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NAME
memmgr - memory manager abstraction functions
SYNOPSIS
#include "memmgr.h"
typedef void *(* MemAllocator)
(char *fileName, int lineNbr, size_t size);
typedef void (* MemDeallocator)
(char *fileName, int lineNbr, void * blk);
typedef void *(* MemAtoPConverter) (unsigned int address);
typedef unsigned int (* MemPtoAConverter) (void * pointer);
unsigned int memmgr_add (char *name,
MemAllocator take,
MemDeallocator release,
MemAtoPConverter AtoP,
MemPtoAConverter PtoA);
int memmgr_find (char *name);
char *memmgr_name (int mgrId);
MemAllocator memmgr_take (int mgrId);
MemDeallocator memmgr_release (int mgrId);
MemAtoPConverter memmgr_AtoP (int mgrId);
MemPtoAConverter memmgr_PtoA (int mgrId;
int memmgr_open (int memKey,
unsigned long memSize,
char **memPtr,
int *smId,
char *partitionName,
PsmPartition *partition,
int *memMgr,
MemAllocator afn,
MemDeallocator ffn,
MemAtoPConverter apfn,
MemPtoAConverter pafn);
void memmgr_destroy (int smId,
PsmPartition *partition);
DESCRIPTION
"memmgr" is an abstraction layer for administration of memory management. It enables
multiple memory managers to coexist in a single application. Each memory manager
specification is required to include pointers to a memory allocation function, a memory
deallocation function, and functions for translating between local memory pointers and
"addresses", which are abstract memory locations that have private meaning to the manager.
The allocation function is expected to return a block of memory of size "size" (in bytes),
initialized to all binary zeroes. The fileName and lineNbr arguments to the allocation
and deallocation functions are expected to be the values of __FILE__ and __LINE__ at the
point at which the functions are called; this supports any memory usage tracing via
sptrace(3) that may be implemented by the underlying memory management system.
Memory managers are identified by number and by name. The identifying number for a memory
manager is an index into a private, fixed-length array of up to 8 memory manager
configuration structures; that is, memory manager number must be in the range 0-7.
However, memory manager numbers are assigned dynamically and not always predictably. To
enable multiple applications to use the same memory manager for a given segment of shared
memory, a memory manager may be located by a predefined name of up to 15 characters that
is known to all the applications.
The memory manager with manager number 0 is always available; its name is "std". Its
memory allocation function is calloc(), its deallocation function is free(), and its
pointer/address translation functions are merely casts.
unsigned int memmgr_add(char *name, MemAllocator take, MemDeallocator release,
MemAtoPConverter AtoP, MemPtoAConverter PtoA)
Add a memory manager to the memory manager array, if not already defined; attempting
to add a previously added memory manager is not considered an error. name is the name
of the memory manager. take is a pointer to the manager's memory allocation function;
release is a pointer to the manager's memory deallocation function. AtoP is a pointer
to the manager's function for converting an address to a local memory pointer; PtoA is
a pointer to the manager's pointer-to-address converter function. Returns the memory
manager ID number assigned to the named manager, or -1 on any error.
NOTE: memmgr_add() is NOT thread-safe. In a multithreaded execution image (e.g.,
VxWorks), all memory managers should be loaded before any subordinate threads or tasks
are spawned.
int memmgr_find(char *name)
Return the memmgr ID of the named manager, or -1 if not found.
char *memmgr_name(int mgrId)
Return the name of the manager given by mgrId.
MemAllocator memmgr_take(int mgrId)
Return the allocator function pointer for the manager given by mgrId.
memDeallocator memmgr_release(int mgrId)
Return the deallocator function pointer for the manager given by mgrId.
MemAtoPConverter memmgr_AtoP(int mgrId)
Return the address-to-pointer converter function pointer for the manager given by
mgrId.
MemPtoAConverter memmgr_PtoA(int mgrId)
Return the pointer-to-address converter function pointer for the manager given by
mgrId.
int memmgr_open(int memKey, unsigned long memSize, char **memPtr, int *smId, char
*partitionName, PsmPartition *partition, int *memMgr, MemAllocator afn, MemDeallocator
ffn, MemAtoPConverter apfn, MemPtoAConverter pafn);
memmgr_open() opens one avenue of access to a PSM managed region of shared memory,
initializing as necessary.
In order for multiple tasks to share access to this memory region, all must cite the
same memkey and partitionName when they call memmgr_open(). If shared access is not
necessary, then memKey can be SM_NO_KEY and partitionName can be any valid partition
name.
If it is known that a prior invocation of memmgr_open() has already initialized the
region, then memSize can be zero and memPtr must be NULL. Otherwise memSize is
required and the required value of memPtr depends on whether or not the memory that is
to be shared and managed has already been allocated (e.g., it's a fixed region of bus
memory). If so, then the memory pointer variable that memPtr points to must contain
the address of that memory region. Otherwise, *memPtr must contain NULL.
memmgr_open() will allocate system memory as necessary and will in any case return the
address of the shared memory region in *memPtr.
If the shared memory is newly allocated or otherwise not yet under PSM management,
then memmgr_open() will invoke psm_manage() to manage the shared memory region. It
will also add a catalogue for the managed shared memory region as necessary.
If memMgr is non-NULL, then memmgr_open() will additionally call memmgr_add() to
establish a new memory manager for this managed shared memory region, as necessary.
The index of the applicable memory manager will be returned in memMgr. If that memory
manager is newly created, then the supplied afn, ffn, apfn, and pafn functions (which
can be written with reference to the memory manager index value returned in memMgr)
have been established as the memory management functions for local private access to
this managed shared memory region.
Returns 0 on success, -1 on any error.
void memmgr_destroy(int smId, PsmPartition *partition);
memmgr_destroy() terminates all access to a PSM managed region of shared memory,
invoking psm_erase() to destroy the partition and sm_ShmDestroy() to destroy the
shared memory object.
EXAMPLE
/* this example uses the calloc/free memory manager, which is
* called "std", and is always defined in memmgr. */
#include "memmgr.h"
main()
{
int mgrId;
MemAllocator myalloc;
MemDeallocator myfree;
char *newBlock;
mgrId = memmgr_find("std");
myalloc = memmgr_take(mgrId);
myfree = memmgr_release(mgrId);
...
newBlock = myalloc(5000);
...
myfree(newBlock);
}
SEE ALSO
psm(3)