Initial sketch for the generic data-transfer interface.

src/core/interface.c

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <assert.h>
+#include <gpxe/interface.h>
+
+/** @file
+ *
+ * Object communication interfaces
+ *
+ */
+
+/**
+ * Obtain reference to interface
+ *
+ * @v intf		Interface
+ * @ret intf		Interface
+ *
+ * Increases the reference count on the interface.
+ */
+static struct interface * intf_get ( struct interface *intf ) {
+	intf->refcnt ( intf, +1 );
+	return intf;
+}
+
+/**
+ * Drop reference to interface
+ *
+ * @v intf		Interface
+ *
+ * Decreases the reference count on the interface.
+ */
+static void intf_put ( struct interface *intf ) {
+	intf->refcnt ( intf, -1 );
+}
+
+/**
+ * Plug an interface into a new destination interface
+ *
+ * @v intf		Interface
+ * @v dest		New destination interface
+ *
+ * The reference to the existing destination interface is dropped, a
+ * reference to the new destination interface is obtained, and the
+ * interface is updated to point to the new destination interface.
+ *
+ * Note that there is no "unplug" call; instead you must plug the
+ * interface into a null interface.
+ */
+void plug ( struct interface *intf, struct interface *dest ) {
+	intf_put ( intf->dest );
+	intf->dest = intf_get ( dest );
+}
+
+/**
+ * Null update reference count
+ *
+ * @v intf		Interface
+ * @v delta		Change to apply to reference count
+ *
+ * Use this as the refcnt() method for an interface that does not need
+ * to support reference counting.
+ */
+void null_refcnt ( struct interface *intf __unused, int delta __unused ) {
+	/* Do nothing */
+}

src/core/xfer.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <errno.h>
+#include <gpxe/xfer.h>
+
+/** @file
+ *
+ * Data transfer interfaces
+ *
+ */
+
+/**
+ * Deliver datagram
+ *
+ * @v xfer		Data-transfer interface
+ * @v iobuf		Datagram I/O buffer
+ * @ret rc		Return status code
+ */
+int deliver ( struct xfer_interface *xfer, struct io_buffer *iobuf ) {
+	struct xfer_interface *dest = xfer_dest ( xfer );
+
+	return dest->op->deliver ( dest, xfer, iobuf );
+}
+
+/**
+ * Null deliver datagram
+ *
+ * @v xfer		Data-transfer interface
+ * @v src		Source interface
+ * @v iobuf		Datagram I/O buffer
+ * @ret rc		Return status code
+ */
+static int null_deliver ( struct xfer_interface *xfer __unused,
+			  struct xfer_interface *src __unused,
+			  struct io_buffer *iobuf ) {
+	free_iob ( iobuf );
+	return -EPIPE;
+}
+
+/** Null data transfer interface operations */
+struct xfer_interface_operations null_xfer_ops = {
+	.deliver = null_deliver,
+};
+
+/**
+ * Null data transfer interface
+ *
+ * This is the interface to which data transfer interfaces are
+ * connected when unplugged.  It will never generate messages, and
+ * will silently absorb all received messages.
+ */
+struct xfer_interface null_xfer = {
+	.intf = {
+		.dest = &null_xfer.intf,
+		.refcnt = null_refcnt,
+	},
+	.op = &null_xfer_ops,
+};

src/include/gpxe/interface.h

@@ -0,0 +1,36 @@
+#ifndef _GPXE_INTERFACE_H
+#define _GPXE_INTERFACE_H
+
+/** @file
+ *
+ * Object communication interfaces
+ *
+ */
+
+/** An object communication interface */
+struct interface {
+	/** Destination interface
+	 *
+	 * When messages are sent via this interface, they will be
+	 * delivered to the destination interface.
+	 *
+	 * This pointer may never be NULL.  When the interface is
+	 * unplugged, it should point to a null interface.
+	 */
+	struct interface *dest;
+	/** Update reference count
+	 *
+	 * @v intf		Interface
+	 * @v delta		Change to apply to reference count
+	 *
+	 * This method updates the reference count for the object
+	 * containing the interface.
+	 */
+	void ( * refcnt ) ( struct interface *intf, int delta );
+};
+
+extern void plug ( struct interface *intf, struct interface *dest );
+
+extern void null_refcnt ( struct interface *intf, int delta );
+
+#endif /* _GPXE_INTERFACE_H */

