1 /*-------------------------------------------------------------------------
4 * POSTGRES memory context node definitions.
7 * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * $PostgreSQL: pgsql/src/include/nodes/memnodes.h,v 1.31 2006/03/05 15:58:56 momjian Exp $
12 *-------------------------------------------------------------------------
17 #include "nodes/nodes.h"
21 * A logical context in which memory allocations occur.
23 * MemoryContext itself is an abstract type that can have multiple
24 * implementations, though for now we have only AllocSetContext.
25 * The function pointers in MemoryContextMethods define one specific
26 * implementation of MemoryContext --- they are a virtual function table
29 * Node types that are actual implementations of memory contexts must
30 * begin with the same fields as MemoryContext.
32 * Note: for largely historical reasons, typedef MemoryContext is a pointer
33 * to the context struct rather than the struct type itself.
36 typedef struct MemoryContextMethods
38 void *(*alloc) (MemoryContext context, Size size);
39 /* call this free_p in case someone #define's free() */
40 void (*free_p) (MemoryContext context, void *pointer);
41 void *(*realloc) (MemoryContext context, void *pointer, Size size);
42 void (*init) (MemoryContext context);
43 void (*reset) (MemoryContext context);
44 void (*delete) (MemoryContext context);
45 Size (*get_chunk_space) (MemoryContext context, void *pointer);
46 bool (*is_empty) (MemoryContext context);
47 void (*stats) (MemoryContext context);
48 #ifdef MEMORY_CONTEXT_CHECKING
49 void (*check) (MemoryContext context);
51 } MemoryContextMethods;
54 typedef struct MemoryContextData
56 NodeTag type; /* identifies exact kind of context */
57 MemoryContextMethods *methods; /* virtual function table */
58 MemoryContext parent; /* NULL if no parent (toplevel context) */
59 MemoryContext firstchild; /* head of linked list of children */
60 MemoryContext nextchild; /* next child of same parent */
61 char *name; /* context name (just for debugging) */
64 /* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
68 * MemoryContextIsValid
69 * True iff memory context is valid.
71 * Add new context types to the set accepted by this macro.
73 #define MemoryContextIsValid(context) \
74 ((context) != NULL && \
75 (IsA((context), AllocSetContext)))
77 #endif /* MEMNODES_H */