/*-
 * Copyright (c) 1982, 1988 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.proprietary.c%
 *
 *	@(#)read.c	7.3 (Berkeley) 05/24/93
 */

#include <sys/param.h>
#include <stand.att/saio.h>

read(fdesc, buf, count)
	int fdesc, count;
	char *buf;
{
	register i, size;
	register struct iob *file;
	register struct fs *fs;
	int lbn, off;

	errno = 0;
#ifndef SMALL
	if (fdesc >= 0 && fdesc <= 2) {
		i = count;
		do {
			*buf = getchar();
		} while (--i && *buf++ != '\n');
		return (count - i);
	}
#endif
	fdesc -= 3;
	if (fdesc < 0 || fdesc >= SOPEN_MAX ||
	    ((file = &iob[fdesc])->i_flgs&F_ALLOC) == 0) {
		errno = EBADF;
		return (-1);
	}
	if ((file->i_flgs&F_READ) == 0) {
		errno = EBADF;
		return (-1);
	}
#ifndef SMALL
	if ((file->i_flgs & F_FILE) == 0) {
		file->i_cc = count;
		file->i_ma = buf;
		file->i_bn = file->i_boff + (file->i_offset / DEV_BSIZE);
		i = devread(file);
		if (i < 0)
			errno = file->i_error;
		else
			file->i_offset += i;
		return (i);
	}
#endif
	if (file->i_offset+count > file->i_ino.di_size)
		count = file->i_ino.di_size - file->i_offset;
	if ((i = count) <= 0)
		return (0);
	/*
	 * While reading full blocks, do I/O into user buffer.
	 * Anything else uses getc().
	 */
	fs = &file->i_fs;
	while (i) {
		off = blkoff(fs, file->i_offset);
		lbn = lblkno(fs, file->i_offset);
		size = dblksize(fs, &file->i_ino, lbn);
#ifndef SMALL
		if (off == 0 && size <= i) {
			file->i_bn = fsbtodb(fs, bmap(file, lbn)) +
			    file->i_boff;
			file->i_cc = size;
			file->i_ma = buf;
			if (devread(file) < 0) {
				errno = file->i_error;
				return (-1);
			}
			file->i_offset += size;
			file->i_cc = 0;
			buf += size;
			i -= size;
		} else {
#endif
			size -= off;
			if (size > i)
				size = i;
			i -= size;
			do {
				*buf++ = getc(fdesc+3);
			} while (--size);
#ifndef	SMALL
		}
#endif
	}
	return (count);
}

getc(fdesc)
	int fdesc;
{
	register struct iob *io;
	register struct fs *fs;
	register char *p;
	int c, lbn, off, size, diff;


#ifndef SMALL
	if (fdesc >= 0 && fdesc <= 2)
		return (getchar());
#endif
	fdesc -= 3;
	if (fdesc < 0 || fdesc >= SOPEN_MAX ||
	    ((io = &iob[fdesc])->i_flgs&F_ALLOC) == 0) {
		errno = EBADF;
		return (-1);
	}
	p = io->i_ma;
	if (io->i_cc <= 0) {
		if ((io->i_flgs & F_FILE) != 0) {
			diff = io->i_ino.di_size - io->i_offset;
			if (diff <= 0)
				return (-1);
			fs = &io->i_fs;
			lbn = lblkno(fs, io->i_offset);
			io->i_bn = fsbtodb(fs, bmap(io, lbn)) + io->i_boff;
			off = blkoff(fs, io->i_offset);
			size = dblksize(fs, &io->i_ino, lbn);
		} else {
			io->i_bn = io->i_offset / DEV_BSIZE + io->i_boff;
			off = 0;
			size = DEV_BSIZE;
		}
		io->i_ma = io->i_buf;
		io->i_cc = size;
		if (devread(io) < 0) {
			errno = io->i_error;
			return (-1);
		}
		if ((io->i_flgs & F_FILE) != 0) {
			if (io->i_offset - off + size >= io->i_ino.di_size)
				io->i_cc = diff + off;
			io->i_cc -= off;
		}
		p = &io->i_buf[off];
	}
	io->i_cc--;
	io->i_offset++;
	c = (unsigned)*p++;
	io->i_ma = p;
	return (c);
}