Add xdr_len, to work out required buffer size

Currently, code which uses xdr_mem needs to take a guess at the
buffer size required, allocate that guess, and error out if the
data being encoded actually exceeds the guess.

This adds a new XDR mechanism - xdr_len, which can return
(using xdr_getpos) the length of the buffer required to XDR
encode a given structure.

Change-Id: I6e04c051118a26441caebdbcb2b5768d3c4389b6
Reviewed-on: http://gerrit.openafs.org/1221
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>

src/rx/Makefile.in

@@ -18,7 +18,7 @@ CFLAGS=${COMMON_CFLAGS} ${XCFLAGS} ${ARCHFLAGS} ${RXDEBUG}
 # Generic xdr objects (or, at least, xdr stuff that's not newly defined for rx).
 # Really the xdr stuff should be in its own directory.
 #
-XDROBJS_common = xdr.o xdr_array.o xdr_rx.o xdr_mem.o xdr_afsuuid.o
+XDROBJS_common = xdr.o xdr_array.o xdr_rx.o xdr_mem.o xdr_len.o xdr_afsuuid.o
 
 XDROBJS = xdr_arrayn.o ${XDROBJS_common}
 

src/rx/xdr_len.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2010 Your Filesystem Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <afsconfig.h>
+#include <afs/param.h>
+
+#include <stdlib.h>
+#include "xdr.h"
+
+static void
+xdrlen_destroy(AFS_XDRS_T axdrs)
+{
+}
+
+static bool_t
+xdrlen_getint32(AFS_XDRS_T axdrs, afs_int32 * lp)
+{
+    return (FALSE);
+}
+
+static bool_t
+xdrlen_putint32(AFS_XDRS_T axdrs, afs_int32 * lp)
+{
+    XDR * xdrs = (XDR *)axdrs;
+
+    xdrs->x_handy += sizeof(afs_int32);
+    return (TRUE);
+}
+
+static bool_t
+xdrlen_getbytes(AFS_XDRS_T axdrs, caddr_t addr, u_int len)
+{
+    return (FALSE);
+}
+
+static bool_t
+xdrlen_putbytes(AFS_XDRS_T axdrs, caddr_t addr, u_int len)
+{
+    XDR * xdrs = (XDR *)axdrs;
+
+    xdrs->x_handy += len;
+    return (TRUE);
+}
+
+static u_int
+xdrlen_getpos(AFS_XDRS_T axdrs)
+{
+    XDR * xdrs = (XDR *)axdrs;
+
+    return xdrs->x_handy;
+}
+
+static bool_t
+xdrlen_setpos(AFS_XDRS_T axdrs, u_int pos)
+{
+    XDR * xdrs = (XDR *)axdrs;
+
+    xdrs->x_handy = pos;
+    return (TRUE);
+}
+
+static afs_int32 *
+xdrlen_inline(AFS_XDRS_T axdrs, u_int len)
+{
+    return NULL;
+}
+
+static struct xdr_ops xdrlen_ops = {
+#ifdef AFS_NT40_ENV
+    /* Windows does not support labeled assigments */
+    xdrlen_getint32,    /* not supported */
+    xdrlen_putint32,    /* serialize an afs_int32 */
+    xdrlen_getbytes,    /* not supported */
+    xdrlen_putbytes,    /* serialize counted bytes */
+    xdrlen_getpos,      /* get offset in the stream */
+    xdrlen_setpos,      /* set offset in the stream */
+    xdrlen_inline,      /* not supported */
+    xdrlen_destroy      /* destroy stream */
+#else
+    .x_getint32 = xdrlen_getint32,
+    .x_putint32 = xdrlen_putint32,
+    .x_getbytes = xdrlen_getbytes,
+    .x_putbytes = xdrlen_putbytes,
+    .x_getpostn = xdrlen_getpos,
+    .x_setpostn = xdrlen_setpos,
+    .x_inline = xdrlen_inline,
+    .x_destroy = xdrlen_destroy
+#endif
+};
+
+/**
+ * Initialise an XDR stream to calculate the space required to encode
+ *
+ * This initialises an XDR stream object which can be used to calculate
+ * the space required to encode a particular structure into memory. No
+ * encoding is actually performed, a later call using xdrmem is necessary
+ * to do so.
+ *
+ * @param xdrs
+ * 	A pointer to a preallocated XDR sized block of memory.
+ */
+void
+xdrlen_create(XDR * xdrs)
+{
+    xdrs->x_op = XDR_ENCODE;
+    xdrs->x_ops = &xdrlen_ops;
+    xdrs->x_handy = 0;
+}

src/rx/xdr_prototypes.h

@@ -66,6 +66,9 @@ extern void   xdr_free(xdrproc_t proc, void *obj);
 extern bool_t xdr_float(XDR * xdrs, float *fp);
 extern bool_t xdr_double(XDR * xdrs, double *dp);
 
+/* xdr_len.c */
+extern void xdrlen_create(XDR *xdrs);
+
 /* xdr_mem.c */
 extern void xdrmem_create(XDR * xdrs, caddr_t addr, u_int size,
 			  enum xdr_op op);