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pg_list.h
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1 /*-------------------------------------------------------------------------
2  *
3  * pg_list.h
4  * interface for PostgreSQL generic linked list package
5  *
6  * This package implements singly-linked homogeneous lists.
7  *
8  * It is important to have constant-time length, append, and prepend
9  * operations. To achieve this, we deal with two distinct data
10  * structures:
11  *
12  * 1. A set of "list cells": each cell contains a data field and
13  * a link to the next cell in the list or NULL.
14  * 2. A single structure containing metadata about the list: the
15  * type of the list, pointers to the head and tail cells, and
16  * the length of the list.
17  *
18  * We support three types of lists:
19  *
20  * T_List: lists of pointers
21  * (in practice usually pointers to Nodes, but not always;
22  * declared as "void *" to minimize casting annoyances)
23  * T_IntList: lists of integers
24  * T_OidList: lists of Oids
25  *
26  * (At the moment, ints and Oids are the same size, but they may not
27  * always be so; try to be careful to maintain the distinction.)
28  *
29  *
30  * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
31  * Portions Copyright (c) 1994, Regents of the University of California
32  *
33  * src/include/nodes/pg_list.h
34  *
35  *-------------------------------------------------------------------------
36  */
37 #ifndef PG_LIST_H
38 #define PG_LIST_H
39 
40 #include "nodes/nodes.h"
41 
42 
43 typedef struct ListCell ListCell;
44 
45 typedef struct List
46 {
47  NodeTag type; /* T_List, T_IntList, or T_OidList */
48  int length;
51 } List;
52 
53 struct ListCell
54 {
55  union
56  {
57  void *ptr_value;
58  int int_value;
60  } data;
62 };
63 
64 /*
65  * The *only* valid representation of an empty list is NIL; in other
66  * words, a non-NIL list is guaranteed to have length >= 1 and
67  * head/tail != NULL
68  */
69 #define NIL ((List *) NULL)
70 
71 /*
72  * These routines are used frequently. However, we can't implement
73  * them as macros, since we want to avoid double-evaluation of macro
74  * arguments. Therefore, we implement them using static inline functions
75  * if supported by the compiler, or as regular functions otherwise.
76  * See STATIC_IF_INLINE in c.h.
77  */
78 #ifndef PG_USE_INLINE
79 extern ListCell *list_head(const List *l);
80 extern ListCell *list_tail(List *l);
81 extern int list_length(const List *l);
82 #endif /* PG_USE_INLINE */
83 #if defined(PG_USE_INLINE) || defined(PG_LIST_INCLUDE_DEFINITIONS)
85 list_head(const List *l)
86 {
87  return l ? l->head : NULL;
88 }
89 
91 list_tail(List *l)
92 {
93  return l ? l->tail : NULL;
94 }
95 
97 list_length(const List *l)
98 {
99  return l ? l->length : 0;
100 }
101 #endif /*-- PG_USE_INLINE || PG_LIST_INCLUDE_DEFINITIONS */
102 
103 /*
104  * NB: There is an unfortunate legacy from a previous incarnation of
105  * the List API: the macro lfirst() was used to mean "the data in this
106  * cons cell". To avoid changing every usage of lfirst(), that meaning
107  * has been kept. As a result, lfirst() takes a ListCell and returns
108  * the data it contains; to get the data in the first cell of a
109  * List, use linitial(). Worse, lsecond() is more closely related to
110  * linitial() than lfirst(): given a List, lsecond() returns the data
111  * in the second cons cell.
