10.5 Using the Region Allocation Routines

Previous examples were primarily concerned with static memory allocation; many applications may find it necessary to do some form of dynamic allocation. For situations where the allocation is always done in fixed size chunks, a family of region allocation routines are provided. These routines will divide up a larger buffer into some fixed memory regions that are managed by the library. The routines of interest are:

osCreateRegion
This function initializes an allocation arena given a memory address, size, and alignment.
osMalloc
This function allocates and returns the address to a single fixed sized and properly aligned buffer from a given region. This function will fail and return NULL if there is no available free buffer in the region.
osFree
This routine returns a previously allocated buffer to the given region pool.
osGetRegionBufCount
This function returns the total number of buffers in the region.
osGetRegionBufSize
This function returns the actual buffer size, after having been possibly padded to the given alignment.

The following code sample creates a region, allocates a buffer, and then frees it. 

void    *region;
char    regionMemory[REGION_SIZE];
u64     *buffer;

region = osCreateRegion(regionMemory,
                sizeof(regionMemory),
                BUFFER_SIZE, OS_RG_ALIGN_16B);
buffer = osMalloc(region);

/* do some work that uses 'buffer' */

osFree(region,buffer);

Incidentally, if the fixed size regions are intended to hold entire segments, the maxsize keyword of the makerom specification file may be of interest. See makerom for details.

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