Struct arrow2::buffer::Buffer

pub struct Buffer<T> { /* private fields */ }

Buffer is a contiguous memory region that can be shared across thread boundaries.

The easiest way to think about Buffer<T> is being equivalent to a Arc<Vec<T>>, with the following differences:

• slicing and cloning is O(1).
• it supports external allocated memory

The easiest way to create one is to use its implementation of From<Vec<T>>.

Examples

use arrow2::buffer::Buffer;

let mut buffer: Buffer<u32> = vec![1, 2, 3].into();
assert_eq!(buffer.as_ref(), [1, 2, 3].as_ref());

// it supports copy-on-write semantics (i.e. back to a `Vec`)
let vec: &mut [u32] = buffer.get_mut().unwrap();
assert_eq!(vec, &mut [1, 2, 3]);

// cloning and slicing is `O(1)` (data is shared)
let mut buffer: Buffer<u32> = vec![1, 2, 3].into();
let slice = buffer.clone().slice(1, 1);
assert_eq!(slice.as_ref(), [2].as_ref());
// but cloning forbids getting mut since `slice` and `buffer` now share data
assert_eq!(buffer.get_mut(), None);

Implementations

impl<T> Buffer<T>

pub fn new() -> Self

Creates an empty Buffer.

Examples found in repository

src/array/fixed_size_binary/mod.rs (line 74)

    pub fn new_empty(data_type: DataType) -> Self {
        Self::new(data_type, Buffer::new(), None)
    }

src/array/primitive/mod.rs (line 357)

    pub fn new_empty(data_type: DataType) -> Self {
        Self::new(data_type, Buffer::new(), None)
    }

src/array/binary/mod.rs (line 319)

    pub fn new_empty(data_type: DataType) -> Self {
        Self::new(data_type, OffsetsBuffer::new(), Buffer::new(), None)
    }

    /// Creates an null [`BinaryArray`], i.e. whose `.null_count() == .len()`.
    #[inline]
    pub fn new_null(data_type: DataType, length: usize) -> Self {
        Self::new(
            data_type,
            Offsets::new_zeroed(length).into(),
            Buffer::new(),
            Some(Bitmap::new_zeroed(length)),
        )
    }

src/array/utf8/mod.rs (line 350)

    pub fn new_empty(data_type: DataType) -> Self {
        unsafe { Self::new_unchecked(data_type, OffsetsBuffer::new(), Buffer::new(), None) }
    }

    /// Returns a new [`Utf8Array`] whose all slots are null / `None`.
    #[inline]
    pub fn new_null(data_type: DataType, length: usize) -> Self {
        Self::new(
            data_type,
            Offsets::new_zeroed(length).into(),
            Buffer::new(),
            Some(Bitmap::new_zeroed(length)),
        )
    }

src/array/union/mod.rs (line 215)

    pub fn new_empty(data_type: DataType) -> Self {
        if let DataType::Union(f, _, mode) = &data_type {
            let fields = f
                .iter()
                .map(|x| new_empty_array(x.data_type().clone()))
                .collect();

            let offsets = if mode.is_sparse() {
                None
            } else {
                Some(Buffer::default())
            };

            Self {
                data_type,
                map: None,
                fields,
                offsets,
                types: Buffer::new(),
                offset: 0,
            }
        } else {
            panic!("Union struct must be created with the corresponding Union DataType")
        }
    }

pub fn len(&self) -> usize

Returns the number of bytes in the buffer

Examples found in repository

src/offset.rs (line 387)

    pub fn len(&self) -> usize {
        self.0.len() - 1
    }

src/array/primitive/mod.rs (line 158)

    pub fn len(&self) -> usize {
        self.values.len()
    }

    /// The values [`Buffer`].
    /// Values on null slots are undetermined (they can be anything).
    #[inline]
    pub fn values(&self) -> &Buffer<T> {
        &self.values
    }

    /// Returns the optional validity.
    #[inline]
    pub fn validity(&self) -> Option<&Bitmap> {
        self.validity.as_ref()
    }

    /// Returns the arrays' [`DataType`].
    #[inline]
    pub fn data_type(&self) -> &DataType {
        &self.data_type
    }

    /// Returns the value at slot `i`.
    ///
    /// Equivalent to `self.values()[i]`. The value of a null slot is undetermined (it can be anything).
    /// # Panic
    /// This function panics iff `i >= self.len`.
    #[inline]
    pub fn value(&self, i: usize) -> T {
        self.values()[i]
    }

