/*-------------------------------------------------------------------------
 *
 * 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) 1996-2015, 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;

/*
 * 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 *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 void *repalloc_huge(void *pointer, Size size);

/*
 * 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.
 *
 * 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
#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 */
#endif   /* FRONTEND */

/*
 * 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);

/* sprintf into a palloc'd buffer --- these are in psprintf.c */
extern char *
psprintf(const char *fmt,...)
__attribute__((format(PG_PRINTF_ATTRIBUTE, 1, 2)));
extern size_t
pvsnprintf(char *buf, size_t len, const char *fmt, va_list args)
__attribute__((format(PG_PRINTF_ATTRIBUTE, 3, 0)));

#endif   /* PALLOC_H */
