be32toh0x01020304

be32toh0x01020304 refers to the application of the be32toh macro or function to the 32‑bit constant 0x01020304. The be32toh macro converts a 32‑bit value that is stored in big‑endian byte order (also called network byte order) into the host machine’s native byte order. It is defined in POSIX‑derived systems in the header <arpa/inet.h> on many Unix‑like operating systems, and in <sys/byteorder.h> on BSD systems.

The symbolic name be32toh0x01020304 therefore denotes the result of applying this conversion to the literal 0x01020304. In network byte order this value is represented as the byte sequence 01 02 03 04. On a little‑endian host such as x86, the macro will exchange the bytes so that the host representation becomes 0x04030201. On a big‑endian host the value is unchanged because the host order already matches network order.

The macro is typically implemented as a compiler builtins or inline assembly that performs an unconditional byte swap on little‑endian architectures and expands to a no‑op on big‑endian ones. It is widely used for interoperating between network protocols, file formats, and native code, ensuring that integer values are interpreted correctly regardless of the underlying hardware. The constant 0x01020304 is often chosen as a teaching example because its byte values are consecutive and easily recognizable.

In practice developers use be32toh together with its counterparts htons, htonl, be16toh, etc., to guarantee correct multi‑byte integer handling when reading or writing data that follows network byte order conventions.