != 0 && newBit != 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("new bit must be 0 or 1")));
 
    len = VARSIZE(arg1);
    result = (VarBit *) palloc(len);
    SET_VARSIZE(result, len);
    VARBITLEN(result) = bitlen;
 
    p = VARBITS(arg1);
    r = VARBITS(result);
 
    memcpy(r, p, VARBITBYTES(arg1));
 
    byteNo = n / BITS_PER_BYTE;
    bitNo = BITS_PER_BYTE - 1 - (n % BITS_PER_BYTE);
 
    /*
     * Update the byte.
     */
    if (newBit == 0)
        r[byteNo] &= (~(1 << bitNo));
    else
        r[byteNo] |= (1 << bitNo);
 
    PG_RETURN_VARBIT_P(result);
}
 
/*
 * bitgetbit
 *
 * returns the value of the Nth bit of a bit array (0 or 1).
 *
 * The bit location is specified left-to-right in a zero-based fashion
 * consistent with the other get_bit and set_bit functions, but
 * inconsistent with the standard substring, position, overlay functions
 */
Datum
bitgetbit(PG_FUNCTION_ARGS)
{
    VarBit     *arg1 = PG_GETARG_VARBIT_P(0);
    int32       n = PG_GETARG_INT32(1);
    int         bitlen;
    bits8      *p;
    int         byteNo,
                bitNo;
 
    bitlen = VARBITLEN(arg1);
    if (n < 0 || n >= bitlen)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("bit index %d out of valid range (0..%d)",
                        n, bitlen - 1)));
 
    p = VARBITS(arg1);
 
    byteNo = n / BITS_PER_BYTE;
    bitNo = BITS_PER_BYTE - 1 - (n % BITS_PER_BYTE);
 
    if (p[byteNo] & (1 << bitNo))
        PG_RETURN_INT32(1);
    else
        PG_RETURN_INT32(0);
}