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keyring: getmsg, sendmsg, senderrmsg - send and receive messages on undelimited streams


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.




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.

KEYRING-GETMSG(2 ) Rev:  Thu Feb 15 14:43:27 GMT 2007