--- name: "memmgr" section: "3" platform: "linux" package: "ion-doc" version: "3.2.1+dfsg-1.1" release: "Debian 9 (Stretch)" platforms: ["linux"] url: "https://new.carta.tech/memmgr" --- # memmgr(3) memory manager abstraction functions ## 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)](/psm/3.md)