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
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
/*!
Utilities for working with I/O using byte strings.

This module currently only exports a single trait, `BufReadExt`, which provides
facilities for conveniently and efficiently working with lines as byte strings.

More APIs may be added in the future.
*/

use alloc::{vec, vec::Vec};

use std::io;

use crate::{ext_slice::ByteSlice, ext_vec::ByteVec};

/// An extension trait for
/// [`std::io::BufRead`](https://doc.rust-lang.org/std/io/trait.BufRead.html)
/// which provides convenience APIs for dealing with byte strings.
pub trait BufReadExt: io::BufRead {
    /// Returns an iterator over the lines of this reader, where each line
    /// is represented as a byte string.
    ///
    /// Each item yielded by this iterator is a `io::Result<Vec<u8>>`, where
    /// an error is yielded if there was a problem reading from the underlying
    /// reader.
    ///
    /// On success, the next line in the iterator is returned. The line does
    /// *not* contain a trailing `\n` or `\r\n`.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::io::BufReadExt;
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor");
    ///
    /// let mut lines = vec![];
    /// for result in cursor.byte_lines() {
    ///     let line = result?;
    ///     lines.push(line);
    /// }
    /// assert_eq!(lines.len(), 3);
    /// assert_eq!(lines[0], "lorem".as_bytes());
    /// assert_eq!(lines[1], "ipsum".as_bytes());
    /// assert_eq!(lines[2], "dolor".as_bytes());
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn byte_lines(self) -> ByteLines<Self>
    where
        Self: Sized,
    {
        ByteLines { buf: self }
    }

    /// Returns an iterator over byte-terminated records of this reader, where
    /// each record is represented as a byte string.
    ///
    /// Each item yielded by this iterator is a `io::Result<Vec<u8>>`, where
    /// an error is yielded if there was a problem reading from the underlying
    /// reader.
    ///
    /// On success, the next record in the iterator is returned. The record
    /// does *not* contain its trailing terminator.
    ///
    /// Note that calling `byte_records(b'\n')` differs from `byte_lines()` in
    /// that it has no special handling for `\r`.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::io::BufReadExt;
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\x00ipsum\x00dolor");
    ///
    /// let mut records = vec![];
    /// for result in cursor.byte_records(b'\x00') {
    ///     let record = result?;
    ///     records.push(record);
    /// }
    /// assert_eq!(records.len(), 3);
    /// assert_eq!(records[0], "lorem".as_bytes());
    /// assert_eq!(records[1], "ipsum".as_bytes());
    /// assert_eq!(records[2], "dolor".as_bytes());
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn byte_records(self, terminator: u8) -> ByteRecords<Self>
    where
        Self: Sized,
    {
        ByteRecords { terminator, buf: self }
    }

    /// Executes the given closure on each line in the underlying reader.
    ///
    /// If the closure returns an error (or if the underlying reader returns an
    /// error), then iteration is stopped and the error is returned. If false
    /// is returned, then iteration is stopped and no error is returned.
    ///
    /// The closure given is called on exactly the same values as yielded by
    /// the [`byte_lines`](trait.BufReadExt.html#method.byte_lines)
    /// iterator. Namely, lines do _not_ contain trailing `\n` or `\r\n` bytes.
    ///
    /// This routine is useful for iterating over lines as quickly as
    /// possible. Namely, a single allocation is reused for each line.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::io::BufReadExt;
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor");
    ///
    /// let mut lines = vec![];
    /// cursor.for_byte_line(|line| {
    ///     lines.push(line.to_vec());
    ///     Ok(true)
    /// })?;
    /// assert_eq!(lines.len(), 3);
    /// assert_eq!(lines[0], "lorem".as_bytes());
    /// assert_eq!(lines[1], "ipsum".as_bytes());
    /// assert_eq!(lines[2], "dolor".as_bytes());
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn for_byte_line<F>(&mut self, mut for_each_line: F) -> io::Result<()>
    where
        Self: Sized,
        F: FnMut(&[u8]) -> io::Result<bool>,
    {
        self.for_byte_line_with_terminator(|line| {
            for_each_line(&trim_line_slice(&line))
        })
    }