112  */
113 
114 #define lnext(lc) ((lc)->next)
115 #define lfirst(lc) ((lc)->data.ptr_value)
116 #define lfirst_int(lc) ((lc)->data.int_value)
117 #define lfirst_oid(lc) ((lc)->data.oid_value)
118 
119 #define linitial(l) lfirst(list_head(l))
120 #define linitial_int(l) lfirst_int(list_head(l))
121 #define linitial_oid(l) lfirst_oid(list_head(l))
122 
123 #define lsecond(l) lfirst(lnext(list_head(l)))
124 #define lsecond_int(l) lfirst_int(lnext(list_head(l)))
125 #define lsecond_oid(l) lfirst_oid(lnext(list_head(l)))
126 
127 #define lthird(l) lfirst(lnext(lnext(list_head(l))))
128 #define lthird_int(l) lfirst_int(lnext(lnext(list_head(l))))
129 #define lthird_oid(l) lfirst_oid(lnext(lnext(list_head(l))))
130 
131 #define lfourth(l) lfirst(lnext(lnext(lnext(list_head(l)))))
132 #define lfourth_int(l) lfirst_int(lnext(lnext(lnext(list_head(l)))))
133 #define lfourth_oid(l) lfirst_oid(lnext(lnext(lnext(list_head(l)))))
134 
135 #define llast(l) lfirst(list_tail(l))
136 #define llast_int(l) lfirst_int(list_tail(l))
137 #define llast_oid(l) lfirst_oid(list_tail(l))
138 
139 /*
140  * Convenience macros for building fixed-length lists
141  */
142 #define list_make1(x1) lcons(x1, NIL)
143 #define list_make2(x1,x2) lcons(x1, list_make1(x2))
144 #define list_make3(x1,x2,x3) lcons(x1, list_make2(x2, x3))
145 #define list_make4(x1,x2,x3,x4) lcons(x1, list_make3(x2, x3, x4))
146 
147 #define list_make1_int(x1) lcons_int(x1, NIL)
148 #define list_make2_int(x1,x2) lcons_int(x1, list_make1_int(x2))
149 #define list_make3_int(x1,x2,x3) lcons_int(x1, list_make2_int(x2, x3))
150 #define list_make4_int(x1,x2,x3,x4) lcons_int(x1, list_make3_int(x2, x3, x4))
151 
152 #define list_make1_oid(x1) lcons_oid(x1, NIL)
153 #define list_make2_oid(x1,x2) lcons_oid(x1, list_make1_oid(x2))
154 #define list_make3_oid(x1,x2,x3) lcons_oid(x1, list_make2_oid(x2, x3))
155 #define list_make4_oid(x1,x2,x3,x4) lcons_oid(x1, list_make3_oid(x2, x3, x4))
156 
157 /*
158  * foreach -
159  * a convenience macro which loops through the list
160  */
161 #define foreach(cell, l) \
162  for ((cell) = list_head(l); (cell) != NULL; (cell) = lnext(cell))
163 
164 /*
165  * for_each_cell -
166  * a convenience macro which loops through a list starting from a
167  * specified cell
168  */
169 #define for_each_cell(cell, initcell) \
170  for ((cell) = (initcell); (cell) != NULL; (cell) = lnext(cell))
171 
172 /*
173  * forboth -
174  * a convenience macro for advancing through two linked lists
175  * simultaneously. This macro loops through both lists at the same
176  * time, stopping when either list runs out of elements. Depending
177  * on the requirements of the call site, it may also be wise to
178  * assert that the lengths of the two lists are equal.
179  */
180 #define forboth(cell1, list1, cell2, list2) \
181  for ((cell1) = list_head(list1), (cell2) = list_head(list2); \
182  (cell1) != NULL && (cell2) != NULL; \
183  (cell1) = lnext(cell1), (cell2) = lnext(cell2))
184 
185 /*
186  * forthree -
187  * the same for three lists
188  */
189 #define forthree(cell1, list1, cell2, list2, cell3, list3) \
190  for ((cell1) = list_head(list1), (cell2) = list_head(list2), (cell3) = list_head(list3); \
191  (cell1) != NULL && (cell2) != NULL && (cell3) != NULL; \
192  (cell1) = lnext(cell1), (cell2) = lnext(cell2), (cell3) = lnext(cell3))
193 
194 extern List *lappend(List *list, void *datum);
195 extern List *lappend_int(List *list, int datum);
196 extern List *lappend_oid(List *list, Oid datum);
197 
198 extern ListCell *lappend_cell(List *list, ListCell *prev, void *datum);
199 extern ListCell *lappend_cell_int(List *list, ListCell *prev, int datum);
200 extern ListCell *lappend_cell_oid(List *list, ListCell *prev, Oid datum);
201 
202 extern List *lcons(void *datum, List *list);
203 extern List *lcons_int(int datum, List *list);
204 extern List *lcons_oid(Oid datum, List *list);
205 
206 extern List *list_concat(List *list1, List *list2);
207 extern List *list_truncate(List *list, int new_size);
208 
209 extern ListCell *list_nth_cell(const List *list, int n);
210 extern void *list_nth(const List *list, int n);
211 extern int list_nth_int(const List *list, int n);
212 extern Oid list_nth_oid(const List *list, int n);
213 
214 extern bool list_member(const List *list, const void *datum);
215 extern bool list_member_ptr(const List *list, const void *datum);
216 extern bool list_member_int(const List *list, int datum);
217 extern bool list_member_oid(const List *list, Oid datum);
218 
