NNG_MSG_INSERT(3)

💖 NNG_MSG_INSERT(3) 💖

okay bestie, welcome to nng_msg_insert(3) from the NNG Reference Manual — this is the one where we shove bytes onto the FRONT of a message body. prepending era, truly. ✨

---

🌸 NAME 🌸

nng_msg_insert — prepend to message body 🎀

---

✨ SYNOPSIS ✨

#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);

---

🦋 DESCRIPTION 🦋

so the nng_msg_insert() family of functions prepends data to the front of the body of message msg, and it reallocates that message if it needs to. it's giving "make room, we're coming through". 💅

the first function, nng_msg_insert(), prepends size bytes and copies them from val. the rest of the squad — nng_msg_insert_u16(), nng_msg_insert_u32(), and nng_msg_insert_u64() — prepend the specified value (like val32) in network-byte order (aka big-endian). no cap, big-endian is the vibe here. 👑

Tip 💡 these functions make use of space that's pre-allocated in front of the message body if it's available, so they can often avoid doing any reallocation at all. literally the glow-up. applications should use these instead of reallocating and copying message content themselves, so they can benefit from this capability. don't do it by hand bestie, use the pre-allocated space, it's free real estate. 🫶

---

💜 RETURN VALUES 💜

these functions return 0 on success, and non-zero otherwise. zero = slay, non-zero = we have a situation. 😭

---

🍓 ERRORS 🍓

• NNG_ENOMEM — insufficient free memory exists. 💀 the memory said no. not enough room, babe.

---

🌈 SEE ALSO 🌈

• 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)

---

and that's the whole page, bestie!! this was the NNG Reference Manual version of NNG_MSG_INSERT(3), and this edition is serving 2026-06-30 energy. NNG_MSG_INSERT(3) forever, periodt. 💖✨🎀🦋🌸💅🫶👑