[syslog] Separate out generic line-based console functionality

Abstract out the generic line-handling portions of the syslog
putchar() routine, to allow use by other console types.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/lineconsole.h

@@ -0,0 +1,33 @@
+#ifndef _IPXE_LINECONSOLE_H
+#define _IPXE_LINECONSOLE_H
+
+/** @file
+ *
+ * Line-based console
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+
+/** A line-based console */
+struct line_console {
+	/** Data buffer
+	 *
+	 * Must initially be filled with NULs
+	 */
+	char *buffer;
+	/** Current index within buffer */
+	size_t index;
+	/** Length of buffer
+	 *
+	 * The final character of the buffer will only ever be used as
+	 * a potential terminating NUL.
+	 */
+	size_t len;
+};
+
+extern size_t line_putchar ( struct line_console *line, int character );
+
+#endif /* _IPXE_LINECONSOLE_H */