queue
The most common channel is the queue. It can be either synchronous or semi-asynchronous. In the synchronous version the writing thread will block until all written data has been read by the reader. In the semi-asynchronous version the writer writes to a buffer within the queue, and only blocks all data does not fit in the buffer. The buffer size is selected by the application when initializing the queue.
The diagram below shows how two threads communicates using a queue. The writer thread writes from its source buffer to the queue. The reader thread reads from the queue to its destination buffer.
The data is either copied directly from the source to the destination buffer (1. in the figure), or via the internal queue buffer (2. in the figure).
- The reader thread is waiting for data. The writer writes from its source buffer directly to the readers' destination buffer.
- The reader thread is not waiting for data. The writer writes from its source buffer into the queue buffer. Later, the reader reads data from the queue buffer to its destination buffer.
Source code: src/sync/queue.h, src/sync/queue.c
Test code: tst/sync/queue/main.c
Test coverage: src/sync/queue.c
Example code: examples/queue/main.c
sync/queue.h