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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <mach.h>
include <config.h>
include "ki.h"
# KB_ZARD -- Asynchronous read from a binary device. We are called only if
# the device does not reside on the local node. In this implementation
# these reads are not actually asynchronous. This is possible but more
# complex to implement than I wanted to get into at this time, particularly
# since FIO is not yet fully asynchronous. The problem is that a node
# channel may be used to multiplex any number of requests to the remote
# node process. If an asynchronous read is pending this must be detected
# and the read completed before processing any other requests.
procedure kb_zard (device, chan, obuf, max_bytes, loffset)
int device # device driver code
int chan # channel assigned device
char obuf[max_bytes] # receives data
int max_bytes # max bytes to read
long loffset # file offset
int server, status
int ki_send(), ki_receive()
include "kichan.com"
include "kii.com"
begin
server = k_node[chan]
if (max_bytes <= 0) {
k_status[chan] = 0
return
}
# Send the request to initiate the read.
p_arg[1] = k_oschan[chan]
p_arg[2] = max_bytes
p_arg[3] = loffset
if (ki_send (server, device, BF_ARD) == ERR) {
status = ERR
} else {
# Wait for the ZAWT packet.
if (ki_receive (server, device, BF_AWT) == ERR)
status = ERR
else
status = p_arg[1]
# Read the data block (if any) directly into caller's buffer.
if (status > 0) {
call ks_aread (server, obuf, status)
call ks_await (server, status)
}
}
k_status[chan] = status
end
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