/*-------------------------------------------------------------------------
 *
 * memutils_internal.h
 *	  This file contains declarations for memory allocation utility
 *	  functions for internal use.
 *
 *
 * Portions Copyright (c) 2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/memutils_internal.h
 *
 *-------------------------------------------------------------------------
 */

#ifndef MEMUTILS_INTERNAL_H
#define MEMUTILS_INTERNAL_H

#include "utils/memutils.h"

/* These functions implement the MemoryContext API for AllocSet context. */
extern void *AllocSetAlloc(MemoryContext context, Size size);
extern void AllocSetFree(void *pointer);
extern void *AllocSetRealloc(void *pointer, Size size);
extern void AllocSetReset(MemoryContext context);
extern void AllocSetDelete(MemoryContext context);
extern MemoryContext AllocSetGetChunkContext(void *pointer);
extern Size AllocSetGetChunkSpace(void *pointer);
extern bool AllocSetIsEmpty(MemoryContext context);
extern void AllocSetStats(MemoryContext context,
						  MemoryStatsPrintFunc printfunc, void *passthru,
						  MemoryContextCounters *totals,
						  bool print_to_stderr);
#ifdef MEMORY_CONTEXT_CHECKING
extern void AllocSetCheck(MemoryContext context);
#endif

/* These functions implement the MemoryContext API for Generation context. */
extern void *GenerationAlloc(MemoryContext context, Size size);
extern void GenerationFree(void *pointer);
extern void *GenerationRealloc(void *pointer, Size size);
extern void GenerationReset(MemoryContext context);
extern void GenerationDelete(MemoryContext context);
extern MemoryContext GenerationGetChunkContext(void *pointer);
extern Size GenerationGetChunkSpace(void *pointer);
extern bool GenerationIsEmpty(MemoryContext context);
extern void GenerationStats(MemoryContext context,
							MemoryStatsPrintFunc printfunc, void *passthru,
							MemoryContextCounters *totals,
							bool print_to_stderr);
#ifdef MEMORY_CONTEXT_CHECKING
extern void GenerationCheck(MemoryContext context);
#endif


/* These functions implement the MemoryContext API for Slab context. */
extern void *SlabAlloc(MemoryContext context, Size size);
extern void SlabFree(void *pointer);
extern void *SlabRealloc(void *pointer, Size size);
extern void SlabReset(MemoryContext context);
extern void SlabDelete(MemoryContext context);
extern MemoryContext SlabGetChunkContext(void *pointer);
extern Size SlabGetChunkSpace(void *pointer);
extern bool SlabIsEmpty(MemoryContext context);
extern void SlabStats(MemoryContext context,
					  MemoryStatsPrintFunc printfunc, void *passthru,
					  MemoryContextCounters *totals,
					  bool print_to_stderr);
#ifdef MEMORY_CONTEXT_CHECKING
extern void SlabCheck(MemoryContext context);
#endif

/*
 * MemoryContextMethodID
 *		A unique identifier for each MemoryContext implementation which
 *		indicates the index into the mcxt_methods[] array. See mcxt.c.
 *		The maximum value for this enum is constrained by
 *		MEMORY_CONTEXT_METHODID_MASK.  If an enum value higher than that is
 *		required then MEMORY_CONTEXT_METHODID_BITS will need to be increased.
 */
typedef enum MemoryContextMethodID
{
	MCTX_ASET_ID,
	MCTX_GENERATION_ID,
	MCTX_SLAB_ID,
} MemoryContextMethodID;

/*
 * The number of bits that 8-byte memory chunk headers can use to encode the
 * MemoryContextMethodID.
 */
#define MEMORY_CONTEXT_METHODID_BITS 3
#define MEMORY_CONTEXT_METHODID_MASK \
	((((uint64) 1) << MEMORY_CONTEXT_METHODID_BITS) - 1)

/*
 * This routine handles the context-type-independent part of memory
 * context creation.  It's intended to be called from context-type-
 * specific creation routines, and noplace else.
 */
extern void MemoryContextCreate(MemoryContext node,
								NodeTag tag,
								MemoryContextMethodID method_id,
								MemoryContext parent,
								const char *name);

/*
 * GetMemoryChunkMethodID
 *		Return the MemoryContextMethodID from the uint64 chunk header which
 *		directly precedes 'pointer'.
 */
static inline MemoryContextMethodID
GetMemoryChunkMethodID(void *pointer)
{
	uint64		header;

	/*
	 * Try to detect bogus pointers handed to us, poorly though we can.
	 * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
	 * allocated chunk.
	 */
	Assert(pointer != NULL);
	Assert(pointer == (void *) MAXALIGN(pointer));

	header = *((uint64 *) ((char *) pointer - sizeof(uint64)));

	return (MemoryContextMethodID) (header & MEMORY_CONTEXT_METHODID_MASK);
}

#endif							/* MEMUTILS_INTERNAL_H */