fuchsia_archive/
read.rs

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1// Copyright 2020 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use crate::{
6    DirectoryEntry, Error, Index, IndexEntry, DIRECTORY_ENTRY_LEN, DIR_CHUNK_TYPE,
7    DIR_NAMES_CHUNK_TYPE, INDEX_ENTRY_LEN, INDEX_LEN, MAGIC_INDEX_VALUE,
8};
9use std::convert::TryInto as _;
10use std::io::{Read, Seek, SeekFrom};
11use zerocopy::IntoBytes as _;
12
13/// A struct to open and read FAR-formatted archive.
14#[derive(Debug)]
15pub struct Reader<T>
16where
17    T: Read + Seek,
18{
19    source: T,
20    directory_entries: Box<[DirectoryEntry]>,
21    path_data: Box<[u8]>,
22}
23
24impl<T> Reader<T>
25where
26    T: Read + Seek,
27{
28    /// Create a new Reader for the provided source.
29    pub fn new(mut source: T) -> Result<Self, Error> {
30        let index = Self::read_index_header(&mut source)?;
31        let (dir_index, dir_name_index, end_of_last_non_content_chunk) =
32            Self::read_index_entries(&mut source, &index)?;
33        let stream_len = source.seek(SeekFrom::End(0)).map_err(Error::Seek)?;
34
35        // Read directory entries
36        if dir_index.length.get() % DIRECTORY_ENTRY_LEN != 0 {
37            return Err(Error::InvalidDirectoryChunkLen(dir_index.length.get()));
38        }
39        let mut directory_entries =
40            vec![
41                DirectoryEntry::default();
42                (dir_index.length.get() / DIRECTORY_ENTRY_LEN)
43                    .try_into()
44                    .map_err(|_| { Error::InvalidDirectoryChunkLen(dir_index.length.get()) })?
45            ];
46        source.seek(SeekFrom::Start(dir_index.offset.get())).map_err(Error::Seek)?;
47        source.read_exact(directory_entries.as_mut_bytes()).map_err(Error::Read)?;
48        let directory_entries = directory_entries.into_boxed_slice();
49
50        // Read path data
51        if dir_name_index.length.get() % 8 != 0 || dir_name_index.length.get() > stream_len {
52            return Err(Error::InvalidDirectoryNamesChunkLen(dir_name_index.length.get()));
53        }
54        let path_data_length = dir_name_index
55            .length
56            .get()
57            .try_into()
58            .map_err(|_| Error::InvalidDirectoryNamesChunkLen(dir_name_index.length.get()))?;
59        let mut path_data = vec![0; path_data_length];
60        source.seek(SeekFrom::Start(dir_name_index.offset.get())).map_err(Error::Seek)?;
61        source.read_exact(path_data.as_mut_slice()).map_err(Error::Read)?;
62        let path_data = path_data.into_boxed_slice();
63
64        let () = crate::validate_directory_entries_and_paths(
65            &directory_entries,
66            &path_data,
67            stream_len,
68            end_of_last_non_content_chunk,
69        )?;
70
71        Ok(Self { source, directory_entries, path_data })
72    }
73
74    // Assumes `source` cursor is at the beginning of the file.
75    fn read_index_header(source: &mut T) -> Result<Index, Error> {
76        let mut index = Index::default();
77        source.read_exact(index.as_mut_bytes()).map_err(Error::Read)?;
78        if index.magic != MAGIC_INDEX_VALUE {
79            Err(Error::InvalidMagic(index.magic))
80        } else if index.length.get() % INDEX_ENTRY_LEN != 0
81            || INDEX_LEN.checked_add(index.length.get()).is_none()
82        {
83            Err(Error::InvalidIndexEntriesLen(index.length.get()))
84        } else {
85            Ok(index)
86        }
87    }
88
89    // Returns (directory_index, directory_names_index, end_of_last_chunk).
90    // Assumes `source` cursor is at the beginning of the index entries.
