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

use crate::{Result, Tape, Value};

macro_rules! reject(() => (raise!("found a malformed number")));

/// A number.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Number {
    /// An integer number.
    Integer(i32),
    /// A real number.
    Real(f32),
}

impl From<f32> for Number {
    #[inline]
    fn from(value: f32) -> Self {
        Number::Real(value)
    }
}

impl From<i32> for Number {
    #[inline]
    fn from(value: i32) -> Self {
        Number::Integer(value)
    }
}

impl Value for Number {
    fn read<T: Tape>(tape: &mut T) -> Result<Self> {
        let first = tape.take::<u8>()?;
        Ok(match first {
            0x20..=0xf6 => Number::Integer(first as i32 - 139),
            0xf7..=0xfa => {
                Number::Integer((first as i32 - 247) * 256 + tape.take::<u8>()? as i32 + 108)
            }
            0xfb..=0xfe => {
                Number::Integer(-(first as i32 - 251) * 256 - tape.take::<u8>()? as i32 - 108)
            }
            0x1c => Number::Integer(tape.take::<u16>()? as i16 as i32),
            0x1d => Number::Integer(tape.take::<u32>()? as i32),
            0x1e => Number::Real(parse(tape)?),
            _ => reject!(),
        })
    }
}

fn parse<T: Tape>(tape: &mut T) -> Result<f32> {
    let mut buffer = String::new();
    let mut byte = 0;
    let mut high = true;
    loop {
        let nibble = match high {
            true => {
                byte = tape.take::<u8>()?;
                byte >> 4
            }
            false => byte & 0x0f,
        };
        high = !high;
        match nibble {
            0..=9 => buffer.push(('0' as u8 + nibble) as char),
            0x0a => buffer.push('.'),
            0x0b => buffer.push('e'),
            0x0c => buffer.push_str("e-"),
            0x0e => buffer.push('-'),
            0x0f => break,
            _ => reject!(),
        }
    }
    match buffer.parse() {
        Ok(value) => Ok(value),
        _ => reject!(),
    }
}

#[cfg(test)]
mod tests {
    use std::io::Cursor;

    use super::Number;
    use crate::Tape;

    #[test]
    fn integer() {
        macro_rules! read(
            ($tape:expr) => (
                match $tape.take().unwrap() {
                    Number::Integer(value) => value,
                    _ => unreachable!(),
                }
            )
        );

        let mut tape = Cursor::new(vec![0x8b]);
        assert_eq!(read!(tape), 0);

        let mut tape = Cursor::new(vec![0xef]);
        assert_eq!(read!(tape), 100);

        let mut tape = Cursor::new(vec![0x27]);
        assert_eq!(read!(tape), -100);

        let mut tape = Cursor::new(vec![0xfa, 0x7c]);
        assert_eq!(read!(tape), 1000);

        let mut tape = Cursor::new(vec![0xfe, 0x7c]);
        assert_eq!(read!(tape), -1000);

        let mut tape = Cursor::new(vec![0x1c, 0x27, 0x10]);
        assert_eq!(read!(tape), 10000);

        let mut tape = Cursor::new(vec![0x1c, 0xd8, 0xf0]);
        assert_eq!(read!(tape), -10000);

        let mut tape = Cursor::new(vec![0x1d, 0x00, 0x01, 0x86, 0xa0]);
        assert_eq!(read!(tape), 100000);

        let mut tape = Cursor::new(vec![0x1d, 0xff, 0xfe, 0x79, 0x60]);
        assert_eq!(read!(tape), -100000);
    }

    #[test]
    fn real() {
        macro_rules! read(
            ($tape:expr) => (
                match $tape.take().unwrap() {
                    Number::Real(value) => value,
                    _ => unreachable!(),
                }
            )
        );

        let mut tape = Cursor::new(vec![0x1e, 0xe2, 0xa2, 0x5f, 0x0f]);
        assert!((read!(tape) + 2.25).abs() < 1e-14);

        let mut tape = Cursor::new(vec![0x1e, 0x0a, 0x14, 0x05, 0x41, 0xc3, 0xff, 0x0f]);
        assert!((read!(tape) - 0.140541e-3).abs() < 1e-14);
    }
}