glib/collections/
ptr_slice.rs

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1// Take a look at the license at the top of the repository in the LICENSE file.
2
3use std::{fmt, marker::PhantomData, mem, ptr};
4
5use crate::{ffi, translate::*};
6
7// rustdoc-stripper-ignore-next
8/// Minimum size of the `PtrSlice` allocation.
9const MIN_SIZE: usize = 16;
10
11// rustdoc-stripper-ignore-next
12/// Slice of elements of type `T` allocated by the GLib allocator.
13///
14/// The underlying memory is always `NULL`-terminated. [`Slice<T>`](crate::collections::slice::Slice)
15/// can be used for a non-`NULL`-terminated slice.
16///
17/// This can be used like a `&[T]`, `&mut [T]` and `Vec<T>`.
18pub struct PtrSlice<T: TransparentPtrType> {
19    ptr: ptr::NonNull<<T as GlibPtrDefault>::GlibType>,
20    // rustdoc-stripper-ignore-next
21    /// Length without the `NULL`-terminator.
22    len: usize,
23    // rustdoc-stripper-ignore-next
24    /// Capacity **with** the `NULL`-terminator, i.e. the actual allocation size.
25    capacity: usize,
26}
27
28impl<T: fmt::Debug + TransparentPtrType> fmt::Debug for PtrSlice<T> {
29    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
30        self.as_slice().fmt(f)
31    }
32}
33
34unsafe impl<T: Send + TransparentPtrType> Send for PtrSlice<T> {}
35
36unsafe impl<T: Sync + TransparentPtrType> Sync for PtrSlice<T> {}
37
38impl<T: PartialEq + TransparentPtrType> PartialEq for PtrSlice<T> {
39    #[inline]
40    fn eq(&self, other: &Self) -> bool {
41        self.as_slice() == other.as_slice()
42    }
43}
44
45impl<T: Eq + TransparentPtrType> Eq for PtrSlice<T> {}
46
47impl<T: PartialOrd + TransparentPtrType> PartialOrd for PtrSlice<T> {
48    #[inline]
49    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
50        self.as_slice().partial_cmp(other.as_slice())
51    }
52}
53
54impl<T: Ord + TransparentPtrType> Ord for PtrSlice<T> {
55    #[inline]
56    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
57        self.as_slice().cmp(other.as_slice())
58    }
59}
60
61impl<T: std::hash::Hash + TransparentPtrType> std::hash::Hash for PtrSlice<T> {
62    #[inline]
63    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
64        self.as_slice().hash(state)
65    }
66}
67
68impl<T: PartialEq + TransparentPtrType> PartialEq<[T]> for PtrSlice<T> {
69    #[inline]
70    fn eq(&self, other: &[T]) -> bool {
71        self.as_slice() == other
72    }
73}
74
75impl<T: PartialEq + TransparentPtrType> PartialEq<PtrSlice<T>> for [T] {
76    #[inline]
77    fn eq(&self, other: &PtrSlice<T>) -> bool {
78        self == other.as_slice()
79    }
80}
81
82impl<T: TransparentPtrType> Drop for PtrSlice<T> {
83    #[inline]
84    fn drop(&mut self) {
85        unsafe {
86            if mem::needs_drop::<T>() {
87                for i in 0..self.len {
88                    ptr::drop_in_place::<T>(self.ptr.as_ptr().add(i) as *mut T);
89                }
90            }
91
92            if self.capacity != 0 {
93                ffi::g_free(self.ptr.as_ptr() as ffi::gpointer);
94            }
95        }
96    }
97}
98
99impl<T: TransparentPtrType> AsRef<[T]> for PtrSlice<T> {
100    #[inline]
101    fn as_ref(&self) -> &[T] {
102        self.as_slice()
103    }
104}
105
106impl<T: TransparentPtrType> AsMut<[T]> for PtrSlice<T> {
107    #[inline]
108    fn as_mut(&mut self) -> &mut [T] {
109        self.as_mut_slice()
110    }
111}
112
113impl<T: TransparentPtrType> std::borrow::Borrow<[T]> for PtrSlice<T> {
114    #[inline]
115    fn borrow(&self) -> &[T] {
116        self.as_slice()
117    }
118}
119
120impl<T: TransparentPtrType> std::borrow::BorrowMut<[T]> for PtrSlice<T> {
121    #[inline]
122    fn borrow_mut(&mut self) -> &mut [T] {
123        self.as_mut_slice()
124    }
125}
126
127impl<T: TransparentPtrType> std::ops::Deref for PtrSlice<T> {
128    type Target = [T];
129
130    #[inline]
131    fn deref(&self) -> &[T] {
132        self.as_slice()
133    }
134}
135
136impl<T: TransparentPtrType> std::ops::DerefMut for PtrSlice<T> {
137    #[inline]
138    fn deref_mut(&mut self) -> &mut [T] {
139        self.as_mut_slice()
140    }
141}
142
143impl<T: TransparentPtrType> Default for PtrSlice<T> {
144    #[inline]
145    fn default() -> Self {
146        Self::new()
147    }
148}
149
150impl<T: TransparentPtrType> std::iter::Extend<T> for PtrSlice<T> {
151    #[inline]
152    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
153        let iter = iter.into_iter();
154        self.reserve(iter.size_hint().0);
155
156        for item in iter {
157            self.push(item);
158        }
159    }
160}
161
162impl<'a, T: TransparentPtrType + 'a> std::iter::Extend<&'a T> for PtrSlice<T> {
163    #[inline]
164    fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
165        let iter = iter.into_iter();
166        self.reserve(iter.size_hint().0);
167
168        for item in iter {
169            self.push(item.clone());
170        }
171    }
172}
173
174impl<T: TransparentPtrType> std::iter::FromIterator<T> for PtrSlice<T> {
175    #[inline]
176    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
177        let iter = iter.into_iter();
178        let mut s = Self::with_capacity(iter.size_hint().0);
179        for item in iter {
180            s.push(item);
181        }
182        s
183    }
184}
185
186impl<'a, T: TransparentPtrType> std::iter::IntoIterator for &'a PtrSlice<T> {
187    type Item = &'a T;
188    type IntoIter = std::slice::Iter<'a, T>;
189
190    #[inline]
191    fn into_iter(self) -> Self::IntoIter {
192        self.as_slice().iter()
193    }
194}
195
196impl<'a, T: TransparentPtrType> std::iter::IntoIterator for &'a mut PtrSlice<T> {
197    type Item = &'a mut T;
198    type IntoIter = std::slice::IterMut<'a, T>;
199
200    #[inline]
201    fn into_iter(self) -> Self::IntoIter {
202        self.as_mut_slice().iter_mut()
203    }
204}
205
206impl<T: TransparentPtrType> std::iter::IntoIterator for PtrSlice<T> {
207    type Item = T;
208    type IntoIter = IntoIter<T>;
209
210    #[inline]
211    fn into_iter(self) -> Self::IntoIter {
212        IntoIter::new(self)
213    }
214}
215
216pub struct IntoIter<T: TransparentPtrType> {
217    ptr: ptr::NonNull<<T as GlibPtrDefault>::GlibType>,
218    idx: ptr::NonNull<<T as GlibPtrDefault>::GlibType>,
219    len: usize,
220    empty: bool,
221}
222
223impl<T: TransparentPtrType> IntoIter<T> {
224    #[inline]
225    fn new(slice: PtrSlice<T>) -> Self {
226        let slice = mem::ManuallyDrop::new(slice);
227        IntoIter {
228            ptr: slice.ptr,
229            idx: slice.ptr,
230            len: slice.len,
231            empty: slice.capacity == 0,
232        }
233    }
234
235    // rustdoc-stripper-ignore-next
236    /// Returns the remaining items as slice.
