mod_slotmem_shm
Slot-based shared memory provider.
Extension
mod_slotmem_shm.c
slotmem_shm_module

`mod_slotmem_shm` is a memory provider which provides for creation and access to a shared memory segment in which the datasets are organized in "slots."

All shared memory is cleared and cleaned with each restart, whether graceful or not. The data itself is stored and restored within a file noted by the `name` parameter in the `create` and `attach` calls. If not specified with an absolute path, the file will be created relative to the path specified by the DefaultRuntimeDir directive.

`mod_slotmem_shm` provides the following API functions:

apr_status_t doall(ap_slotmem_instance_t *s, ap_slotmem_callback_fn_t *func, void *data, apr_pool_t *pool)
  call the callback on all worker slots
apr_status_t create(ap_slotmem_instance_t **new, const char *name, apr_size_t item_size, unsigned int item_num, ap_slotmem_type_t type, apr_pool_t *pool)
  create a new slotmem with each item size is item_size. `name` is used to generate a filename for the persistent store of the shared memory if configured. Values are:
  `"none"`
    `Anonymous shared memory and no persistent store`
  `"file-name"`
    `[DefaultRuntimeDir]/file-name`
  `"/absolute-file-name"`
    `Absolute file name`
apr_status_t attach(ap_slotmem_instance_t **new, const char *name, apr_size_t *item_size, unsigned int *item_num, apr_pool_t *pool)
  attach to an existing slotmem. See `create` for description of `name` parameter.
apr_status_t dptr(ap_slotmem_instance_t *s, unsigned int item_id, void**mem)
  get the direct pointer to the memory associated with this worker slot.
apr_status_t get(ap_slotmem_instance_t *s, unsigned int item_id, unsigned char *dest, apr_size_t dest_len)
  get/read the memory from this slot to dest
apr_status_t put(ap_slotmem_instance_t *slot, unsigned int item_id, unsigned char *src, apr_size_t src_len)
  put/write the data from src to this slot
unsigned int num_slots(ap_slotmem_instance_t *s)
  return the total number of slots in the segment
apr_size_t slot_size(ap_slotmem_instance_t *s)
  return the total data size, in bytes, of a slot in the segment
apr_status_t grab(ap_slotmem_instance_t *s, unsigned int *item_id);
  grab or allocate the first free slot and mark as in-use (does not do any data copying)
apr_status_t fgrab(ap_slotmem_instance_t *s, unsigned int item_id);
  forced grab or allocate the specified slot and mark as in-use (does not do any data copying)
apr_status_t release(ap_slotmem_instance_t *s, unsigned int item_id);
  release or free a slot and mark as not in-use (does not do any data copying)