    /// Returns the value at index `i`.
    /// The value on null slots is undetermined (it can be anything).
    /// # Safety
    /// Caller must be sure that `i < self.len()`
    #[inline]
    pub unsafe fn value_unchecked(&self, i: usize) -> T {
        *self.values.get_unchecked(i)
    }

    /// Returns a clone of this [`PrimitiveArray`] sliced by an offset and length.
    /// # Implementation
    /// This operation is `O(1)` as it amounts to increase two ref counts.
    /// # Examples
    /// ```
    /// use arrow2::array::PrimitiveArray;
    ///
    /// let array = PrimitiveArray::from_vec(vec![1, 2, 3]);
    /// assert_eq!(format!("{:?}", array), "Int32[1, 2, 3]");
    /// let sliced = array.slice(1, 1);
    /// assert_eq!(format!("{:?}", sliced), "Int32[2]");
    /// // note: `sliced` and `array` share the same memory region.
    /// ```
    /// # Panic
    /// This function panics iff `offset + length > self.len()`.
    #[inline]
    #[must_use]
    pub fn slice(&self, offset: usize, length: usize) -> Self {
        assert!(
            offset + length <= self.len(),
            "offset + length may not exceed length of array"
        );
        unsafe { self.slice_unchecked(offset, length) }
    }

    /// Returns a clone of this [`PrimitiveArray`] sliced by an offset and length.
    /// # Implementation
    /// This operation is `O(1)` as it amounts to increase two ref counts.
    /// # Safety
    /// The caller must ensure that `offset + length <= self.len()`.
    #[inline]
    #[must_use]
    pub unsafe fn slice_unchecked(&self, offset: usize, length: usize) -> Self {
        let validity = self
            .validity
            .clone()
            .map(|bitmap| bitmap.slice_unchecked(offset, length))
            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
        Self {
            data_type: self.data_type.clone(),
            values: self.values.clone().slice_unchecked(offset, length),
            validity,
        }
    }

    /// Returns this [`PrimitiveArray`] with a new validity.
    /// # Panics
    /// This function panics iff `validity.len() != self.len()`.
    #[must_use]
    pub fn with_validity(mut self, validity: Option<Bitmap>) -> Self {
        self.set_validity(validity);
        self
    }

    /// Sets the validity of this [`PrimitiveArray`].
    /// # Panics
    /// This function panics iff `validity.len() != self.len()`.
    pub fn set_validity(&mut self, validity: Option<Bitmap>) {
        if matches!(&validity, Some(bitmap) if bitmap.len() != self.len()) {
            panic!("validity's length must be equal to the array's length")
        }
        self.validity = validity;
    }

    /// Returns this [`PrimitiveArray`] with new values.
    /// # Panics
    /// This function panics iff `values.len() != self.len()`.
    #[must_use]
    pub fn with_values(mut self, values: Buffer<T>) -> Self {
        self.set_values(values);
        self
    }

    /// Update the values of this [`PrimitiveArray`].
    /// # Panics
    /// This function panics iff `values.len() != self.len()`.
    pub fn set_values(&mut self, values: Buffer<T>) {
        assert_eq!(
            values.len(),
            self.len(),
            "values' length must be equal to this arrays' length"
        );
        self.values = values;
    }

    /// Applies a function `f` to the validity of this array.
    ///
    /// This is an API to leverage clone-on-write
    /// # Panics
    /// This function panics if the function `f` modifies the length of the [`Bitmap`].
    pub fn apply_validity<F: FnOnce(Bitmap) -> Bitmap>(&mut self, f: F) {
        if let Some(validity) = std::mem::take(&mut self.validity) {
            self.set_validity(Some(f(validity)))
        }
    }

    /// Returns an option of a mutable reference to the values of this [`PrimitiveArray`].
    pub fn get_mut_values(&mut self) -> Option<&mut [T]> {
        self.values.get_mut().map(|x| x.as_mut())
    }

    /// Returns its internal representation
    #[must_use]
    pub fn into_inner(self) -> (DataType, Buffer<T>, Option<Bitmap>) {
        let Self {
            data_type,
            values,
            validity,
        } = self;
        (data_type, values, validity)
    }

