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
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
//! # ReadFilter: Wrappers for `Read`able things.
//!
//! A collection of structs you can wrap around something `Read`able in order to transparently
//! filter out unwanted content.
use std::io::{self, Read};

const BUF_SIZE: usize = 8 * 1024;
//const BUF_SIZE: usize = 16;

/// The common bits that each stream iterator/reader has, and the only bits
/// needed to impl Read on each of them.
struct Common<T>
where
    T: Read,
{
    /// The lower layer. The place where bytes are read from before processing.
    source: T,
    /// Stores and accumulates bytes read from source.
    working_buf: [u8; BUF_SIZE],
    /// The byte right after the last byte in the `working_buf`. The next byte that should be written
    /// into, and the byte right after the last valid byte that can be read.  When this is 0,
    /// `working_buf` is empty. Sometimes when we are read from, we might be told to fill a buffer
    /// that is smaller than the amount of bytes we have read from the lower layer already. If this
    /// ends up being the case, `.read()` stores a non-zero value here so `.next()` can be signaled
    /// to not overwrite data at the very beginning of `working_buffer`.
    unconsumed_bytes: usize,
}

impl<T> Common<T>
where
    T: Read,
{
    fn new(source: T) -> Self {
        Self {
            source,
            working_buf: [0; BUF_SIZE],
            unconsumed_bytes: 0,
        }
    }
}

/// Removes all non-whitelisted characters from the wrapped stream.
///
/// Non-utf8 characters are lost due to internal string conversions using
/// [String::from_utf8_lossy()][String::from_utf8_lossy].
///
/// ```
/// use readfilter::CharWhitelist;
/// use std::io::Read;
/// let buf = "aabbccddee".as_bytes();
/// let mut wrapped = CharWhitelist::new(buf, "ace");
/// let mut s = String::new();
/// wrapped.read_to_string(&mut s).unwrap();
/// assert_eq!(&s, "aaccee");
/// ```
///
/// ```no_run
/// use readfilter::CharWhitelist;
/// use std::fs::OpenOptions;
/// use std::io::Read;
/// let mut output = vec![];
/// let fd = OpenOptions::new().read(true).open("input.txt").unwrap();
/// let mut input = CharWhitelist::new(fd, "01");
/// input.read_to_end(&mut output);
/// // output only contains the '0' and '1' characters from input.txt
/// ```
pub struct CharWhitelist<T>
where
    T: Read,
{
    common: Common<T>,
    allowed_chars: Vec<char>,
}

impl<T> CharWhitelist<T>
where
    T: Read,
{
    pub fn new(source: T, allowed_chars: &str) -> Self {
        Self {
            common: Common::new(source),
            allowed_chars: allowed_chars.chars().collect(),
        }
    }

    fn next(&mut self) -> Option<io::Result<usize>> {
        let mut read_previously = self.common.unconsumed_bytes;
        // keep looping until we get an error, fail to read any bytes, or have
        // read a full buffer
        loop {
            let read_this_time = self
                .common
                .source
                .read(&mut self.common.working_buf[read_previously..]);
            // return the error if there is one
            if let Err(e) = read_this_time {
                return Some(Err(e));
            }
            let read_this_time = read_this_time.unwrap();
            // if we didn't read anything, time to stop looping
            if read_this_time < 1 {
                return Some(Ok(read_previously));
            }
            assert!(read_this_time > 0);
            // convert [u8, BUF_SIZE] (with length read_this_time) to String
            let buf = String::from_utf8_lossy(
                &self.common.working_buf[read_previously..read_previously + read_this_time],
            )
            .into_owned();
            for c in buf.chars() {
                if self.allowed_chars.contains(&c) {
                    let _ = c.encode_utf8(&mut self.common.working_buf[read_previously..]);
                    read_previously += c.len_utf8();
                }
            }
        }
    }
}

