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
use std::borrow::Borrow;
use std::cmp;
use std::convert::TryFrom;
use std::fmt;
use std::hash::{Hash, Hasher};
use std::mem::MaybeUninit;
use std::ops::{Deref, DerefMut};
use std::ptr;
use std::slice;
use std::str;
use std::str::FromStr;
use std::str::Utf8Error;

use crate::CapacityError;
use crate::LenUint;
use crate::char::encode_utf8;
use crate::utils::MakeMaybeUninit;

#[cfg(feature="serde")]
use serde::{Serialize, Deserialize, Serializer, Deserializer};


/// A string with a fixed capacity.
///
/// The `ArrayString` is a string backed by a fixed size array. It keeps track
/// of its length, and is parameterized by `CAP` for the maximum capacity.
///
/// `CAP` is of type `usize` but is range limited to `u32::MAX`; attempting to create larger
/// arrayvecs with larger capacity will panic.
///
/// The string is a contiguous value that you can store directly on the stack
/// if needed.
#[derive(Copy)]
pub struct ArrayString<const CAP: usize> {
    // the `len` first elements of the array are initialized
    xs: [MaybeUninit<u8>; CAP],
    len: LenUint,
}

impl<const CAP: usize> Default for ArrayString<CAP>
{
    /// Return an empty `ArrayString`
    fn default() -> ArrayString<CAP> {
        ArrayString::new()
    }
}

impl<const CAP: usize> ArrayString<CAP>
{
    /// Create a new empty `ArrayString`.
    ///
    /// Capacity is inferred from the type parameter.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<16>::new();
    /// string.push_str("foo");
    /// assert_eq!(&string[..], "foo");
    /// assert_eq!(string.capacity(), 16);
    /// ```
    pub const fn new() -> ArrayString<CAP> {
        assert_capacity_limit!(CAP);
        ArrayString { xs: MakeMaybeUninit::ARRAY, len: 0 }
    }

    /// Return the length of the string.
    #[inline]
    pub fn len(&self) -> usize { self.len as usize }

    /// Returns whether the string is empty.
    #[inline]
    pub fn is_empty(&self) -> bool { self.len() == 0 }

    /// Create a new `ArrayString` from a `str`.
    ///
    /// Capacity is inferred from the type parameter.
    ///
    /// **Errors** if the backing array is not large enough to fit the string.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<3>::from("foo").unwrap();
    /// assert_eq!(&string[..], "foo");
    /// assert_eq!(string.len(), 3);
    /// assert_eq!(string.capacity(), 3);
    /// ```
    pub fn from(s: &str) -> Result<Self, CapacityError<&str>> {
        let mut arraystr = Self::new();
        arraystr.try_push_str(s)?;
        Ok(arraystr)
    }

    /// Create a new `ArrayString` from a byte string literal.
    ///
    /// **Errors** if the byte string literal is not valid UTF-8.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let string = ArrayString::from_byte_string(b"hello world").unwrap();
    /// ```
    pub fn from_byte_string(b: &[u8; CAP]) -> Result<Self, Utf8Error> {
        let len = str::from_utf8(b)?.len();
        debug_assert_eq!(len, CAP);
        let mut vec = Self::new();
        unsafe {
            (b as *const [u8; CAP] as *const [MaybeUninit<u8>; CAP])
                .copy_to_nonoverlapping(&mut vec.xs as *mut [MaybeUninit<u8>; CAP], 1);
            vec.set_len(CAP);
        }
        Ok(vec)
    }

    /// Return the capacity of the `ArrayString`.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let string = ArrayString::<3>::new();
    /// assert_eq!(string.capacity(), 3);
    /// ```
    #[inline(always)]
    pub fn capacity(&self) -> usize { CAP }

    /// Return if the `ArrayString` is completely filled.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<1>::new();
    /// assert!(!string.is_full());
    /// string.push_str("A");
    /// assert!(string.is_full());
    /// ```
    pub fn is_full(&self) -> bool { self.len() == self.capacity() }

    /// Adds the given char to the end of the string.
    ///
    /// ***Panics*** if the backing array is not large enough to fit the additional char.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<2>::new();
    ///
    /// string.push('a');
    /// string.push('b');
    ///
    /// assert_eq!(&string[..], "ab");
    /// ```
    pub fn push(&mut self, c: char) {
        self.try_push(c).unwrap();
    }

