2 * Copyright (C) 2006-2010 B.A.T.M.A.N. contributors:
4 * Simon Wunderlich, Marek Lindner
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of version 2 of the GNU General Public
8 * License as published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
25 /* returns true if the corresponding bit in the given seq_bits indicates true
26 * and curr_seqno is within range of last_seqno */
27 uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint16_t last_seqno,
30 int16_t diff, word_offset, word_num;
32 diff = last_seqno - curr_seqno;
33 if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) {
37 word_num = (last_seqno - curr_seqno) / WORD_BIT_SIZE;
38 /* which position in the selected word */
39 word_offset = (last_seqno - curr_seqno) % WORD_BIT_SIZE;
41 if (seq_bits[word_num] & 1 << word_offset)
48 /* turn corresponding bit on, so we can remember that we got the packet */
49 void bit_mark(TYPE_OF_WORD *seq_bits, int32_t n)
51 int32_t word_offset, word_num;
53 /* if too old, just drop it */
54 if (n < 0 || n >= TQ_LOCAL_WINDOW_SIZE)
58 word_num = n / WORD_BIT_SIZE;
59 /* which position in the selected word */
60 word_offset = n % WORD_BIT_SIZE;
62 seq_bits[word_num] |= 1 << word_offset; /* turn the position on */
65 /* shift the packet array by n places. */
66 void bit_shift(TYPE_OF_WORD *seq_bits, int32_t n)
68 int32_t word_offset, word_num;
71 if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE)
74 word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */
75 word_num = n / WORD_BIT_SIZE; /* shift over how much (full) words */
77 for (i = NUM_WORDS - 1; i > word_num; i--) {
78 /* going from old to new, so we don't overwrite the data we copy
81 * left is high, right is low: FEDC BA98 7654 3210
84 * ^^^^ = from, vvvvv =to, we'd have word_num==1 and
85 * word_offset==WORD_BIT_SIZE/2 ????? in this example.
88 * our desired output would be: 9876 5432 1000 0000
92 (seq_bits[i - word_num] << word_offset) +
93 /* take the lower port from the left half, shift it left
94 * to its final position */
95 (seq_bits[i - word_num - 1] >>
96 (WORD_BIT_SIZE-word_offset));
97 /* and the upper part of the right half and shift it left to
99 /* for our example that would be: word[0] = 9800 + 0076 =
102 /* now for our last word, i==word_num, we only have the it's "left"
103 * half. that's the 1000 word in our example.*/
105 seq_bits[i] = (seq_bits[i - word_num] << word_offset);
107 /* pad the rest with 0, if there is anything */
114 static void bit_reset_window(TYPE_OF_WORD *seq_bits)
117 for (i = 0; i < NUM_WORDS; i++)
122 /* receive and process one packet within the sequence number window.
125 * 1 if the window was moved (either new or very old)
126 * 0 if the window was not moved/shifted.
128 char bit_get_packet(TYPE_OF_WORD *seq_bits, int16_t seq_num_diff,
131 /* sequence number is slightly older. We already got a sequence number
132 * higher than this one, so we just mark it. */
134 if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) {
136 bit_mark(seq_bits, -seq_num_diff);
140 /* sequence number is slightly newer, so we shift the window and
141 * set the mark if required */
143 if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) {
144 bit_shift(seq_bits, seq_num_diff);
147 bit_mark(seq_bits, 0);
151 /* sequence number is much newer, probably missed a lot of packets */
153 if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE)
154 || (seq_num_diff < EXPECTED_SEQNO_RANGE)) {
156 "We missed a lot of packets (%i) !\n",
158 bit_reset_window(seq_bits);
160 bit_mark(seq_bits, 0);
164 /* received a much older packet. The other host either restarted
165 * or the old packet got delayed somewhere in the network. The
166 * packet should be dropped without calling this function if the
167 * seqno window is protected. */
169 if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE)
170 || (seq_num_diff >= EXPECTED_SEQNO_RANGE)) {
173 "Other host probably restarted!\n");
175 bit_reset_window(seq_bits);
177 bit_mark(seq_bits, 0);
186 /* count the hamming weight, how many good packets did we receive? just count
187 * the 1's. The inner loop uses the Kernighan algorithm, see
188 * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan
190 int bit_packet_count(TYPE_OF_WORD *seq_bits)
195 for (i = 0; i < NUM_WORDS; i++) {