grib 0.15.4

GRIB format parser & writer for Rust
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

use std::iter::Peekable;

use crate::decoder::DecodeError;

pub(crate) struct BitmapDecodeIterator<B: Iterator, I> {
    bitmap: Peekable<B>,
    values: I,
    len: usize,
    offset: usize,
}

impl<'b, B, I> BitmapDecodeIterator<B, I>
where
    B: Iterator<Item = &'b u8>,
{
    pub(crate) fn new(bitmap: B, values: I, len: usize) -> Result<Self, DecodeError> {
        let (bitmap_len, _) = bitmap.size_hint();
        if bitmap_len * 8 < len {
            return Err(DecodeError::LengthMismatch);
        }
        Ok(Self {
            bitmap: bitmap.peekable(),
            values,
            len,
            offset: 0,
        })
    }
}

impl<'b, B, I> Iterator for BitmapDecodeIterator<B, I>
where
    B: Iterator<Item = &'b u8>,
    I: Iterator<Item = f32>,
{
    type Item = f32;

    fn next(&mut self) -> Option<Self::Item> {
        if self.len == 0 {
            return None;
        }
        self.len -= 1;

        let offset = self.offset;
        let byte = if self.offset < 7 {
            self.offset += 1;
            self.bitmap.peek()?
        } else {
            self.offset = 0;
            self.bitmap.next()?
        };

        if has_zero_at_offset(byte, &offset) {
            Some(f32::NAN)
        } else {
            self.values.next()
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let size = self.len;
        (size, Some(size))
    }
}

const MASK: u8 = 0b10000000;

fn has_zero_at_offset(byte: &u8, offset: &usize) -> bool {
    let masked = byte & (MASK >> offset);
    masked == 0
}

pub(crate) fn dummy_bitmap_for_nonnullable_data(num_points: usize) -> Vec<u8> {
    let size = super::helpers::num_octets(num_points);
    vec![0b11111111u8; size]
}

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

    #[test]
    fn bitmap_iterator_works() {
        let bitmap = [0b01001100u8, 0b01110000, 0b11110000];
        let values = (0..10).map(|n| n as f32).collect::<Vec<_>>();
        let values = values.into_iter();

        let iter = BitmapDecodeIterator::new(bitmap.iter(), values, 24).unwrap();
        let actual = iter.collect::<Vec<_>>();
        let expected = [
            f32::NAN,
            0.0,
            f32::NAN,
            f32::NAN,
            1.0,
            2.0,
            f32::NAN,
            f32::NAN,
            f32::NAN,
            3.0,
            4.0,
            5.0,
            f32::NAN,
            f32::NAN,
            f32::NAN,
            f32::NAN,
            6.0,
            7.0,
            8.0,
            9.0,
            f32::NAN,
            f32::NAN,
            f32::NAN,
            f32::NAN,
        ];

        assert_eq!(actual.len(), expected.len());
        actual
            .iter()
            .zip(expected.iter())
            .all(|(a, b)| (a.is_nan() && b.is_nan()) || (a == b));
    }

    #[test]
    fn bitmap_iterator_length() {
        let bitmap = [0b01001100u8, 0b01110000];
        let values = (0..6).map(|n| n as f32).collect::<Vec<_>>();
        let values = values.into_iter();

        let iter = BitmapDecodeIterator::new(bitmap.iter(), values, 12).unwrap();
        let actual = iter.collect::<Vec<_>>();
        let expected = [
            f32::NAN,
            0.0,
            f32::NAN,
            f32::NAN,
            1.0,
            2.0,
            f32::NAN,
            f32::NAN,
            f32::NAN,
            3.0,
            4.0,
            5.0,
        ];

        assert_eq!(actual.len(), expected.len());
        actual
            .iter()
            .zip(expected.iter())
            .all(|(a, b)| (a.is_nan() && b.is_nan()) || (a == b));
    }

    #[test]
    fn bitmap_iterator_size_hint() {
        let bitmap = [0b01001100u8, 0b01110000, 0b11110000];
        let values = (0..10).map(|n| n as f32).collect::<Vec<_>>();
        let values = values.into_iter();

        let mut iter = BitmapDecodeIterator::new(bitmap.iter(), values, 24).unwrap();

        assert_eq!(iter.size_hint(), (24, Some(24)));
        let _ = iter.next();
        assert_eq!(iter.size_hint(), (23, Some(23)));
    }
}