docs/reference/syscalls/fifo_write.md

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# zx_fifo_write

## Summary

Write data to a fifo.

## Declaration

```c
#include <zircon/syscalls.h>

zx_status_t zx_fifo_write(zx_handle_t handle,
                          size_t elem_size,
                          const void* data,
                          size_t count,
                          size_t* actual_count);
```

## Description

`zx_fifo_write()` attempts to write up to *count* elements
(`count * elem_size` bytes) from *data* to the fifo specified by *handle*.

Fewer elements may be written than requested if there is insufficient
room in the fifo to contain all of them. The number of
elements actually written is returned via *actual_count*.

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

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

It is not legal to write zero elements.

## Rights

*handle* must be of type **ZX_OBJ_TYPE_FIFO** and have **ZX_RIGHT_WRITE**.

## Return value

`zx_fifo_write()` returns **ZX_OK** on success, and returns
the number of elements written (at least one) via *actual_count*.

## Errors

**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_WRITE**.

**ZX_ERR_PEER_CLOSED**  The other side of the fifo is closed.

**ZX_ERR_SHOULD_WAIT**  The fifo is full.

## See also

 - [`zx_fifo_create()`]
 - [`zx_fifo_read()`]

[`zx_fifo_create()`]: fifo_create.md
[`zx_fifo_read()`]: fifo_read.md