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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <config.h>
include <syserr.h>
include <fio.h>
# READ -- Read binary chars from a file. Data is read in "chunks" from
# the file buffer into the output buffer supplied by the calling procedure,
# refilling the file buffer as necessary. The read terminates, possibly
# returning fewer than the maximum number of chars, if the file buffer
# cannot be filled (as occurs at the EOF of a binary file, or when reading
# from a terminal or pipe).
int procedure read (fd, buffer, maxchars)
int fd
char buffer[ARB]
int maxchars
int maxch
bool stream
int nchars, chunk_size, nchars_read, filbuf()
errchk filbuf, filerr
include <fio.com>
begin
if (fd <= 0 || fiodes[fd] == NULL)
call syserr (SYS_FILENOTOPEN)
nchars = 0
maxch = maxchars
stream = (FBLKSIZE(fiodes[fd]) == 0)
while (nchars < maxch) {
if (iop[fd] < bufptr[fd] || iop[fd] >= itop[fd]) {
nchars_read = filbuf (fd)
if (nchars_read == EOF)
break # return EOF only if nchars = 0
else {
# Don't loop if record structured device or EOF.
if (itop[fd] < buftop[fd] || stream)
maxch = min (maxchars, nchars + nchars_read)
}
}
chunk_size = min (maxch - nchars, itop[fd] - iop[fd])
if (chunk_size <= 0)
break
else {
call amovc (Memc[iop[fd]], buffer[nchars+1], chunk_size)
iop[fd] = iop[fd] + chunk_size
nchars = nchars + chunk_size
}
}
FILSTAT(fiodes[fd]) = nchars
FNCHARS(fiodes[fd]) = nchars
if (nchars == 0)
return (EOF)
else
return (nchars)
end
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