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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <mach.h>
include <syserr.h>
include <config.h>
include <fio.h>
# AREADB -- Asychronous byte-oriented block read from a binary file. Reads
# can only start at a character offset which is an integral multiple of the
# file block size.
procedure areadb (fd, buffer, maxbytes, byte_offset)
int fd # FIO file descriptor
int maxbytes # maximum number of machine bytes to read
char buffer[ARB] # buffer into to which data is to be read
long byte_offset # one-indexed byte offset in file
long file_offset
int junk, awaitb()
errchk filerr, syserr
include <fio.com>
begin
fp = fiodes[fd]
if (fd <= 0 || fp == NULL)
call syserr (SYS_FILENOTOPEN)
# If channel is active, wait for completion. Do not abort if await is
# not called between i/o requests, since this is what happens when an
# error occurs, ant it would lead to a file error following error
# restart.
if (FCIOMODE(fp) != INACTIVE)
junk = awaitb (FAFD(fp))
if (FBLKSIZE(fp) == 0) # streaming device
;
else if (byte_offset < 1)
call filerr (FNAME(fp), SYS_FARDOOB)
else if (FILSIZE(fp) >= 0 && byte_offset - (FILSIZE(fp)*SZB_CHAR) > 1) {
FNBYTES(fp) = 0 # return EOF
return
}
# If not a streaming device, check alignment of block. If streaming
# device, file offset passed to z-routine must be zero.
file_offset = byte_offset
if (FBLKSIZE(fp) > 0) {
if (mod (byte_offset-1, (FBLKSIZE(fp)*SZB_CHAR)) != 0)
call filerr (FNAME(fp), SYS_FARDALIGN)
} else
file_offset = 0
call zlocva (buffer, FLOCBUF(fp))
FCIOMODE(fp) = READ_IN_PROGRESS
FFIOMODE(fp) = READ_IN_PROGRESS
FAFD(fp) = fd
# If the CLOSE flag is set for the channel, open and close the channel
# at the host level every time an i/o operation takes place. (Used to
# save host channel descriptors). The code is structured so that the
# FCLOSEFD flag may change state at any time, with the channel being
# left either closed or open the next time we are called. Any open or
# read errors are reported as read errors when AWAITB is later called.
if (FCLOSEFD(fp) == NO && FCHAN(fp) != ERR)
call zcall4 (ZARDBF(fp), FCHAN(fp), buffer, maxbytes, file_offset)
else {
if (FCHAN(fp) == ERR)
call zcall3 (FDEVOPEN(fp), FPKOSFN(fp), FMODE(fp), FCHAN(fp))
if (FCHAN(fp) != ERR) {
call zcall4 (ZARDBF(fp),
FCHAN(fp), buffer, maxbytes, file_offset)
if (FCLOSEFD(fp) == YES) {
junk = awaitb (FAFD(fp))
call zcall2 (ZCLSBF(fp), FCHAN(fp), junk)
FCHAN(fp) = ERR
}
}
}
end
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