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

// 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.

pub struct Bitmap {
    bits: Vec<u8>
}

impl Bitmap {

    pub fn new(n: usize) -> Self {
        let r = n % 64;
        let len = if r==0 { n } else { n + 64-r };
        let mut v = Vec::with_capacity(len);
        for _ in 0 .. len {
            v.push(0);
        }
        Bitmap { bits: v }
    }

    pub fn len(&self) -> usize {
        self.bits.len()
    }

    pub fn is_set(&self, i: usize) -> bool {
        let byte_offset = i / 8;
        self.bits[byte_offset] & (1_u8 << ((i % 8) as u8)) > 0
    }

    pub fn set(&mut self, i: usize) {
        let byte_offset = i / 8;
        self.bits[byte_offset] = self.bits[byte_offset] | (1_u8 << ((i % 8) as u8));
    }

    pub fn clear(&mut self, i: usize) {
        let byte_offset = i / 8;
        self.bits[byte_offset] = self.bits[byte_offset] ^ (1_u8 << ((i % 8) as u8));
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_bitmap_length() {
        assert_eq!(64, Bitmap::new(63).len());
        assert_eq!(64, Bitmap::new(64).len());
        assert_eq!(128, Bitmap::new(65).len());
    }

    #[test]
    fn test_set_bit() {
        let mut b = Bitmap::new(64);
        assert_eq!(false, b.is_set(12));
        b.set(12);
        assert_eq!(true, b.is_set(12));
    }

    #[test]
    fn test_clear_bit() {
        let mut b = Bitmap::new(64);
        assert_eq!(false, b.is_set(12));
        b.set(12);
        assert_eq!(true, b.is_set(12));
        b.clear(12);
        assert_eq!(false, b.is_set(12));
    }

}