htobe64

htobe64 is a macro or function provided by endianness utilities in many Unix-like systems to convert a 64-bit integer from host byte order to big-endian (network) byte order. It is used when data must be represented in a standard big-endian format for transmission or storage.

The operation depends on the host’s endianness. On big-endian hosts, htobe64 typically performs a no-op and returns the input unchanged. On little-endian hosts, it rearranges the bytes to produce a big-endian representation. The exact implementation may map to a simple byte swap or to an intrinsic instruction, depending on the platform and compiler.

Availability and portability notes: htobe64 is commonly declared in endian.h or a related header on Linux, BSDs, and macOS. The exact header and name conventions can vary between systems, so portable code often uses platform-specific checks or relies on be64toh/htobe64 families of functions with the corresponding 32-bit variants (htobe32, be64toh, etc.). Windows environments typically use alternative byte-swap utilities such as _byteswap_uint64 or platform-specific htonll/ntohll equivalents.

Usage: htobe64 is used when serializing 64-bit values for formats that require big-endian encoding, such as certain network protocols or file formats. Converting back from big-endian to host order is done with be64toh.

See also: be64toh, htobe32, be32toh, htole64, be64toh. These helpers standardize conversions between host, big-endian, and little-endian byte orders for 16-, 32-, and 64-bit integers.