---
name: "zmq_msg_init_data"
section: "3"
platform: "linux"
package: "zeromq"
version: "4.3.5-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/zmq_msg_init_data"
---

# zmq\_msg\_init\_data(3)

initialise 0MQ message from a supplied buffer

## NAME

zmq\_msg\_init\_data - initialise 0MQ message from a supplied buffer

## SYNOPSIS

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

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

## DESCRIPTION

The *zmq\_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 0MQ 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 0MQ, with the *data* and *hint* arguments supplied to *zmq\_msg\_init\_data()*.

**Caution**\

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

**Caution**\

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

**Caution**\

If the deallocation function is not provided, the allocated memory will not be freed, and this may cause a memory leak.

**Caution**\

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

## RETURN VALUE

The *zmq\_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);
zmq_msg_t msg;
rc = zmq_msg_init_data (&msg, data, 6, my_free, NULL);
assert (rc == 0);
```

## SEE ALSO

[**zmq\_msg\_init\_size**(3)](/zmq_msg_init_size/3.md) [**zmq\_msg\_init\_buffer**(3)](/zmq_msg_init_buffer/3.md) [**zmq\_msg\_init**(3)](/zmq_msg_init/3.md) [**zmq\_msg\_close**(3)](/zmq_msg_close/3.md) [**zmq\_msg\_data**(3)](/zmq_msg_data/3.md) [**zmq\_msg\_size**(3)](/zmq_msg_size/3.md) [**zmq**(7)](/zmq/7.md)

## AUTHORS

This page was written by the 0MQ community. To make a change please read the 0MQ Contribution Policy at **http://www.zeromq.org/docs:contributing**.