237    #[inline]
238    pub fn as_slice(&self) -> &[T] {
239        unsafe {
240            if self.len == 0 {
241                &[]
242            } else {
243                std::slice::from_raw_parts(self.idx.as_ptr() as *mut T, self.len)
244            }
245        }
246    }
247
248    // rustdoc-stripper-ignore-next
249    /// Returns the remaining items as mutable slice.
250    #[inline]
251    pub fn as_mut_slice(&mut self) -> &mut [T] {
252        unsafe {
253            if self.len == 0 {
254                &mut []
255            } else {
256                std::slice::from_raw_parts_mut(self.idx.as_ptr() as *mut T, self.len)
257            }
258        }
259    }
260}
261
262impl<T: TransparentPtrType> Drop for IntoIter<T> {
263    #[inline]
264    fn drop(&mut self) {
265        unsafe {
266            if mem::needs_drop::<T>() {
267                for i in 0..self.len {
268                    ptr::drop_in_place::<T>(self.idx.as_ptr().add(i) as *mut T);
269                }
270            }
271
272            if !self.empty {
273                ffi::g_free(self.ptr.as_ptr() as ffi::gpointer);
274            }
275        }
276    }
277}
278
279impl<T: TransparentPtrType> Iterator for IntoIter<T> {
280    type Item = T;
281
282    #[inline]
283    fn next(&mut self) -> Option<Self::Item> {
284        if self.len == 0 {
285            return None;
286        }
287
288        unsafe {
289            let p = self.idx.as_ptr();
290            self.len -= 1;
291            self.idx = ptr::NonNull::new_unchecked(p.add(1));
292            Some(ptr::read(p as *mut T))
293        }
294    }
295
296    #[inline]
297    fn size_hint(&self) -> (usize, Option<usize>) {
298        (self.len, Some(self.len))
299    }
300
301    #[inline]
302    fn count(self) -> usize {
303        self.len
304    }
305
306    #[inline]
307    fn last(mut self) -> Option<T> {
308        if self.len == 0 {
309            None
310        } else {
311            self.len -= 1;
312            Some(unsafe { ptr::read(self.idx.as_ptr().add(self.len) as *mut T) })
313        }
314    }
315}
316
317impl<T: TransparentPtrType> DoubleEndedIterator for IntoIter<T> {
318    #[inline]
319    fn next_back(&mut self) -> Option<T> {
320        if self.len == 0 {
321            None
322        } else {
323            self.len -= 1;
324            Some(unsafe { ptr::read(self.idx.as_ptr().add(self.len) as *mut T) })
325        }
326    }
327}
328
329impl<T: TransparentPtrType> ExactSizeIterator for IntoIter<T> {}
330
331impl<T: TransparentPtrType> std::iter::FusedIterator for IntoIter<T> {}
332
333impl<T: TransparentPtrType> From<PtrSlice<T>> for Vec<T> {
334    #[inline]
335    fn from(mut value: PtrSlice<T>) -> Self {
336        unsafe {
337            let mut s = Vec::with_capacity(value.len);
338            ptr::copy_nonoverlapping(value.ptr.as_ptr() as *const T, s.as_mut_ptr(), value.len);
339            s.set_len(value.len);
340            value.len = 0;
341            s
342        }
343    }
344}
345
346impl<T: TransparentPtrType> From<Vec<T>> for PtrSlice<T> {
347    #[inline]
348    fn from(mut value: Vec<T>) -> Self {
349        unsafe {
350            let mut s = Self::with_capacity(value.len());
351            ptr::copy_nonoverlapping(value.as_ptr(), s.ptr.as_ptr() as *mut T, value.len());
352            s.len = value.len();
353            value.set_len(0);
354            ptr::write(
355                s.ptr.as_ptr().add(s.len),
356                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
357            );
358            s
359        }
360    }
361}
362
363impl<T: TransparentPtrType, const N: usize> From<[T; N]> for PtrSlice<T> {
364    #[inline]
365    fn from(value: [T; N]) -> Self {
366        unsafe {
367            let value = mem::ManuallyDrop::new(value);
368            let len = value.len();
369            let mut s = Self::with_capacity(len);
370            ptr::copy_nonoverlapping(value.as_ptr(), s.ptr.as_ptr() as *mut T, len);
371            s.len = len;
372            ptr::write(
373                s.ptr.as_ptr().add(len),
374                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
375            );
376            s
377        }
378    }
379}
380
381impl<'a, T: TransparentPtrType> From<&'a [T]> for PtrSlice<T> {
382    #[inline]
383    fn from(value: &'a [T]) -> Self {
384        unsafe {
385            let mut s = Self::with_capacity(value.len());
386            for (i, item) in value.iter().enumerate() {
387                ptr::write(s.ptr.as_ptr().add(i) as *mut T, item.clone());
388            }
389            s.len = value.len();
390            ptr::write(
391                s.ptr.as_ptr().add(s.len),
392                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
393            );
394            s
395        }
396    }
397}
398
399impl<'a, T: TransparentPtrType> From<&'a [&'a T]> for PtrSlice<T> {
400    #[inline]
401    fn from(value: &'a [&'a T]) -> Self {
402        unsafe {
403            let mut s = Self::with_capacity(value.len());
404            for (i, item) in value.iter().enumerate() {
405                ptr::write(s.ptr.as_ptr().add(i) as *mut T, (*item).clone());
406            }
407            s.len = value.len();
408            ptr::write(
409                s.ptr.as_ptr().add(s.len),
410                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
411            );
412            s
413        }
414    }
415}
416
417impl<T: TransparentPtrType> Clone for PtrSlice<T> {
418    #[inline]
419    fn clone(&self) -> Self {
420        Self::from(self.as_slice())
421    }
422}
423
424impl<T: TransparentPtrType> PtrSlice<T> {
425    // rustdoc-stripper-ignore-next
426    /// Borrows a C array.
