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# Memory pool Management Functions

These functions are fully supported in this release:

    ER get_blf(
        VP *p_blf,    ID mpfid )

    ER pget_blf(
        VP *p_blf,    ID mpfid )

    ER tget_blf(
        VP *p_blf,    ID mpfid,    TMO tmout )

    ER rel_blf(
        ID mpfid,    VP blf )

    ER ref_mpf(
        T_RMPF *pk_rmpf,    ID mpfid )

    ER get_blk(
        VP *p_blk,    ID mplid,    INT blksz )

    ER pget_blk(
        VP *p_blk,    ID mplid,    INT blksz )

    ER tget_blk(
        VP *p_blk,    ID mplid,    INT blksz,    TMO tmout )

    ER rel_blk(
        ID mplid,    VP blk )

    ER ref_mpl(
        T_RMPL *pk_rmpl,    ID mplid )

Note that of the memory provided for a particular pool to manage in the static initialization of the memory pool objects, some memory will be used to manage the pool itself. Therefore the number of blocks * the blocksize will be less than the total memory size.

The following functions are supported in this release, when enabled with `CYGPKG_UITRON_MEMPOOLVAR_CREATE_DELETE` or `CYGPKG_UITRON_MEMPOOLFIXED_CREATE_DELETE` as appropriate, with some restrictions:

    ER cre_mpl(
        ID mplid,    T_CMPL *pk_cmpl )

    ER del_mpl(
        ID mplid )

    ER cre_mpf(
        ID mpfid,    T_CMPF *pk_cmpf )

    ER del_mpf(
        ID mpfid )

Because of the static initialization facilities provided for system objects, a memory pool is allocated a region of memory to manage statically in the configuration. So while memory pools can be created and deleted, the same area of memory is used for that memory pool (memory pool ID number) each time. The requested variable pool size (pk_cmpl->mplsz) or the number of fixed-size blocks (pk_cmpf->mpfcnt) times the block size (pk_cmpf->blfsz) are checked for fitting within the statically allocated memory area, so if a create call succeeds, the resulting pool will be at least as large as that requested. For this reason `del_mpl()` and `del_mpf()` do not in any sense free the memory that was managed by the deleted pool for use by other pools; it may only be managed by a pool of the same object id.

For both fixed and variable memory pools, the queueing order when waiting on a synchronization object depends on the underlying kernel configuration. The multi-level queue scheduler is required for strict µITRON conformance and it queues tasks in FIFO order, so requests to create an object with priority queueing of tasks (pk_cxxx->xxxatr = TA_TPRI) are rejected with E_RSATR. Additional undefined bits in the attributes fields must be zero.

In general, extended information (pk_cxxx->exinf) is ignored.

## Error checking

The following conditions are only checked for, and only return errors if `CYGSEM_UITRON_BAD_PARAMS_RETURN_ERRORS` is enabled:

- invalid object id; less than 1 or greater than `CYGNUM_UITRON_MEMPOOLVAR/MEMPOOLFIXED` as appropriate returns E_ID

- dispatching is enabled in any call which can sleep, or E_CTX

- tmout must be positive, otherwise E_PAR

- pk_cxxx pointers in `cre_xxx()` must be valid pointers, or E_PAR

- return value pointer in `ref_xxx()` is a valid pointer, or E_PAR

- return value pointers in get block routines is a valid pointer, or E_PAR

- blocksize request in get variable block routines is greater than zero, or E_PAR

The following conditions are checked for, and can return error codes, regardless of the setting of `CYGSEM_UITRON_BAD_PARAMS_RETURN_ERRORS`:

- When create and delete functions `cre_xxx()` and `del_xxx()` are supported, all calls which use a valid object ID number check that the object exists. If not, E_NOEXS is returned.

- When create functions `cre_xxx()` are supported, if the object already exists, then E_OBJ

- In any call which can sleep, such as `get_blk()` : return codes E_TMOUT, E_RLWAI, E_DLT or of course E_OK are returned depending on the reason for terminating the sleep

- In polling functions such as `pget_blk()` return codes E_TMOUT or E_OK are returned depending on the state of the synchronization object

- In creation functions, the attributes must be compatible with the selected underlying kernel configuration: in `cre_mpl()` `pk_cmpl->mplatr` must be equal to `TA_TFIFO` else E_RSATR.

- In `cre_mpf()` `pk_cmpf->mpfatr` must be equal to `TA_TFIFO` else E_RSATR.

- In creation functions, the requested size of the memory pool must not be larger than that statically configured for the pool else E_RSATR; see the configuration option “Option: Static initializers”. In `cre_mpl()` `pk_cmpl->mplsz` is the field of interest

- In `cre_mpf()` the product of `pk_cmpf->blfsz` and `pk_cmpf->mpfcnt` must be smaller than the memory statically configured for the pool else E_RSATR

- In functions which return memory to the pool `rel_blk()` and `rel_blf()` , if the free fails, for example because the memory did not come from that pool originally, then E_PAR is returned

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