[xfer] Generalise metadata "whence" field to "flags" field

iPXE has never supported SEEK_END; the usage of "whence" offers only
the options of SEEK_SET and SEEK_CUR and so is effectively a boolean
flag.  Further flags will be required to support additional metadata
required by the Fibre Channel network model, so repurpose the "whence"
field as a generic "flags" field.

xfer_seek() has always been used with SEEK_SET, so remove the "whence"
field altogether from its argument list.

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

src/arch/i386/interface/pxe/pxe_tftp.c

 	int rc = 0;
 
 	/* Calculate new buffer position */
-	if ( meta->whence != SEEK_CUR )
+	if ( meta->flags & XFER_FL_ABS_OFFSET )
 		pxe_tftp->offset = 0;
 	pxe_tftp->offset += meta->offset;
 

src/core/downloader.c

 	int rc;
 
 	/* Calculate new buffer position */
-	if ( meta->whence != SEEK_CUR )
+	if ( meta->flags & XFER_FL_ABS_OFFSET )
 		downloader->pos = 0;
 	downloader->pos += meta->offset;
 

src/core/posix_io.c

 				     struct xfer_metadata *meta ) {
 
 	/* Keep track of file position solely for the filesize */
-	if ( meta->whence != SEEK_CUR )
+	if ( meta->flags & XFER_FL_ABS_OFFSET )
 		file->pos = 0;
 	file->pos += meta->offset;
 	if ( file->filesize < file->pos )

src/core/xfer.c

  *
  * @v intf		Data transfer interface
  * @v offset		Offset to new position
- * @v whence		Basis for new position
  * @ret rc		Return status code
  */
-int xfer_seek ( struct interface *intf, off_t offset, int whence ) {
+int xfer_seek ( struct interface *intf, off_t offset ) {
 	struct io_buffer *iobuf;
 	struct xfer_metadata meta = {
+		.flags = XFER_FL_ABS_OFFSET,
 		.offset = offset,
-		.whence = whence,
 	};
 
-	DBGC ( INTF_COL ( intf ), "INTF " INTF_FMT " seek %s+%ld\n",
-	       INTF_DBG ( intf ), whence_text ( whence ), offset );
+	DBGC ( INTF_COL ( intf ), "INTF " INTF_FMT " seek to %ld\n",
+	       INTF_DBG ( intf ), offset );
 
 	/* Allocate and send a zero-length data buffer */
 	iobuf = xfer_alloc_iob ( intf, 0 );

src/include/ipxe/xfer.h

 struct sockaddr;
 struct net_device;
 
-/** Basis positions for seek() events */
-enum seek_whence {
-	SEEK_CUR = 0,
-	SEEK_SET,
-};
-
 /** Data transfer metadata */
 struct xfer_metadata {
-	/** Position of data within stream */
-	off_t offset;
-	/** Basis for data position
+	/** Flags
+	 *
+	 * This is the bitwise OR of zero or more @c XFER_FL_XXX
+	 * constants.
+	 */
+	unsigned int flags;
+	/** Offset of data within stream
 	 *
-	 * Must be one of @c SEEK_CUR or @c SEEK_SET.
+	 * This is an absolute offset if the @c XFER_FL_ABS_OFFSET
+	 * flag is set, otherwise a relative offset.  (A freshly
+	 * zeroed @c xfer_metadata structure therefore represents a
+	 * relative offset of zero, i.e. no offset from the current
+	 * position.)
 	 */
-	int whence;
+	off_t offset;
 	/** Source socket address, or NULL */
 	struct sockaddr *src;
 	/** Destination socket address, or NULL */
 	struct net_device *netdev;
 };
 
-/**
- * Describe seek basis
- *
- * @v whence		Basis for new position
- */
-static inline __attribute__ (( always_inline )) const char *
-whence_text ( int whence ) {
-	switch ( whence ) {
-	case SEEK_CUR:	return "CUR";
-	case SEEK_SET:	return "SET";
-	default:	return "INVALID";
-	}
-}
+/** Offset is absolute */
+#define XFER_FL_ABS_OFFSET 0x0001
 
 /* Data transfer interface operations */
 
 			  const char *format, va_list args );
 extern int __attribute__ (( format ( printf, 2, 3 ) ))
 xfer_printf ( struct interface *intf, const char *format, ... );
-extern int xfer_seek ( struct interface *intf, off_t offset, int whence );
+extern int xfer_seek ( struct interface *intf, off_t offset );
 
 #endif /* _IPXE_XFER_H */

src/net/tcp/http.c

 	}
 
 	/* Use seek() to notify recipient of filesize */
-	xfer_seek ( &http->xfer, http->content_length, SEEK_SET );
-	xfer_seek ( &http->xfer, 0, SEEK_SET );
+	xfer_seek ( &http->xfer, http->content_length );
+	xfer_seek ( &http->xfer, 0 );
 
 	return 0;
 }

src/net/udp/slam.c

 	}
 
 	/* Notify recipient of file size */
-	xfer_seek ( &slam->xfer, slam->total_bytes, SEEK_SET );
+	xfer_seek ( &slam->xfer, slam->total_bytes );
 
 	return 0;
 }
 
 	/* Pass to recipient */
 	memset ( &meta, 0, sizeof ( meta ) );
-	meta.whence = SEEK_SET;
+	meta.flags = XFER_FL_ABS_OFFSET;
 	meta.offset = ( packet * slam->block_size );
 	if ( ( rc = xfer_deliver ( &slam->xfer, iobuf, &meta ) ) != 0 )
 		goto err;

src/net/udp/tftp.c

 	tftp->filesize = filesize;
 
 	/* Notify recipient of file size */
-	xfer_seek ( &tftp->xfer, filesize, SEEK_SET );
-	xfer_seek ( &tftp->xfer, 0, SEEK_SET );
+	xfer_seek ( &tftp->xfer, filesize );
+	xfer_seek ( &tftp->xfer, 0 );
 
 	/* Calculate expected number of blocks.  Note that files whose
 	 * length is an exact multiple of the blocksize will have a
 
 	/* Deliver data */
 	memset ( &meta, 0, sizeof ( meta ) );
-	meta.whence = SEEK_SET;
+	meta.flags = XFER_FL_ABS_OFFSET;
 	meta.offset = offset;
 	if ( ( rc = xfer_deliver ( &tftp->xfer, iob_disown ( iobuf ),
 				   &meta ) ) != 0 ) {