    /// Try to convert this [`PrimitiveArray`] to a [`MutablePrimitiveArray`] via copy-on-write semantics.
    ///
    /// A [`PrimitiveArray`] is backed by a [`Buffer`] and [`Bitmap`] which are essentially `Arc<Vec<_>>`.
    /// This function returns a [`MutablePrimitiveArray`] (via [`std::sync::Arc::get_mut`]) iff both values
    /// and validity have not been cloned / are unique references to their underlying vectors.
    ///
    /// This function is primarily used to re-use memory regions.
    #[must_use]
    pub fn into_mut(mut self) -> Either<Self, MutablePrimitiveArray<T>> {
        use Either::*;

        if let Some(bitmap) = self.validity {
            match bitmap.into_mut() {
                Left(bitmap) => Left(PrimitiveArray::new(
                    self.data_type,
                    self.values,
                    Some(bitmap),
                )),
                Right(mutable_bitmap) => match self.values.get_mut().map(std::mem::take) {
                    Some(values) => Right(
                        MutablePrimitiveArray::try_new(
                            self.data_type,
                            values,
                            Some(mutable_bitmap),
                        )
                        .unwrap(),
                    ),
                    None => Left(PrimitiveArray::new(
                        self.data_type,
                        self.values,
                        Some(mutable_bitmap.into()),
                    )),
                },
            }
        } else {
            match self.values.get_mut().map(std::mem::take) {
                Some(values) => {
                    Right(MutablePrimitiveArray::try_new(self.data_type, values, None).unwrap())
                }
                None => Left(PrimitiveArray::new(self.data_type, self.values, None)),
            }
        }
    }

    /// Returns a new empty (zero-length) [`PrimitiveArray`].
    pub fn new_empty(data_type: DataType) -> Self {
        Self::new(data_type, Buffer::new(), None)
    }

    /// Returns a new [`PrimitiveArray`] where all slots are null / `None`.
    #[inline]
    pub fn new_null(data_type: DataType, length: usize) -> Self {
        Self::new(
            data_type,
            vec![T::default(); length].into(),
            Some(Bitmap::new_zeroed(length)),
        )
    }

    /// Creates a (non-null) [`PrimitiveArray`] from an iterator of values.
    /// # Implementation
    /// This does not assume that the iterator has a known length.
    pub fn from_values<I: IntoIterator<Item = T>>(iter: I) -> Self {
        Self::new(T::PRIMITIVE.into(), Vec::<T>::from_iter(iter).into(), None)
    }

    /// Creates a (non-null) [`PrimitiveArray`] from a slice of values.
    /// # Implementation
    /// This is essentially a memcopy and is thus `O(N)`
    pub fn from_slice<P: AsRef<[T]>>(slice: P) -> Self {
        Self::new(
            T::PRIMITIVE.into(),
            Vec::<T>::from(slice.as_ref()).into(),
            None,
        )
    }

    /// Creates a (non-null) [`PrimitiveArray`] from a [`TrustedLen`] of values.
    /// # Implementation
    /// This does not assume that the iterator has a known length.
    pub fn from_trusted_len_values_iter<I: TrustedLen<Item = T>>(iter: I) -> Self {
        MutablePrimitiveArray::<T>::from_trusted_len_values_iter(iter).into()
    }

    /// Creates a new [`PrimitiveArray`] from an iterator over values
    /// # Safety
    /// The iterator must be [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
    /// I.e. that `size_hint().1` correctly reports its length.
    pub unsafe fn from_trusted_len_values_iter_unchecked<I: Iterator<Item = T>>(iter: I) -> Self {
        MutablePrimitiveArray::<T>::from_trusted_len_values_iter_unchecked(iter).into()
    }

    /// Creates a [`PrimitiveArray`] from a [`TrustedLen`] of optional values.
    pub fn from_trusted_len_iter<I: TrustedLen<Item = Option<T>>>(iter: I) -> Self {
        MutablePrimitiveArray::<T>::from_trusted_len_iter(iter).into()
    }

    /// Creates a [`PrimitiveArray`] from an iterator of optional values.
    /// # Safety
    /// The iterator must be [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
    /// I.e. that `size_hint().1` correctly reports its length.
    pub unsafe fn from_trusted_len_iter_unchecked<I: Iterator<Item = Option<T>>>(iter: I) -> Self {
        MutablePrimitiveArray::<T>::from_trusted_len_iter_unchecked(iter).into()
    }

