1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
|
/*-------------------------------------------------------------------------
*
* palloc.h
* POSTGRES memory allocator definitions.
*
* This file contains the basic memory allocation interface that is
* needed by almost every backend module. It is included directly by
* postgres.h, so the definitions here are automatically available
* everywhere. Keep it lean!
*
* Memory allocation occurs within "contexts". Every chunk obtained from
* palloc()/MemoryContextAlloc() is allocated within a specific context.
* The entire contents of a context can be freed easily and quickly by
* resetting or deleting the context --- this is both faster and less
* prone to memory-leakage bugs than releasing chunks individually.
* We organize contexts into context trees to allow fine-grain control
* over chunk lifetime while preserving the certainty that we will free
* everything that should be freed. See utils/mmgr/README for more info.
*
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/palloc.h
*
*-------------------------------------------------------------------------
*/
#ifndef PALLOC_H
#define PALLOC_H
/*
* Type MemoryContextData is declared in nodes/memnodes.h. Most users
* of memory allocation should just treat it as an abstract type, so we
* do not provide the struct contents here.
*/
typedef struct MemoryContextData *MemoryContext;
/*
* A memory context can have callback functions registered on it. Any such
* function will be called once just before the context is next reset or
* deleted. The MemoryContextCallback struct describing such a callback
* typically would be allocated within the context itself, thereby avoiding
* any need to manage it explicitly (the reset/delete action will free it).
*/
typedef void (*MemoryContextCallbackFunction) (void *arg);
typedef struct MemoryContextCallback
{
MemoryContextCallbackFunction func; /* function to call */
void *arg; /* argument to pass it */
struct MemoryContextCallback *next; /* next in list of callbacks */
} MemoryContextCallback;
/*
* CurrentMemoryContext is the default allocation context for palloc().
* Avoid accessing it directly! Instead, use MemoryContextSwitchTo()
* to change the setting.
*/
extern PGDLLIMPORT MemoryContext CurrentMemoryContext;
/*
* Flags for MemoryContextAllocExtended.
*/
#define MCXT_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
#define MCXT_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
#define MCXT_ALLOC_ZERO 0x04 /* zero allocated memory */
/*
* Fundamental memory-allocation operations (more are in utils/memutils.h)
*/
extern void *MemoryContextAlloc(MemoryContext context, Size size);
extern void *MemoryContextAllocZero(MemoryContext context, Size size);
extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
extern void *MemoryContextAllocExtended(MemoryContext context,
Size size, int flags);
extern void *palloc(Size size);
extern void *palloc0(Size size);
extern void *palloc_extended(Size size, int flags);
extern pg_nodiscard void *repalloc(void *pointer, Size size);
extern void pfree(void *pointer);
/*
* The result of palloc() is always word-aligned, so we can skip testing
* alignment of the pointer when deciding which MemSet variant to use.
* Note that this variant does not offer any advantage, and should not be
* used, unless its "sz" argument is a compile-time constant; therefore, the
* issue that it evaluates the argument multiple times isn't a problem in
* practice.
*/
#define palloc0fast(sz) \
( MemSetTest(0, sz) ? \
MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
MemoryContextAllocZero(CurrentMemoryContext, sz) )
/* Higher-limit allocators. */
extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
extern pg_nodiscard void *repalloc_huge(void *pointer, Size size);
/*
* Although this header file is nominally backend-only, certain frontend
* programs like pg_controldata include it via postgres.h. For some compilers
* it's necessary to hide the inline definition of MemoryContextSwitchTo in
* this scenario; hence the #ifndef FRONTEND.
*/
#ifndef FRONTEND
static inline MemoryContext
MemoryContextSwitchTo(MemoryContext context)
{
MemoryContext old = CurrentMemoryContext;
CurrentMemoryContext = context;
return old;
}
#endif /* FRONTEND */
/* Registration of memory context reset/delete callbacks */
extern void MemoryContextRegisterResetCallback(MemoryContext context,
MemoryContextCallback *cb);
/*
* These are like standard strdup() except the copied string is
* allocated in a context, not with malloc().
*/
extern char *MemoryContextStrdup(MemoryContext context, const char *string);
extern char *pstrdup(const char *in);
extern char *pnstrdup(const char *in, Size len);
extern char *pchomp(const char *in);
/* sprintf into a palloc'd buffer --- these are in psprintf.c */
extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);
extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0);
#endif /* PALLOC_H */
|