src/include/gpxe/iobuf.h

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+#ifndef _GPXE_IOBUF_H
+#define _GPXE_IOBUF_H
+
+/** @file
+ *
+ * I/O buffers
+ *
+ */
+
+#include <stdint.h>
+#include <assert.h>
+#include <gpxe/list.h>
+
+/**
+ * A persistent I/O buffer
+ *
+ * This data structure encapsulates a long-lived I/O buffer.  The
+ * buffer may be passed between multiple owners, queued for possible
+ * retransmission, etc.
+ */
+struct io_buffer {
+	/** List of which this buffer is a member
+	 *
+	 * The list must belong to the current owner of the buffer.
+	 * Different owners may maintain different lists (e.g. a
+	 * retransmission list for TCP).
+	 */
+	struct list_head list;
+
+	/** Start of the buffer */
+	void *head;
+	/** Start of data */
+	void *data;
+	/** End of data */
+	void *tail;
+	/** End of the buffer */
+        void *end;
+};
+
+/**
+ * Reserve space at start of I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @v len	Length to reserve
+ * @ret data	Pointer to new start of buffer
+ */
+static inline void * iob_reserve ( struct io_buffer *iob, size_t len ) {
+	iob->data += len;
+	iob->tail += len;
+	assert ( iob->tail <= iob->end );
+	return iob->data;
+}
+
+/**
+ * Add data to start of I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @v len	Length to add
+ * @ret data	Pointer to new start of buffer
+ */
+static inline void * iob_push ( struct io_buffer *iob, size_t len ) {
+	iob->data -= len;
+	assert ( iob->data >= iob->head );
+	return iob->data;
+}
+
+/**
+ * Remove data from start of I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @v len	Length to remove
+ * @ret data	Pointer to new start of buffer
+ */
+static inline void * iob_pull ( struct io_buffer *iob, size_t len ) {
+	iob->data += len;
+	assert ( iob->data <= iob->tail );
+	return iob->data;
+}
+
+/**
+ * Add data to end of I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @v len	Length to add
+ * @ret data	Pointer to newly added space
+ */
+static inline void * iob_put ( struct io_buffer *iob, size_t len ) {
+	void *old_tail = iob->tail;
+	iob->tail += len;
+	assert ( iob->tail <= iob->end );
+	return old_tail;
+}
+
+/**
+ * Remove data from end of I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @v len	Length to remove
+ */
+static inline void iob_unput ( struct io_buffer *iob, size_t len ) {
+	iob->tail -= len;
+	assert ( iob->tail >= iob->data );
+}
+
+/**
+ * Empty an I/O buffer
+ *
+ * @v iob	I/O buffer
+ */
+static inline void iob_empty ( struct io_buffer *iob ) {
+	iob->tail = iob->data;
+}
+
+/**
+ * Calculate length of data in an I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @ret len	Length of data in buffer
+ */
+static inline size_t iob_len ( struct io_buffer *iob ) {
+	return ( iob->tail - iob->data );
+}
+
+/**
+ * Calculate available space at start of an I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @ret len	Length of data available at start of buffer
+ */
+static inline size_t iob_headroom ( struct io_buffer *iob ) {
+	return ( iob->data - iob->head );
+}
+
+/**
+ * Calculate available space at end of an I/O buffer
+ *
+ * @v iob	I/O buffer
+ * @ret len	Length of data available at end of buffer
+ */
+static inline size_t iob_tailroom ( struct io_buffer *iob ) {
+	return ( iob->end - iob->tail );
+}
+
+extern struct io_buffer * alloc_iob ( size_t len );
+extern void free_iob ( struct io_buffer *iob );
+extern void iob_pad ( struct io_buffer *iob, size_t min_len );
+
+#endif /* _GPXE_IOBUF_H */

src/include/gpxe/xfer.h

@@ -0,0 +1,78 @@
+#ifndef _GPXE_XFER_H
+#define _GPXE_XFER_H
+
+/** @file
+ *
+ * Data transfer interfaces
+ *
+ */
+
+#include <stddef.h>
+#include <gpxe/interface.h>
+#include <gpxe/iobuf.h>
+
+struct xfer_interface;
+
+/** Data transfer interface operations */
+struct xfer_interface_operations {
+	/** Deliver datagram
+	 *
+	 * @v xfer		Data-transfer interface
+	 * @v src		Source  interface
+	 * @v iobuf		Datagram I/O buffer
+	 * @ret rc		Return status code
+	 */
+	int ( * deliver ) ( struct xfer_interface *xfer,
+			    struct xfer_interface *src,
+			    struct io_buffer *iobuf );
+};
+
+/** A data transfer interface */
+struct xfer_interface {
+	/** Generic object communication interface */
+	struct interface intf;
+	/** Operations for received messages */
+	struct xfer_interface_operations *op;
+};
+
+extern struct xfer_interface null_xfer;
+extern struct xfer_interface_operations null_xfer_ops;
+
+static inline struct xfer_interface *
+xfer_dest ( struct xfer_interface *xfer ) {
+	return container_of ( xfer->intf.dest, struct xfer_interface, intf );
+}
+
+/**
+ * Plug a data-transfer interface into a new destination interface
+ *
+ * @v xfer		Data-transfer interface
+ * @v dest		New destination interface
+ */
+static inline void xfer_plug ( struct xfer_interface *xfer,
+			       struct xfer_interface *dest ) {
+	plug ( &xfer->intf, &dest->intf );
+}
+
+/**
+ * Unplug a data-transfer interface
+ *
+ * @v xfer		Data-transfer interface
+ */
+static inline void xfer_unplug ( struct xfer_interface *xfer ) {
+	plug ( &xfer->intf, &null_xfer.intf );
+}
+
+/**
+ * Terminate a data-transfer interface
+ *
+ * @v xfer		Data-transfer interface
+ *
+ * After calling this method, no further messages will be received via
+ * the interface.
+ */
+static inline void xfer_terminate ( struct xfer_interface *xfer ) {
+	xfer->op = &null_xfer_ops;
+};
+
+#endif /* _GPXE_XFER_H */