    /// Boxes self into a [`Box<dyn Array>`].
    pub fn boxed(self) -> Box<dyn Array> {
        Box::new(self)
    }

    /// Boxes self into a [`std::sync::Arc<dyn Array>`].
    pub fn arced(self) -> std::sync::Arc<dyn Array> {
        std::sync::Arc::new(self)
    }

    /// Alias for `Self::try_new(..).unwrap()`.
    /// # Panics
    /// This function errors iff:
    /// * The validity is not `None` and its length is different from `values`'s length
    /// * The `data_type`'s [`PhysicalType`] is not equal to [`PhysicalType::Primitive`].
    pub fn new(data_type: DataType, values: Buffer<T>, validity: Option<Bitmap>) -> Self {
        Self::try_new(data_type, values, validity).unwrap()
    }
}

impl<T: NativeType> Array for PrimitiveArray<T> {
    #[inline]
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    #[inline]
    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
        self
    }

    #[inline]
    fn len(&self) -> usize {
        self.values.len()
    }

src/buffer/immutable.rs (line 93)

    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Returns the byte slice stored in this buffer
    #[inline]
    pub fn as_slice(&self) -> &[T] {
        // Safety:
        // invariant of this struct `offset + length <= data.len()`
        debug_assert!(self.offset + self.length <= self.data.len());
        unsafe {
            self.data
                .get_unchecked(self.offset..self.offset + self.length)
        }
    }

    /// Returns the byte slice stored in this buffer
    /// # Safety
    /// `index` must be smaller than `len`
    #[inline]
    pub(super) unsafe fn get_unchecked(&self, index: usize) -> &T {
        // Safety:
        // invariant of this function
        debug_assert!(index < self.length);
        unsafe { self.data.get_unchecked(self.offset + index) }
    }

    /// Returns a new [`Buffer`] that is a slice of this buffer starting at `offset`.
    /// Doing so allows the same memory region to be shared between buffers.
    /// # Panics
    /// Panics iff `offset` is larger than `len`.
    #[inline]
    pub fn slice(self, offset: usize, length: usize) -> Self {
        assert!(
            offset + length <= self.len(),
            "the offset of the new Buffer cannot exceed the existing length"
        );
        // Safety: we just checked bounds
        unsafe { self.slice_unchecked(offset, length) }
    }

src/buffer/iterator.rs (line 17)

    pub fn new(values: Buffer<T>) -> Self {
        let end = values.len();
        Self {
            values,
            index: 0,
            end,
        }
    }

src/array/binary/mod.rs (line 81)

    pub fn try_new(
        data_type: DataType,
        offsets: OffsetsBuffer<O>,
        values: Buffer<u8>,
        validity: Option<Bitmap>,
    ) -> Result<Self, Error> {
        try_check_offsets_bounds(&offsets, values.len())?;

        if validity
            .as_ref()
            .map_or(false, |validity| validity.len() != offsets.len())
        {
            return Err(Error::oos(
                "validity mask length must match the number of values",
            ));
        }

        if data_type.to_physical_type() != Self::default_data_type().to_physical_type() {
            return Err(Error::oos(
                "BinaryArray can only be initialized with DataType::Binary or DataType::LargeBinary",
            ));
        }

        Ok(Self {
            data_type,
            offsets,
            values,
            validity,
        })
    }

src/array/utf8/mod.rs (line 391)

    pub unsafe fn try_new_unchecked(
        data_type: DataType,
        offsets: OffsetsBuffer<O>,
        values: Buffer<u8>,
        validity: Option<Bitmap>,
    ) -> Result<Self> {
        try_check_offsets_bounds(&offsets, values.len())?;

        if validity
            .as_ref()
            .map_or(false, |validity| validity.len() != offsets.len())
        {
            return Err(Error::oos(
                "validity mask length must match the number of values",
            ));
        }

        if data_type.to_physical_type() != Self::default_data_type().to_physical_type() {
            return Err(Error::oos(
                "BinaryArray can only be initialized with DataType::Utf8 or DataType::LargeUtf8",
            ));
        }

        Ok(Self {
            data_type,
            offsets,
            values,
            validity,
        })
    }

Additional examples can be found in:

• src/array/fixed_size_binary/mod.rs
• src/io/ipc/write/serialize.rs
• src/compute/aggregate/memory.rs
• src/array/union/mod.rs

pub fn is_empty(&self) -> bool

Returns whether the buffer is empty.

