bitar 0.14.0

bita archive utilities
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205

use crate::rolling_hash::RollingHash;

const BUZHASH_SEED: u32 = 0x1032_4195;

#[allow(clippy::unreadable_literal)]
static BUZHASH_TABLE: &[u32] = &[
    0xa40cc360, 0xbb785af8, 0x32c790bc, 0x6c64cd34, 0x83b4aa73, 0x36b691a5, 0x4631ad79, 0x5e49d231,
    0xcab22600, 0x6d45bfdf, 0xcd26dfc8, 0xf2e63bec, 0x18cb0c69, 0x817876fd, 0xb8c88ca8, 0xfabcc7d3,
    0x21211be3, 0x7bbd8a4b, 0xa7bc508f, 0xcf35be6, 0x5bb76463, 0x900cc253, 0xa1bf6569, 0xb5fc01ff,
    0xd9d8d709, 0xf2fdd75b, 0x8cf7fdcc, 0x7a24b10f, 0xc2dfa4ea, 0xaec2a258, 0xb8e51edf, 0x81944196,
    0x1040fd08, 0x728857d5, 0xd4ec5341, 0x2e547382, 0x337cab71, 0x792f8dac, 0x6932136a, 0x211f28b,
    0xeba45b99, 0x47a35907, 0x77271fb4, 0xbc09c6fb, 0x2d4eaf65, 0xfd7b53c0, 0xed4c2634, 0x54c8155d,
    0x8078f561, 0xd87a7a9, 0x4e75f462, 0x251c62a7, 0xb038d1a8, 0x57d57b20, 0x500b6495, 0xee5fbf54,
    0x97bb0e7c, 0xfe5ca9ad, 0xa91746dd, 0x160b7122, 0xafc5ceee, 0x7d850b16, 0x15c28cc5, 0x655bc438,
    0x6ed4a616, 0x1a0e18f, 0xaae23461, 0xe387536b, 0x8b2470b1, 0x92be2ce1, 0xb18b3370, 0x803d5e25,
    0x8a94f196, 0xcd225534, 0xee4f24dc, 0x51749bfb, 0xcf068d2e, 0xc859a603, 0xfc12373b, 0x8e422af2,
    0xf28be938, 0x7619c3f8, 0xea77dc6b, 0x5006f1e4, 0x297c8237, 0x445bd977, 0x67cad7ed, 0xefde9644,
    0x626bed36, 0x276970b, 0x1e699630, 0x373ee5db, 0xe83a37b3, 0x2b3938bc, 0xb2132f15, 0x66e60490,
    0x72e4e7ef, 0x8c4c2912, 0x6f7aab32, 0xc8f2eb65, 0x9b1c772b, 0xf48fb997, 0xd7b70417, 0x5a1476bd,
    0xfe547592, 0x82c7e59c, 0xede3935b, 0x8954101, 0x79f75116, 0x18a6b281, 0x90d2f6e6, 0x9c0139d9,
    0xba4a4d22, 0xfa3ab4db, 0xfc18be27, 0x47f414d, 0xba7ff7b4, 0xcc2b1b72, 0x756145da, 0xf12ff6c0,
    0xae78b289, 0x55935d1d, 0xfd849c3e, 0xae586a4f, 0x8948b6f5, 0xa079d886, 0xd7f5a118, 0x9ca03cf1,
    0xc500e85d, 0x8ce73a6c, 0x6725bb68, 0xfdb46ea2, 0x2ec367c4, 0x8fcdee2f, 0x21b13487, 0x67b41d6b,
    0xe662a354, 0x9cad336e, 0x8b284ff5, 0x1cf3c8b3, 0x6de04fd1, 0xf8ed762d, 0xc30471d4, 0x2c4ecebc,
    0x7211a0b8, 0xa34ee19c, 0x47b4bb79, 0x90777b6, 0x77f02513, 0x7cba4a74, 0xd87c18d3, 0xad8b9c5e,
    0x430c3f91, 0x72122ed, 0xc489ce87, 0x5798ec5, 0xc21e987b, 0x4eb62176, 0x8dfafefe, 0xfaeebadc,
    0x6fdc0b01, 0x60ebe6ee, 0x4244a970, 0x22d97939, 0x7ae88397, 0x76434679, 0xf8a624b6, 0x45ebdb60,
    0x68808c40, 0x628db2cb, 0xb6e16fe, 0x8fbd2c92, 0xf5737f03, 0x562d3fc5, 0xd3306769, 0x97bd2f93,
    0x7a5312e6, 0x2065be8, 0xb0c0a57, 0x80ad5f0e, 0x30e049bd, 0x5cd85bbc, 0xf981af4b, 0xbc18728f,
    0x85ce9d03, 0xc2c97922, 0xbedb47dd, 0x420f23c2, 0x40b504d3, 0x9d28e6fe, 0x7549831f, 0xa9668219,
    0xd24b01ae, 0x8e1c6dd7, 0xe5c94cf8, 0x34a91576, 0x48a005e5, 0x5c671015, 0xef4797c5, 0xd7476c01,
    0x37c339e7, 0xae017bab, 0xb5d8e74f, 0x50c5fc5b, 0x3b14aa64, 0xfc693cb1, 0x9cc65b82, 0x407c538f,
    0x71b2a28a, 0x297e5b01, 0xa3f7007e, 0x742f937, 0xe05c4998, 0x6fd8e28f, 0x65036a03, 0xdc7f1a37,
    0x4b73b787, 0xf4fa5820, 0x85097266, 0x567d4e36, 0xdcc0aa2f, 0x5ff8969b, 0x464620a0, 0x8c694162,
    0x868a341a, 0x7bd4619e, 0x2c90aa84, 0x25668b2, 0xca4d0465, 0xcb579718, 0xdc7aa0eb, 0xa3605310,
    0x7a7910c6, 0x6a8ecffc, 0x6598058a, 0xfc5fb823, 0xbc3ef53a, 0xf0d09546, 0xeb210009, 0xf58cb960,
    0xbecbb337, 0xb84b6459, 0x4ebf437d, 0x85610fd2, 0x16e79f2f, 0x849cce5, 0x77c3bd48, 0x955719e2,
    0x87abd4a7, 0x2799ae4f, 0x3b80cac, 0xd56e7604, 0x8b07ed07, 0x944552c5, 0x5b93e058, 0x8fbd2c92,
];

