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

/* Copyright 2018 Mozilla Foundation
 *
 * Licensed 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.
 */

use crate::{BinaryReaderError, Result};
use std::ops::Range;

mod component;
mod core;

pub use self::component::*;
pub use self::core::*;

/// A trait implemented by section readers.
pub trait SectionReader {
    /// The item returned by the reader.
    type Item;

    /// Reads an item from the section.
    fn read(&mut self) -> Result<Self::Item>;

    /// Determines if the reader is at end-of-section.
    fn eof(&self) -> bool;

    /// Gets the original position of the reader.
    fn original_position(&self) -> usize;

    /// Gets the range of the reader.
    fn range(&self) -> Range<usize>;

    /// Ensures the reader is at the end of the section.
    ///
    /// This methods returns an error if there is more data in the section
    /// than what is described by the section's header.
    fn ensure_end(&self) -> Result<()> {
        if self.eof() {
            return Ok(());
        }
        Err(BinaryReaderError::new(
            "section size mismatch: unexpected data at the end of the section",
            self.original_position(),
        ))
    }
}

/// Implemented by sections with a limited number of items.
pub trait SectionWithLimitedItems {
    /// Gets the count of the items in the section.
    fn get_count(&self) -> u32;
}

/// An iterator over items in a section.
pub struct SectionIterator<R>
where
    R: SectionReader,
{
    reader: R,
    err: bool,
}

impl<R> SectionIterator<R>
where
    R: SectionReader,
{
    /// Constructs a new `SectionIterator` for the given section reader.
    pub fn new(reader: R) -> SectionIterator<R> {
        SectionIterator { reader, err: false }
    }
}

impl<R> Iterator for SectionIterator<R>
where
    R: SectionReader,
{
    type Item = Result<R::Item>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.err || self.reader.eof() {
            return None;
        }
        let result = self.reader.read();
        self.err = result.is_err();
        Some(result)
    }
}

/// An iterator over a limited section iterator.
pub struct SectionIteratorLimited<R>
where
    R: SectionReader + SectionWithLimitedItems,
{
    reader: R,
    left: u32,
    end: bool,
}

impl<R> SectionIteratorLimited<R>
where
    R: SectionReader + SectionWithLimitedItems,
{
    /// Constructs a new `SectionIteratorLimited` for the given limited section reader.
    pub fn new(reader: R) -> SectionIteratorLimited<R> {
        let left = reader.get_count();
        SectionIteratorLimited {
            reader,
            left,
            end: false,
        }
    }
}

impl<R> Iterator for SectionIteratorLimited<R>
where
    R: SectionReader + SectionWithLimitedItems,
{
    type Item = Result<R::Item>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.end {
            return None;
        }
        if self.left == 0 {
            return match self.reader.ensure_end() {
                Ok(()) => None,
                Err(err) => {
                    self.end = true;
                    Some(Err(err))
                }
            };
        }
        let result = self.reader.read();
        self.end = result.is_err();
        self.left -= 1;
        Some(result)
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let count = self.reader.get_count() as usize;
        (count, Some(count))
    }
}