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- /****************************************************************************
- * net/utils/net_ipv6_mask2pref.c
- *
- * Copyright (C) 2016 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * 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.
- * 3. Neither the name NuttX 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 OWNER 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.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <stdint.h>
- #include <arpa/inet.h>
- #include "utils/utils.h"
- #ifdef CONFIG_NET_IPv6
- /****************************************************************************
- * Private Data
- ****************************************************************************/
- static const uint8_t g_nibblemap[16] =
- {
- 0, 0, 0, 0, 0, 0, 0, 0, /* 0: No bits, 1-7: Should not happen */
- 1, 1, 1, 1, /* 8: 1 bit, 9-b: Should not happen */
- 2, 2, 3, 4 /* c: 2 bits, d: Should not happen, e: 3 bits, f: 4 bits */
- };
- /****************************************************************************
- * Private Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: net_msbits4
- *
- * Description:
- * Count the number of leading '1' bits in an 4-bit nibble
- *
- ****************************************************************************/
- static inline uint8_t net_msbits4(uint8_t nibble)
- {
- /* Return the number of leading zeroes: 0-4) */
- return g_nibblemap[nibble];
- }
- /****************************************************************************
- * Name: net_msbits8
- *
- * Description:
- * Count the number of leading '1' bits in an 8-bit byte
- *
- ****************************************************************************/
- static uint8_t net_msbits8(uint8_t byval)
- {
- uint8_t ones;
- /* Check the MS nibble */
- ones = net_msbits4(byval >> 4);
- if (ones == 4)
- {
- /* All ones, try the LS nibble */
- ones += net_msbits4(byval & 0x0f);
- }
- /* Return the number of leading ones (0-8) */
- return ones;
- }
- /****************************************************************************
- * Name: net_msbits16
- *
- * Description:
- * Count the number of leading '1' bits in a 16-bit half-workd
- *
- ****************************************************************************/
- static inline uint8_t net_msbits16(uint16_t hword)
- {
- uint8_t ones;
- /* Look at the MS byte of the 16-bit value */
- ones = net_msbits8((uint8_t)(hword >> 8));
- if (ones == 8)
- {
- /* All '1's, try the LS byte */
- ones += net_msbits8((uint8_t)(hword & 0xff));
- }
- /* Return the number of leading ones (0-15) */
- return ones;
- }
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: net_ipv6_mask2pref
- *
- * Description:
- * Convert a 128-bit netmask to a prefix length. The Nuttx IPv6
- * networking uses 128-bit network masks internally. This function
- * converts the IPv6 netmask to a prefix length.
- *
- * The prefix length is the number of MS '1' bits on in the netmask.
- * This, of course, assumes that all MS bits are '1' and all LS bits are
- * '0' with no intermixed 1's and 0's. This function searches from the MS
- * bit until the first '0' is found (this does not necessary mean that
- * there might not be additional '1' bits following the firs '0', but that
- * will be a malformed netmask.
- *
- * Input Parameters:
- * mask Points to an IPv6 netmask in the form of uint16_t[8]
- *
- * Returned Value:
- * The prefix length, range 0-128 on success; This function will not
- * fail.
- *
- ****************************************************************************/
- uint8_t net_ipv6_mask2pref(FAR const uint16_t *mask)
- {
- uint8_t preflen;
- int i;
- /* Count the leading all '1' 16-bit groups */
- for (i = 0, preflen = 0; i < 8 && mask[i] == 0xffff; i++, preflen += 16);
- /* Now i either, (1) indexes past the end of the mask, or (2) is the index
- * to the first half-word that is not equal to 0xffff.
- */
- if (i < 8)
- {
- preflen += net_msbits16(ntohs(mask[i]));
- }
- /* Return the prefix length */
- return preflen;
- }
- #endif /* CONFIG_NET_IPv6 */
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