src/xdr_rec.c

/*
 * Copyright (c) 2009, Sun Microsystems, 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:
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - 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.
 * - Neither the name of Sun Microsystems, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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 <config.h>
#include <sys/cdefs.h>
#include <sys/cdefs.h>

/*
 * xdr_rec.c, Implements TCP/IP based XDR streams with a "record marking"
 * layer above tcp (for rpc's use).
 *
 * Copyright (C) 1984, Sun Microsystems, Inc.
 *
 * These routines interface XDRSTREAMS to a tcp/ip connection.
 * There is a record marking layer between the xdr stream
 * and the tcp transport level.  A record is composed on one or more
 * record fragments.  A record fragment is a thirty-two bit header followed
 * by n bytes of data, where n is contained in the header.  The header
 * is represented as a htonl(u_long).  Thegh order bit encodes
 * whether or not the fragment is the last fragment of the record
 * (1 => fragment is last, 0 => more fragments to follow.
 * The other 31 bits encode the byte length of the fragment.
 */

#include <sys/types.h>

#if !defined(_WIN32)
#include <netinet/in.h>
#include <err.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <rpc/types.h>
#include <misc/portable.h>
#include <rpc/xdr.h>
#include <rpc/rpc.h>
#include <rpc/auth.h>
#include <rpc/svc_auth.h>
#include <rpc/svc.h>
#include <rpc/clnt.h>
#include <stddef.h>
#include "rpc_com.h"
static bool xdrrec_getlong(XDR *, long *);
static bool xdrrec_putlong(XDR *, const long *);
static bool xdrrec_getbytes(XDR *, char *, u_int);

static bool xdrrec_putbytes(XDR *, const char *, u_int);
static u_int xdrrec_getpos(XDR *);
static bool xdrrec_setpos(XDR *, u_int);
static int32_t *xdrrec_inline(XDR *, u_int);
static void xdrrec_destroy(XDR *);
static bool xdrrec_noop(void);

typedef bool (*dummyfunc3) (XDR *, int, void *);
typedef bool (*dummy_getbufs) (XDR *, xdr_uio *, u_int);
typedef bool (*dummy_putbufs) (XDR *, xdr_uio *, u_int);

static const struct  xdr_ops xdrrec_ops = {
	xdrrec_getlong,
	xdrrec_putlong,
	xdrrec_getbytes,
	xdrrec_putbytes,
	xdrrec_getpos,
	xdrrec_setpos,
	xdrrec_inline,
	xdrrec_destroy,
	(dummyfunc3) xdrrec_noop,       /* x_control */
	(dummy_getbufs) xdrrec_noop,    /* x_getbufs */
	(dummy_putbufs) xdrrec_noop     /* x_putbufs */
};

/*
 * A record is composed of one or more record fragments.
 * A record fragment is a four-byte header followed by zero to
 * 2**32-1 bytes.  The header is treated as a long unsigned and is
 * encode/decoded to the network via htonl/ntohl.  The low order 31 bits
 * are a byte count of the fragment.  The highest order bit is a boolean:
 * 1 => this fragment is the last fragment of the record,
 * 0 => this fragment is followed by more fragment(s).
 *
 * The fragment/record machinery is not general;  it is constructed to
 * meet the needs of xdr and rpc based on tcp.
 */

#define LAST_FRAG ((u_int32_t)(1 << 31))

typedef struct rec_strm {
	XDR *xdrs;
	char *tcp_handle;
	/*
	 * out-goung bits
	 */
	int (*writeit) (XDR *, void *, void *, int);
	char *out_base;		/* output buffer (points to frag header) */
	char *out_finger;	/* next output position */
	char *out_boundry;	/* data cannot up to this address */
	u_int32_t *frag_header;	/* beginning of curren fragment */
	bool frag_sent;		/* true if buffer sent in middle of record */
	/*
	 * in-coming bits
	 */
	int (*readit) (XDR *, void *, void *, int);
	u_long in_size;		/* fixed size of the input buffer */
	char *in_base;
	char *in_finger;	/* location of next byte to be had */
	char *in_boundry;	/* can read up to this location */
	long fbtbc;		/* fragment bytes to be consumed */
	bool last_frag;
	u_int sendsize;
	u_int recvsize;