pub fn as_slice(&self) -> &[T]

Returns the byte slice stored in this buffer

Examples found in repository

src/buffer/immutable.rs (line 198)

    fn deref(&self) -> &[T] {
        self.as_slice()
    }

src/offset.rs (line 393)

    pub fn as_slice(&self) -> &[O] {
        self.0.as_slice()
    }

src/compute/sort/primitive/indices.rs (line 21)

pub fn indices_sorted_unstable_by<I, T, F>(
    array: &PrimitiveArray<T>,
    cmp: F,
    options: &SortOptions,
    limit: Option<usize>,
) -> PrimitiveArray<I>
where
    I: Index,
    T: NativeType,
    F: Fn(&T, &T) -> std::cmp::Ordering,
{
    let values = array.values().as_slice();
    unsafe {
        common::indices_sorted_unstable_by(
            array.validity(),
            |x: usize| *values.get_unchecked(x),
            cmp,
            array.len(),
            options,
            limit,
        )
    }
}

src/array/growable/primitive.rs (line 48)

    pub fn new(
        arrays: Vec<&'a PrimitiveArray<T>>,
        mut use_validity: bool,
        capacity: usize,
    ) -> Self {
        // if any of the arrays has nulls, insertions from any array requires setting bits
        // as there is at least one array with nulls.
        if !use_validity & arrays.iter().any(|array| array.null_count() > 0) {
            use_validity = true;
        };

        let data_type = arrays[0].data_type().clone();

        let extend_null_bits = arrays
            .iter()
            .map(|array| build_extend_null_bits(*array, use_validity))
            .collect();

        let arrays = arrays
            .iter()
            .map(|array| array.values().as_slice())
            .collect::<Vec<_>>();

        Self {
            data_type,
            arrays,
            values: Vec::with_capacity(capacity),
            validity: MutableBitmap::with_capacity(capacity),
            extend_null_bits,
        }
    }

src/array/growable/dictionary.rs (line 60)

    pub fn new(arrays: &[&'a DictionaryArray<T>], mut use_validity: bool, capacity: usize) -> Self {
        let data_type = arrays[0].data_type().clone();

        // if any of the arrays has nulls, insertions from any array requires setting bits
        // as there is at least one array with nulls.
        if arrays.iter().any(|array| array.null_count() > 0) {
            use_validity = true;
        };

        let arrays_keys = arrays.iter().map(|array| array.keys()).collect::<Vec<_>>();
        let keys_values = arrays_keys
            .iter()
            .map(|array| array.values().as_slice())
            .collect::<Vec<_>>();

        let extend_null_bits = arrays
            .iter()
            .map(|array| build_extend_null_bits(array.keys(), use_validity))
            .collect();

        let arrays_values = arrays
            .iter()
            .map(|array| array.values().as_ref())
            .collect::<Vec<_>>();

        let (values, offsets) = concatenate_values(&arrays_keys, &arrays_values, capacity);

        Self {
            data_type,
            offsets,
            values,
            keys_values,
            key_values: Vec::with_capacity(capacity),
            key_validity: MutableBitmap::with_capacity(capacity),
            extend_null_bits,
        }
    }

pub fn slice(self, offset: usize, length: usize) -> Self

Returns a new Buffer that is a slice of this buffer starting at offset. Doing so allows the same memory region to be shared between buffers.

Panics

Panics iff offset is larger than len.

Examples found in repository

src/ffi/array.rs (line 242)

unsafe fn create_buffer<T: NativeType>(
    array: &ArrowArray,
    data_type: &DataType,
    owner: InternalArrowArray,
    index: usize,
) -> Result<Buffer<T>> {
    let ptr = get_buffer_ptr(array, data_type, index)?;

    let len = buffer_len(array, data_type, index)?;
    let offset = buffer_offset(array, data_type, index);
    let bytes = Bytes::from_foreign(ptr, len, owner);

    Ok(Buffer::from_bytes(bytes).slice(offset, len - offset))
}

src/array/union/ffi.rs (line 53)

    unsafe fn try_from_ffi(array: A) -> Result<Self> {
        let data_type = array.data_type().clone();
        let fields = Self::get_fields(&data_type);

        let mut types = unsafe { array.buffer::<i8>(0) }?;
        let offsets = if Self::is_sparse(&data_type) {
            None
        } else {
            Some(unsafe { array.buffer::<i32>(1) }?)
        };

        let length = array.array().len();
        let offset = array.array().offset();
        let fields = (0..fields.len())
            .map(|index| {
                let child = array.child(index)?;
                ffi::try_from(child)
            })
            .collect::<Result<Vec<Box<dyn Array>>>>()?;

        if offset > 0 {
            types = types.slice(offset, length);
        };

        Self::try_new(data_type, types, fields, offsets)
    }

pub unsafe fn slice_unchecked(self, offset: usize, length: usize) -> Self

Returns a new Buffer that is a slice of this buffer starting at offset. Doing so allows the same memory region to be shared between buffers.