    /// Executes the given closure on each byte-terminated record in the
    /// underlying reader.
    ///
    /// If the closure returns an error (or if the underlying reader returns an
    /// error), then iteration is stopped and the error is returned. If false
    /// is returned, then iteration is stopped and no error is returned.
    ///
    /// The closure given is called on exactly the same values as yielded by
    /// the [`byte_records`](trait.BufReadExt.html#method.byte_records)
    /// iterator. Namely, records do _not_ contain a trailing terminator byte.
    ///
    /// This routine is useful for iterating over records as quickly as
    /// possible. Namely, a single allocation is reused for each record.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::io::BufReadExt;
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\x00ipsum\x00dolor");
    ///
    /// let mut records = vec![];
    /// cursor.for_byte_record(b'\x00', |record| {
    ///     records.push(record.to_vec());
    ///     Ok(true)
    /// })?;
    /// assert_eq!(records.len(), 3);
    /// assert_eq!(records[0], "lorem".as_bytes());
    /// assert_eq!(records[1], "ipsum".as_bytes());
    /// assert_eq!(records[2], "dolor".as_bytes());
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn for_byte_record<F>(
        &mut self,
        terminator: u8,
        mut for_each_record: F,
    ) -> io::Result<()>
    where
        Self: Sized,
        F: FnMut(&[u8]) -> io::Result<bool>,
    {
        self.for_byte_record_with_terminator(terminator, |chunk| {
            for_each_record(&trim_record_slice(&chunk, terminator))
        })
    }

    /// Executes the given closure on each line in the underlying reader.
    ///
    /// If the closure returns an error (or if the underlying reader returns an
    /// error), then iteration is stopped and the error is returned. If false
    /// is returned, then iteration is stopped and no error is returned.
    ///
    /// Unlike
    /// [`for_byte_line`](trait.BufReadExt.html#method.for_byte_line),
    /// the lines given to the closure *do* include the line terminator, if one
    /// exists.
    ///
    /// This routine is useful for iterating over lines as quickly as
    /// possible. Namely, a single allocation is reused for each line.
    ///
    /// This is identical to `for_byte_record_with_terminator` with a
    /// terminator of `\n`.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::io::BufReadExt;
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor");
    ///
    /// let mut lines = vec![];
    /// cursor.for_byte_line_with_terminator(|line| {
    ///     lines.push(line.to_vec());
    ///     Ok(true)
    /// })?;
    /// assert_eq!(lines.len(), 3);
    /// assert_eq!(lines[0], "lorem\n".as_bytes());
    /// assert_eq!(lines[1], "ipsum\r\n".as_bytes());
    /// assert_eq!(lines[2], "dolor".as_bytes());
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn for_byte_line_with_terminator<F>(
        &mut self,
        for_each_line: F,
    ) -> io::Result<()>
    where
        Self: Sized,
        F: FnMut(&[u8]) -> io::Result<bool>,
    {
        self.for_byte_record_with_terminator(b'\n', for_each_line)
    }

    /// Executes the given closure on each byte-terminated record in the
    /// underlying reader.
    ///
    /// If the closure returns an error (or if the underlying reader returns an
    /// error), then iteration is stopped and the error is returned. If false
    /// is returned, then iteration is stopped and no error is returned.
    ///
    /// Unlike
    /// [`for_byte_record`](trait.BufReadExt.html#method.for_byte_record),
    /// the lines given to the closure *do* include the record terminator, if
    /// one exists.
    ///
    /// This routine is useful for iterating over records as quickly as
    /// possible. Namely, a single allocation is reused for each record.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::io;
    ///
    /// use bstr::{io::BufReadExt, B};
    ///
    /// # fn example() -> Result<(), io::Error> {
    /// let mut cursor = io::Cursor::new(b"lorem\x00ipsum\x00dolor");
    ///
    /// let mut records = vec![];
    /// cursor.for_byte_record_with_terminator(b'\x00', |record| {
    ///     records.push(record.to_vec());
    ///     Ok(true)
    /// })?;
    /// assert_eq!(records.len(), 3);
    /// assert_eq!(records[0], B(b"lorem\x00"));
    /// assert_eq!(records[1], B("ipsum\x00"));
    /// assert_eq!(records[2], B("dolor"));
    /// # Ok(()) }; example().unwrap()
    /// ```
    fn for_byte_record_with_terminator<F>(
        &mut self,
        terminator: u8,
        mut for_each_record: F,
    ) -> io::Result<()>
    where
        Self: Sized,
        F: FnMut(&[u8]) -> io::Result<bool>,
    {
        let mut bytes = vec![];
        let mut res = Ok(());
        let mut consumed = 0;
        'outer: loop {
            // Lend out complete record slices from our buffer
            {
                let mut buf = self.fill_buf()?;
                if buf.is_empty() {
                    break;
                }
                while let Some(index) = buf.find_byte(terminator) {
                    let (record, rest) = buf.split_at(index + 1);
                    buf = rest;
                    consumed += record.len();
                    match for_each_record(&record) {
                        Ok(false) => break 'outer,
                        Err(err) => {
                            res = Err(err);
                            break 'outer;
                        }
                        _ => (),
                    }
                }