	bool nonblock;
	bool in_haveheader;
	u_int32_t in_header;
	char *in_hdrp;
	int in_hdrlen;
	int in_reclen;
	int in_received;
	int in_maxrec;
} RECSTREAM;

static u_int fix_buf_size(u_int);
static bool flush_out(RECSTREAM *, bool);
static bool fill_input_buf(RECSTREAM *);
static bool get_input_bytes(RECSTREAM *, char *, int);
static bool set_input_fragment(RECSTREAM *);
static bool skip_input_bytes(RECSTREAM *, long);
static bool realloc_stream(RECSTREAM *, int);

/*
 * Create an xdr handle for xdrrec
 * xdrrec_create fills in xdrs.  Sendsize and recvsize are
 * send and recv buffer sizes (0 => use default).
 * tcp_handle is an opaque handle that is passed as the first parameter to
 * the procedures readit and writeit.  Readit and writeit are read and
 * write respectively.   They are like the system
 * calls expect that they take an opaque handle rather than an fd.
 */
void
xdrrec_create(XDR *xdrs, u_int sendsize, u_int recvsize, void *tcp_handle,
	      /* like read, but pass it a tcp_handle, not sock */
	      int (*readit) (XDR *, void *, void *, int),
	      /* like write, but pass it a tcp_handle, not sock */
	      int (*writeit) (XDR *, void *, void *, int))
{
	RECSTREAM *rstrm = mem_alloc(sizeof(RECSTREAM));

	if (rstrm == NULL) {
		__warnx(TIRPC_DEBUG_FLAG_XDRREC,
			"xdrrec_create: out of memory");
		/*
		 *  This is bad.  Should rework xdrrec_create to
		 *  return a handle, and in this case return NULL
		 */
		return;
	}
	rstrm->sendsize = sendsize = fix_buf_size(sendsize);
	rstrm->out_base = mem_alloc(rstrm->sendsize);
	if (rstrm->out_base == NULL) {
		__warnx(TIRPC_DEBUG_FLAG_XDRREC,
			"xdrrec_create: out of memory");
		mem_free(rstrm, sizeof(RECSTREAM));
		return;
	}
	rstrm->recvsize = recvsize = fix_buf_size(recvsize);
	rstrm->in_base = mem_alloc(recvsize);
	if (rstrm->in_base == NULL) {
		__warnx(TIRPC_DEBUG_FLAG_XDRREC,
			"xdrrec_create: out of memory");
		mem_free(rstrm->out_base, sendsize);
		mem_free(rstrm, sizeof(RECSTREAM));
		return;
	}
	/*
	 * now the rest ...
	 */
	xdrs->x_ops = &xdrrec_ops;
	xdrs->x_lib[0] = NULL;
	xdrs->x_lib[1] = NULL;
	xdrs->x_public = NULL;
	xdrs->x_private = rstrm;
	rstrm->xdrs = xdrs;
	rstrm->tcp_handle = tcp_handle;
	rstrm->readit = readit;
	rstrm->writeit = writeit;
	rstrm->out_finger = rstrm->out_boundry = rstrm->out_base;
	rstrm->frag_header = (u_int32_t *) (void *)rstrm->out_base;
	rstrm->out_finger += sizeof(u_int32_t);
	rstrm->out_boundry += sendsize;
	rstrm->frag_sent = false;
	rstrm->in_size = recvsize;
	rstrm->in_boundry = rstrm->in_base;
	rstrm->in_finger = (rstrm->in_boundry += recvsize);
	rstrm->fbtbc = 0;
	rstrm->last_frag = true;
	rstrm->in_haveheader = false;
	rstrm->in_hdrlen = 0;
	rstrm->in_hdrp = (char *)(void *)&rstrm->in_header;
	rstrm->nonblock = false;
	rstrm->in_reclen = 0;
	rstrm->in_received = 0;
}

