6.12.2.14. Bitiwse operations

Manipulate endianess

Note

The libstd’s libARPA implementation is not a network stack implementation but an implementation of the minimalist network bytes order encoding/decoding API.

6.12.2.14.1. Synopsis

When writing a protocol stack that need to interact with the external word, the information encoding (MSB, LSB) may not be the host encoding.

The host encoding varies, depending on the hardware architecture and sometimes the system configuration (e.g. ARM, which support both MSB and LSB encoding).

To guarantee the correct encoding of numerical data, the POSIX standard has defined an API historically defined for network communications.

The Libstd API implements this API and permits its usage for any encoding conformance usage.

The endianess manipulation API is the following

#include "api/arpa/inet.h"

uint16_t htons(uint16_t hostshort);
uint32_t htonl(uint32_t hostlong);
uint16_t ntohs(uint16_t netshort);
uint32_t ntohl(uint32_t netlong);

6.12.2.14.2. Description

htons() and htonl() convert a short integer and a long integer into a MSB encoded value.

ntohs() and ntohl() convert a short integer and a long integer from a MSB encoded value into the host endianess encoding.