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/*-------------------------------------------------------------------------
*
* tupmacs.h
* Tuple macros used by both index tuples and heap tuples.
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/tupmacs.h
*
*-------------------------------------------------------------------------
*/
#ifndef TUPMACS_H
#define TUPMACS_H
#include "catalog/pg_type_d.h" /* for TYPALIGN macros */
/*
* Check a tuple's null bitmap to determine whether the attribute is null.
* Note that a 0 in the null bitmap indicates a null, while 1 indicates
* non-null.
*/
static inline bool
att_isnull(int ATT, const bits8 *BITS)
{
return !(BITS[ATT >> 3] & (1 << (ATT & 0x07)));
}
#ifndef FRONTEND
/*
* Given a Form_pg_attribute and a pointer into a tuple's data area,
* return the correct value or pointer.
*
* We return a Datum value in all cases. If the attribute has "byval" false,
* we return the same pointer into the tuple data area that we're passed.
* Otherwise, we return the correct number of bytes fetched from the data
* area and extended to Datum form.
*
* On machines where Datum is 8 bytes, we support fetching 8-byte byval
* attributes; otherwise, only 1, 2, and 4-byte values are supported.
*
* Note that T must already be properly aligned for this to work correctly.
*/
#define fetchatt(A,T) fetch_att(T, (A)->attbyval, (A)->attlen)
/*
* Same, but work from byval/len parameters rather than Form_pg_attribute.
*/
static inline Datum
fetch_att(const void *T, bool attbyval, int attlen)
{
if (attbyval)
{
switch (attlen)
{
case sizeof(char):
return CharGetDatum(*((const char *) T));
case sizeof(int16):
return Int16GetDatum(*((const int16 *) T));
case sizeof(int32):
return Int32GetDatum(*((const int32 *) T));
#if SIZEOF_DATUM == 8
case sizeof(Datum):
return *((const Datum *) T);
#endif
default:
elog(ERROR, "unsupported byval length: %d", attlen);
return 0;
}
}
else
return PointerGetDatum(T);
}
#endif /* FRONTEND */
/*
* att_align_datum aligns the given offset as needed for a datum of alignment
* requirement attalign and typlen attlen. attdatum is the Datum variable
* we intend to pack into a tuple (it's only accessed if we are dealing with
* a varlena type). Note that this assumes the Datum will be stored as-is;
* callers that are intending to convert non-short varlena datums to short
* format have to account for that themselves.
*/
#define att_align_datum(cur_offset, attalign, attlen, attdatum) \
( \
((attlen) == -1 && VARATT_IS_SHORT(DatumGetPointer(attdatum))) ? \
(uintptr_t) (cur_offset) : \
att_align_nominal(cur_offset, attalign) \
)
/*
* att_align_pointer performs the same calculation as att_align_datum,
* but is used when walking a tuple. attptr is the current actual data
* pointer; when accessing a varlena field we have to "peek" to see if we
* are looking at a pad byte or the first byte of a 1-byte-header datum.
* (A zero byte must be either a pad byte, or the first byte of a correctly
* aligned 4-byte length word; in either case we can align safely. A non-zero
* byte must be either a 1-byte length word, or the first byte of a correctly
* aligned 4-byte length word; in either case we need not align.)
*
* Note: some callers pass a "char *" pointer for cur_offset. This is
* a bit of a hack but should work all right as long as uintptr_t is the
* correct width.
*/
#define att_align_pointer(cur_offset, attalign, attlen, attptr) \
( \
((attlen) == -1 && VARATT_NOT_PAD_BYTE(attptr)) ? \
(uintptr_t) (cur_offset) : \
att_align_nominal(cur_offset, attalign) \
)
/*
* att_align_nominal aligns the given offset as needed for a datum of alignment
* requirement attalign, ignoring any consideration of packed varlena datums.
* There are three main use cases for using this macro directly:
* * we know that the att in question is not varlena (attlen != -1);
* in this case it is cheaper than the above macros and just as good.
* * we need to estimate alignment padding cost abstractly, ie without
* reference to a real tuple. We must assume the worst case that
* all varlenas are aligned.
* * within arrays and multiranges, we unconditionally align varlenas (XXX this
* should be revisited, probably).
*
* The attalign cases are tested in what is hopefully something like their
* frequency of occurrence.
*/
#define att_align_nominal(cur_offset, attalign) \
( \
((attalign) == TYPALIGN_INT) ? INTALIGN(cur_offset) : \
(((attalign) == TYPALIGN_CHAR) ? (uintptr_t) (cur_offset) : \
(((attalign) == TYPALIGN_DOUBLE) ? DOUBLEALIGN(cur_offset) : \
( \
AssertMacro((attalign) == TYPALIGN_SHORT), \
SHORTALIGN(cur_offset) \
))) \
)
/*
* att_addlength_datum increments the given offset by the space needed for
* the given Datum variable. attdatum is only accessed if we are dealing
* with a variable-length attribute.
*/
#define att_addlength_datum(cur_offset, attlen, attdatum) \
att_addlength_pointer(cur_offset, attlen, DatumGetPointer(attdatum))
/*
* att_addlength_pointer performs the same calculation as att_addlength_datum,
* but is used when walking a tuple --- attptr is the pointer to the field
* within the tuple.
*
* Note: some callers pass a "char *" pointer for cur_offset. This is
* actually perfectly OK, but probably should be cleaned up along with
* the same practice for att_align_pointer.
*/
#define att_addlength_pointer(cur_offset, attlen, attptr) \
( \
((attlen) > 0) ? \
( \
(cur_offset) + (attlen) \
) \
: (((attlen) == -1) ? \
( \
(cur_offset) + VARSIZE_ANY(attptr) \
) \
: \
( \
AssertMacro((attlen) == -2), \
(cur_offset) + (strlen((char *) (attptr)) + 1) \
)) \
)
#ifndef FRONTEND
/*
* store_att_byval is a partial inverse of fetch_att: store a given Datum
* value into a tuple data area at the specified address. However, it only
* handles the byval case, because in typical usage the caller needs to
* distinguish by-val and by-ref cases anyway, and so a do-it-all function
* wouldn't be convenient.
*/
static inline void
store_att_byval(void *T, Datum newdatum, int attlen)
{
switch (attlen)
{
case sizeof(char):
*(char *) T = DatumGetChar(newdatum);
break;
case sizeof(int16):
*(int16 *) T = DatumGetInt16(newdatum);
break;
case sizeof(int32):
*(int32 *) T = DatumGetInt32(newdatum);
break;
#if SIZEOF_DATUM == 8
case sizeof(Datum):
*(Datum *) T = newdatum;
break;
#endif
default:
elog(ERROR, "unsupported byval length: %d", attlen);
}
}
#endif /* FRONTEND */
#endif /* TUPMACS_H */
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