91    fn read_index_entries(
92        source: &mut T,
93        index: &Index,
94    ) -> Result<(IndexEntry, IndexEntry, u64), Error> {
95        let mut dir_index: Option<IndexEntry> = None;
96        let mut dir_name_index: Option<IndexEntry> = None;
97        let mut previous_entry: Option<IndexEntry> = None;
98        for _ in 0..index.length.get() / INDEX_ENTRY_LEN {
99            let mut entry = IndexEntry::default();
100            source.read_exact(entry.as_mut_bytes()).map_err(Error::Read)?;
101
102            let expected_offset = if let Some(previous_entry) = previous_entry {
103                if previous_entry.chunk_type >= entry.chunk_type {
104                    return Err(Error::IndexEntriesOutOfOrder {
105                        prev: previous_entry.chunk_type,
106                        next: entry.chunk_type,
107                    });
108                }
109                previous_entry.offset.get() + previous_entry.length.get()
110            } else {
111                INDEX_LEN + index.length.get()
112            };
113            if entry.offset.get() != expected_offset {
114                return Err(Error::InvalidChunkOffset {
115                    chunk_type: entry.chunk_type,
116                    expected: expected_offset,
117                    actual: entry.offset.get(),
118                });
119            }
120            if entry.offset.get().checked_add(entry.length.get()).is_none() {
121                return Err(Error::InvalidChunkLength {
122                    chunk_type: entry.chunk_type,
123                    offset: entry.offset.get(),
124                    length: entry.length.get(),
125                });
126            }
127
128            match entry.chunk_type {
129                DIR_CHUNK_TYPE => {
130                    dir_index = Some(entry);
131                }
132                DIR_NAMES_CHUNK_TYPE => {
133                    dir_name_index = Some(entry);
134                }
135                // FAR spec does not forbid unknown chunk types
136                _ => {}
137            }
138            previous_entry = Some(entry);
139        }
140        let end_of_last_chunk = if let Some(previous_entry) = previous_entry {
141            previous_entry.offset.get() + previous_entry.length.get()
142        } else {
143            INDEX_LEN
144        };
145        Ok((
146            dir_index.ok_or(Error::MissingDirectoryChunkIndexEntry)?,
147            dir_name_index.ok_or(Error::MissingDirectoryNamesChunkIndexEntry)?,
148            end_of_last_chunk,
149        ))
150    }
151
152    /// Return a list of the items in the archive
153    pub fn list(&self) -> impl ExactSizeIterator<Item = crate::Entry<'_>> {
154        crate::list(&self.directory_entries, &self.path_data)
155    }
156
157    /// Read the entire contents of the entry with the specified path.
158    /// O(log(# directory entries))
159    pub fn read_file(&mut self, path: &[u8]) -> Result<Vec<u8>, Error> {
160        let entry = crate::find_directory_entry(&self.directory_entries, &self.path_data, path)?;
161        let mut data = vec![
162            0;
163            usize::try_from(entry.data_length.get()).map_err(|_| {
164                Error::ContentChunkDoesNotFitInMemory {
165                    name: path.into(),
166                    chunk_size: entry.data_length.get(),
167                }
168            })?
169        ];
170        let _: u64 =
171            self.source.seek(SeekFrom::Start(entry.data_offset.get())).map_err(Error::Seek)?;
172        let () = self.source.read_exact(&mut data).map_err(Error::Read)?;
173        Ok(data)
174    }
175
176    /// Get the size in bytes of the entry with the specified path.
177    /// O(log(# directory entries))
178    pub fn get_size(&mut self, path: &[u8]) -> Result<u64, Error> {
179        Ok(crate::find_directory_entry(&self.directory_entries, &self.path_data, path)?
180            .data_length
181            .get())
182    }
183}
184
185#[cfg(test)]
186mod tests {
187    use super::*;
188    use crate::tests::example_archive;
189    use assert_matches::assert_matches;
190    use std::io::Cursor;
191
192    #[test]
193    fn list() {
194        let example = example_archive();
195        let reader = Reader::new(Cursor::new(&example)).unwrap();
196        itertools::assert_equal(
197            reader.list(),
198            [
199                crate::Entry { path: b"a", offset: 4096, length: 2 },
200                crate::Entry { path: b"b", offset: 8192, length: 2 },
201                crate::Entry { path: b"dir/c", offset: 12288, length: 6 },
202            ],
203        );
204    }
205
206    #[test]
207    fn read_file() {
208        let example = example_archive();
209        let mut reader = Reader::new(Cursor::new(&example)).unwrap();
210        for one_name in ["a", "b", "dir/c"].iter().map(|s| s.as_bytes()) {
211            let content = reader.read_file(one_name).unwrap();
212            let content_str = std::str::from_utf8(&content).unwrap();
213            let expected = format!("{}\n", std::str::from_utf8(one_name).unwrap());
214            assert_eq!(content_str, &expected);
215        }
216    }
217
218    #[test]
219    fn get_size() {
220        let example = example_archive();
221        let mut reader = Reader::new(Cursor::new(&example)).unwrap();
222        for one_name in ["a", "b", "dir/c"].iter().map(|s| s.as_bytes()) {
223            let returned_size = reader.get_size(one_name).unwrap();
224            let expected_size = one_name.len() + 1;
225            assert_eq!(returned_size, u64::try_from(expected_size).unwrap());
226        }
227    }
228
229    #[test]
230    fn accessors_error_on_missing_path() {
231        let example = example_archive();
232        let mut reader = Reader::new(Cursor::new(&example)).unwrap();
233        assert_matches!(
234            reader.read_file(b"missing-path"),
235            Err(Error::PathNotPresent(path)) if path == b"missing-path"
236        );
237        assert_matches!(
238            reader.get_size(b"missing-path"),
239            Err(Error::PathNotPresent(path)) if path == b"missing-path"
240        );
241    }
242}
fuchsia_archive/read.rs

fuchsia_archive/
read.rs
