Variable-size Memory Pool

A variable-size memory pool is an object for dynamically managing memory blocks of any size. Functions are provided for creating and deleting a variable-size memory pool, allocating and returning memory blocks in a variable-size memory pool, and referencing the status of a variable-size memory pool. A variable-size memory pool is an object identified by an ID number called a variable-size memory pool ID.

A variable-size memory pool has a memory space used as the variable-size memory pool (called a variable-size memory pool area or simply memory pool area), and a queue for tasks waiting for memory block allocation. A task wanting to allocate a memory block from a variable-size memory pool that lacks sufficient available memory space goes to WAIT state for variable-size memory block until memory blocks are returned to the pool. A task in this state is put in the task queue of the variable-size memory pool.

[Additional Notes]

When tasks are waiting for memory block allocation from a variable-size memory pool, they are served in queued order. If, for example, Task A requesting a 400-byte memory block from a variable-size memory pool is queued along with Task B requesting a 100-byte block, in A-B order, then even if 200 bytes of space are free, Task B is made to wait until Task A has acquired the requested memory block.

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