/*
 * The routines defined below are the xdr ops which will go into the
 * xdr handle filled in by xdrrec_create.
 */

static bool
xdrrec_getlong(XDR *xdrs, long *lp)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	int32_t *buflp = (int32_t *) (void *)(rstrm->in_finger);
	int32_t mylong;

	/* first try the inline, fast case */
	if ((rstrm->fbtbc >= sizeof(int32_t))
	    && ((PtrToUlong(rstrm->in_boundry) - PtrToUlong(buflp)) >=
		sizeof(int32_t))) {
		*lp = (long)ntohl((u_int32_t) (*buflp));
		rstrm->fbtbc -= sizeof(int32_t);
		rstrm->in_finger += sizeof(int32_t);
	} else {
		if (!xdrrec_getbytes
		    (xdrs, (char *)(void *)&mylong, sizeof(int32_t)))
			return (false);
		*lp = (long)ntohl((u_int32_t) mylong);
	}
	return (true);
}

static bool
xdrrec_putlong(XDR *xdrs, const long *lp)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	int32_t *dest_lp = ((int32_t *) (void *)(rstrm->out_finger));

	rstrm->out_finger += sizeof(int32_t);
	if (rstrm->out_finger > rstrm->out_boundry) {
		/*
		 * this case should almost never happen so the code is
		 * inefficient
		 */
		rstrm->out_finger -= sizeof(int32_t);
		rstrm->frag_sent = true;
		if (!flush_out(rstrm, false))
			return (false);
		dest_lp = ((int32_t *) (void *)(rstrm->out_finger));
		rstrm->out_finger += sizeof(int32_t);
	}
	*dest_lp = (int32_t) htonl((u_int32_t) (*lp));
	return (true);
}

static bool /* must manage buffers, fragments, and records */
xdrrec_getbytes(XDR *xdrs, char *addr, u_int len)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	int current;

	while (len > 0) {
		current = (int)rstrm->fbtbc;
		if (current == 0) {
			if (rstrm->last_frag)
				return (false);
			if (!set_input_fragment(rstrm))
				return (false);
			continue;
		}
		current = (len < current) ? len : current;
		if (!get_input_bytes(rstrm, addr, current))
			return (false);
		addr += current;
		rstrm->fbtbc -= current;
		len -= current;
	}
	return (true);
}

static bool
xdrrec_putbytes(XDR *xdrs, const char *addr, u_int len)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	size_t current;

	while (len > 0) {
		current =
		    (size_t) (PtrToUlong(rstrm->out_boundry) -
			      PtrToUlong(rstrm->out_finger));
		current = (len < current) ? len : current;
		memmove(rstrm->out_finger, addr, current);
		rstrm->out_finger += current;
		addr += current;
		len -= current;
		if (rstrm->out_finger == rstrm->out_boundry) {
			rstrm->frag_sent = true;
			if (!flush_out(rstrm, false))
				return (false);
		}
	}
	return (true);
}

static u_int
xdrrec_getpos(XDR *xdrs)
{
	RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
	off_t pos;

	switch (xdrs->x_op) {

	case XDR_ENCODE:
		pos = rstrm->out_finger - rstrm->out_base - BYTES_PER_XDR_UNIT;
		break;

	case XDR_DECODE:
		pos = rstrm->in_boundry - rstrm->in_finger - BYTES_PER_XDR_UNIT;
		break;

	default:
		/* XXX annoys Coverity */
		pos = (off_t) -1;
		break;
	}
	return ((u_int) pos);
}

static bool
xdrrec_setpos(XDR *xdrs, u_int pos)
{
	RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
	u_int currpos = xdrrec_getpos(xdrs);
	int delta = currpos - pos;
	char *newpos;

	if ((int)currpos != -1)
		switch (xdrs->x_op) {

		case XDR_ENCODE:
			newpos = rstrm->out_finger - delta;
			if ((newpos > (char *)(void *)(rstrm->frag_header))
			    && (newpos < rstrm->out_boundry)) {
				rstrm->out_finger = newpos;
				return (true);
			}
			break;

