'\" t
.\"     Title: zmq_msg_init_data
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 10/23/2023
.\"    Manual: 0MQ Manual
.\"    Source: 0MQ 4.3.5
.\"  Language: English
.\"
.TH "ZMQ_MSG_INIT_DATA" "3" "10/23/2023" "0MQ 4\&.3\&.5" "0MQ Manual"
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.SH "NAME"
zmq_msg_init_data \- initialise 0MQ message from a supplied buffer
.SH "SYNOPSIS"
.sp
\fBtypedef void (zmq_free_fn) (void \fR\fB\fI*data\fR\fR\fB, void \fR\fB\fI*hint\fR\fR\fB);\fR
.sp
\fBint zmq_msg_init_data (zmq_msg_t \fR\fB\fI*msg\fR\fR\fB, void \fR\fB\fI*data\fR\fR\fB, size_t \fR\fB\fIsize\fR\fR\fB, zmq_free_fn \fR\fB\fI*ffn\fR\fR\fB, void \fR\fB\fI*hint\fR\fR\fB);\fR
.SH "DESCRIPTION"
.sp
The \fIzmq_msg_init_data()\fR function shall initialise the message object referenced by \fImsg\fR to represent the content referenced by the buffer located at address \fIdata\fR, \fIsize\fR bytes long\&. No copy of \fIdata\fR shall be performed and 0MQ shall take ownership of the supplied buffer\&.
.sp
If provided, the deallocation function \fIffn\fR shall be called once the data buffer is no longer required by 0MQ, with the \fIdata\fR and \fIhint\fR arguments supplied to \fIzmq_msg_init_data()\fR\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBCaution\fR
.ps -1
.br
.sp
Never access \fIzmq_msg_t\fR members directly, instead always use the \fIzmq_msg\fR family of functions\&.
.sp .5v
.RE
.if n \{\
.sp
.\}
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.it 1 an-trap
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\fBCaution\fR
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.sp
The deallocation function \fIffn\fR needs to be thread\-safe, since it will be called from an arbitrary thread\&.
.sp .5v
.RE
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
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\fBCaution\fR
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.sp
If the deallocation function is not provided, the allocated memory will not be freed, and this may cause a memory leak\&.
.sp .5v
.RE
.if n \{\
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.\}
.RS 4
.it 1 an-trap
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\fBCaution\fR
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The functions \fIzmq_msg_init()\fR, \fIzmq_msg_init_data()\fR, \fIzmq_msg_init_size()\fR and \fIzmq_msg_init_buffer()\fR are mutually exclusive\&. Never initialise the same \fIzmq_msg_t\fR twice\&.
.sp .5v
.RE
.SH "RETURN VALUE"
.sp
The \fIzmq_msg_init_data()\fR function shall return zero if successful\&. Otherwise it shall return \-1 and set \fIerrno\fR to one of the values defined below\&.
.SH "ERRORS"
.PP
\fBENOMEM\fR
.RS 4
Insufficient storage space is available\&.
.RE
.SH "EXAMPLE"
.PP
\fBInitialising a message from a supplied buffer\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
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);
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.sp
\fBzmq_msg_init_size\fR(3) \fBzmq_msg_init_buffer\fR(3) \fBzmq_msg_init\fR(3) \fBzmq_msg_close\fR(3) \fBzmq_msg_data\fR(3) \fBzmq_msg_size\fR(3) \fBzmq\fR(7)
.SH "AUTHORS"
.sp
This page was written by the 0MQ community\&. To make a change please read the 0MQ Contribution Policy at \m[blue]\fBhttp://www\&.zeromq\&.org/docs:contributing\fR\m[]\&.