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fifo_create.md

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zx_fifo_create

SUMMARY

Create a fifo.

DECLARATION

#include <zircon/syscalls.h>

zx_status_t zx_fifo_create(size_t elem_count,
                           size_t elem_size,
                           uint32_t options,
                           zx_handle_t* out0,
                           zx_handle_t* out1);

DESCRIPTION

zx_fifo_create() creates a fifo, which is actually a pair of fifos of elem_count entries of elem_size bytes. Two endpoints are returned. Writing to one endpoint enqueues an element into the fifo that the opposing endpoint reads from.

Fifos are intended to be the control plane for shared memory transports. Their read and write operations are more efficient than sockets or channels, but there are severe restrictions on the size of elements and buffers.

The total size of each fifo (elem_count * elem_size) may not exceed 4096 bytes.

The options argument must be 0.

RIGHTS

Caller job policy must allow ZX_POL_NEW_FIFO.

RETURN VALUE

zx_fifo_create() returns ZX_OK on success. In the event of failure, one of the following values is returned.

ERRORS

ZX_ERR_INVALID_ARGS out0 or out1 is an invalid pointer or NULL or options is any value other than 0.

ZX_ERR_OUT_OF_RANGE elem_count or elem_size is zero, or elem_count * elem_size is greater than 4096.

ZX_ERR_NO_MEMORY Failure due to lack of memory. There is no good way for userspace to handle this (unlikely) error. In a future build this error will no longer occur.

SEE ALSO