                // Copy the final record fragment to our local buffer. This
                // saves read_until() from re-scanning a buffer we know
                // contains no remaining terminators.
                bytes.extend_from_slice(&buf);
                consumed += buf.len();
            }

            self.consume(consumed);
            consumed = 0;

            // N.B. read_until uses a different version of memchr that may
            // be slower than the memchr crate that bstr uses. However, this
            // should only run for a fairly small number of records, assuming a
            // decent buffer size.
            self.read_until(terminator, &mut bytes)?;
            if bytes.is_empty() || !for_each_record(&bytes)? {
                break;
            }
            bytes.clear();
        }
        self.consume(consumed);
        res
    }
}

impl<B: io::BufRead> BufReadExt for B {}

/// An iterator over lines from an instance of
/// [`std::io::BufRead`](https://doc.rust-lang.org/std/io/trait.BufRead.html).
///
/// This iterator is generally created by calling the
/// [`byte_lines`](trait.BufReadExt.html#method.byte_lines)
/// method on the
/// [`BufReadExt`](trait.BufReadExt.html)
/// trait.
#[derive(Debug)]
pub struct ByteLines<B> {
    buf: B,
}

/// An iterator over records from an instance of
/// [`std::io::BufRead`](https://doc.rust-lang.org/std/io/trait.BufRead.html).
///
/// A byte record is any sequence of bytes terminated by a particular byte
/// chosen by the caller. For example, NUL separated byte strings are said to
/// be NUL-terminated byte records.
///
/// This iterator is generally created by calling the
/// [`byte_records`](trait.BufReadExt.html#method.byte_records)
/// method on the
/// [`BufReadExt`](trait.BufReadExt.html)
/// trait.
#[derive(Debug)]
pub struct ByteRecords<B> {
    buf: B,
    terminator: u8,
}

impl<B: io::BufRead> Iterator for ByteLines<B> {
    type Item = io::Result<Vec<u8>>;

    fn next(&mut self) -> Option<io::Result<Vec<u8>>> {
        let mut bytes = vec![];
        match self.buf.read_until(b'\n', &mut bytes) {
            Err(e) => Some(Err(e)),
            Ok(0) => None,
            Ok(_) => {
                trim_line(&mut bytes);
                Some(Ok(bytes))
            }
        }
    }
}

impl<B: io::BufRead> Iterator for ByteRecords<B> {
    type Item = io::Result<Vec<u8>>;

    fn next(&mut self) -> Option<io::Result<Vec<u8>>> {
        let mut bytes = vec![];
        match self.buf.read_until(self.terminator, &mut bytes) {
            Err(e) => Some(Err(e)),
            Ok(0) => None,
            Ok(_) => {
                trim_record(&mut bytes, self.terminator);
                Some(Ok(bytes))
            }
        }
    }
}

fn trim_line(line: &mut Vec<u8>) {
    if line.last_byte() == Some(b'\n') {
        line.pop_byte();
        if line.last_byte() == Some(b'\r') {
            line.pop_byte();
        }
    }
}

fn trim_line_slice(mut line: &[u8]) -> &[u8] {
    if line.last_byte() == Some(b'\n') {
        line = &line[..line.len() - 1];
        if line.last_byte() == Some(b'\r') {
            line = &line[..line.len() - 1];
        }
    }
    line
}

fn trim_record(record: &mut Vec<u8>, terminator: u8) {
    if record.last_byte() == Some(terminator) {
        record.pop_byte();
    }
}

fn trim_record_slice(mut record: &[u8], terminator: u8) -> &[u8] {
    if record.last_byte() == Some(terminator) {
        record = &record[..record.len() - 1];
    }
    record
}

