1/*-------------------------------------------------------------------------
2 *
3 * varbit.h
4 * Functions for the SQL datatypes BIT() and BIT VARYING().
5 *
6 * Code originally contributed by Adriaan Joubert.
7 *
8 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
9 * Portions Copyright (c) 1994, Regents of the University of California
10 *
11 * src/include/utils/varbit.h
12 *
13 *-------------------------------------------------------------------------
14 */
15#ifndef VARBIT_H
16#define VARBIT_H
17
18#include <limits.h>
19
20#include "fmgr.h"
21
22/*
23 * Modeled on struct varlena from postgres.h, but data type is bits8.
24 *
25 * Caution: if bit_len is not a multiple of BITS_PER_BYTE, the low-order
26 * bits of the last byte of bit_dat[] are unused and MUST be zeroes.
27 * (This allows bit_cmp() to not bother masking the last byte.)
28 * Also, there should not be any excess bytes counted in the header length.
29 */
30typedef struct
31{
32 int32 vl_len_; /* varlena header (do not touch directly!) */
33 int32 bit_len; /* number of valid bits */
34 bits8 bit_dat[FLEXIBLE_ARRAY_MEMBER]; /* bit string, most sig. byte
35 * first */
36} VarBit;
37
38/*
39 * fmgr interface macros
40 *
41 * BIT and BIT VARYING are toastable varlena types. They are the same
42 * as far as representation goes, so we just have one set of macros.
43 */
44#define DatumGetVarBitP(X) ((VarBit *) PG_DETOAST_DATUM(X))
45#define DatumGetVarBitPCopy(X) ((VarBit *) PG_DETOAST_DATUM_COPY(X))
46#define VarBitPGetDatum(X) PointerGetDatum(X)
47#define PG_GETARG_VARBIT_P(n) DatumGetVarBitP(PG_GETARG_DATUM(n))
48#define PG_GETARG_VARBIT_P_COPY(n) DatumGetVarBitPCopy(PG_GETARG_DATUM(n))
49#define PG_RETURN_VARBIT_P(x) return VarBitPGetDatum(x)
50
51/* Header overhead *in addition to* VARHDRSZ */
52#define VARBITHDRSZ sizeof(int32)
53/* Number of bits in this bit string */
54#define VARBITLEN(PTR) (((VarBit *) (PTR))->bit_len)
55/* Pointer to the first byte containing bit string data */
56#define VARBITS(PTR) (((VarBit *) (PTR))->bit_dat)
57/* Number of bytes in the data section of a bit string */
58#define VARBITBYTES(PTR) (VARSIZE(PTR) - VARHDRSZ - VARBITHDRSZ)
59/* Padding of the bit string at the end (in bits) */
60#define VARBITPAD(PTR) (VARBITBYTES(PTR)*BITS_PER_BYTE - VARBITLEN(PTR))
61/* Number of bytes needed to store a bit string of a given length */
62#define VARBITTOTALLEN(BITLEN) (((BITLEN) + BITS_PER_BYTE-1)/BITS_PER_BYTE + \
63 VARHDRSZ + VARBITHDRSZ)
64/*
65 * Maximum number of bits. Several code sites assume no overflow from
66 * computing bitlen + X; VARBITTOTALLEN() has the largest such X.
67 */
68#define VARBITMAXLEN (INT_MAX - BITS_PER_BYTE + 1)
69/* pointer beyond the end of the bit string (like end() in STL containers) */
70#define VARBITEND(PTR) (((bits8 *) (PTR)) + VARSIZE(PTR))
71/* Mask that will cover exactly one byte, i.e. BITS_PER_BYTE bits */
72#define BITMASK 0xFF
73
74#endif
75