427    #[inline]
428    pub unsafe fn from_glib_borrow<'a>(ptr: *const <T as GlibPtrDefault>::GlibType) -> &'a [T] {
429        let mut len = 0;
430        if !ptr.is_null() {
431            while !(*ptr.add(len)).is_null() {
432                len += 1;
433            }
434        }
435        Self::from_glib_borrow_num(ptr, len)
436    }
437
438    // rustdoc-stripper-ignore-next
439    /// Borrows a C array.
440    #[inline]
441    pub unsafe fn from_glib_borrow_num<'a>(
442        ptr: *const <T as GlibPtrDefault>::GlibType,
443        len: usize,
444    ) -> &'a [T] {
445        debug_assert_eq!(
446            mem::size_of::<T>(),
447            mem::size_of::<<T as GlibPtrDefault>::GlibType>()
448        );
449        debug_assert!(!ptr.is_null() || len == 0);
450
451        if len == 0 {
452            &[]
453        } else {
454            std::slice::from_raw_parts(ptr as *const T, len)
455        }
456    }
457
458    // rustdoc-stripper-ignore-next
459    /// Create a new `PtrSlice` around a C array.
460    #[inline]
461    pub unsafe fn from_glib_none_num(
462        ptr: *const <T as GlibPtrDefault>::GlibType,
463        len: usize,
464        _null_terminated: bool,
465    ) -> Self {
466        debug_assert_eq!(
467            mem::size_of::<T>(),
468            mem::size_of::<<T as GlibPtrDefault>::GlibType>()
469        );
470        debug_assert!(!ptr.is_null() || len == 0);
471
472        if len == 0 {
473            PtrSlice::default()
474        } else {
475            // Need to fully copy the array here.
476            let s = Self::from_glib_borrow_num(ptr, len);
477            Self::from(s)
478        }
479    }
480
481    // rustdoc-stripper-ignore-next
482    /// Create a new `PtrSlice` around a C array.
483    #[inline]
484    pub unsafe fn from_glib_container_num(
485        ptr: *mut <T as GlibPtrDefault>::GlibType,
486        len: usize,
487        null_terminated: bool,
488    ) -> Self {
489        debug_assert_eq!(
490            mem::size_of::<T>(),
491            mem::size_of::<<T as GlibPtrDefault>::GlibType>()
492        );
493        debug_assert!(!ptr.is_null() || len == 0);
494
495        if len == 0 {
496            ffi::g_free(ptr as ffi::gpointer);
497            PtrSlice::default()
498        } else {
499            // Need to clone every item because we don't own it here
500            for i in 0..len {
501                let p = ptr.add(i) as *mut T;
502                let clone: T = (*p).clone();
503                ptr::write(p, clone);
504            }
505
506            // And now it can be handled exactly the same as `from_glib_full_num()`.
507            Self::from_glib_full_num(ptr, len, null_terminated)
508        }
509    }
510
511    // rustdoc-stripper-ignore-next
512    /// Create a new `PtrSlice` around a C array.
513    #[inline]
514    pub unsafe fn from_glib_full_num(
515        ptr: *mut <T as GlibPtrDefault>::GlibType,
516        len: usize,
517        null_terminated: bool,
518    ) -> Self {
519        debug_assert_eq!(
520            mem::size_of::<T>(),
521            mem::size_of::<<T as GlibPtrDefault>::GlibType>()
522        );
523        debug_assert!(!ptr.is_null() || len == 0);
524
525        if len == 0 {
526            ffi::g_free(ptr as ffi::gpointer);
527            PtrSlice::default()
528        } else {
529            if null_terminated {
530                return PtrSlice {
531                    ptr: ptr::NonNull::new_unchecked(ptr),
532                    len,
533                    capacity: len + 1,
534                };
535            }
536
537            // Need to re-allocate here for adding the NULL-terminator
538            let capacity = len + 1;
539            assert_ne!(capacity, 0);
540            let ptr = ffi::g_realloc(
541                ptr as *mut _,
542                mem::size_of::<T>().checked_mul(capacity).unwrap(),
543            ) as *mut <T as GlibPtrDefault>::GlibType;
544
545            ptr::write(
546                ptr.add(len),
547                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
548            );
549
550            PtrSlice {
551                ptr: ptr::NonNull::new_unchecked(ptr),
552                len,
553                capacity,
554            }
555        }
556    }
557
558    // rustdoc-stripper-ignore-next
559    /// Create a new `PtrSlice` around a `NULL`-terminated C array.
