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bd4e2fd97d
Using the new interface MemoryContextAllocExtended, callers can specify MCXT_ALLOC_NO_OOM if they are prepared to handle a NULL return value. Michael Paquier, reviewed and somewhat revised by me.
127 lines
4.6 KiB
C
127 lines
4.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* palloc.h
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* POSTGRES memory allocator definitions.
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*
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* This file contains the basic memory allocation interface that is
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* needed by almost every backend module. It is included directly by
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* postgres.h, so the definitions here are automatically available
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* everywhere. Keep it lean!
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*
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* Memory allocation occurs within "contexts". Every chunk obtained from
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* palloc()/MemoryContextAlloc() is allocated within a specific context.
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* The entire contents of a context can be freed easily and quickly by
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* resetting or deleting the context --- this is both faster and less
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* prone to memory-leakage bugs than releasing chunks individually.
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* We organize contexts into context trees to allow fine-grain control
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* over chunk lifetime while preserving the certainty that we will free
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* everything that should be freed. See utils/mmgr/README for more info.
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*
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*
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* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/palloc.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PALLOC_H
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#define PALLOC_H
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/*
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* Type MemoryContextData is declared in nodes/memnodes.h. Most users
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* of memory allocation should just treat it as an abstract type, so we
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* do not provide the struct contents here.
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*/
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typedef struct MemoryContextData *MemoryContext;
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/*
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* CurrentMemoryContext is the default allocation context for palloc().
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* Avoid accessing it directly! Instead, use MemoryContextSwitchTo()
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* to change the setting.
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*/
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extern PGDLLIMPORT MemoryContext CurrentMemoryContext;
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/*
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* Flags for MemoryContextAllocExtended.
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*/
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#define MCXT_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
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#define MCXT_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
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#define MCXT_ALLOC_ZERO 0x04 /* zero allocated memory */
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/*
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* Fundamental memory-allocation operations (more are in utils/memutils.h)
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*/
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extern void *MemoryContextAlloc(MemoryContext context, Size size);
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extern void *MemoryContextAllocZero(MemoryContext context, Size size);
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extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
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extern void *MemoryContextAllocExtended(MemoryContext context,
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Size size, int flags);
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extern void *palloc(Size size);
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extern void *palloc0(Size size);
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extern void *repalloc(void *pointer, Size size);
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extern void pfree(void *pointer);
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/*
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* The result of palloc() is always word-aligned, so we can skip testing
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* alignment of the pointer when deciding which MemSet variant to use.
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* Note that this variant does not offer any advantage, and should not be
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* used, unless its "sz" argument is a compile-time constant; therefore, the
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* issue that it evaluates the argument multiple times isn't a problem in
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* practice.
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*/
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#define palloc0fast(sz) \
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( MemSetTest(0, sz) ? \
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MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
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MemoryContextAllocZero(CurrentMemoryContext, sz) )
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/* Higher-limit allocators. */
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extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
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extern void *repalloc_huge(void *pointer, Size size);
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/*
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* MemoryContextSwitchTo can't be a macro in standard C compilers.
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* But we can make it an inline function if the compiler supports it.
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* See STATIC_IF_INLINE in c.h.
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*
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* Although this header file is nominally backend-only, certain frontend
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* programs like pg_controldata include it via postgres.h. For some compilers
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* it's necessary to hide the inline definition of MemoryContextSwitchTo in
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* this scenario; hence the #ifndef FRONTEND.
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*/
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#ifndef FRONTEND
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#ifndef PG_USE_INLINE
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extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
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#endif /* !PG_USE_INLINE */
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#if defined(PG_USE_INLINE) || defined(MCXT_INCLUDE_DEFINITIONS)
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STATIC_IF_INLINE MemoryContext
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MemoryContextSwitchTo(MemoryContext context)
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{
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MemoryContext old = CurrentMemoryContext;
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CurrentMemoryContext = context;
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return old;
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}
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#endif /* PG_USE_INLINE || MCXT_INCLUDE_DEFINITIONS */
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#endif /* FRONTEND */
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/*
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* These are like standard strdup() except the copied string is
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* allocated in a context, not with malloc().
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*/
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extern char *MemoryContextStrdup(MemoryContext context, const char *string);
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extern char *pstrdup(const char *in);
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extern char *pnstrdup(const char *in, Size len);
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/* sprintf into a palloc'd buffer --- these are in psprintf.c */
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extern char *
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psprintf(const char *fmt,...)
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__attribute__((format(PG_PRINTF_ATTRIBUTE, 1, 2)));
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extern size_t
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pvsnprintf(char *buf, size_t len, const char *fmt, va_list args)
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__attribute__((format(PG_PRINTF_ATTRIBUTE, 3, 0)));
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#endif /* PALLOC_H */
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