keyring: getmsg, sendmsg, senderrmsg - send and receive messages on undelimited streams .EX include "keyring.m"; keyring := load Keyring Keyring->PATH; getmsg: fn(fd: ref Sys->FD): array of byte; sendmsg: fn(fd: ref Sys->FD, buf: array of byte, n: int): int; senderrmsg: fn(fd: ref Sys->FD, s: string): int; These functions allow arbitrary data, packed into arrays of bytes, to be exchanged on network connections using connection-oriented transport protocols that do not preserve record boundaries (eg, TCP/IP without ssl (3)). They are used to implement various authentication protocols, including auth (6), as implemented by keyring-auth (2).

Each data message is transmitted with a five-byte header containing a four-character zero-padded decimal count n terminated by a newline, followed by n bytes of message data. An error message has a similar structure, except that the first character of the count is replaced by an exclamation mark ( ! ); the message data following contains the diagnostic string in its UTF-8 encoding (see utf (6)).

Getmsg reads the next message from fd and returns its data content.

Sendmsg sends the first n bytes of buf as a message on fd , and returns n .

Senderrmsg sends the error message s .

/libinterp/keyring.c Sendmsg and senderrmsg return -1 if there was an error writing to fd ; they set the system error string. Getmsg returns nil if there was an error reading from fd ; it sets the system error string to reflect the cause. It also returns nil if an error message was received instead of a data message; the system error string will contain the error message's diagnostic.