560    #[inline]
561    pub unsafe fn from_glib_none(ptr: *const <T as GlibPtrDefault>::GlibType) -> Self {
562        let mut len = 0;
563        if !ptr.is_null() {
564            while !(*ptr.add(len)).is_null() {
565                len += 1;
566            }
567        }
568
569        PtrSlice::from_glib_none_num(ptr, len, true)
570    }
571
572    // rustdoc-stripper-ignore-next
573    /// Create a new `PtrSlice` around a `NULL`-terminated C array.
574    #[inline]
575    pub unsafe fn from_glib_container(ptr: *mut <T as GlibPtrDefault>::GlibType) -> Self {
576        let mut len = 0;
577        if !ptr.is_null() {
578            while !(*ptr.add(len)).is_null() {
579                len += 1;
580            }
581        }
582
583        PtrSlice::from_glib_container_num(ptr, len, true)
584    }
585
586    // rustdoc-stripper-ignore-next
587    /// Create a new `PtrSlice` around a `NULL`-terminated C array.
588    #[inline]
589    pub unsafe fn from_glib_full(ptr: *mut <T as GlibPtrDefault>::GlibType) -> Self {
590        let mut len = 0;
591        if !ptr.is_null() {
592            while !(*ptr.add(len)).is_null() {
593                len += 1;
594            }
595        }
596
597        PtrSlice::from_glib_full_num(ptr, len, true)
598    }
599
600    // rustdoc-stripper-ignore-next
601    /// Creates a new empty slice.
602    #[inline]
603    pub fn new() -> Self {
604        debug_assert_eq!(
605            mem::size_of::<T>(),
606            mem::size_of::<<T as GlibPtrDefault>::GlibType>()
607        );
608
609        PtrSlice {
610            ptr: ptr::NonNull::dangling(),
611            len: 0,
612            capacity: 0,
613        }
614    }
615
616    // rustdoc-stripper-ignore-next
617    /// Creates a new empty slice with the given capacity.
618    #[inline]
619    pub fn with_capacity(capacity: usize) -> Self {
620        let mut s = Self::new();
621        s.reserve(capacity);
622        s
623    }
624
625    // rustdoc-stripper-ignore-next
626    /// Returns the underlying pointer.
627    ///
628    /// This is guaranteed to be `NULL`-terminated.
629    #[inline]
630    pub fn as_ptr(&self) -> *const <T as GlibPtrDefault>::GlibType {
631        if self.len == 0 {
632            static EMPTY: [usize; 1] = [0];
633
634            EMPTY.as_ptr() as *const _
635        } else {
636            self.ptr.as_ptr()
637        }
638    }
639
640    // rustdoc-stripper-ignore-next
641    /// Returns the underlying pointer.
642    ///
643    /// This is guaranteed to be `NULL`-terminated.
644    #[inline]
645    pub fn as_mut_ptr(&mut self) -> *mut <T as GlibPtrDefault>::GlibType {
646        if self.len == 0 {
647            static EMPTY: [usize; 1] = [0];
648
649            EMPTY.as_ptr() as *mut _
650        } else {
651            self.ptr.as_ptr()
652        }
653    }
654
655    // rustdoc-stripper-ignore-next
656    /// Consumes the slice and returns the underlying pointer.
657    ///
658    /// This is guaranteed to be `NULL`-terminated.
659    #[inline]
660    pub fn into_raw(mut self) -> *mut <T as GlibPtrDefault>::GlibType {
661        if self.len == 0 {
662            ptr::null_mut()
663        } else {
664            self.len = 0;
665            self.capacity = 0;
666            self.ptr.as_ptr()
667        }
668    }
669
670    // rustdoc-stripper-ignore-next
671    /// Gets the length of the slice.
672    #[inline]
673    pub fn len(&self) -> usize {
674        self.len
675    }
676
677    // rustdoc-stripper-ignore-next
678    /// Returns `true` if the slice is empty.
679    #[inline]
680    pub fn is_empty(&self) -> bool {
681        self.len == 0
682    }
683
684    // rustdoc-stripper-ignore-next
685    /// Returns the capacity of the slice.
686    ///
687    /// This includes the space that is reserved for the `NULL`-terminator.
688    #[inline]
689    pub fn capacity(&self) -> usize {
690        self.capacity
691    }
692
693    // rustdoc-stripper-ignore-next
694    /// Sets the length of the slice to `len`.
695    ///
696    /// # SAFETY
697    ///
698    /// There must be at least `len` valid items and a `NULL`-terminator after the last item.
699    pub unsafe fn set_len(&mut self, len: usize) {
700        self.len = len;
701    }
702
703    // rustdoc-stripper-ignore-next
704    /// Reserves at least this much additional capacity.
705    #[allow(clippy::int_plus_one)]
706    pub fn reserve(&mut self, additional: usize) {
707        // Nothing new to reserve as there's still enough space
708        if self.len + additional + 1 <= self.capacity {
709            return;
710        }
711
712        let new_capacity =
713            usize::next_power_of_two(std::cmp::max(self.len + additional, MIN_SIZE) + 1);
714        assert_ne!(new_capacity, 0);
715        assert!(new_capacity > self.capacity);
716
717        unsafe {
718            let ptr = if self.capacity == 0 {
719                ptr::null_mut()
720            } else {
721                self.ptr.as_ptr() as *mut _
722            };
723            let new_ptr =
724                ffi::g_realloc(ptr, mem::size_of::<T>().checked_mul(new_capacity).unwrap())
725                    as *mut <T as GlibPtrDefault>::GlibType;
726            if self.capacity == 0 {
727                ptr::write(
728                    new_ptr,
729                    Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
730                );
731            }
732            self.ptr = ptr::NonNull::new_unchecked(new_ptr);
733            self.capacity = new_capacity;
734        }
735    }
736
737    // rustdoc-stripper-ignore-next
738    /// Borrows this slice as a `&[T]`.
739    #[inline]
740    pub fn as_slice(&self) -> &[T] {
741        unsafe {
742            if self.len == 0 {
743                &[]
744            } else {
745                std::slice::from_raw_parts(self.ptr.as_ptr() as *const T, self.len)
746            }
747        }
748    }
749
750    // rustdoc-stripper-ignore-next
751    /// Borrows this slice as a `&mut [T]`.