/// Removes comments from the wrapped stream.
///
/// A comment starts with `#` and ends with a newline `\n` or the end of file.
///
/// ```
/// use readfilter::CommentStrip;
/// use std::io::Read;
/// let mut input = CommentStrip::new("a\nb# foo\nc#bar".as_bytes());
/// let mut output = String::new();
/// input.read_to_string(&mut output);
/// assert_eq!(output, "a\nbc");
/// ```
pub struct CommentStrip<T>
where
    T: Read,
{
    common: Common<T>,
    /// Sometimes reads from source will end with a comment that isn't finished
    /// yet. This flag is used to keep track of whether or not we need to keep
    /// ignoring bytes until the comment ends (i.e. we see a newline)
    ignore_until_next_newline: bool,
}

impl<T> CommentStrip<T>
where
    T: Read,
{
    pub fn new(source: T) -> Self {
        Self {
            common: Common::new(source),
            ignore_until_next_newline: false,
        }
    }

    fn next(&mut self) -> Option<io::Result<usize>> {
        let mut read_previously = self.common.unconsumed_bytes;
        // keep looping until we get an error, fail to read any bytes, or have
        // read a full buffer
        loop {
            let read_this_time = self
                .common
                .source
                .read(&mut self.common.working_buf[read_previously..]);
            // return the error if there is one
            if let Err(e) = read_this_time {
                return Some(Err(e));
            }
            let read_this_time = read_this_time.unwrap();
            // if we didn't read anything, time to stop looping
            if read_this_time < 1 {
                return Some(Ok(read_previously));
            }
            assert!(read_this_time > 0);
            // convert [u8, BUF_SIZE] (with length read_this_time) to String
            let mut buf = String::from_utf8_lossy(
                &self.common.working_buf[read_previously..read_previously + read_this_time],
            )
            .into_owned();
            // if needed, ignore bytes up through a newline
            buf = if self.ignore_until_next_newline {
                match buf.find('\n') {
                    // found a newline. ignore bytes up through it, keep bytes after it, and unset
                    // ignore_until_next_newline
                    Some(idx) => {
                        self.ignore_until_next_newline = false;
                        buf[idx + 1..].to_string()
                    }
                    // didn't find newline. ignore all bytes
                    None => String::new(),
                }
            } else {
                buf
            };
            // if buffer empty, end early
            if buf.is_empty() {
                return Some(Ok(read_previously));
            }
            // loop until no more comments in buf
            loop {
                // look for comment character. if found, ignore bytes after it until newline
                let start_idx = buf.find('#');
                if start_idx.is_none() {
                    break;
                }
                let start_idx = start_idx.unwrap();
                buf = match buf[start_idx..].find('\n') {
                    // newline found. ignore bytes between comment char and newline
                    Some(end_idx) => {
                        String::from(&buf[..start_idx]) + &buf[start_idx + end_idx + 1..]
                    }
                    // no newline found. ignore all bytes after comment char and set flag to keep
                    // ignoring on next loop
                    None => {
                        self.ignore_until_next_newline = true;
                        buf[..start_idx].to_string()
                    }
                };
            }
            let remaining_len = buf.len();
            if remaining_len > 0 {
                self.common.working_buf[read_previously..read_previously + remaining_len]
                    .copy_from_slice(buf.as_bytes());
                read_previously += remaining_len;
            }
        }
    }
}

