Read data from a fifo.


#include <zircon/syscalls.h>

zx_status_t zx_fifo_read(zx_handle_t handle,
                         size_t elem_size,
                         void* data,
                         size_t count,
                         size_t* actual_count);


zx_fifo_read() attempts to read up to count elements from the fifo handle into data.

Fewer elements may be read than requested if there are insufficient elements in the fifo to fulfill the entire request. The number of elements actually read is returned via actual_count.

The element size specified by elem_size must match the element size that was passed into zx_fifo_create().

data must have a size of at least count * elem_size bytes.

actual_count is allowed to be NULL. This is useful when reading a single element: if count is 1 and zx_fifo_read() returns ZX_OK, actual_count is guaranteed to be 1 and thus can be safely ignored.

It is not legal to read zero elements.


handle must be of type ZX_OBJ_TYPE_FIFO and have ZX_RIGHT_READ.

Return value

zx_fifo_read() returns ZX_OK on success, and returns the number of elements read (at least one) via actual_count.


ZX_ERR_BAD_HANDLE handle is not a valid handle.

ZX_ERR_WRONG_TYPE handle is not a fifo handle.

ZX_ERR_INVALID_ARGS data is an invalid pointer or actual_count is an invalid pointer.

ZX_ERR_OUT_OF_RANGE count is zero or elem_size is not equal to the element size of the fifo.

ZX_ERR_ACCESS_DENIED handle does not have ZX_RIGHT_READ.

ZX_ERR_PEER_CLOSED The other side of the fifo is closed.

ZX_ERR_SHOULD_WAIT The fifo is empty.

See also