752    #[inline]
753    pub fn as_mut_slice(&mut self) -> &mut [T] {
754        unsafe {
755            if self.len == 0 {
756                &mut []
757            } else {
758                std::slice::from_raw_parts_mut(self.ptr.as_ptr() as *mut T, self.len)
759            }
760        }
761    }
762
763    // rustdoc-stripper-ignore-next
764    /// Removes all items from the slice.
765    #[inline]
766    pub fn clear(&mut self) {
767        unsafe {
768            if mem::needs_drop::<T>() {
769                for i in 0..self.len {
770                    ptr::drop_in_place::<T>(self.ptr.as_ptr().add(i) as *mut T);
771                }
772            }
773
774            self.len = 0;
775        }
776    }
777
778    // rustdoc-stripper-ignore-next
779    /// Clones and appends all elements in `slice` to the slice.
780    #[inline]
781    pub fn extend_from_slice(&mut self, other: &[T]) {
782        // Nothing new to reserve as there's still enough space
783        if self.len + other.len() + 1 > self.capacity {
784            self.reserve(other.len());
785        }
786
787        unsafe {
788            for item in other {
789                ptr::write(self.ptr.as_ptr().add(self.len) as *mut T, item.clone());
790                self.len += 1;
791            }
792
793            ptr::write(
794                self.ptr.as_ptr().add(self.len),
795                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
796            );
797        }
798    }
799
800    // rustdoc-stripper-ignore-next
801    /// Inserts `item` at position `index` of the slice, shifting all elements after it to the
802    /// right.
803    #[inline]
804    pub fn insert(&mut self, index: usize, item: T) {
805        assert!(index <= self.len);
806
807        // Nothing new to reserve as there's still enough space
808        if self.len + 1 + 1 > self.capacity {
809            self.reserve(1);
810        }
811
812        unsafe {
813            if index == self.len {
814                ptr::write(self.ptr.as_ptr().add(self.len) as *mut T, item);
815            } else {
816                let p = self.ptr.as_ptr().add(index);
817                ptr::copy(p, p.add(1), self.len - index);
818                ptr::write(self.ptr.as_ptr().add(index) as *mut T, item);
819            }
820
821            self.len += 1;
822
823            ptr::write(
824                self.ptr.as_ptr().add(self.len),
825                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
826            );
827        }
828    }
829
830    // rustdoc-stripper-ignore-next
831    /// Pushes `item` to the end of the slice.
832    #[inline]
833    pub fn push(&mut self, item: T) {
834        // Nothing new to reserve as there's still enough space
835        if self.len + 1 + 1 > self.capacity {
836            self.reserve(1);
837        }
838
839        unsafe {
840            ptr::write(self.ptr.as_ptr().add(self.len) as *mut T, item);
841            self.len += 1;
842
843            ptr::write(
844                self.ptr.as_ptr().add(self.len),
845                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
846            );
847        }
848    }
849
850    // rustdoc-stripper-ignore-next
851    /// Removes item from position `index` of the slice, shifting all elements after it to the
852    /// left.
853    #[inline]
854    pub fn remove(&mut self, index: usize) -> T {
855        assert!(index < self.len);
856
857        unsafe {
858            let p = self.ptr.as_ptr().add(index);
859            let item = ptr::read(p as *mut T);
860            ptr::copy(p.add(1), p, self.len - index - 1);
861
862            self.len -= 1;
863
864            ptr::write(
865                self.ptr.as_ptr().add(self.len),
866                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
867            );
868
869            item
870        }
871    }
872
873    // rustdoc-stripper-ignore-next
874    /// Removes the last item of the slice and returns it.
875    #[inline]
876    pub fn pop(&mut self) -> Option<T> {
877        if self.len == 0 {
878            return None;
879        }
880
881        unsafe {
882            self.len -= 1;
883            let p = self.ptr.as_ptr().add(self.len);
884            let item = ptr::read(p as *mut T);
885
886            ptr::write(
887                self.ptr.as_ptr().add(self.len),
888                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
889            );
890
891            Some(item)
892        }
893    }
894
895    // rustdoc-stripper-ignore-next
896    /// Shortens the slice by keeping the last `len` items.
897    ///
898    /// If there are fewer than `len` items then this has no effect.
