my solution to lab5

lab/lib/console.c

@@ -15,11 +15,114 @@ cputchar(int ch)
 int
 getchar(void)
 {
+	unsigned char c;
 	int r;
-	// sys_cgetc does not block, but getchar should.
-	while ((r = sys_cgetc()) == 0)
-		sys_yield();
-	return r;
+
+	// JOS does, however, support standard _input_ redirection,
+	// allowing the user to redirect script files to the shell and such.
+	// getchar() reads a character from file descriptor 0.
+	r = read(0, &c, 1);
+	if (r < 0)
+		return r;
+	if (r < 1)
+		return -E_EOF;
+	return c;
 }
 
 
+// "Real" console file descriptor implementation.
+// The putchar/getchar functions above will still come here by default,
+// but now can be redirected to files, pipes, etc., via the fd layer.
+
+static ssize_t devcons_read(struct Fd*, void*, size_t);
+static ssize_t devcons_write(struct Fd*, const void*, size_t);
+static int devcons_close(struct Fd*);
+static int devcons_stat(struct Fd*, struct Stat*);
+
+struct Dev devcons =
+{
+	.dev_id =	'c',
+	.dev_name =	"cons",
+	.dev_read =	devcons_read,
+	.dev_write =	devcons_write,
+	.dev_close =	devcons_close,
+	.dev_stat =	devcons_stat
+};
+
+int
+iscons(int fdnum)
+{
+	int r;
+	struct Fd *fd;
+
+	if ((r = fd_lookup(fdnum, &fd)) < 0)
+		return r;
+	return fd->fd_dev_id == devcons.dev_id;
+}
+
+int
+opencons(void)
+{
+	int r;
+	struct Fd* fd;
+
+	if ((r = fd_alloc(&fd)) < 0)
+		return r;
+	if ((r = sys_page_alloc(0, fd, PTE_P|PTE_U|PTE_W|PTE_SHARE)) < 0)
+		return r;
+	fd->fd_dev_id = devcons.dev_id;
+	fd->fd_omode = O_RDWR;
+	return fd2num(fd);
+}
+
+static ssize_t
+devcons_read(struct Fd *fd, void *vbuf, size_t n)
+{
+	int c;
+
+	if (n == 0)
+		return 0;
+
+	while ((c = sys_cgetc()) == 0)
+		sys_yield();
+	if (c < 0)
+		return c;
+	if (c == 0x04)	// ctl-d is eof
+		return 0;
+	*(char*)vbuf = c;
+	return 1;
+}
+
+static ssize_t
+devcons_write(struct Fd *fd, const void *vbuf, size_t n)
+{
+	int tot, m;
+	char buf[128];
+
+	// mistake: have to nul-terminate arg to sys_cputs,
+	// so we have to copy vbuf into buf in chunks and nul-terminate.
+	for (tot = 0; tot < n; tot += m) {
+		m = n - tot;
+		if (m > sizeof(buf) - 1)
+			m = sizeof(buf) - 1;
+		memmove(buf, (char*)vbuf + tot, m);
+		sys_cputs(buf, m);
+	}
+	return tot;
+}
+
+static int
+devcons_close(struct Fd *fd)
+{
+	USED(fd);
+
+	return 0;
+}
+
+static int
+devcons_stat(struct Fd *fd, struct Stat *stat)
+{
+	strcpy(stat->st_name, "<cons>");
+	return 0;
+}
+