asexp 0.1.2

Advanced S-expression-like format suitable for configuration and serialization
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

#![feature(str_char)]

use std::char;

#[derive(Debug, PartialEq)]
enum Atom {
    // Unquoted string
    Str(String),

    // Quoted string
    QStr(String),

    // Unsigned 64-bit integer
    UInt(u64),

    // Signed 64-bit integer
    SInt(i64),

    // 64-bit floating point number
    Float(f64),
}

#[derive(Debug, PartialEq)]
enum Expr {
    Atom(Atom),

    // ( ... )
    Tuple(Vec<Atom>),

    // [ ... ]
    Array(Vec<Atom>),

    // { key val ... }
    Map(Vec<(Atom, Atom)>),
}

#[derive(Debug, PartialEq)]
enum ParseError {
    PrematureEOS,
}

impl Atom {
    fn from_str(s: &str) -> Result<(Atom, &str), ParseError> {
        let delim: &[_] = &[' ', '\n', '\t', '(', ')', '[', ']', '{', '}'];
        match s.find(delim) {
            Some(pos) => Ok((Atom::Str(s[..pos].to_string()), &s[pos..])),
            None => {
                // complete string
                Ok((Atom::Str(s.to_string()), ""))
            }
        }
    }
}

#[derive(Debug, PartialEq)]
enum Token<'a> {
    Error,

    Str(&'a str),
    QStr(&'a str),

    OpenBracket,
    CloseBracket,
    OpenBrace,
    CloseBrace,
    OpenCurly,
    CloseCurly,

    Int(&'a str),
    Float(&'a str),
}

#[inline]
fn scan<F: Fn(char) -> bool>(s: &str, cond: F) -> (&str, &str) {
    // split at the first non-"cond" character
    match s.find(|c: char| !cond(c)) {
        None => (s, ""),
        Some(pos) => s.split_at(pos),
    }
}


#[inline]
fn is_token_delim(c: char) -> bool {
    c.is_whitespace() || c == '(' || c == ')' || c == '[' || c == ']' || c == '{' || c == '}' ||
    c == '"'
}

fn skip_ws(s: &str) -> &str {
    scan(s, char::is_whitespace).1
}


// ; comment
fn next_token<'a>(s: &'a str) -> Option<(Token<'a>, &'a str)> {
    let s = skip_ws(s);
    match s.slice_shift_char() {
        None => None,
        Some((c, s2)) => {
            match c {
                '(' => Some((Token::OpenBrace, s2)),
                ')' => Some((Token::CloseBrace, s2)),

                '[' => Some((Token::OpenBracket, s2)),
                ']' => Some((Token::CloseBracket, s2)),

                '{' => Some((Token::OpenCurly, s2)),
                '}' => Some((Token::CloseCurly, s2)),

                '"' => {
                    // TODO: QStr
                    None
                }

                '+' | '-' => {
                    // TODO
                    None
                }

                '0'...'9' => {
                    // Int, Float

                    let (basis, rest) = scan(s, char::is_numeric);
                    match rest.slice_shift_char() {
                        Some(('.', mantisse)) => {
                            // integer followed by "." => float
                            let (mantisse, _) = scan(mantisse, char::is_numeric);
                            let (full_float, rest) = s.split_at(basis.len() + 1 + mantisse.len());

                            Some((Token::Float(full_float), rest))
                        }
                        _ => Some((Token::Int(basis), rest)),
                    }
                }

                _ => {
                    // Str
                    let (string, rest) = scan(s, |c| !is_token_delim(c));
                    Some((Token::Str(string), rest))
                }
            }
        }
    }
}

#[test]
fn test_tokenize() {
    assert_eq!(Some((Token::Str("abc"), "")), next_token("  abc"));
    assert_eq!(Some((Token::Str("abc"), "")), next_token("abc"));
    assert_eq!(Some((Token::Str("abc"), "(")), next_token("abc("));

    assert_eq!(Some((Token::OpenBrace, ")")), next_token("()"));

    assert_eq!(Some((Token::Int("12345"), "")), next_token("12345"));
    assert_eq!(Some((Token::Int("12345"), " ")), next_token("12345 "));
    assert_eq!(Some((Token::Int("12345"), "+")), next_token("12345+"));
    assert_eq!(Some((Token::Float("12345.123"), "")),
               next_token("12345.123"));
    assert_eq!(Some((Token::Float("12345.123"), "(")),
               next_token("12345.123("));
}