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arrayaccess.h
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1 /*-------------------------------------------------------------------------
2  *
3  * arrayaccess.h
4  * Declarations for element-by-element access to Postgres arrays.
5  *
6  *
7  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * src/include/utils/arrayaccess.h
11  *
12  *-------------------------------------------------------------------------
13  */
14 #ifndef ARRAYACCESS_H
15 #define ARRAYACCESS_H
16 
17 #include "access/tupmacs.h"
18 #include "utils/array.h"
19 
20 
21 /*
22  * Functions for iterating through elements of a flat or expanded array.
23  * These require a state struct "array_iter iter".
24  *
25  * Use "array_iter_setup(&iter, arrayptr);" to prepare to iterate, and
26  * "datumvar = array_iter_next(&iter, &isnullvar, index, ...);" to fetch
27  * the next element into datumvar/isnullvar.
28  * "index" must be the zero-origin element number; we make caller provide
29  * this since caller is generally counting the elements anyway. Despite
30  * that, these functions can only fetch elements sequentially.
31  */
32 
33 typedef struct array_iter
34 {
35  /* datumptr being NULL or not tells if we have flat or expanded array */
36 
37  /* Fields used when we have an expanded array */
38  Datum *datumptr; /* Pointer to Datum array */
39  bool *isnullptr; /* Pointer to isnull array */
40 
41  /* Fields used when we have a flat array */
42  char *dataptr; /* Current spot in the data area */
43  bits8 *bitmapptr; /* Current byte of the nulls bitmap, or NULL */
44  int bitmask; /* mask for current bit in nulls bitmap */
45 } array_iter;
46 
47 
48 static inline void
50 {
52  {
53  if (a->xpn.dvalues)
54  {
55  it->datumptr = a->xpn.dvalues;
56  it->isnullptr = a->xpn.dnulls;
57  /* we must fill all fields to prevent compiler warnings */
58  it->dataptr = NULL;
59  it->bitmapptr = NULL;
60  }
61  else
62  {
63  /* Work with flat array embedded in the expanded datum */
64  it->datumptr = NULL;
65  it->isnullptr = NULL;
66  it->dataptr = ARR_DATA_PTR(a->xpn.fvalue);
68  }
69  }
70  else
71  {
72  it->datumptr = NULL;
73  it->isnullptr = NULL;
74  it->dataptr = ARR_DATA_PTR(&a->flt);
75  it->bitmapptr = ARR_NULLBITMAP(&a->flt);
76  }
77  it->bitmask = 1;
78 }
79 
80 static inline Datum
81 array_iter_next(array_iter *it, bool *isnull, int i,
82  int elmlen, bool elmbyval, char elmalign)
83 {
84  Datum ret;
85 
86  if (it->datumptr)
87  {
88  ret = it->datumptr[i];
89  *isnull = it->isnullptr ? it->isnullptr[i] : false;
90  }
91  else
92  {
93  if (it->bitmapptr && (*(it->bitmapptr) & it->bitmask) == 0)
94  {
95  *isnull = true;
96  ret = (Datum) 0;
97  }
98  else
99  {
100  *isnull = false;
101  ret = fetch_att(it->dataptr, elmbyval, elmlen);
102  it->dataptr = att_addlength_pointer(it->dataptr, elmlen,
103  it->dataptr);
104  it->dataptr = (char *) att_align_nominal(it->dataptr, elmalign);
105  }
106  it->bitmask <<= 1;
107  if (it->bitmask == 0x100)
108  {
109  if (it->bitmapptr)
110  it->bitmapptr++;
111  it->bitmask = 1;
112  }
113  }
114 
115  return ret;
116 }
117 
118 #endif /* ARRAYACCESS_H */
bits8 * bitmapptr
Definition: arrayaccess.h:43
#define att_align_nominal(cur_offset, attalign)
Definition: tupmacs.h:144
static Datum array_iter_next(array_iter *it, bool *isnull, int i, int elmlen, bool elmbyval, char elmalign)
Definition: arrayaccess.h:81
char * dataptr
Definition: arrayaccess.h:42
ExpandedArrayHeader xpn
Definition: array.h:161
Datum * dvalues
Definition: array.h:130
struct array_iter array_iter
#define ARR_DATA_PTR(a)
Definition: array.h:303
static void array_iter_setup(array_iter *it, AnyArrayType *a)
Definition: arrayaccess.h:49
#define att_addlength_pointer(cur_offset, attlen, attptr)
Definition: tupmacs.h:172
Datum * datumptr
Definition: arrayaccess.h:38
ArrayType * fvalue
Definition: array.h:149
uint8 bits8
Definition: c.h:272
uintptr_t Datum
Definition: postgres.h:374
bool * isnullptr
Definition: arrayaccess.h:39
#define NULL
Definition: c.h:226
#define VARATT_IS_EXPANDED_HEADER(PTR)
#define fetch_att(T, attbyval, attlen)
Definition: tupmacs.h:71
ArrayType flt
Definition: array.h:160
int i
#define ARR_NULLBITMAP(a)
Definition: array.h:281