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

// Copyright 2019 statiolake <statiolake@gmail.com>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be copied, modified, or
// distributed except according to those terms.

use super::Source;
use std::io::BufRead;
use std::iter::Peekable;
use std::str::SplitWhitespace;

/// Source reading stream line by line.
///
/// It is a wrapper for `BufRead`.  You can create `LineSource` from any type implementing
/// `BufRead`.
pub struct LineSource<R: BufRead> {
    // FIXME: This is actually not 'static but it is treated as 'static for the
    // same reason with crate::source::once::Source.  Also there is no way to
    // separate context and tokens since they are private field, this is safe.
    tokens: Peekable<SplitWhitespace<'static>>,

    // context `tokens` reffering to
    current_context: Box<str>,

    reader: R,
}

impl<R: BufRead> LineSource<R> {
    /// Creates a `LineSource` by specified `BufRead`.
    pub fn new(reader: R) -> LineSource<R> {
        // dummy values.
        LineSource {
            current_context: "".to_string().into_boxed_str(),
            tokens: "".split_whitespace().peekable(),
            reader,
        }
    }

    fn prepare(&mut self) {
        while self.tokens.peek().is_none() {
            let mut line = String::new();
            let num_bytes = self
                .reader
                .read_line(&mut line)
                .expect("failed to get linel maybe an IO error.");

            if num_bytes == 0 {
                // reached EOF
                return;
            }

            self.current_context = line.into_boxed_str();
            self.tokens = unsafe { std::mem::transmute::<_, &'static str>(&*self.current_context) }
                .split_whitespace()
                .peekable();
        }
    }
}

impl<R: BufRead> Source<R> for LineSource<R> {
    /// Gets a next token.
    fn next_token(&mut self) -> Option<&str> {
        // while tokens are empty, reads a new line.
        self.prepare();
        self.tokens.next()
    }

    /// Check if tokens are empty
    fn is_empty(&mut self) -> bool {
        self.prepare();
        self.tokens.peek().is_none()
    }
}

use std::io::BufReader;

/// You can create `LineSource` from `&str`.  Since `&[u8]` is a `Read`, `BufRead` can be easily
/// created by wrapping using `BufReader`.
impl<'a> From<&'a str> for LineSource<BufReader<&'a [u8]>> {
    fn from(s: &'a str) -> LineSource<BufReader<&'a [u8]>> {
        LineSource::new(BufReader::new(s.as_bytes()))
    }
}