nng_msg_insert - prepend to message body

       The nng_msg_insert() family of functions prepends data to the front of the body of message msg,
       reallocating it if necessary. The first function prepends size bytes, copying them from val. The
       remaining functions prepend the specified value (such as val32) in network-byte order (big-endian).

           Tip

           These functions make use of space pre-allocated in front of the message body if available, so they
           can often avoid performing any reallocation. Applications should use these instead of reallocating
           and copying message content themselves, in order to benefit from this capability.

       NNG_ENOMEM
           Insufficient free memory exists.

       nng_msg_insert - prepend to message body

       These functions return 0 on success, and non-zero otherwise.

nng_msg_alloc(3), nng_msg_append(3), nng_msg_body(3), nng_msg_chop(3), nng_msg_free(3), nng_msg_len(3),
       nng_msg_realloc(3), nng_msg_trim(3), nng_strerror(3), nng_msg(5), nng(7)

                                                   2025-04-20                                  NNG_MSG_INSERT(3)

           #include <nng/nng.h>

           int nng_msg_insert(nng_msg *msg, const void *val, size_t size);
           int nng_msg_insert_u16(nng_msg *msg, uint16_t val16);
           int nng_msg_insert_u32(nng_msg *msg, uint32_t val32);
           int nng_msg_insert_u64(nng_msg *msg, uint64_t val64);