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Chapter 23
Memory Management
This chapter describes the global functions you use to perform memory management.
NSPR provides heap based memory management functions
that map to familiar malloc(), calloc(), realloc(), and free().
Heap Functions and Macros
The functions PR_Malloc, PR_Calloc, PR_Realloc, PR_Free have the same function
signatures as do the LIBC functions malloc, calloc, realloc, free respectively.
They function similarly.
PR_Malloc
Syntax
#include <prmem.h>
PR_EXTERN(void *) PR_Malloc(PRUint32 size);
Parameter
| size
|
The size memory to be allocated. |
Returns
A pointer to the allocated memory, or if the allocation attempt fails:
NULL.
Description
PR_Malloc() allocates memory of the requested size from the heap.
PR_Calloc
Syntax
#include <prmem.h>
void *PR_Calloc(PRUint32 nelem, PRUint32 elsize);
Parameter
| nelem
|
The number of elements of size elsize to
be allocated. |
|
elsize
|
The size of an individual element. |
Returns
A pointer to the allocated memory, or if the allocation attempt fails:
NULL.
Description
PR_Calloc() allocates nelem objects of size elsize. The all bytes in the
allocated memory are cleared.
PR_Realloc
Syntax
#include <prmem.h>
void *PR_Realloc(void *ptr, PRUint32 size);
Parameter
| ptr
|
Pointer to the existing memory object
being resized. |
|
size
|
The size of the new memory object. |
Returns
A pointer to the allocated memory, or if the resize attempt fails: NULL.
Description
PR_Realloc() attempts to enlarge or shrink the memory element addressed by
ptr to a new size. The contents of the memory addressed by ptr will be
the same up to the lesser of its old size or new size unless the new memory
object's address is different than the original address.
PR_Free
Syntax
#include <prmem.h>
void PR_Free(void *ptr);
Parameter
| ptr
|
The address of the memory to be freed. |
Returns
void
Description
The memory addressed by ptr is returned to the heap.
PR_MALLOC
Syntax
#include <prmem.h>
void * PR_MALLOC(_bytes)
Parameter
| _bytes
|
Size of the requested memory object. |
Returns
A pointer to an allocated memory object or NULL in case of error.
Description
Allocated memory from the heap.
PR_NEW
Syntax
#include <prmem.h>
(_struct *) PR_NEW(_struct)
Parameter
| _struct
|
The name of a structure type. |
Returns
A pointer of type _struct *. or NULL on error.
Description
PR_NEW allocates memory whose size is SIZEOF(_struct) and returns a pointer
to that memory.
PR_REALLOC
Syntax
#include <prmem.h>
void * PR_REALLOC(_ptr, _size)
Parameter
| _ptr
|
pointer of memory to be re-sized. |
|
_size
|
The requested new size. |
Returns
A pointer to re-sized memory or NULL on error.
Description
PR_REALLOC() re-allocates memory: _ptr and sets its size to _size. See
also PR_Realloc()
PR_CALLOC
Syntax
#include <prmem.h>
void * PR_CALLOC(_size)
Parameter
| _size
|
The size of memory to be allocated. |
Returns
A pointer to the newly allocated memory or NULL on error.
Description
PR_CALLOC() allocates a single object of size _size from the heap and clears
the memory.
PR_NEWZAP
Syntax
#include <prmem.h>
(_struct *) PR_NEWZAP(_struct)
Parameter
| _struct
|
The name of a structure. |
Returns
A pointer to memory of size SIZEOF(_struct) whose contents are set to zero
or NULL on error.
Description
PR_NEWZAP() allocates an element of memory from the heap and sets the content
of that memory to zero.
PR_DELETE
Syntax
#include <prmem.h>
void PR_DELETE(_ptr)
Parameter
| _ptr
|
The address of memory to be returned
to the heap. |
Returns
void
Description
PR_DELETE() returns the memory pointed to by _ptr
to the heap and then sets _ptr to NULL.
PR_FREEIF
Syntax
#include <prmem.h>
#define PR_FREEIF(_ptr)
Returns
void
Description
PR_FREEIF() conditionally returns memory to the heap. When _ptr
is not NULL, memory is returned.
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Last Updated: Tue Jul 14 17:52:23 PDT 1998
Copyright © 1998 Netscape
Communications Corporation
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