Safety

The caller must ensure offset + length <= self.len()

Examples found in repository

src/offset.rs (line 432)

    pub unsafe fn slice_unchecked(self, offset: usize, length: usize) -> Self {
        Self(self.0.slice_unchecked(offset, length))
    }

src/buffer/immutable.rs (line 130)

    pub fn slice(self, offset: usize, length: usize) -> Self {
        assert!(
            offset + length <= self.len(),
            "the offset of the new Buffer cannot exceed the existing length"
        );
        // Safety: we just checked bounds
        unsafe { self.slice_unchecked(offset, length) }
    }

src/array/primitive/mod.rs (line 239)

    pub unsafe fn slice_unchecked(&self, offset: usize, length: usize) -> Self {
        let validity = self
            .validity
            .clone()
            .map(|bitmap| bitmap.slice_unchecked(offset, length))
            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
        Self {
            data_type: self.data_type.clone(),
            values: self.values.clone().slice_unchecked(offset, length),
            validity,
        }
    }

src/array/union/mod.rs (line 261)

    pub unsafe fn slice_unchecked(&self, offset: usize, length: usize) -> Self {
        debug_assert!(offset + length <= self.len());
        Self {
            data_type: self.data_type.clone(),
            fields: self.fields.clone(),
            map: self.map,
            types: self.types.clone().slice_unchecked(offset, length),
            offsets: self
                .offsets
                .clone()
                .map(|offsets| offsets.slice_unchecked(offset, length)),
            offset: self.offset + offset,
        }
    }

src/array/fixed_size_binary/mod.rs (line 129)

    pub unsafe fn slice_unchecked(&self, offset: usize, length: usize) -> Self {
        let validity = self
            .validity
            .clone()
            .map(|bitmap| bitmap.slice_unchecked(offset, length))
            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
        let values = self
            .values
            .clone()
            .slice_unchecked(offset * self.size, length * self.size);
        Self {
            data_type: self.data_type.clone(),
            size: self.size,
            values,
            validity,
        }
    }

pub fn offset(&self) -> usize

Returns the offset of this buffer.

Examples found in repository

src/array/union/ffi.rs (line 23)

    fn offset(&self) -> Option<usize> {
        Some(self.types.offset())
    }

src/array/primitive/ffi.rs (line 21)

    fn offset(&self) -> Option<usize> {
        let offset = self.values.offset();
        if let Some(bitmap) = self.validity.as_ref() {
            if bitmap.offset() == offset {
                Some(offset)
            } else {
                None
            }
        } else {
            Some(offset)
        }
    }

    fn to_ffi_aligned(&self) -> Self {
        let offset = self.values.offset();

        let validity = self.validity.as_ref().map(|bitmap| {
            if bitmap.offset() == offset {
                bitmap.clone()
            } else {
                align(bitmap, offset)
            }
        });

        Self {
            data_type: self.data_type.clone(),
            validity,
            values: self.values.clone(),
        }
    }

src/array/binary/ffi.rs (line 22)

    fn offset(&self) -> Option<usize> {
        let offset = self.offsets.buffer().offset();
        if let Some(bitmap) = self.validity.as_ref() {
            if bitmap.offset() == offset {
                Some(offset)
            } else {
                None
            }
        } else {
            Some(offset)
        }
    }

    fn to_ffi_aligned(&self) -> Self {
        let offset = self.offsets.buffer().offset();

        let validity = self.validity.as_ref().map(|bitmap| {
            if bitmap.offset() == offset {
                bitmap.clone()
            } else {
                align(bitmap, offset)
            }
        });