#[cfg(all(test, feature = "std"))]
mod tests {
    use alloc::{vec, vec::Vec};

    use crate::bstring::BString;

    use super::BufReadExt;

    fn collect_lines<B: AsRef<[u8]>>(slice: B) -> Vec<BString> {
        let mut lines = vec![];
        slice
            .as_ref()
            .for_byte_line(|line| {
                lines.push(BString::from(line.to_vec()));
                Ok(true)
            })
            .unwrap();
        lines
    }

    fn collect_lines_term<B: AsRef<[u8]>>(slice: B) -> Vec<BString> {
        let mut lines = vec![];
        slice
            .as_ref()
            .for_byte_line_with_terminator(|line| {
                lines.push(BString::from(line.to_vec()));
                Ok(true)
            })
            .unwrap();
        lines
    }

    #[test]
    fn lines_without_terminator() {
        assert_eq!(collect_lines(""), Vec::<BString>::new());

        assert_eq!(collect_lines("\n"), vec![""]);
        assert_eq!(collect_lines("\n\n"), vec!["", ""]);
        assert_eq!(collect_lines("a\nb\n"), vec!["a", "b"]);
        assert_eq!(collect_lines("a\nb"), vec!["a", "b"]);
        assert_eq!(collect_lines("abc\nxyz\n"), vec!["abc", "xyz"]);
        assert_eq!(collect_lines("abc\nxyz"), vec!["abc", "xyz"]);

        assert_eq!(collect_lines("\r\n"), vec![""]);
        assert_eq!(collect_lines("\r\n\r\n"), vec!["", ""]);
        assert_eq!(collect_lines("a\r\nb\r\n"), vec!["a", "b"]);
        assert_eq!(collect_lines("a\r\nb"), vec!["a", "b"]);
        assert_eq!(collect_lines("abc\r\nxyz\r\n"), vec!["abc", "xyz"]);
        assert_eq!(collect_lines("abc\r\nxyz"), vec!["abc", "xyz"]);

        assert_eq!(collect_lines("abc\rxyz"), vec!["abc\rxyz"]);
    }

    #[test]
    fn lines_with_terminator() {
        assert_eq!(collect_lines_term(""), Vec::<BString>::new());

        assert_eq!(collect_lines_term("\n"), vec!["\n"]);
        assert_eq!(collect_lines_term("\n\n"), vec!["\n", "\n"]);
        assert_eq!(collect_lines_term("a\nb\n"), vec!["a\n", "b\n"]);
        assert_eq!(collect_lines_term("a\nb"), vec!["a\n", "b"]);
        assert_eq!(collect_lines_term("abc\nxyz\n"), vec!["abc\n", "xyz\n"]);
        assert_eq!(collect_lines_term("abc\nxyz"), vec!["abc\n", "xyz"]);

        assert_eq!(collect_lines_term("\r\n"), vec!["\r\n"]);
        assert_eq!(collect_lines_term("\r\n\r\n"), vec!["\r\n", "\r\n"]);
        assert_eq!(collect_lines_term("a\r\nb\r\n"), vec!["a\r\n", "b\r\n"]);
        assert_eq!(collect_lines_term("a\r\nb"), vec!["a\r\n", "b"]);
        assert_eq!(
            collect_lines_term("abc\r\nxyz\r\n"),
            vec!["abc\r\n", "xyz\r\n"]
        );
        assert_eq!(collect_lines_term("abc\r\nxyz"), vec!["abc\r\n", "xyz"]);

        assert_eq!(collect_lines_term("abc\rxyz"), vec!["abc\rxyz"]);
    }
}