    /// Adds the given char to the end of the string.
    ///
    /// Returns `Ok` if the push succeeds.
    ///
    /// **Errors** if the backing array is not large enough to fit the additional char.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<2>::new();
    ///
    /// string.try_push('a').unwrap();
    /// string.try_push('b').unwrap();
    /// let overflow = string.try_push('c');
    ///
    /// assert_eq!(&string[..], "ab");
    /// assert_eq!(overflow.unwrap_err().element(), 'c');
    /// ```
    pub fn try_push(&mut self, c: char) -> Result<(), CapacityError<char>> {
        let len = self.len();
        unsafe {
            let ptr = self.as_mut_ptr().add(len);
            let remaining_cap = self.capacity() - len;
            match encode_utf8(c, ptr, remaining_cap) {
                Ok(n) => {
                    self.set_len(len + n);
                    Ok(())
                }
                Err(_) => Err(CapacityError::new(c)),
            }
        }
    }

    /// Adds the given string slice to the end of the string.
    ///
    /// ***Panics*** if the backing array is not large enough to fit the string.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<2>::new();
    ///
    /// string.push_str("a");
    /// string.push_str("d");
    ///
    /// assert_eq!(&string[..], "ad");
    /// ```
    pub fn push_str(&mut self, s: &str) {
        self.try_push_str(s).unwrap()
    }

    /// Adds the given string slice to the end of the string.
    ///
    /// Returns `Ok` if the push succeeds.
    ///
    /// **Errors** if the backing array is not large enough to fit the string.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<2>::new();
    ///
    /// string.try_push_str("a").unwrap();
    /// let overflow1 = string.try_push_str("bc");
    /// string.try_push_str("d").unwrap();
    /// let overflow2 = string.try_push_str("ef");
    ///
    /// assert_eq!(&string[..], "ad");
    /// assert_eq!(overflow1.unwrap_err().element(), "bc");
    /// assert_eq!(overflow2.unwrap_err().element(), "ef");
    /// ```
    pub fn try_push_str<'a>(&mut self, s: &'a str) -> Result<(), CapacityError<&'a str>> {
        if s.len() > self.capacity() - self.len() {
            return Err(CapacityError::new(s));
        }
        unsafe {
            let dst = self.as_mut_ptr().add(self.len());
            let src = s.as_ptr();
            ptr::copy_nonoverlapping(src, dst, s.len());
            let newl = self.len() + s.len();
            self.set_len(newl);
        }
        Ok(())
    }

    /// Removes the last character from the string and returns it.
    ///
    /// Returns `None` if this `ArrayString` is empty.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    /// 
    /// let mut s = ArrayString::<3>::from("foo").unwrap();
    ///
    /// assert_eq!(s.pop(), Some('o'));
    /// assert_eq!(s.pop(), Some('o'));
    /// assert_eq!(s.pop(), Some('f'));
    ///
    /// assert_eq!(s.pop(), None);
    /// ```
    pub fn pop(&mut self) -> Option<char> {
        let ch = match self.chars().rev().next() {
            Some(ch) => ch,
            None => return None,
        };
        let new_len = self.len() - ch.len_utf8();
        unsafe {
            self.set_len(new_len);
        }
        Some(ch)
    }

    /// Shortens this `ArrayString` to the specified length.
    ///
    /// If `new_len` is greater than the string’s current length, this has no
    /// effect.
    ///
    /// ***Panics*** if `new_len` does not lie on a `char` boundary.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    ///
    /// let mut string = ArrayString::<6>::from("foobar").unwrap();
    /// string.truncate(3);
    /// assert_eq!(&string[..], "foo");
    /// string.truncate(4);
    /// assert_eq!(&string[..], "foo");
    /// ```
    pub fn truncate(&mut self, new_len: usize) {
        if new_len <= self.len() {
            assert!(self.is_char_boundary(new_len));
            unsafe { 
                // In libstd truncate is called on the underlying vector,
                // which in turns drops each element.
                // As we know we don't have to worry about Drop,
                // we can just set the length (a la clear.)
                self.set_len(new_len);
            }
        }
    }

