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1 : /*-------------------------------------------------------------------------
2 : *
3 : * palloc.h
4 : * POSTGRES memory allocator definitions.
5 : *
6 : * This file contains the basic memory allocation interface that is
7 : * needed by almost every backend module. It is included directly by
8 : * postgres.h, so the definitions here are automatically available
9 : * everywhere. Keep it lean!
10 : *
11 : * Memory allocation occurs within "contexts". Every chunk obtained from
12 : * palloc()/MemoryContextAlloc() is allocated within a specific context.
13 : * The entire contents of a context can be freed easily and quickly by
14 : * resetting or deleting the context --- this is both faster and less
15 : * prone to memory-leakage bugs than releasing chunks individually.
16 : * We organize contexts into context trees to allow fine-grain control
17 : * over chunk lifetime while preserving the certainty that we will free
18 : * everything that should be freed. See utils/mmgr/README for more info.
19 : *
20 : *
21 : * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
22 : * Portions Copyright (c) 1994, Regents of the University of California
23 : *
24 : * src/include/utils/palloc.h
25 : *
26 : *-------------------------------------------------------------------------
27 : */
28 : #ifndef PALLOC_H
29 : #define PALLOC_H
30 :
31 : /*
32 : * Type MemoryContextData is declared in nodes/memnodes.h. Most users
33 : * of memory allocation should just treat it as an abstract type, so we
34 : * do not provide the struct contents here.
35 : */
36 : typedef struct MemoryContextData *MemoryContext;
37 :
38 : /*
39 : * A memory context can have callback functions registered on it. Any such
40 : * function will be called once just before the context is next reset or
41 : * deleted. The MemoryContextCallback struct describing such a callback
42 : * typically would be allocated within the context itself, thereby avoiding
43 : * any need to manage it explicitly (the reset/delete action will free it).
44 : */
45 : typedef void (*MemoryContextCallbackFunction) (void *arg);
46 :
47 : typedef struct MemoryContextCallback
48 : {
49 : MemoryContextCallbackFunction func; /* function to call */
50 : void *arg; /* argument to pass it */
51 : struct MemoryContextCallback *next; /* next in list of callbacks */
52 : } MemoryContextCallback;
53 :
54 : /*
55 : * CurrentMemoryContext is the default allocation context for palloc().
56 : * Avoid accessing it directly! Instead, use MemoryContextSwitchTo()
57 : * to change the setting.
58 : */
59 : extern PGDLLIMPORT MemoryContext CurrentMemoryContext;
60 :
61 : /*
62 : * Flags for MemoryContextAllocExtended.
63 : */
64 : #define MCXT_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
65 : #define MCXT_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
66 : #define MCXT_ALLOC_ZERO 0x04 /* zero allocated memory */
67 :
68 : /*
69 : * Fundamental memory-allocation operations (more are in utils/memutils.h)
70 : */
71 : extern void *MemoryContextAlloc(MemoryContext context, Size size);
72 : extern void *MemoryContextAllocZero(MemoryContext context, Size size);
73 : extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
74 : extern void *MemoryContextAllocExtended(MemoryContext context,
75 : Size size, int flags);
76 :
77 : extern void *palloc(Size size);
78 : extern void *palloc0(Size size);
79 : extern void *palloc_extended(Size size, int flags);
80 : extern void *repalloc(void *pointer, Size size);
81 : extern void pfree(void *pointer);
82 :
83 : /*
84 : * The result of palloc() is always word-aligned, so we can skip testing
85 : * alignment of the pointer when deciding which MemSet variant to use.
86 : * Note that this variant does not offer any advantage, and should not be
87 : * used, unless its "sz" argument is a compile-time constant; therefore, the
88 : * issue that it evaluates the argument multiple times isn't a problem in
89 : * practice.
90 : */
91 : #define palloc0fast(sz) \
92 : ( MemSetTest(0, sz) ? \
93 : MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
94 : MemoryContextAllocZero(CurrentMemoryContext, sz) )
95 :
96 : /* Higher-limit allocators. */
97 : extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
98 : extern void *repalloc_huge(void *pointer, Size size);
99 :
100 : /*
101 : * Although this header file is nominally backend-only, certain frontend
102 : * programs like pg_controldata include it via postgres.h. For some compilers
103 : * it's necessary to hide the inline definition of MemoryContextSwitchTo in
104 : * this scenario; hence the #ifndef FRONTEND.
105 : */
106 :
107 : #ifndef FRONTEND
108 : static inline MemoryContext
109 81180624 : MemoryContextSwitchTo(MemoryContext context)
110 : {
111 81180624 : MemoryContext old = CurrentMemoryContext;
112 :
113 81180624 : CurrentMemoryContext = context;
114 81180624 : return old;
115 : }
116 : #endif /* FRONTEND */
117 :
118 : /* Registration of memory context reset/delete callbacks */
119 : extern void MemoryContextRegisterResetCallback(MemoryContext context,
120 : MemoryContextCallback *cb);
121 :
122 : /*
123 : * These are like standard strdup() except the copied string is
124 : * allocated in a context, not with malloc().
125 : */
126 : extern char *MemoryContextStrdup(MemoryContext context, const char *string);
127 : extern char *pstrdup(const char *in);
128 : extern char *pnstrdup(const char *in, Size len);
129 :
130 : extern char *pchomp(const char *in);
131 :
132 : /* sprintf into a palloc'd buffer --- these are in psprintf.c */
133 : extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);
134 : extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0);
135 :
136 : #endif /* PALLOC_H */
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