rsmount 0.2.2

Safe Rust wrapper around the `util-linux/libmount` C library
Documentation 
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
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327

// Copyright (c) 2023 Nick Piaddo
// SPDX-License-Identifier: Apache-2.0 OR MIT

// From dependency library

// From standard library
use std::mem::MaybeUninit;

// From this library
use crate::core::entries::SwapsEntryDiff;
use crate::core::errors::SwapsDiffIterError;
use crate::core::iter::Direction;
use crate::core::iter::GenIterator;
use crate::tables::SwapsDiff;

/// Iterate over [`SwapsDiff`] entries.
#[derive(Debug)]
pub struct SwapsDiffIter<'diff, 's, 'o> {
    table_diff: &'diff SwapsDiff<'s, 'o>,
    /// Forward iterator.
    fwd_iter: GenIterator,
    /// Backward iterator.
    bwd_iter: GenIterator,
    /// Current item in forward iteration from the first table.
    first_fwd_cursor: *mut libmount::libmnt_fs,
    /// Current item in forward iteration from the second table.
    second_fwd_cursor: *mut libmount::libmnt_fs,
    /// Current item in backward iteration from the first table.
    first_bwd_cursor: *mut libmount::libmnt_fs,
    /// Current item in backward iteration from the second table.
    second_bwd_cursor: *mut libmount::libmnt_fs,
    /// Indicator of forward and backward iterators meeting in the middle.
    have_iterators_met: bool,
}

impl<'diff, 's, 'o> SwapsDiffIter<'diff, 's, 'o> {
    #[doc(hidden)]
    /// Creates a new instance.
    #[allow(dead_code)]
    pub(crate) fn new(
        table_diff: &'diff SwapsDiff<'s, 'o>,
    ) -> Result<SwapsDiffIter<'diff, 's, 'o>, SwapsDiffIterError> {
        let fwd_iter = GenIterator::new(Direction::Forward)?;
        let bwd_iter = GenIterator::new(Direction::Backward)?;
        let first_fwd_cursor = std::ptr::null_mut();
        let second_fwd_cursor = std::ptr::null_mut();
        let first_bwd_cursor = std::ptr::null_mut();
        let second_bwd_cursor = std::ptr::null_mut();
        let have_iterators_met = false;

        let iterator = Self {
            table_diff,
            fwd_iter,
            bwd_iter,
            first_fwd_cursor,
            second_fwd_cursor,
            first_bwd_cursor,
            second_bwd_cursor,
            have_iterators_met,
        };

        Ok(iterator)
    }
}

impl<'diff, 's, 'o> Iterator for SwapsDiffIter<'diff, 's, 'o> {
    type Item = SwapsEntryDiff<'diff, 's, 'o>;

    fn next(&mut self) -> Option<Self::Item> {
        log::debug!("SwapsDiffIter::next getting next table changes");

        let mut source_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
        let mut other_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
        let mut flags = MaybeUninit::<libc::c_int>::zeroed();

        let result = unsafe {
            libmount::mnt_tabdiff_next_change(
                self.table_diff.inner,
                self.fwd_iter.inner,
                source_entry_inner.as_mut_ptr(),
                other_entry_inner.as_mut_ptr(),
                flags.as_mut_ptr(),
            )
        };

        match result {
            0 => {
                let source_entry_inner = unsafe { source_entry_inner.assume_init() };
                let other_entry_inner = unsafe { other_entry_inner.assume_init() };
                let flags = unsafe { flags.assume_init() };

                // Per the documentation of `DoubleEndedIterator`
                // "It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle."
                if self.have_iterators_met
                    || ((self.first_fwd_cursor != self.first_bwd_cursor)
                        && (self.second_fwd_cursor != self.second_bwd_cursor)
                        && (source_entry_inner == self.first_bwd_cursor
                            && other_entry_inner == self.second_bwd_cursor))
                {
                    log::debug!(
                        "SwapsDiffIter::next forward and backward iterators have met in the middle"
                    );

                    self.have_iterators_met = true;

                    None
                } else {
                    log::debug!("SwapsDiffIter::next got next table changes");
                    self.first_fwd_cursor = source_entry_inner;
                    self.second_fwd_cursor = other_entry_inner;
                    let diff_entry = SwapsEntryDiff::new(
                        self.table_diff,
                        source_entry_inner,
                        other_entry_inner,
                        flags,
                    );

                    Some(diff_entry)
                }
            }
            1 => {
                log::debug!("SwapsDiffIter::next reached the end of `SwapsDiffIter`");

                None
            }
            code => {
                let err_msg = "failed to get next changes".to_owned();
                log::debug!( "SwapsDiffIter::next {err_msg}. libmount::mnt_tabdiff_next_change returned error code: {code:?}");

                None
            }
        }
    }

    fn nth(&mut self, n: usize) -> Option<Self::Item> {
        log::debug!("SwapsDiffIter::nth getting {n:?}th table diff item");

        let mut result;
        let mut flags = MaybeUninit::<libc::c_int>::zeroed();

        // Skip n-1 entries, and update cursors along the way.
        for i in 0..n {
            let mut source_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
            let mut other_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();

            result = unsafe {
                libmount::mnt_tabdiff_next_change(
                    self.table_diff.inner,
                    self.fwd_iter.inner,
                    source_entry_inner.as_mut_ptr(),
                    other_entry_inner.as_mut_ptr(),
                    flags.as_mut_ptr(),
                )
            };

            match result {
                0 => {
                    let source_entry_inner = unsafe { source_entry_inner.assume_init() };
                    let other_entry_inner = unsafe { other_entry_inner.assume_init() };

