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memnodes.h
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1 /*-------------------------------------------------------------------------
2  *
3  * memnodes.h
4  * POSTGRES memory context node definitions.
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/nodes/memnodes.h
11  *
12  *-------------------------------------------------------------------------
13  */
14 #ifndef MEMNODES_H
15 #define MEMNODES_H
16 
17 #include "nodes/nodes.h"
18 
19 /*
20  * MemoryContextCounters
21  * Summarization state for MemoryContextStats collection.
22  *
23  * The set of counters in this struct is biased towards AllocSet; if we ever
24  * add any context types that are based on fundamentally different approaches,
25  * we might need more or different counters here. A possible API spec then
26  * would be to print only nonzero counters, but for now we just summarize in
27  * the format historically used by AllocSet.
28  */
29 typedef struct MemoryContextCounters
30 {
31  Size nblocks; /* Total number of malloc blocks */
32  Size freechunks; /* Total number of free chunks */
33  Size totalspace; /* Total bytes requested from malloc */
34  Size freespace; /* The unused portion of totalspace */
36 
37 /*
38  * MemoryContext
39  * A logical context in which memory allocations occur.
40  *
41  * MemoryContext itself is an abstract type that can have multiple
42  * implementations, though for now we have only AllocSetContext.
43  * The function pointers in MemoryContextMethods define one specific
44  * implementation of MemoryContext --- they are a virtual function table
45  * in C++ terms.
46  *
47  * Node types that are actual implementations of memory contexts must
48  * begin with the same fields as MemoryContext.
49  *
50  * Note: for largely historical reasons, typedef MemoryContext is a pointer
51  * to the context struct rather than the struct type itself.
52  */
53 
54 typedef struct MemoryContextMethods
55 {
56  void *(*alloc) (MemoryContext context, Size size);
57  /* call this free_p in case someone #define's free() */
58  void (*free_p) (MemoryContext context, void *pointer);
59  void *(*realloc) (MemoryContext context, void *pointer, Size size);
60  void (*init) (MemoryContext context);
61  void (*reset) (MemoryContext context);
62  void (*delete_context) (MemoryContext context);
63  Size (*get_chunk_space) (MemoryContext context, void *pointer);
64  bool (*is_empty) (MemoryContext context);
65  void (*stats) (MemoryContext context, int level, bool print,
66  MemoryContextCounters *totals);
67 #ifdef MEMORY_CONTEXT_CHECKING
68  void (*check) (MemoryContext context);
69 #endif
71 
72 
73 typedef struct MemoryContextData
74 {
75  NodeTag type; /* identifies exact kind of context */
76  /* these two fields are placed here to minimize alignment wastage: */
77  bool isReset; /* T = no space alloced since last reset */
78  bool allowInCritSection; /* allow palloc in critical section */
79  MemoryContextMethods *methods; /* virtual function table */
80  MemoryContext parent; /* NULL if no parent (toplevel context) */
81  MemoryContext firstchild; /* head of linked list of children */
82  MemoryContext prevchild; /* previous child of same parent */
83  MemoryContext nextchild; /* next child of same parent */
84  char *name; /* context name (just for debugging) */
85  MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
87 
88 /* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
89 
90 
91 /*
92  * MemoryContextIsValid
93  * True iff memory context is valid.
94  *
95  * Add new context types to the set accepted by this macro.
96  */
97 #define MemoryContextIsValid(context) \
98  ((context) != NULL && \
99  (IsA((context), AllocSetContext) || IsA((context), SlabContext)))
100 
101 #endif /* MEMNODES_H */
MemoryContextCallback * reset_cbs
Definition: memnodes.h:85
void print(const void *obj)
Definition: print.c:35
MemoryContextMethods * methods
Definition: memnodes.h:79
bool allowInCritSection
Definition: memnodes.h:78
NodeTag
Definition: nodes.h:26
void(* free_p)(MemoryContext context, void *pointer)
Definition: memnodes.h:58
char bool
Definition: c.h:202
void(* delete_context)(MemoryContext context)
Definition: memnodes.h:62
struct MemoryContextMethods MemoryContextMethods
bool(* is_empty)(MemoryContext context)
Definition: memnodes.h:64
MemoryContext firstchild
Definition: memnodes.h:81
void(* stats)(MemoryContext context, int level, bool print, MemoryContextCounters *totals)
Definition: memnodes.h:65
void(* reset)(MemoryContext context)
Definition: memnodes.h:61
MemoryContext prevchild
Definition: memnodes.h:82
size_t Size
Definition: c.h:356
struct MemoryContextCounters MemoryContextCounters
MemoryContext parent
Definition: memnodes.h:80
Size(* get_chunk_space)(MemoryContext context, void *pointer)
Definition: memnodes.h:63
void(* init)(MemoryContext context)
Definition: memnodes.h:60
MemoryContext nextchild
Definition: memnodes.h:83
struct MemoryContextData MemoryContextData
NodeTag type
Definition: memnodes.h:75