		case XDR_DECODE:
			newpos = rstrm->in_finger - delta;
			if ((delta < (int)(rstrm->fbtbc))
			    && (newpos <= rstrm->in_boundry)
			    && (newpos >= rstrm->in_base)) {
				rstrm->in_finger = newpos;
				rstrm->fbtbc -= delta;
				return (true);
			}
			break;

		case XDR_FREE:
			break;
		}
	return (false);
}

static int32_t *
xdrrec_inline(XDR *xdrs, u_int len)
{
	RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
	int32_t *buf = NULL;

	switch (xdrs->x_op) {

	case XDR_ENCODE:
		if ((rstrm->out_finger + len) <= rstrm->out_boundry) {
			buf = (int32_t *) (void *)rstrm->out_finger;
			rstrm->out_finger += len;
		}
		break;

	case XDR_DECODE:
		if ((len <= rstrm->fbtbc)
		    && ((rstrm->in_finger + len) <= rstrm->in_boundry)) {
			buf = (int32_t *) (void *)rstrm->in_finger;
			rstrm->fbtbc -= len;
			rstrm->in_finger += len;
		}
		break;

	case XDR_FREE:
		break;
	}
	return (buf);
}

static void
xdrrec_destroy(XDR *xdrs)
{
	RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;

	mem_free(rstrm->out_base, rstrm->sendsize);
	mem_free(rstrm->in_base, rstrm->recvsize);
	mem_free(rstrm, sizeof(RECSTREAM));
}

/*
 * Exported routines to manage xdr records
 */

/*
 * Before reading (deserializing from the stream, one should always call
 * this procedure to guarantee proper record alignment.
 */
bool
xdrrec_skiprecord(XDR *xdrs)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	enum xprt_stat xstat;

	if (rstrm->nonblock) {
		if (__xdrrec_getrec(xdrs, &xstat, false)) {
			rstrm->fbtbc = 0;
			return true;
		}
		if (rstrm->in_finger == rstrm->in_boundry
		    && xstat == XPRT_MOREREQS) {
			rstrm->fbtbc = 0;
			return true;
		}
		return false;
	}

	while (rstrm->fbtbc > 0 || (!rstrm->last_frag)) {
		if (!skip_input_bytes(rstrm, rstrm->fbtbc))
			return (false);
		rstrm->fbtbc = 0;
		if ((!rstrm->last_frag) && (!set_input_fragment(rstrm)))
			return (false);
	}
	rstrm->last_frag = false;
	return (true);
}

/*
 * Look ahead function.
 * Returns true iff there is no more input in the buffer
 * after consuming the rest of the current record.
 */
bool
xdrrec_eof(XDR *xdrs)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);

	while (rstrm->fbtbc > 0 || (!rstrm->last_frag)) {
		if (!skip_input_bytes(rstrm, rstrm->fbtbc))
			return (true);
		rstrm->fbtbc = 0;
		if ((!rstrm->last_frag) && (!set_input_fragment(rstrm)))
			return (true);
	}
	if (rstrm->in_finger == rstrm->in_boundry)
		return (true);
	return (false);
}

/*
 * The client must tell the package when an end-of-record has occurred.
 * The second paramter tells whether the record should be flushed to the
 * (output) tcp stream.  (This let's the package support batched or
 * pipelined procedure calls.)  true => immmediate flush to tcp connection.
 */
bool
xdrrec_endofrecord(XDR *xdrs, bool sendnow)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	u_long len;		/* fragment length */

	if (sendnow || rstrm->frag_sent
	    || (PtrToUlong(rstrm->out_finger) + sizeof(u_int32_t) >=
		PtrToUlong(rstrm->out_boundry))) {
		rstrm->frag_sent = false;
		return (flush_out(rstrm, true));
	}
	len =
	    PtrToUlong((rstrm->out_finger)) - PtrToUlong((rstrm->frag_header)) -
	    sizeof(u_int32_t);
	*(rstrm->frag_header) = htonl((u_int32_t) len | LAST_FRAG);
	rstrm->frag_header = (u_int32_t *) (void *)rstrm->out_finger;
	rstrm->out_finger += sizeof(u_int32_t);
	return (true);
}