/// Each type impls Read. As all the hard work is done in self.next(), this can
/// be generalized. .read() is probably how the user should be using these types.
macro_rules! impl_read_trait_for_stream_iter {
    ($MyType:ty) => {
        impl<T> Read for $MyType
        where
            T: Read,
        {
            fn read(&mut self, out_buf: &mut [u8]) -> io::Result<usize> {
                let mut bytes_given = 0;
                if self.common.unconsumed_bytes >= out_buf.len() {
                    // We have more data already buffered than the user wants to read.
                    // 1. Copy to them the max amount of data
                    // 2. Update our buffer so that it starts with the buffered bytes
                    // right after the ones we just gave them
                    // 3. Update the length of our buffer
                    // Then we're done. We shouldn't read anything more because we can't
                    // even give it to them yet.
                    let out_buf_len = out_buf.len();
                    out_buf[..out_buf_len].copy_from_slice(&self.common.working_buf[..out_buf_len]);
                    self.common
                        .working_buf
                        .copy_within(out_buf_len..self.common.unconsumed_bytes, 0);
                    self.common.unconsumed_bytes -= out_buf_len;
                    return Ok(out_buf.len());
                } else {
                    // We have less data already buffered than what the user wants to read.
                    // 1. Copy to them all that we have.
                    // 2. Update the length of our buffer to be zero.
                    // 3. Note that we've given them some bytes.
                    // Continue with this function. We might be able to give them more.
                    out_buf[..self.common.unconsumed_bytes]
                        .copy_from_slice(&self.common.working_buf[..self.common.unconsumed_bytes]);
                    bytes_given += self.common.unconsumed_bytes;
                    self.common.unconsumed_bytes = 0;
                }
                assert_eq!(self.common.unconsumed_bytes, 0);
                // If we're here, then we must need to read some more bytes and give
                // them to the out_buf. First try to read more.
                let next_res = self.next();
                if let Some(Ok(working_buf_len)) = next_res {
                    // We successfully read something. working_buf_len is the number of bytes at
                    // the front of the working buf that are valid. We have access to the working
                    // buf since it is ours.
                    let max_bytes_to_give = out_buf.len() - bytes_given;
                    if working_buf_len >= max_bytes_to_give {
                        // If we read too many bytes, then
                        // 1. Give as many as possible to the out_buf
                        // 2. Move the remaining working_buf bytes to the front of the working_buf
                        // 3. Update the len of the working_buf And then we're done and can return.
                        out_buf[bytes_given..]
                            .copy_from_slice(&self.common.working_buf[..max_bytes_to_give]);
                        self.common
                            .working_buf
                            .copy_within(max_bytes_to_give..working_buf_len, 0);
                        self.common.unconsumed_bytes = working_buf_len - max_bytes_to_give;
                        bytes_given += max_bytes_to_give;
                        return Ok(bytes_given);
                    } else {
                        // We read fewer bytes than there is remaining space in out_buf. We can
                        // give it all the bytes. For simplicity, just return after doing so. We
                        // could loop around and do all this again.
                        out_buf[bytes_given..bytes_given + working_buf_len]
                            .copy_from_slice(&self.common.working_buf[..working_buf_len]);
                        bytes_given += working_buf_len;
                        return Ok(bytes_given);
                    }
                } else if let Some(Err(e)) = next_res {
                    return Err(e);
                } else {
                    // We failed to iterate forward in the stream. Must be done.
                    return Ok(bytes_given);
                }
            }
        }
    };
}

impl_read_trait_for_stream_iter!(CharWhitelist<T>);
impl_read_trait_for_stream_iter!(CommentStrip<T>);

#[cfg(test)]
fn read_to_string(mut buf: impl Read) -> String {
    let mut s = String::new();
    buf.read_to_string(&mut s).unwrap();
    s
}

#[cfg(test)]
mod test_comment_strip_iter {
    use super::{read_to_string, CommentStrip, BUF_SIZE};

    #[test]
    fn empty_is_empty() {
        let s = "".as_bytes();
        assert_eq!(read_to_string(CommentStrip::new(s)).len(), 0);
    }

    #[test]
    fn ignore_all_short() {
        for s in &["#foo baz", "#foo baz\n", "#    ", "#    \n", "#", "#\n"] {
            assert_eq!(read_to_string(CommentStrip::new(s.as_bytes())).len(), 0);
        }
    }

    #[test]
    fn ignore_all_long_1() {
        // just less than a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE - 2]);
        assert_eq!(s.len(), BUF_SIZE - 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // exactly a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE - 1]);
        assert_eq!(s.len(), BUF_SIZE);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // just over a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE]);
        assert_eq!(s.len(), BUF_SIZE + 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // over 2 buffers in size
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE * 2 + 2]);
        assert_eq!(s.len(), BUF_SIZE * 2 + 3);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);
    }

    #[test]
    fn ignore_all_long_2() {
        // just less than a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE - 3]);
        s.push('\n' as u8);
        assert_eq!(s.len(), BUF_SIZE - 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // exactly a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE - 2]);
        s.push('\n' as u8);
        assert_eq!(s.len(), BUF_SIZE);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // just over a full buffer
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE - 1]);
        s.push('\n' as u8);
        assert_eq!(s.len(), BUF_SIZE + 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);

        // over 2 buffers in size
        let mut s = vec!['#' as u8];
        s.append(&mut vec![' ' as u8; BUF_SIZE * 2 + 1]);
        s.push('\n' as u8);
        assert_eq!(s.len(), BUF_SIZE * 2 + 3);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])).len(), 0);
    }

