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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) 1996-2024, 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 static inline VarBit *
46 {
47  return (VarBit *) PG_DETOAST_DATUM(X);
48 }
49 
50 static inline VarBit *
52 {
53  return (VarBit *) PG_DETOAST_DATUM_COPY(X);
54 }
55 
56 static inline Datum
58 {
59  return PointerGetDatum(X);
60 }
61 
62 #define PG_GETARG_VARBIT_P(n) DatumGetVarBitP(PG_GETARG_DATUM(n))
63 #define PG_GETARG_VARBIT_P_COPY(n) DatumGetVarBitPCopy(PG_GETARG_DATUM(n))
64 #define PG_RETURN_VARBIT_P(x) return VarBitPGetDatum(x)
65 
66 /* Header overhead *in addition to* VARHDRSZ */
67 #define VARBITHDRSZ sizeof(int32)
68 /* Number of bits in this bit string */
69 #define VARBITLEN(PTR) (((VarBit *) (PTR))->bit_len)
70 /* Pointer to the first byte containing bit string data */
71 #define VARBITS(PTR) (((VarBit *) (PTR))->bit_dat)
72 /* Number of bytes in the data section of a bit string */
73 #define VARBITBYTES(PTR) (VARSIZE(PTR) - VARHDRSZ - VARBITHDRSZ)
74 /* Padding of the bit string at the end (in bits) */
75 #define VARBITPAD(PTR) (VARBITBYTES(PTR)*BITS_PER_BYTE - VARBITLEN(PTR))
76 /* Number of bytes needed to store a bit string of a given length */
77 #define VARBITTOTALLEN(BITLEN) (((BITLEN) + BITS_PER_BYTE-1)/BITS_PER_BYTE + \
78  VARHDRSZ + VARBITHDRSZ)
79 /*
80  * Maximum number of bits. Several code sites assume no overflow from
81  * computing bitlen + X; VARBITTOTALLEN() has the largest such X.
82  */
83 #define VARBITMAXLEN (INT_MAX - BITS_PER_BYTE + 1)
84 /* pointer beyond the end of the bit string (like end() in STL containers) */
85 #define VARBITEND(PTR) (((bits8 *) (PTR)) + VARSIZE(PTR))
86 /* Mask that will cover exactly one byte, i.e. BITS_PER_BYTE bits */
87 #define BITMASK 0xFF
88 
89 #endif
signed int int32
Definition: c.h:481
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:385
uint8 bits8
Definition: c.h:500
#define PG_DETOAST_DATUM_COPY(datum)
Definition: fmgr.h:242
#define PG_DETOAST_DATUM(datum)
Definition: fmgr.h:240
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:322
uintptr_t Datum
Definition: postgres.h:64
Definition: varbit.h:31
int32 bit_len
Definition: varbit.h:33
int32 vl_len_
Definition: varbit.h:32
static Datum VarBitPGetDatum(const VarBit *X)
Definition: varbit.h:57
static VarBit * DatumGetVarBitP(Datum X)
Definition: varbit.h:45
static VarBit * DatumGetVarBitPCopy(Datum X)
Definition: varbit.h:51