= nng_msg_header_trim(3)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nng_msg_header_trim - remove data from start of message header

== SYNOPSIS

[source, c]
----
#include <nng/nng.h>

int nng_msg_header_trim(nng_msg *msg, size_t size);
int nng_msg_header_trim_u16(nng_msg *msg, uint16_t *val16);
int nng_msg_header_trim_u32(nng_msg *msg, uint32_t *val32);
int nng_msg_header_trim_u64(nng_msg *msg, uint64_t *val64);
----

== DESCRIPTION

The `nng_msg_header_trim()` family of functions remove
data from the start of the header of message _msg_.
The first function removes _size_ bytes.
The remaining functions removes 2, 4, or 8 bytes, and stores them in the
value (such as _val32_),
after converting them from network-byte order (big-endian) to native
byte order.

== RETURN VALUES

This function returns 0 on success, and non-zero otherwise.

== ERRORS

[horizontal]
`NNG_EINVAL`:: The message header is too short to remove the requested data.

== SEE ALSO

[.text-left]
xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
xref:nng_msg_header.3.adoc[nng_msg_header(3)],
xref:nng_msg_header_append.3.adoc[nng_msg_header_append(3)],
xref:nng_msg_header_chop.3.adoc[nng_msg_header_chop(3)],
xref:nng_msg_header_insert.3.adoc[nng_msg_header_insert(3)],
xref:nng_msg_header_len.3.adoc[nng_msg_header_len(3)],
xref:nng_msg_free.3.adoc[nng_msg_free(3)],
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_msg.5.adoc[nng_msg(5)],
xref:nng.7.adoc[nng(7)]