    #[test]
    fn keep_end_short() {
        for s in &["#\nfoo", "#  \nfoo"] {
            let out = read_to_string(CommentStrip::new(s.as_bytes()));
            assert_eq!(out, "foo");
        }

        for s in &["#\nfoo  foo", "#  \nfoo  foo"] {
            let out = read_to_string(CommentStrip::new(s.as_bytes()));
            assert_eq!(out, "foo  foo");
        }

        for s in &["#\nfoo \n foo", "#  \nfoo \n foo"] {
            let out = read_to_string(CommentStrip::new(s.as_bytes()));
            assert_eq!(out, "foo \n foo");
        }
    }

    #[test]
    fn keep_end_long() {
        let content = " foo \n foo ";

        // just under BUF_SIZE
        let mut s = vec!['#' as u8; BUF_SIZE - content.len() - 1 - 1];
        s.push('\n' as u8);
        for c in content.chars() {
            s.push(c as u8);
        }
        assert_eq!(s.len(), BUF_SIZE - 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])), content);

        // equal to BUF_SIZE
        let mut s = vec!['#' as u8; BUF_SIZE - content.len() - 1];
        s.push('\n' as u8);
        for c in content.chars() {
            s.push(c as u8);
        }
        assert_eq!(s.len(), BUF_SIZE);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])), content);

        // just over BUF_SIZE
        let mut s = vec!['#' as u8; BUF_SIZE - content.len() - 1 + 1];
        s.push('\n' as u8);
        for c in content.chars() {
            s.push(c as u8);
        }
        assert_eq!(s.len(), BUF_SIZE + 1);
        assert_eq!(read_to_string(CommentStrip::new(&s[..])), content);

        // comment is over BUF_SIZE by itself
        let mut s = vec!['#' as u8; BUF_SIZE + 1];
        s.push('\n' as u8);
        for c in content.chars() {
            s.push(c as u8);
        }
        assert_eq!(s.len(), BUF_SIZE + 2 + content.len());
        assert_eq!(read_to_string(CommentStrip::new(&s[..])), content);
    }
}

#[cfg(test)]
mod test_char_whitelist_iter {
    use super::{read_to_string, CharWhitelist};

    #[test]
    fn empty_whitelist() {
        let in_buf = "A\u{00a1}\u{01d6a9}".as_bytes();
        assert_eq!(read_to_string(CharWhitelist::new(in_buf, "")).len(), 0);
    }

    #[test]
    fn whitelist_allows_all() {
        let s = "A\u{00a1}\u{1d6a9}";
        assert_eq!(read_to_string(CharWhitelist::new(s.as_bytes(), s)), s);
    }

    #[test]
    fn whitelist_allows_single() {
        for allowed in vec!["A", "\u{00a1}", "\u{1d6a9}"] {
            let in_buf = "A\u{00a1}\u{1d6a9}".as_bytes();
            assert_eq!(read_to_string(CharWhitelist::new(in_buf, allowed)), allowed);
        }
    }
}

#[cfg(test)]
mod test_comment_strip_iter_read {
    use super::{CommentStrip, BUF_SIZE};
    use std::io::Read;

    #[test]
    fn just_comment_returns_empty() {
        let in_buf = "# foo \n".as_bytes();
        let mut out_buf = [0; 1];
        let mut csi = CommentStrip::new(&in_buf[..]);
        let len = csi.read(&mut out_buf).unwrap();
        assert_eq!(len, 0);
    }

    #[test]
    fn just_byte_before_comment() {
        let in_buf = "a# foo \n".as_bytes();
        let mut out_buf = [0; BUF_SIZE];
        let mut csi = CommentStrip::new(&in_buf[..]);
        let len = csi.read(&mut out_buf).unwrap();
        assert_eq!(String::from_utf8_lossy(&out_buf[..len]), "a");
    }

    #[test]
    fn just_byte_after_comment() {
        let in_buf = "# foo \na".as_bytes();
        let mut out_buf = [0; BUF_SIZE];
        let mut csi = CommentStrip::new(&in_buf[..]);
        let len = csi.read(&mut out_buf).unwrap();
        assert_eq!(String::from_utf8_lossy(&out_buf[..len]), "a");
    }

