Table of Contents
OSLIB Objects FIFOs
Objects FIFOs implements in an elegant way a simple use case, sending fixed-size objects from one end to another of a FIFO.
- No dynamic allocation.
- Copy-less operations.
- Able to work from thread and/or ISR context.
The Objects FIFO
This object is an aggregation of two other objects present in OSLIB:
- A guarded pool allocator, used for storing the objects to be transferred.
- A mailbox as FIFO structure.
Operations
Four basic operations are defined:
- Take, allocates an object from the guarded pool, waiting if an object is not yet available.
- Send, sends the allocated object through the mailbox.
- Receive, receives an object from the mailbox.
- Return, returns a received object from the pool.
Note that the pool and the mailbox have the same size so can accommodate the same number of objects, this means:
- Take can wait if the guarded pool is currently empty (or fail if called from an ISR where it is not possible to wait).
- Send never waits because there is always enough space in the mailbox by design.
- Receive can wait if the mailbox is empty (or fail if called from an ISR where it is not possible to wait).
- Return never waits by design.
Also note that objects are not copied into the mailbox, the mailbox just transports a pointer to the object, the object itself is static, it does not move.
Objects FIFOs API
objects_fifo_t | Type of an objects FIFO object. |
chFifoObjectInit() | Initializes an objects FIFO object of type objects_fifo_t. |
chFifoObjectInitAligned() | Initializes an objects FIFO object of type objects_fifo_t with alignment constraints. |
chFifoTakeObjectTimeout() | Takes a free object with timeout. |
chFifoTakeObjectTimeoutS() | Takes a free object with timeout (S-Class variant). |
chFifoTakeObjectI() | Takes a free object (I-Class variant). |
chFifoReturnObject() | Returns an object to the pool. |
chFifoReturnObjectS() | Returns an object to the pool (S-Class variant). |
chFifoReturnObjectI() | Returns an object to the pool (I-Class variant). |
chFifoSendObject() | Sends an object through the mailbox. |
chFifoSendObjectS() | Sends an object through the mailbox (S-Class variant). |
chFifoSendObjectI() | Sends an object through the mailbox (I-Class variant). |
chFifoSendObjectAhead() | Sends an object through the mailbox with priority. |
chFifoSendObjectAheadS() | Sends an object through the mailbox with priority (S-Class variant). |
chFifoSendObjectAheadI() | Sends an object through the mailbox with priority (I-Class variant). |
chFifoReceiveObjectTimeout() | Receives an object from the mailbox with timeout. |
chFifoReceiveObjectTimeoutS() | Receives an object from the mailbox with timeout (S-Class variant). |
chFifoReceiveObjectI() | Receives an object from the mailbox (I-Class variant). |