Page 89 - DCAP408_WEB_PROGRAMMING

Unit 5: Memory Management (I)

5.3 Using Fixed Memory Blocks Notes

Fixed size memory blocks allocation algorithm has been established to permit technique of
memory allocation in static time, separately to number of allocated blocks. This method is
extensively used in real-time applications.
First plan that should be executed is to arrange the memory by means of stFixedMemInit
function. Just after it can be utilized stFixedMemAlloc to assign memory blocks and
stFixedMemFree to release assigned memory blocks in a provided memory.

All of the allocated blocks have a fixed size, defined throughout memory initialization. The size
is allocated to value stated in AR_MEMORY_ALIGNMENT constant, defined in architecture
specific files. Block addresses are always allocated not relatively to the NULL but to address
specified throughout memory initialization.
Functions do not sets the previous error code on breakdown. Access to the fixed size memory is
never harmonized. If it is compulsory it should be implemented.
If the fixed size memory management module will not be utilized, it can be expelled from
compilation by setting ST_USE_FIXMEM for 0.
Now we illustrate some examples of using fixed size memory management module.

Example: Fixed size memory pool initialization
The example below displays how to initialize memory pool for fixed size memory blocks
allocation.

#include <stdio.h>
#include “ST_API.h”

UINT8 MemoryPool[1024];

int main(void)
{
PVOID Block;

/* Initialization */
arInit();
stInit();

/* Initialize memory pool for fixed-size memory blocks allocation.
Size of the memory block is set to 16 bytes */
if(!stFixedMemInit(MemoryPool, sizeof(MemoryPool), 16))
{
printf(“Failure during memory pool initialization.\n”);
return 0;
}

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