                    // Per the documentation of `DoubleEndedIterator`
                    // "It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle."
                    if self.have_iterators_met
                        || ((self.first_fwd_cursor != self.first_bwd_cursor)
                            && (self.second_fwd_cursor != self.second_bwd_cursor)
                            && (source_entry_inner == self.first_bwd_cursor
                                && other_entry_inner == self.second_bwd_cursor))
                    {
                        log::debug!( "SwapsDiffIter::next forward and backward iterators have met in the middle");

                        self.have_iterators_met = true;

                        return None;
                    } else {
                        log::debug!("SwapsDiffIter::nth got {i:?}th table diff item");
                        self.first_fwd_cursor = source_entry_inner;
                        self.second_fwd_cursor = other_entry_inner;
                    }
                }
                1 => {
                    log::debug!("SwapsDiffIter::nth reached the end of `SwapsDiffIter`");

                    return None;
                }
                code => {
                    let err_msg = format!("failed to get {:?}th table diff item", n);
                    log::debug!( "SwapsDiffIter::nth {err_msg}. libmount::mnt_tabdiff_next_change returned error code: {code:?}");

                    return None;
                }
            }
        }

        self.next()
    }
}

impl<'diff, 's, 'o> DoubleEndedIterator for SwapsDiffIter<'diff, 's, 'o> {
    fn next_back(&mut self) -> Option<Self::Item> {
        log::debug!("SwapsDiffIter::next_back getting next table diff item from the back");

        let mut source_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
        let mut other_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
        let mut flags = MaybeUninit::<libc::c_int>::zeroed();

        let result = unsafe {
            libmount::mnt_tabdiff_next_change(
                self.table_diff.inner,
                self.bwd_iter.inner,
                source_entry_inner.as_mut_ptr(),
                other_entry_inner.as_mut_ptr(),
                flags.as_mut_ptr(),
            )
        };

        match result {
            0 => {
                let source_entry_inner = unsafe { source_entry_inner.assume_init() };
                let other_entry_inner = unsafe { other_entry_inner.assume_init() };
                let flags = unsafe { flags.assume_init() };

                // Per the documentation of `DoubleEndedIterator`
                // "It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle."
                if self.have_iterators_met
                    || ((self.first_fwd_cursor != self.first_bwd_cursor)
                        && (self.second_fwd_cursor != self.second_bwd_cursor)
                        && (source_entry_inner == self.first_fwd_cursor
                            && other_entry_inner == self.second_fwd_cursor))
                {
                    log::debug!( "SwapsDiffIter::next_back forward and backward iterators have met in the middle");

                    self.have_iterators_met = true;

                    None
                } else {
                    log::debug!(
                        "SwapsDiffIter::next_back got next table changes iterating backward"
                    );

                    self.first_bwd_cursor = source_entry_inner;
                    self.second_bwd_cursor = other_entry_inner;
                    let diff_entry = SwapsEntryDiff::new(
                        self.table_diff,
                        source_entry_inner,
                        other_entry_inner,
                        flags,
                    );

                    Some(diff_entry)
                }
            }
            1 => {
                log::debug!("SwapsDiffIter::next_back reached the end of `SwapsDiffIter`");

                None
            }
            code => {
                let err_msg = "failed to get next changes iterating backward".to_owned();
                log::debug!( "SwapsDiffIter::next_back {err_msg}. libmount::mnt_tabdiff_next_change returned error code: {code:?}");

                None
            }
        }
    }

    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
        log::debug!("SwapsDiffIter::nth_back getting {n:?}th table diff item from the back");

        let mut result;
        let mut flags = MaybeUninit::<libc::c_int>::zeroed();

        // Skip n-1 entries, and update cursors along the way.
        for i in 0..n {
            let mut source_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();
            let mut other_entry_inner = MaybeUninit::<*mut libmount::libmnt_fs>::zeroed();

            result = unsafe {
                libmount::mnt_tabdiff_next_change(
                    self.table_diff.inner,
                    self.bwd_iter.inner,
                    source_entry_inner.as_mut_ptr(),
                    other_entry_inner.as_mut_ptr(),
                    flags.as_mut_ptr(),
                )
            };

            match result {
                0 => {
                    let source_entry_inner = unsafe { source_entry_inner.assume_init() };
                    let other_entry_inner = unsafe { other_entry_inner.assume_init() };

                    // Per the documentation of `DoubleEndedIterator`
                    // "It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle."
                    if self.have_iterators_met
                        || ((self.first_fwd_cursor != self.first_bwd_cursor)
                            && (self.second_fwd_cursor != self.second_bwd_cursor)
                            && (source_entry_inner == self.first_fwd_cursor
                                && other_entry_inner == self.second_fwd_cursor))
                    {
                        log::debug!( "SwapsDiffIter::nth_back forward and backward iterators have met in the middle");

                        self.have_iterators_met = true;

                        return None;
                    } else {
                        log::debug!("SwapsDiffIter::nth got {i:?}th table diff item from the back");
                        self.first_bwd_cursor = source_entry_inner;
                        self.second_bwd_cursor = other_entry_inner;
                    }
                }
                1 => {
                    log::debug!("SwapsDiffIter::nth_back reached the beginning of `SwapsDiffIter`");

                    return None;
                }
                code => {
                    let err_msg = format!("failed to get {:?}th table diff item from the back", n);
                    log::debug!( "SwapsDiffIter::nth_back {err_msg}. libmount::mnt_tabdiff_next_change returned error code: {code:?}");

                    return None;
                }
            }
        }

        self.next_back()
    }
}