899    #[inline]
900    pub fn truncate(&mut self, len: usize) {
901        if self.len <= len {
902            return;
903        }
904
905        unsafe {
906            while self.len > len {
907                self.len -= 1;
908                let p = self.ptr.as_ptr().add(self.len);
909                ptr::drop_in_place::<T>(p as *mut T);
910                ptr::write(
911                    p,
912                    Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
913                );
914            }
915        }
916    }
917}
918
919impl<T: TransparentPtrType>
920    FromGlibContainer<<T as GlibPtrDefault>::GlibType, *mut <T as GlibPtrDefault>::GlibType>
921    for PtrSlice<T>
922{
923    #[inline]
924    unsafe fn from_glib_none_num(ptr: *mut <T as GlibPtrDefault>::GlibType, num: usize) -> Self {
925        Self::from_glib_none_num(ptr, num, false)
926    }
927
928    #[inline]
929    unsafe fn from_glib_container_num(
930        ptr: *mut <T as GlibPtrDefault>::GlibType,
931        num: usize,
932    ) -> Self {
933        Self::from_glib_container_num(ptr, num, false)
934    }
935
936    #[inline]
937    unsafe fn from_glib_full_num(ptr: *mut <T as GlibPtrDefault>::GlibType, num: usize) -> Self {
938        Self::from_glib_full_num(ptr, num, false)
939    }
940}
941
942impl<T: TransparentPtrType>
943    FromGlibContainer<<T as GlibPtrDefault>::GlibType, *const <T as GlibPtrDefault>::GlibType>
944    for PtrSlice<T>
945{
946    unsafe fn from_glib_none_num(ptr: *const <T as GlibPtrDefault>::GlibType, num: usize) -> Self {
947        Self::from_glib_none_num(ptr, num, false)
948    }
949
950    unsafe fn from_glib_container_num(
951        _ptr: *const <T as GlibPtrDefault>::GlibType,
952        _num: usize,
953    ) -> Self {
954        unimplemented!();
955    }
956
957    unsafe fn from_glib_full_num(
958        _ptr: *const <T as GlibPtrDefault>::GlibType,
959        _num: usize,
960    ) -> Self {
961        unimplemented!();
962    }
963}
964
965impl<T: TransparentPtrType>
966    FromGlibPtrContainer<<T as GlibPtrDefault>::GlibType, *mut <T as GlibPtrDefault>::GlibType>
967    for PtrSlice<T>
968{
969    #[inline]
970    unsafe fn from_glib_none(ptr: *mut <T as GlibPtrDefault>::GlibType) -> Self {
971        Self::from_glib_none(ptr)
972    }
973
974    #[inline]
975    unsafe fn from_glib_container(ptr: *mut <T as GlibPtrDefault>::GlibType) -> Self {
976        Self::from_glib_container(ptr)
977    }
978
979    #[inline]
980    unsafe fn from_glib_full(ptr: *mut <T as GlibPtrDefault>::GlibType) -> Self {
981        Self::from_glib_full(ptr)
982    }
983}
984
985impl<T: TransparentPtrType>
986    FromGlibPtrContainer<<T as GlibPtrDefault>::GlibType, *const <T as GlibPtrDefault>::GlibType>
987    for PtrSlice<T>
988{
989    #[inline]
990    unsafe fn from_glib_none(ptr: *const <T as GlibPtrDefault>::GlibType) -> Self {
991        Self::from_glib_none(ptr)
992    }
993
994    unsafe fn from_glib_container(_ptr: *const <T as GlibPtrDefault>::GlibType) -> Self {
995        unimplemented!();
996    }
997
998    unsafe fn from_glib_full(_ptr: *const <T as GlibPtrDefault>::GlibType) -> Self {
999        unimplemented!();
1000    }
1001}
1002
1003impl<'a, T: TransparentPtrType + 'a> ToGlibPtr<'a, *mut <T as GlibPtrDefault>::GlibType>
1004    for PtrSlice<T>
1005{
1006    type Storage = PhantomData<&'a Self>;
1007
1008    #[inline]
1009    fn to_glib_none(&'a self) -> Stash<'a, *mut <T as GlibPtrDefault>::GlibType, Self> {
1010        Stash(self.as_ptr() as *mut _, PhantomData)
1011    }
1012
1013    #[inline]
1014    fn to_glib_container(&'a self) -> Stash<'a, *mut <T as GlibPtrDefault>::GlibType, Self> {
1015        unsafe {
1016            let ptr = ffi::g_malloc(mem::size_of::<T>().checked_mul(self.len() + 1).unwrap())
1017                as *mut <T as GlibPtrDefault>::GlibType;
1018            ptr::copy_nonoverlapping(self.as_ptr(), ptr, self.len() + 1);
1019            Stash(ptr, PhantomData)
1020        }
1021    }
1022
1023    #[inline]
1024    fn to_glib_full(&self) -> *mut <T as GlibPtrDefault>::GlibType {
1025        self.clone().into_raw()
1026    }
1027}
1028
1029impl<'a, T: TransparentPtrType + 'a> ToGlibPtr<'a, *const <T as GlibPtrDefault>::GlibType>
1030    for PtrSlice<T>
1031{
1032    type Storage = PhantomData<&'a Self>;
1033
1034    #[inline]
1035    fn to_glib_none(&'a self) -> Stash<'a, *const <T as GlibPtrDefault>::GlibType, Self> {
1036        Stash(self.as_ptr(), PhantomData)
1037    }
1038}
1039
1040impl<'a, T: TransparentPtrType + 'a> ToGlibPtrMut<'a, *mut <T as GlibPtrDefault>::GlibType>
1041    for PtrSlice<T>
1042{
1043    type Storage = PhantomData<&'a mut Self>;
1044
1045    #[inline]
1046    fn to_glib_none_mut(&'a mut self) -> StashMut<'a, *mut <T as GlibPtrDefault>::GlibType, Self> {
1047        StashMut(self.as_mut_ptr(), PhantomData)
1048    }
1049}
1050
1051impl<T: TransparentPtrType> IntoGlibPtr<*mut <T as GlibPtrDefault>::GlibType> for PtrSlice<T> {
1052    #[inline]
1053    unsafe fn into_glib_ptr(self) -> *mut <T as GlibPtrDefault>::GlibType {
1054        self.into_raw()
1055    }
1056}
1057
1058impl<T: TransparentPtrType> From<super::Slice<T>> for PtrSlice<T> {
1059    fn from(value: super::Slice<T>) -> Self {
1060        let len = value.len();
1061        let capacity = value.capacity();
1062        unsafe {
1063            let ptr = value.into_raw();
1064            let mut s = PtrSlice::<T> {
1065                ptr: ptr::NonNull::new_unchecked(ptr),
1066                len,
1067                capacity,
1068            };
1069
1070            // Reserve space for the `NULL`-terminator if needed
1071            if len == capacity {
1072                s.reserve(0);
1073            }
1074
1075            ptr::write(
1076                s.ptr.as_ptr().add(s.len()),
1077                Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
1078            );
1079
1080            s
1081        }
1082    }
1083}
1084
1085// rustdoc-stripper-ignore-next
1086/// A trait to accept both `&[T]` or `PtrSlice<T>` as an argument.
1087pub trait IntoPtrSlice<T: TransparentPtrType> {
1088    // rustdoc-stripper-ignore-next
1089    /// Runs the given closure with a `NULL`-terminated array.
1090    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R;
1091}
1092
1093impl<T: TransparentPtrType> IntoPtrSlice<T> for PtrSlice<T> {
1094    #[inline]
1095    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R {
1096        <&Self>::run_with_ptr_slice(&self, f)
1097    }
1098}
1099
1100impl<T: TransparentPtrType> IntoPtrSlice<T> for &'_ PtrSlice<T> {
1101    #[inline]
1102    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R {
1103        f(unsafe { std::slice::from_raw_parts(self.as_ptr() as *mut _, self.len() + 1) })
1104    }
1105}
1106
1107// rustdoc-stripper-ignore-next
1108/// Maximum number of pointers to stack-allocate before falling back to a heap allocation.