219 extern List *list_delete(List *list, void *datum);
220 extern List *list_delete_ptr(List *list, void *datum);
221 extern List *list_delete_int(List *list, int datum);
222 extern List *list_delete_oid(List *list, Oid datum);
223 extern List *list_delete_first(List *list);
224 extern List *list_delete_cell(List *list, ListCell *cell, ListCell *prev);
225 
226 extern List *list_union(const List *list1, const List *list2);
227 extern List *list_union_ptr(const List *list1, const List *list2);
228 extern List *list_union_int(const List *list1, const List *list2);
229 extern List *list_union_oid(const List *list1, const List *list2);
230 
231 extern List *list_intersection(const List *list1, const List *list2);
232 
233 /* currently, there's no need for list_intersection_int etc */
234 
235 extern List *list_difference(const List *list1, const List *list2);
236 extern List *list_difference_ptr(const List *list1, const List *list2);
237 extern List *list_difference_int(const List *list1, const List *list2);
238 extern List *list_difference_oid(const List *list1, const List *list2);
239 
240 extern List *list_append_unique(List *list, void *datum);
241 extern List *list_append_unique_ptr(List *list, void *datum);
242 extern List *list_append_unique_int(List *list, int datum);
243 extern List *list_append_unique_oid(List *list, Oid datum);
244 
245 extern List *list_concat_unique(List *list1, List *list2);
246 extern List *list_concat_unique_ptr(List *list1, List *list2);
247 extern List *list_concat_unique_int(List *list1, List *list2);
248 extern List *list_concat_unique_oid(List *list1, List *list2);
249 
250 extern void list_free(List *list);
251 extern void list_free_deep(List *list);
252 
253 extern List *list_copy(const List *list);
254 extern List *list_copy_tail(const List *list, int nskip);
255 
256 /*
257  * To ease migration to the new list API, a set of compatibility
258  * macros are provided that reduce the impact of the list API changes
259  * as far as possible. Until client code has been rewritten to use the
260  * new list API, the ENABLE_LIST_COMPAT symbol can be defined before
261  * including pg_list.h
262  */
263 #ifdef ENABLE_LIST_COMPAT
264 
265 #define lfirsti(lc) lfirst_int(lc)
266 #define lfirsto(lc) lfirst_oid(lc)
267 
268 #define makeList1(x1) list_make1(x1)
269 #define makeList2(x1, x2) list_make2(x1, x2)
270 #define makeList3(x1, x2, x3) list_make3(x1, x2, x3)
271 #define makeList4(x1, x2, x3, x4) list_make4(x1, x2, x3, x4)
272 
273 #define makeListi1(x1) list_make1_int(x1)
274 #define makeListi2(x1, x2) list_make2_int(x1, x2)
275 
276 #define makeListo1(x1) list_make1_oid(x1)
277 #define makeListo2(x1, x2) list_make2_oid(x1, x2)
278 
279 #define lconsi(datum, list) lcons_int(datum, list)
280 #define lconso(datum, list) lcons_oid(datum, list)
281 
282 #define lappendi(list, datum) lappend_int(list, datum)
283 #define lappendo(list, datum) lappend_oid(list, datum)
284 
285 #define nconc(l1, l2) list_concat(l1, l2)
286 
287 #define nth(n, list) list_nth(list, n)
288 
289 #define member(datum, list) list_member(list, datum)
290 #define ptrMember(datum, list) list_member_ptr(list, datum)
291 #define intMember(datum, list) list_member_int(list, datum)
292 #define oidMember(datum, list) list_member_oid(list, datum)
293 
294 /*
295  * Note that the old lremove() determined equality via pointer
296  * comparison, whereas the new list_delete() uses equal(); in order to
297  * keep the same behavior, we therefore need to map lremove() calls to
298  * list_delete_ptr() rather than list_delete()
299  */
300 #define lremove(elem, list) list_delete_ptr(list, elem)
301 #define LispRemove(elem, list) list_delete(list, elem)
302 #define lremovei(elem, list) list_delete_int(list, elem)
303 #define lremoveo(elem, list) list_delete_oid(list, elem)
304 
305 #define ltruncate(n, list) list_truncate(list, n)
306 
307 #define set_union(l1, l2) list_union(l1, l2)
308 #define set_uniono(l1, l2) list_union_oid(l1, l2)
309 #define set_ptrUnion(l1, l2) list_union_ptr(l1, l2)
310 
311 #define set_difference(l1, l2) list_difference(l1, l2)
312 #define set_differenceo(l1, l2) list_difference_oid(l1, l2)
313 #define set_ptrDifference(l1, l2) list_difference_ptr(l1, l2)
314 
315 #define equali(l1, l2) equal(l1, l2)
316 #define equalo(l1, l2) equal(l1, l2)
317 
318 #define freeList(list) list_free(list)
319 
320 #define listCopy(list) list_copy(list)
321 
322 extern int length(List *list);
323 #endif /* ENABLE_LIST_COMPAT */
324 
325 #endif /* PG_LIST_H */