KEYRING-GETMSG(2) KEYRING-GETMSG(2)
NAME
keyring: getmsg, sendmsg, senderrmsg - send and receive
messages on undelimited streams
SYNOPSIS
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;
DESCRIPTION
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 ter-
minated 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.
SOURCE
/libinterp/keyring.c
DIAGNOSTICS
Sendmsg and senderrmsg return -1 if there was an error writ-
ing to fd; they set the system error string. Getmsg returns
nil if there was an error reading from fd; it sets the sys-
tem 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.
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