    /// Removes a `char` from this `ArrayString` at a byte position and returns it.
    ///
    /// This is an `O(n)` operation, as it requires copying every element in the
    /// array.
    ///
    /// ***Panics*** if `idx` is larger than or equal to the `ArrayString`’s length,
    /// or if it does not lie on a `char` boundary.
    ///
    /// ```
    /// use arrayvec::ArrayString;
    /// 
    /// let mut s = ArrayString::<3>::from("foo").unwrap();
    ///
    /// assert_eq!(s.remove(0), 'f');
    /// assert_eq!(s.remove(1), 'o');
    /// assert_eq!(s.remove(0), 'o');
    /// ```
    pub fn remove(&mut self, idx: usize) -> char {
        let ch = match self[idx..].chars().next() {
            Some(ch) => ch,
            None => panic!("cannot remove a char from the end of a string"),
        };

        let next = idx + ch.len_utf8();
        let len = self.len();
        unsafe {
            ptr::copy(self.as_ptr().add(next),
                      self.as_mut_ptr().add(idx),
                      len - next);
            self.set_len(len - (next - idx));
        }
        ch
    }

    /// Make the string empty.
    pub fn clear(&mut self) {
        unsafe {
            self.set_len(0);
        }
    }

    /// Set the strings’s length.
    ///
    /// This function is `unsafe` because it changes the notion of the
    /// number of “valid” bytes in the string. Use with care.
    ///
    /// This method uses *debug assertions* to check the validity of `length`
    /// and may use other debug assertions.
    pub unsafe fn set_len(&mut self, length: usize) {
        // type invariant that capacity always fits in LenUint
        debug_assert!(length <= self.capacity());
        self.len = length as LenUint;
    }

    /// Return a string slice of the whole `ArrayString`.
    pub fn as_str(&self) -> &str {
        self
    }

    fn as_ptr(&self) -> *const u8 {
        self.xs.as_ptr() as *const u8
    }

    fn as_mut_ptr(&mut self) -> *mut u8 {
        self.xs.as_mut_ptr() as *mut u8
    }
}

impl<const CAP: usize> Deref for ArrayString<CAP>
{
    type Target = str;
    #[inline]
    fn deref(&self) -> &str {
        unsafe {
            let sl = slice::from_raw_parts(self.as_ptr(), self.len());
            str::from_utf8_unchecked(sl)
        }
    }
}

impl<const CAP: usize> DerefMut for ArrayString<CAP>
{
    #[inline]
    fn deref_mut(&mut self) -> &mut str {
        unsafe {
            let len = self.len();
            let sl = slice::from_raw_parts_mut(self.as_mut_ptr(), len);
            str::from_utf8_unchecked_mut(sl)
        }
    }
}

impl<const CAP: usize> PartialEq for ArrayString<CAP>
{
    fn eq(&self, rhs: &Self) -> bool {
        **self == **rhs
    }
}

impl<const CAP: usize> PartialEq<str> for ArrayString<CAP>
{
    fn eq(&self, rhs: &str) -> bool {
        &**self == rhs
    }
}

impl<const CAP: usize> PartialEq<ArrayString<CAP>> for str
{
    fn eq(&self, rhs: &ArrayString<CAP>) -> bool {
        self == &**rhs
    }
}

impl<const CAP: usize> Eq for ArrayString<CAP> 
{ }

impl<const CAP: usize> Hash for ArrayString<CAP>
{
    fn hash<H: Hasher>(&self, h: &mut H) {
        (**self).hash(h)
    }
}

impl<const CAP: usize> Borrow<str> for ArrayString<CAP>
{
    fn borrow(&self) -> &str { self }
}

impl<const CAP: usize> AsRef<str> for ArrayString<CAP>
{
    fn as_ref(&self) -> &str { self }
}

impl<const CAP: usize> fmt::Debug for ArrayString<CAP>
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }
}

impl<const CAP: usize> fmt::Display for ArrayString<CAP>
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }
}

