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/*-------------------------------------------------------------------------
*
* memutils.h
* This file contains declarations for memory allocation utility
* functions. These are functions that are not quite widely used
* enough to justify going in utils/palloc.h, but are still part
* of the API of the memory management subsystem.
*
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: memutils.h,v 1.43 2001/03/22 04:01:13 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef MEMUTILS_H
#define MEMUTILS_H
#include "nodes/memnodes.h"
/*
* MaxAllocSize
* Quasi-arbitrary limit on size of allocations.
*
* Note:
* There is no guarantee that allocations smaller than MaxAllocSize
* will succeed. Allocation requests larger than MaxAllocSize will
* be summarily denied.
*
* XXX This is deliberately chosen to correspond to the limiting size
* of varlena objects under TOAST. See VARATT_MASK_SIZE in postgres.h.
*/
#define MaxAllocSize ((Size) 0x3fffffff) /* 1 gigabyte - 1 */
#define AllocSizeIsValid(size) (0 < (size) && (size) <= MaxAllocSize)
/*
* All chunks allocated by any memory context manager are required to be
* preceded by a StandardChunkHeader at a spacing of STANDARDCHUNKHEADERSIZE.
* A currently-allocated chunk must contain a backpointer to its owning
* context as well as the allocated size of the chunk. The backpointer is
* used by pfree() and repalloc() to find the context to call. The allocated
* size is not absolutely essential, but it's expected to be needed by any
* reasonable implementation.
*/
typedef struct StandardChunkHeader
{
MemoryContext context; /* owning context */
Size size; /* size of data space allocated in chunk */
#ifdef MEMORY_CONTEXT_CHECKING
/* when debugging memory usage, also store actual requested size */
Size requested_size;
#endif
} StandardChunkHeader;
#define STANDARDCHUNKHEADERSIZE MAXALIGN(sizeof(StandardChunkHeader))
/*
* Standard top-level memory contexts.
*
* Only TopMemoryContext and ErrorContext are initialized by
* MemoryContextInit() itself.
*/
extern DLLIMPORT MemoryContext TopMemoryContext;
extern DLLIMPORT MemoryContext ErrorContext;
extern DLLIMPORT MemoryContext PostmasterContext;
extern DLLIMPORT MemoryContext CacheMemoryContext;
extern DLLIMPORT MemoryContext QueryContext;
extern DLLIMPORT MemoryContext TopTransactionContext;
extern DLLIMPORT MemoryContext TransactionCommandContext;
/*
* Memory-context-type-independent functions in mcxt.c
*/
extern void MemoryContextInit(void);
extern void MemoryContextReset(MemoryContext context);
extern void MemoryContextDelete(MemoryContext context);
extern void MemoryContextResetChildren(MemoryContext context);
extern void MemoryContextDeleteChildren(MemoryContext context);
extern void MemoryContextResetAndDeleteChildren(MemoryContext context);
extern void MemoryContextStats(MemoryContext context);
extern void MemoryContextCheck(MemoryContext context);
extern bool MemoryContextContains(MemoryContext context, void *pointer);
/*
* 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 MemoryContext MemoryContextCreate(NodeTag tag, Size size,
MemoryContextMethods *methods,
MemoryContext parent,
const char *name);
/*
* Memory-context-type-specific functions
*/
/* aset.c */
extern MemoryContext AllocSetContextCreate(MemoryContext parent,
const char *name,
Size minContextSize,
Size initBlockSize,
Size maxBlockSize);
/*
* Recommended default alloc parameters, suitable for "ordinary" contexts
* that might hold quite a lot of data.
*/
#define ALLOCSET_DEFAULT_MINSIZE (8 * 1024)
#define ALLOCSET_DEFAULT_INITSIZE (8 * 1024)
#define ALLOCSET_DEFAULT_MAXSIZE (8 * 1024 * 1024)
#endif /* MEMUTILS_H */
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