    #[test]
    fn just_byte_before_and_after_comment() {
        let in_buf = "a# foo \nB".as_bytes();
        let mut out_buf = [0; BUF_SIZE];
        let mut csi = CommentStrip::new(&in_buf[..]);
        let len = csi.read(&mut out_buf).unwrap();
        assert_eq!(String::from_utf8_lossy(&out_buf[..len]), "aB");
    }
}

macro_rules! impl_tests_for_common_read {
    ($mod_name:ident, $MyType:ident) => {
        #[cfg(test)]
        mod $mod_name {
            use super::{$MyType, BUF_SIZE};
            use std::io::Read;

            #[test]
            fn empty() {
                let in_buf = vec![];
                let mut out_buf = [0; 1];
                let mut csi = $MyType::new(&in_buf[..]);
                let len = csi.read(&mut out_buf).unwrap();
                assert_eq!(len, 0);
            }

            #[test]
            fn many_tiny_reads() {
                let in_buf = "abc123".as_bytes();
                let mut out_buf = [0; 1];
                let mut acc = String::new();
                let mut csi = $MyType::new(&in_buf[..]);
                for _ in 0..in_buf.len() {
                    let len = csi.read(&mut out_buf).unwrap();
                    acc += &String::from_utf8_lossy(&out_buf[..len]);
                }
                assert_eq!(acc, "abc123");
                // future reads should be length zero
                assert_eq!(csi.read(&mut out_buf).unwrap(), 0);
            }

            #[test]
            fn big_inbuf_tiny_outbuf() {
                let mut in_buf = vec!['a' as u8; BUF_SIZE / 2];
                in_buf.append(&mut vec!['b' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['c' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['d' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['e' as u8; BUF_SIZE / 2]);
                let mut out_buf = [0; 2];
                let mut acc = String::new();
                let mut csi = $MyType::new(&in_buf[..]);
                loop {
                    let len = csi.read(&mut out_buf).unwrap();
                    acc += &String::from_utf8_lossy(&out_buf[..len]);
                    if len < 1 {
                        break;
                    }
                }
                assert_eq!(acc, String::from_utf8_lossy(&in_buf[..]));
            }

            #[test]
            fn big_inbuf_just_smaller_outbuf() {
                let mut in_buf = vec!['a' as u8; BUF_SIZE / 2];
                in_buf.append(&mut vec!['b' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['c' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['d' as u8; BUF_SIZE / 2]);
                assert_eq!(in_buf.len(), BUF_SIZE * 2);
                let mut out_buf = [0; BUF_SIZE * 2 - 1];
                let mut acc = String::new();
                let mut csi = $MyType::new(&in_buf[..]);
                loop {
                    let len = csi.read(&mut out_buf).unwrap();
                    acc += &String::from_utf8_lossy(&out_buf[..len]);
                    if len < 1 {
                        break;
                    }
                }
                assert_eq!(acc, String::from_utf8_lossy(&in_buf[..]));
            }

            #[test]
            fn big_inbuf_just_larger_outbuf() {
                let mut in_buf = vec!['a' as u8; BUF_SIZE / 2];
                in_buf.append(&mut vec!['b' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['c' as u8; BUF_SIZE / 2]);
                in_buf.append(&mut vec!['d' as u8; BUF_SIZE / 2]);
                assert_eq!(in_buf.len(), BUF_SIZE * 2);
                let mut out_buf = [0; BUF_SIZE * 2 + 1];
                let mut acc = String::new();
                let mut csi = $MyType::new(&in_buf[..]);
                loop {
                    let len = csi.read(&mut out_buf).unwrap();
                    acc += &String::from_utf8_lossy(&out_buf[..len]);
                    if len < 1 {
                        break;
                    }
                }
                assert_eq!(acc, String::from_utf8_lossy(&in_buf[..]));
            }
        }
    };
}

impl_tests_for_common_read!(test_read_common_with_comment_strip_iter, CommentStrip);
// can't test because its .new() requires more than just the source
//impl_tests_for_common_read!(test_read_common_with_char_whitelist_iter, CharWhitelist);