1109const MAX_STACK_ALLOCATION: usize = 16;
1110
1111impl<T: TransparentPtrType> IntoPtrSlice<T> for Vec<T> {
1112    #[inline]
1113    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R {
1114        if self.len() < MAX_STACK_ALLOCATION {
1115            unsafe {
1116                let mut s = mem::MaybeUninit::<
1117                    [<T as GlibPtrDefault>::GlibType; MAX_STACK_ALLOCATION],
1118                >::uninit();
1119                let ptr = s.as_mut_ptr() as *mut <T as GlibPtrDefault>::GlibType;
1120                ptr::copy_nonoverlapping(
1121                    self.as_ptr() as *mut <T as GlibPtrDefault>::GlibType,
1122                    ptr,
1123                    self.len(),
1124                );
1125                ptr::write(
1126                    ptr.add(self.len()),
1127                    Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
1128                );
1129                f(std::slice::from_raw_parts(ptr, self.len() + 1))
1130            }
1131        } else {
1132            PtrSlice::<T>::from(self).run_with_ptr_slice(f)
1133        }
1134    }
1135}
1136
1137impl<T: TransparentPtrType, const N: usize> IntoPtrSlice<T> for [T; N] {
1138    #[inline]
1139    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R {
1140        if self.len() < MAX_STACK_ALLOCATION {
1141            unsafe {
1142                let mut s = mem::MaybeUninit::<
1143                    [<T as GlibPtrDefault>::GlibType; MAX_STACK_ALLOCATION],
1144                >::uninit();
1145                let ptr = s.as_mut_ptr() as *mut <T as GlibPtrDefault>::GlibType;
1146                ptr::copy_nonoverlapping(
1147                    self.as_ptr() as *mut <T as GlibPtrDefault>::GlibType,
1148                    ptr,
1149                    self.len(),
1150                );
1151                ptr::write(
1152                    ptr.add(self.len()),
1153                    Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
1154                );
1155                f(std::slice::from_raw_parts(ptr, self.len() + 1))
1156            }
1157        } else {
1158            PtrSlice::<T>::from(self).run_with_ptr_slice(f)
1159        }
1160    }
1161}
1162
1163impl<T: TransparentPtrType> IntoPtrSlice<T> for &'_ [T] {
1164    #[inline]
1165    fn run_with_ptr_slice<R, F: FnOnce(&[<T as GlibPtrDefault>::GlibType]) -> R>(self, f: F) -> R {
1166        if self.len() < MAX_STACK_ALLOCATION {
1167            unsafe {
1168                let mut s = mem::MaybeUninit::<
1169                    [<T as GlibPtrDefault>::GlibType; MAX_STACK_ALLOCATION],
1170                >::uninit();
1171                let ptr = s.as_mut_ptr() as *mut <T as GlibPtrDefault>::GlibType;
1172                ptr::copy_nonoverlapping(
1173                    self.as_ptr() as *mut <T as GlibPtrDefault>::GlibType,
1174                    ptr,
1175                    self.len(),
1176                );
1177                ptr::write(
1178                    ptr.add(self.len()),
1179                    Ptr::from(ptr::null_mut::<<T as GlibPtrDefault>::GlibType>()),
1180                );
1181                f(std::slice::from_raw_parts(ptr, self.len() + 1))
1182            }
1183        } else {
1184            PtrSlice::<T>::from(self).run_with_ptr_slice(f)
1185        }
1186    }
1187}
1188
1189#[cfg(test)]
1190mod test {
1191    use super::*;
1192
1193    #[test]
1194    fn test_from_glib_full() {
1195        let items = [
1196            crate::Error::new(crate::FileError::Failed, "Failed 1"),
1197            crate::Error::new(crate::FileError::Noent, "Failed 2"),
1198            crate::Error::new(crate::FileError::Io, "Failed 3"),
1199            crate::Error::new(crate::FileError::Perm, "Failed 4"),
1200        ];
1201
1202        let slice = unsafe {
1203            let ptr = ffi::g_malloc(mem::size_of::<ffi::GDate>() * 4) as *mut *mut ffi::GError;
1204            ptr::write(ptr.add(0), items[0].to_glib_full());
1205            ptr::write(ptr.add(1), items[1].to_glib_full());
1206            ptr::write(ptr.add(2), items[2].to_glib_full());
1207            ptr::write(ptr.add(3), items[3].to_glib_full());
1208
1209            PtrSlice::<crate::Error>::from_glib_full_num(ptr, 4, false)
1210        };
1211
1212        for (a, b) in Iterator::zip(items.iter(), slice.iter()) {
1213            assert_eq!(a.message(), b.message());
1214            assert_eq!(
1215                a.kind::<crate::FileError>().unwrap(),
1216                b.kind::<crate::FileError>().unwrap()
1217            );
1218        }
1219    }
1220
1221    #[test]
1222    fn test_from_glib_none() {
1223        let items = [
1224            crate::Error::new(crate::FileError::Failed, "Failed 1"),
1225            crate::Error::new(crate::FileError::Noent, "Failed 2"),
1226            crate::Error::new(crate::FileError::Io, "Failed 3"),
1227            crate::Error::new(crate::FileError::Perm, "Failed 4"),
1228        ];
1229
1230        let slice = unsafe {
1231            PtrSlice::<crate::Error>::from_glib_none_num(
1232                items.as_ptr() as *const *mut ffi::GError,
1233                4,
1234                false,
1235            )
1236        };
1237
1238        for (a, b) in Iterator::zip(items.iter(), slice.iter()) {
1239            assert_eq!(a.message(), b.message());
1240            assert_eq!(
1241                a.kind::<crate::FileError>().unwrap(),
1242                b.kind::<crate::FileError>().unwrap()
1243            );
1244        }
1245    }
1246
1247    #[test]
1248    fn test_safe_api() {
1249        let items = [
1250            crate::Error::new(crate::FileError::Failed, "Failed 1"),
