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- /****************************************************************************
- * net/utils/net_ipv6_mask2pref.c
- *
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership. The
- * ASF licenses this file to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance with the
- * License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
- * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
- * License for the specific language governing permissions and limitations
- * under the License.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.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 ones: 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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