/// `Write` appends written data to the end of the string.
impl<const CAP: usize> fmt::Write for ArrayString<CAP>
{
    fn write_char(&mut self, c: char) -> fmt::Result {
        self.try_push(c).map_err(|_| fmt::Error)
    }

    fn write_str(&mut self, s: &str) -> fmt::Result {
        self.try_push_str(s).map_err(|_| fmt::Error)
    }
}

impl<const CAP: usize> Clone for ArrayString<CAP>
{
    fn clone(&self) -> ArrayString<CAP> {
        *self
    }
    fn clone_from(&mut self, rhs: &Self) {
        // guaranteed to fit due to types matching.
        self.clear();
        self.try_push_str(rhs).ok();
    }
}

impl<const CAP: usize> PartialOrd for ArrayString<CAP>
{
    fn partial_cmp(&self, rhs: &Self) -> Option<cmp::Ordering> {
        (**self).partial_cmp(&**rhs)
    }
    fn lt(&self, rhs: &Self) -> bool { **self < **rhs }
    fn le(&self, rhs: &Self) -> bool { **self <= **rhs }
    fn gt(&self, rhs: &Self) -> bool { **self > **rhs }
    fn ge(&self, rhs: &Self) -> bool { **self >= **rhs }
}

impl<const CAP: usize> PartialOrd<str> for ArrayString<CAP>
{
    fn partial_cmp(&self, rhs: &str) -> Option<cmp::Ordering> {
        (**self).partial_cmp(rhs)
    }
    fn lt(&self, rhs: &str) -> bool { &**self < rhs }
    fn le(&self, rhs: &str) -> bool { &**self <= rhs }
    fn gt(&self, rhs: &str) -> bool { &**self > rhs }
    fn ge(&self, rhs: &str) -> bool { &**self >= rhs }
}

impl<const CAP: usize> PartialOrd<ArrayString<CAP>> for str
{
    fn partial_cmp(&self, rhs: &ArrayString<CAP>) -> Option<cmp::Ordering> {
        self.partial_cmp(&**rhs)
    }
    fn lt(&self, rhs: &ArrayString<CAP>) -> bool { self < &**rhs }
    fn le(&self, rhs: &ArrayString<CAP>) -> bool { self <= &**rhs }
    fn gt(&self, rhs: &ArrayString<CAP>) -> bool { self > &**rhs }
    fn ge(&self, rhs: &ArrayString<CAP>) -> bool { self >= &**rhs }
}

impl<const CAP: usize> Ord for ArrayString<CAP>
{
    fn cmp(&self, rhs: &Self) -> cmp::Ordering {
        (**self).cmp(&**rhs)
    }
}

impl<const CAP: usize> FromStr for ArrayString<CAP>
{
    type Err = CapacityError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Self::from(s).map_err(CapacityError::simplify)
    }
}

#[cfg(feature="serde")]
/// Requires crate feature `"serde"`
impl<const CAP: usize> Serialize for ArrayString<CAP>
{
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where S: Serializer
    {
        serializer.serialize_str(&*self)
    }
}

#[cfg(feature="serde")]
/// Requires crate feature `"serde"`
impl<'de, const CAP: usize> Deserialize<'de> for ArrayString<CAP> 
{
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where D: Deserializer<'de>
    {
        use serde::de::{self, Visitor};
        use std::marker::PhantomData;

        struct ArrayStringVisitor<const CAP: usize>(PhantomData<[u8; CAP]>);

        impl<'de, const CAP: usize> Visitor<'de> for ArrayStringVisitor<CAP> {
            type Value = ArrayString<CAP>;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                write!(formatter, "a string no more than {} bytes long", CAP)
            }

            fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
                where E: de::Error,
            {
                ArrayString::from(v).map_err(|_| E::invalid_length(v.len(), &self))
            }

            fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
                where E: de::Error,
            {
                let s = str::from_utf8(v).map_err(|_| E::invalid_value(de::Unexpected::Bytes(v), &self))?;

                ArrayString::from(s).map_err(|_| E::invalid_length(s.len(), &self))
            }
        }

        deserializer.deserialize_str(ArrayStringVisitor(PhantomData))
    }
}

impl<'a, const CAP: usize> TryFrom<&'a str> for ArrayString<CAP>
{
    type Error = CapacityError<&'a str>;

    fn try_from(f: &'a str) -> Result<Self, Self::Error> {
        let mut v = Self::new();
        v.try_push_str(f)?;
        Ok(v)
    }
}

impl<'a, const CAP: usize> TryFrom<fmt::Arguments<'a>> for ArrayString<CAP>
{
    type Error = CapacityError<fmt::Error>;

    fn try_from(f: fmt::Arguments<'a>) -> Result<Self, Self::Error> {
        use fmt::Write;
        let mut v = Self::new();
        v.write_fmt(f).map_err(|e| CapacityError::new(e))?;
        Ok(v)
    }
}