palloc.h

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/*-------------------------------------------------------------------------
 *
 * 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) 1996-2013, 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;

#ifndef FRONTEND

/*
 * CurrentMemoryContext is the default allocation context for palloc().
 * We declare it here so that palloc() can be a macro.  Avoid accessing it
 * directly!  Instead, use MemoryContextSwitchTo() to change the setting.
 */
extern PGDLLIMPORT MemoryContext CurrentMemoryContext;

/*
 * 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);

/*
 * 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) )

/*
 * MemoryContextSwitchTo can't be a macro in standard C compilers.
 * But we can make it an inline function if the compiler supports it.
 * See STATIC_IF_INLINE in c.h.
 */

#ifndef PG_USE_INLINE
extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
#endif   /* !PG_USE_INLINE */
#if defined(PG_USE_INLINE) || defined(MCXT_INCLUDE_DEFINITIONS)
STATIC_IF_INLINE MemoryContext
MemoryContextSwitchTo(MemoryContext context)
{
    MemoryContext old = CurrentMemoryContext;

    CurrentMemoryContext = context;
    return old;
}
#endif   /* PG_USE_INLINE || MCXT_INCLUDE_DEFINITIONS */

/*
 * 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);
#endif /* !FRONTEND */

extern char *pstrdup(const char *in);
extern char *pnstrdup(const char *in, Size len);
extern void *palloc(Size size);
extern void *palloc0(Size size);
extern void pfree(void *pointer);
extern void *repalloc(void *pointer, Size size);

#endif   /* PALLOC_H */