        Self {
            data_type: self.data_type.clone(),
            validity,
            offsets: self.offsets.clone(),
            values: self.values.clone(),
        }
    }

src/array/list/ffi.rs (line 21)

    fn offset(&self) -> Option<usize> {
        let offset = self.offsets.buffer().offset();
        if let Some(bitmap) = self.validity.as_ref() {
            if bitmap.offset() == offset {
                Some(offset)
            } else {
                None
            }
        } else {
            Some(offset)
        }
    }

    fn to_ffi_aligned(&self) -> Self {
        let offset = self.offsets.buffer().offset();

        let validity = self.validity.as_ref().map(|bitmap| {
            if bitmap.offset() == offset {
                bitmap.clone()
            } else {
                align(bitmap, offset)
            }
        });

        Self {
            data_type: self.data_type.clone(),
            validity,
            offsets: self.offsets.clone(),
            values: self.values.clone(),
        }
    }

src/array/map/ffi.rs (line 19)

    fn offset(&self) -> Option<usize> {
        let offset = self.offsets.buffer().offset();
        if let Some(bitmap) = self.validity.as_ref() {
            if bitmap.offset() == offset {
                Some(offset)
            } else {
                None
            }
        } else {
            Some(offset)
        }
    }

    fn to_ffi_aligned(&self) -> Self {
        let offset = self.offsets.buffer().offset();

        let validity = self.validity.as_ref().map(|bitmap| {
            if bitmap.offset() == offset {
                bitmap.clone()
            } else {
                align(bitmap, offset)
            }
        });

        Self {
            data_type: self.data_type.clone(),
            validity,
            offsets: self.offsets.clone(),
            field: self.field.clone(),
        }
    }

src/array/utf8/ffi.rs (line 21)

    fn offset(&self) -> Option<usize> {
        let offset = self.offsets.buffer().offset();
        if let Some(bitmap) = self.validity.as_ref() {
            if bitmap.offset() == offset {
                Some(offset)
            } else {
                None
            }
        } else {
            Some(offset)
        }
    }

    fn to_ffi_aligned(&self) -> Self {
        let offset = self.offsets.buffer().offset();

        let validity = self.validity.as_ref().map(|bitmap| {
            if bitmap.offset() == offset {
                bitmap.clone()
            } else {
                align(bitmap, offset)
            }
        });

        Self {
            data_type: self.data_type.clone(),
            validity,
            offsets: self.offsets.clone(),
            values: self.values.clone(),
        }
    }

Additional examples can be found in:

• src/array/fixed_size_binary/ffi.rs

pub fn get_mut(&mut self) -> Option<&mut Vec<T>>

Returns a mutable reference to its underlying Vec, if possible.

This operation returns Some iff this Buffer:

• has not been sliced with an offset
• has not been cloned (i.e. Arc::get_mut yields Some)
• has not been imported from the c data interface (FFI)

Examples found in repository

src/array/primitive/mod.rs (line 297)

    pub fn get_mut_values(&mut self) -> Option<&mut [T]> {
        self.values.get_mut().map(|x| x.as_mut())
    }

    /// Returns its internal representation
    #[must_use]
    pub fn into_inner(self) -> (DataType, Buffer<T>, Option<Bitmap>) {
        let Self {
            data_type,
            values,
            validity,
        } = self;
        (data_type, values, validity)
    }

    /// Try to convert this [`PrimitiveArray`] to a [`MutablePrimitiveArray`] via copy-on-write semantics.
    ///
    /// A [`PrimitiveArray`] is backed by a [`Buffer`] and [`Bitmap`] which are essentially `Arc<Vec<_>>`.
    /// This function returns a [`MutablePrimitiveArray`] (via [`std::sync::Arc::get_mut`]) iff both values
    /// and validity have not been cloned / are unique references to their underlying vectors.
    ///
    /// This function is primarily used to re-use memory regions.
    #[must_use]
    pub fn into_mut(mut self) -> Either<Self, MutablePrimitiveArray<T>> {
        use Either::*;

        if let Some(bitmap) = self.validity {
            match bitmap.into_mut() {
                Left(bitmap) => Left(PrimitiveArray::new(
                    self.data_type,
                    self.values,
                    Some(bitmap),
                )),
                Right(mutable_bitmap) => match self.values.get_mut().map(std::mem::take) {
                    Some(values) => Right(
                        MutablePrimitiveArray::try_new(
                            self.data_type,
                            values,
                            Some(mutable_bitmap),
                        )
                        .unwrap(),
                    ),
                    None => Left(PrimitiveArray::new(
                        self.data_type,
                        self.values,
                        Some(mutable_bitmap.into()),
                    )),
                },
            }
        } else {
            match self.values.get_mut().map(std::mem::take) {
                Some(values) => {
                    Right(MutablePrimitiveArray::try_new(self.data_type, values, None).unwrap())
                }
                None => Left(PrimitiveArray::new(self.data_type, self.values, None)),
            }
        }
    }

