---
name: "xs_msg_init_data"
section: "3"
platform: "linux"
package: "libxs-dev"
version: "1.2.0-2"
release: "Debian 10 (Buster)"
platforms: ["linux"]
url: "https://new.carta.tech/xs_msg_init_data"
---

# xs\_msg\_init\_data(3)

initialise Crossroads message from a supplied buffer

## NAME

xs\_msg\_init\_data - initialise Crossroads message from a supplied buffer

## SYNOPSIS

**typedef void (xs\_free\_fn) (void** *\*data***, void** *\*hint***);**

**int xs\_msg\_init\_data (xs\_msg\_t** *\*msg***, void** *\*data***, size\_t** *size***, xs\_free\_fn** *\*ffn***, void** *\*hint***);**

## DESCRIPTION

The *xs\_msg\_init\_data()* function shall initialise the message object referenced by *msg* to represent the content referenced by the buffer located at address *data*, *size* bytes long. No copy of *data* shall be performed and the library shall take ownership of the supplied buffer.

If provided, the deallocation function *ffn* shall be called once the data buffer is no longer required by the library, with the *data* and *hint* arguments supplied to *xs\_msg\_init\_data()*.

**Caution**\

Never access *xs\_msg\_t* members directly, instead always use the *xs\_msg* family of functions.

**Caution**\

The deallocation function *ffn* needs to be thread-safe, since it will be called from an arbitrary thread.

**Caution**\

The functions *xs\_msg\_init()*, *xs\_msg\_init\_data()* and *xs\_msg\_init\_size()* are mutually exclusive. Never initialize the same *xs\_msg\_t* twice.

## RETURN VALUE

The *xs\_msg\_init\_data()* function shall return zero if successful. Otherwise it shall return -1 and set *errno* to one of the values defined below.

## ERRORS

**ENOMEM**

Insufficient storage space is available.

## EXAMPLE

**Initialising a message from a supplied buffer**.

```
void my_free (void *data, void *hint)
{
    free (data);
}
    /*  ...  */
void *data = malloc (6);
assert (data);
memcpy (data, "ABCDEF", 6);
xs_msg_t msg;
rc = xs_msg_init_data (&msg, data, 6, my_free, NULL);
assert (rc == 0);
```

## SEE ALSO

[**xs\_msg\_init\_size**(3)](/xs_msg_init_size/3.md) [**xs\_msg\_init**(3)](/xs_msg_init/3.md) [**xs\_msg\_close**(3)](/xs_msg_close/3.md) [**xs\_msg\_data**(3)](/xs_msg_data/3.md) [**xs\_msg\_size**(3)](/xs_msg_size/3.md) [**xs**(7)](/xs/7.md)

## AUTHORS

The Crossroads documentation was written by Martin Sustrik \<**sustrik@250bpm.com**\[1\]\> and Martin Lucina \<**martin@lucina.net**\[2\]\>.

## NOTES

- 1\.

  sustrik@250bpm.com

  mailto:sustrik@250bpm.com

- 2\.

  martin@lucina.net

  mailto:martin@lucina.net