/*
 * Fill the stream buffer with a record for a non-blocking connection.
 * Return true if a record is available in the buffer, false if not.
 */
bool
__xdrrec_getrec(XDR *xdrs, enum xprt_stat *statp, bool expectdata)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);
	ssize_t n;
	int fraglen;

	if (!rstrm->in_haveheader) {
		n = rstrm->readit(xdrs, rstrm->tcp_handle, rstrm->in_hdrp,
				  (int)sizeof(rstrm->in_header) -
				  rstrm->in_hdrlen);
		if (n == 0) {
			*statp = expectdata ? XPRT_DIED : XPRT_IDLE;
			return false;
		}
		if (n < 0) {
			*statp = XPRT_DIED;
			return false;
		}
		rstrm->in_hdrp += n;
		rstrm->in_hdrlen += n;
		if (rstrm->in_hdrlen < sizeof(rstrm->in_header)) {
			*statp = XPRT_MOREREQS;
			return false;
		}
		rstrm->in_header = ntohl(rstrm->in_header);
		fraglen = (int)(rstrm->in_header & ~LAST_FRAG);
		if (fraglen == 0 || fraglen > rstrm->in_maxrec
		    || (rstrm->in_reclen + fraglen) > rstrm->in_maxrec) {
			*statp = XPRT_DIED;
			return false;
		}
		rstrm->in_reclen += fraglen;
		if (rstrm->in_reclen > rstrm->recvsize)
			realloc_stream(rstrm, rstrm->in_reclen);
		if (rstrm->in_header & LAST_FRAG) {
			rstrm->in_header &= ~LAST_FRAG;
			rstrm->last_frag = true;
		}
	}

	n = rstrm->readit(xdrs, rstrm->tcp_handle,
			  rstrm->in_base + rstrm->in_received,
			  (rstrm->in_reclen - rstrm->in_received));

	if (n < 0) {
		*statp = XPRT_DIED;
		return false;
	}

	if (n == 0) {
		*statp = expectdata ? XPRT_DIED : XPRT_IDLE;
		return false;
	}

	rstrm->in_received += n;

	if (rstrm->in_received == rstrm->in_reclen) {
		rstrm->in_haveheader = false;
		rstrm->in_hdrp = (char *)(void *)&rstrm->in_header;
		rstrm->in_hdrlen = 0;
		if (rstrm->last_frag) {
			rstrm->fbtbc = rstrm->in_reclen;
			rstrm->in_boundry = rstrm->in_base + rstrm->in_reclen;
			rstrm->in_finger = rstrm->in_base;
			rstrm->in_reclen = rstrm->in_received = 0;
			*statp = XPRT_MOREREQS;
			return true;
		}
	}

	*statp = XPRT_MOREREQS;
	return false;
}

bool
__xdrrec_setnonblock(XDR *xdrs, int maxrec)
{
	RECSTREAM *rstrm = (RECSTREAM *) (xdrs->x_private);

	rstrm->nonblock = true;
	if (maxrec == 0)
		maxrec = rstrm->recvsize;
	rstrm->in_maxrec = maxrec;
	return true;
}

/*
 * Internal useful routines
 */
static bool
flush_out(RECSTREAM *rstrm, bool eor)
{
	u_int32_t eormask = (eor == true) ? LAST_FRAG : 0;
	u_int32_t len =
	    (u_int32_t) (PtrToUlong(rstrm->out_finger) -
			 PtrToUlong(rstrm->frag_header) - sizeof(u_int32_t));