/// Rolling hash algorithm which can be used for chunking.
#[derive(Clone)]
pub struct BuzHash {
    buf: Vec<u32>,
    index: usize,
    window: usize,
    hash_sum: u32,
    buzhash_table: Vec<u32>,
    window_full: bool,
    last_input: u8,
    repeated_input: usize,
}

impl BuzHash {
    /// Create a new instance of BuzHash with the given window size.
    pub fn new(window: usize) -> Self {
        BuzHash {
            index: 0,
            buf: vec![0; window],
            window,
            hash_sum: 0,
            buzhash_table: Self::generate_seeded_table(BUZHASH_SEED),
            window_full: false,
            last_input: 0,
            repeated_input: 0,
        }
    }
    fn generate_seeded_table(seed: u32) -> Vec<u32> {
        BUZHASH_TABLE.iter().map(|x| x ^ seed).collect()
    }
    /// Should be used for processing input until hash is valid.
    pub fn init(&mut self, in_val: u8) {
        if !self.window_full {
            let in_val = self.buzhash_table[in_val as usize];
            // Initialize sequence until window is full
            let shift = self.window - (self.index + 1);
            self.hash_sum ^= in_val.rotate_left(shift as u32);
            self.window_full = self.index >= (self.window - 1);
            self.buf[self.index] = in_val;
            self.index += 1;
            if self.index >= self.window {
                self.index = 0;
            }
        }
    }
    /// Process a byte.
    pub fn input(&mut self, in_val: u8) {
        // If the buzhash window is full of the same value then there is no
        // need pushing another one of the same as it won't change the hash.
        if in_val == self.last_input {
            self.repeated_input += 1;
        } else {
            self.repeated_input = 0;
            self.last_input = in_val;
        }
        if self.repeated_input < self.window {
            let in_val = self.buzhash_table[in_val as usize];

            let out_val = self.buf[self.index];
            self.hash_sum =
                self.hash_sum.rotate_left(1) ^ out_val.rotate_left(self.window as u32) ^ in_val;
            self.buf[self.index] = in_val;
            self.index += 1;
            if self.index >= self.window {
                self.index = 0;
            }
        }
    }
    /// Get current hash sum.
    pub fn sum(&self) -> u32 {
        self.hash_sum
    }
}

impl RollingHash for BuzHash {
    fn init_done(&self) -> bool {
        self.window_full
    }
    fn init(&mut self, value: u8) {
        self.init(value)
    }
    fn input(&mut self, value: u8) {
        self.input(value)
    }
    fn sum(&self) -> u32 {
        self.sum()
    }
}

#[cfg(test)]
mod tests {
    use crate::rolling_hash::BuzHash;
    #[test]
    fn equal_sums_for_equal_range() {
        let window_size = 8;
        let mut h = BuzHash::new(window_size);
        let data1 = [
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
        ];
        let data2 = [
            1, 99, 99, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
        ];
        let sums1: Vec<u32> = data1
            .iter()
            .map(|v| {
                h.input(*v);
                h.sum()
            })
            .collect();

        let sums2: Vec<u32> = data2
            .iter()
            .map(|v| {
                h.input(*v);
                h.sum()
            })
            .collect();

        assert_eq!(sums1[11..], sums2[11..]);
    }
    #[test]
    fn first_valid_correct_sum() {
        let window_size = 5;
        let sums: Vec<u32> = {
            let mut h = BuzHash::new(window_size);
            [1, 2, 3, 4, 5]
                .iter()
                .filter_map(|&v| {
                    if !h.window_full {
                        h.init(v);
                    } else {
                        h.input(v);
                    }
                    if h.window_full {
                        return Some(h.sum());
                    }
                    None
                })
                .collect()
        };
        assert_eq!(sums[0], 1_406_929_643);
    }
    #[test]
    fn last_valid_correct_sum() {
        let window_size = 5;
        let sums: Vec<u32> = {
            let mut h = BuzHash::new(window_size);
            [10, 20, 30, 40, 50, 60, 70, 80, 90, 1, 2, 3, 4, 5]
                .iter()
                .filter_map(|&v| {
                    if !h.window_full {
                        h.init(v);
                    } else {
                        h.input(v);
                    }
                    if h.window_full {
                        return Some(h.sum());
                    }
                    None
                })
                .collect()
        };
        assert_eq!(sums[9], 1_406_929_643);
    }
}