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varbit.h
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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) 1996-2020, 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  */
30 typedef 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
int32 bit_len
Definition: varbit.h:33
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:276
int32 vl_len_
Definition: varbit.h:32
signed int int32
Definition: c.h:355
Definition: varbit.h:30
uint8 bits8
Definition: c.h:374