	*(rstrm->frag_header) = htonl(len | eormask);
	len =
	    (u_int32_t) (PtrToUlong(rstrm->out_finger) -
			 PtrToUlong(rstrm->out_base));
	if ((*(rstrm->writeit))
	    (rstrm->xdrs, rstrm->tcp_handle, rstrm->out_base,
	     (int)len) != (int)len)
		return (false);
	rstrm->frag_header = (u_int32_t *) (void *)rstrm->out_base;
	rstrm->out_finger = (char *)rstrm->out_base + sizeof(u_int32_t);
	return (true);
}

static bool /* knows nothing about records!  Only about input buffers */
fill_input_buf(RECSTREAM *rstrm)
{
	char *where;
	u_int32_t i;
	int len;

	if (rstrm->nonblock)
		return false;

	where = rstrm->in_base;
	i = (u_int32_t) (PtrToUlong(rstrm->in_boundry) % BYTES_PER_XDR_UNIT);
	where += i;
	len = (u_int32_t) (rstrm->in_size - i);
	len = (*(rstrm->readit)) (rstrm->xdrs, rstrm->tcp_handle, where, len);
	if (len == -1)
		return (false);
	rstrm->in_finger = where;
	where += len;
	rstrm->in_boundry = where;
	return (true);
}

static bool /* knows nothing about records!  Only about input buffers */
get_input_bytes(RECSTREAM *rstrm, char *addr, int len)
{
	size_t current;

	if (rstrm->nonblock) {
		if (len > (int)(rstrm->in_boundry - rstrm->in_finger))
			return false;
		memcpy(addr, rstrm->in_finger, (size_t) len);
		rstrm->in_finger += len;
		return true;
	}

	while (len > 0) {
		current =
		    (size_t) (PtrToUlong(rstrm->in_boundry) -
			      PtrToUlong(rstrm->in_finger));
		if (current == 0) {
			if (!fill_input_buf(rstrm))
				return (false);
			continue;
		}
		current = (len < current) ? len : current;
		memmove(addr, rstrm->in_finger, current);
		rstrm->in_finger += current;
		addr += current;
		len -= current;
	}
	return (true);
}

static bool /* next two bytes of the input stream are treated as a header */
set_input_fragment(RECSTREAM *rstrm)
{
	u_int32_t header;

	if (rstrm->nonblock)
		return false;
	if (!get_input_bytes(rstrm, (char *)(void *)&header, sizeof(header)))
		return (false);
	header = ntohl(header);
	rstrm->last_frag = ((header & LAST_FRAG) == 0) ? false : true;
	/*
	 * Sanity check. Try not to accept wildly incorrect
	 * record sizes. Unfortunately, the only record size
	 * we can positively identify as being 'wildly incorrect'
	 * is zero. Ridiculously large record sizes may look wrong,
	 * but we don't have any way to be certain that they aren't
	 * what the client actually intended to send us.
	 */
	if (header == 0)
		return (false);
	rstrm->fbtbc = header & (~LAST_FRAG);
	return (true);
}

static bool /* consumes input bytes; knows nothing about records! */
skip_input_bytes(RECSTREAM *rstrm, long cnt)
{
	u_int32_t current;

	while (cnt > 0) {
		current =
		    (size_t) (PtrToUlong(rstrm->in_boundry) -
			      PtrToUlong(rstrm->in_finger));
		if (current == 0) {
			if (!fill_input_buf(rstrm))
				return (false);
			continue;
		}
		current = (u_int32_t) ((cnt < current) ? cnt : current);
		rstrm->in_finger += current;
		cnt -= current;
	}
	return (true);
}

static u_int
fix_buf_size(u_int s)
{
	if (s < 100)
		s = 4000;
	return (RNDUP(s));
}

/*
 * Reallocate the input buffer for a non-block stream.
 */
static bool
realloc_stream(RECSTREAM *rstrm, int size)
{
	ptrdiff_t diff;
	char *buf;

	if (size > rstrm->recvsize) {
		buf = realloc(rstrm->in_base, (size_t) size);
		if (buf == NULL)
			return false;
		diff = buf - rstrm->in_base;
		rstrm->in_finger += diff;
		rstrm->in_base = buf;
		rstrm->in_boundry = buf + size;
		rstrm->recvsize = size;
		rstrm->in_size = size;
	}

	return (true);
}

static bool
xdrrec_noop(void)
{
	return (false);
}