1251            crate::Error::new(crate::FileError::Noent, "Failed 2"),
1252            crate::Error::new(crate::FileError::Io, "Failed 3"),
1253        ];
1254
1255        let mut slice = PtrSlice::from(&items[..]);
1256        assert_eq!(slice.len(), 3);
1257        slice.push(crate::Error::new(crate::FileError::Perm, "Failed 4"));
1258        assert_eq!(slice.len(), 4);
1259
1260        for (a, b) in Iterator::zip(items.iter(), slice.iter()) {
1261            assert_eq!(a.message(), b.message());
1262            assert_eq!(
1263                a.kind::<crate::FileError>().unwrap(),
1264                b.kind::<crate::FileError>().unwrap()
1265            );
1266        }
1267        assert_eq!(slice[3].message(), "Failed 4");
1268
1269        let vec = Vec::from(slice);
1270        assert_eq!(vec.len(), 4);
1271        for (a, b) in Iterator::zip(items.iter(), vec.iter()) {
1272            assert_eq!(a.message(), b.message());
1273            assert_eq!(
1274                a.kind::<crate::FileError>().unwrap(),
1275                b.kind::<crate::FileError>().unwrap()
1276            );
1277        }
1278        assert_eq!(vec[3].message(), "Failed 4");
1279
1280        let mut slice = PtrSlice::from(vec);
1281        assert_eq!(slice.len(), 4);
1282        let e = slice.pop().unwrap();
1283        assert_eq!(e.message(), "Failed 4");
1284        assert_eq!(slice.len(), 3);
1285        slice.insert(2, e);
1286        assert_eq!(slice.len(), 4);
1287        assert_eq!(slice[0].message(), "Failed 1");
1288        assert_eq!(slice[1].message(), "Failed 2");
1289        assert_eq!(slice[2].message(), "Failed 4");
1290        assert_eq!(slice[3].message(), "Failed 3");
1291        let e = slice.remove(2);
1292        assert_eq!(e.message(), "Failed 4");
1293        assert_eq!(slice.len(), 3);
1294        slice.push(e);
1295        assert_eq!(slice.len(), 4);
1296
1297        let slice2 = crate::Slice::from(slice.clone());
1298
1299        for (a, b) in Iterator::zip(items.iter(), slice.into_iter()) {
1300            assert_eq!(a.message(), b.message());
1301            assert_eq!(
1302                a.kind::<crate::FileError>().unwrap(),
1303                b.kind::<crate::FileError>().unwrap()
1304            );
1305        }
1306
1307        let slice3 = crate::PtrSlice::from(slice2.clone());
1308
1309        for (a, b) in Iterator::zip(items.iter(), slice2.into_iter()) {
1310            assert_eq!(a.message(), b.message());
1311            assert_eq!(
1312                a.kind::<crate::FileError>().unwrap(),
1313                b.kind::<crate::FileError>().unwrap()
1314            );
1315        }
1316
1317        for (a, b) in Iterator::zip(items.iter(), slice3.into_iter()) {
1318            assert_eq!(a.message(), b.message());
1319            assert_eq!(
1320                a.kind::<crate::FileError>().unwrap(),
1321                b.kind::<crate::FileError>().unwrap()
1322            );
1323        }
1324    }
1325
1326    #[test]
1327    fn test_into_ptrslice() {
1328        let items = [
1329            crate::Error::new(crate::FileError::Failed, "Failed 1"),
1330            crate::Error::new(crate::FileError::Noent, "Failed 2"),
1331            crate::Error::new(crate::FileError::Io, "Failed 3"),
1332            crate::Error::new(crate::FileError::Perm, "Failed 4"),
1333        ];
1334
1335        items[..].run_with_ptr_slice(|s| unsafe {
1336            assert!(s[4].is_null());
1337            assert_eq!(s.len(), items.len() + 1);
1338            let s = std::slice::from_raw_parts(s.as_ptr() as *const crate::Error, items.len());
1339            assert_eq!(s, items);
1340        });
1341
1342        Vec::from(&items[..]).run_with_ptr_slice(|s| unsafe {
1343            assert!(s[4].is_null());
1344            assert_eq!(s.len(), items.len() + 1);
1345            let s = std::slice::from_raw_parts(s.as_ptr() as *const crate::Error, items.len());
1346            for (a, b) in Iterator::zip(items.iter(), s.iter()) {
1347                assert_eq!(a.message(), b.message());
1348                assert_eq!(
1349                    a.kind::<crate::FileError>().unwrap(),
1350                    b.kind::<crate::FileError>().unwrap()
1351                );
1352            }
1353        });
1354
1355        PtrSlice::<crate::Error>::from(&items[..]).run_with_ptr_slice(|s| unsafe {
1356            assert!(s[4].is_null());
1357            assert_eq!(s.len(), items.len() + 1);
1358            let s = std::slice::from_raw_parts(s.as_ptr() as *const crate::Error, items.len());
1359            for (a, b) in Iterator::zip(items.iter(), s.iter()) {
1360                assert_eq!(a.message(), b.message());
1361                assert_eq!(
1362                    a.kind::<crate::FileError>().unwrap(),
1363                    b.kind::<crate::FileError>().unwrap()
1364                );
1365            }
1366        });
1367
1368        let v = Vec::from(&items[..]);
1369        items.run_with_ptr_slice(|s| unsafe {
1370            assert!(s[4].is_null());
1371            assert_eq!(s.len(), v.len() + 1);
1372            let s = std::slice::from_raw_parts(s.as_ptr() as *const crate::Error, v.len());
1373            for (a, b) in Iterator::zip(v.iter(), s.iter()) {
1374                assert_eq!(a.message(), b.message());
1375                assert_eq!(
1376                    a.kind::<crate::FileError>().unwrap(),
1377                    b.kind::<crate::FileError>().unwrap()
1378                );
1379            }
1380        });
1381    }
1382}
glib/collections/ptr_slice.rs

glib/collections/
ptr_slice.rs