src/offset.rs (line 368)

    pub fn get_mut(&mut self) -> Option<Offsets<O>> {
        self.0
            .get_mut()
            .map(|x| {
                let mut new = vec![O::zero()];
                std::mem::swap(x, &mut new);
                new
            })
            // Safety: Offsets and OffsetsBuffer share invariants
            .map(|offsets| unsafe { Offsets::new_unchecked(offsets) })
    }

src/array/binary/mod.rs (line 255)

    pub fn into_mut(mut self) -> Either<Self, MutableBinaryArray<O>> {
        use Either::*;
        if let Some(bitmap) = self.validity {
            match bitmap.into_mut() {
                // Safety: invariants are preserved
                Left(bitmap) => Left(BinaryArray::new(
                    self.data_type,
                    self.offsets,
                    self.values,
                    Some(bitmap),
                )),
                Right(mutable_bitmap) => match (
                    self.values.get_mut().map(std::mem::take),
                    self.offsets.get_mut(),
                ) {
                    (None, None) => Left(BinaryArray::new(
                        self.data_type,
                        self.offsets,
                        self.values,
                        Some(mutable_bitmap.into()),
                    )),
                    (None, Some(offsets)) => Left(BinaryArray::new(
                        self.data_type,
                        offsets.into(),
                        self.values,
                        Some(mutable_bitmap.into()),
                    )),
                    (Some(mutable_values), None) => Left(BinaryArray::new(
                        self.data_type,
                        self.offsets,
                        mutable_values.into(),
                        Some(mutable_bitmap.into()),
                    )),
                    (Some(values), Some(offsets)) => Right(
                        MutableBinaryArray::try_new(
                            self.data_type,
                            offsets,
                            values,
                            Some(mutable_bitmap),
                        )
                        .unwrap(),
                    ),
                },
            }
        } else {
            match (
                self.values.get_mut().map(std::mem::take),
                self.offsets.get_mut(),
            ) {
                (None, None) => Left(BinaryArray::new(
                    self.data_type,
                    self.offsets,
                    self.values,
                    None,
                )),
                (None, Some(offsets)) => Left(BinaryArray::new(
                    self.data_type,
                    offsets.into(),
                    self.values,
                    None,
                )),
                (Some(values), None) => Left(BinaryArray::new(
                    self.data_type,
                    self.offsets,
                    values.into(),
                    None,
                )),
                (Some(values), Some(offsets)) => Right(
                    MutableBinaryArray::try_new(self.data_type, offsets, values, None).unwrap(),
                ),
            }
        }
    }

src/array/utf8/mod.rs (line 278)

    pub fn into_mut(mut self) -> Either<Self, MutableUtf8Array<O>> {
        use Either::*;
        if let Some(bitmap) = self.validity {
            match bitmap.into_mut() {
                // Safety: invariants are preserved
                Left(bitmap) => Left(unsafe {
                    Utf8Array::new_unchecked(
                        self.data_type,
                        self.offsets,
                        self.values,
                        Some(bitmap),
                    )
                }),
                Right(mutable_bitmap) => match (
                    self.values.get_mut().map(std::mem::take),
                    self.offsets.get_mut(),
                ) {
                    (None, None) => {
                        // Safety: invariants are preserved
                        Left(unsafe {
                            Utf8Array::new_unchecked(
                                self.data_type,
                                self.offsets,
                                self.values,
                                Some(mutable_bitmap.into()),
                            )
                        })
                    }
                    (None, Some(offsets)) => {
                        // Safety: invariants are preserved
                        Left(unsafe {
                            Utf8Array::new_unchecked(
                                self.data_type,
                                offsets.into(),
                                self.values,
                                Some(mutable_bitmap.into()),
                            )
                        })
                    }
                    (Some(mutable_values), None) => {
                        // Safety: invariants are preserved
                        Left(unsafe {
                            Utf8Array::new_unchecked(
                                self.data_type,
                                self.offsets,
                                mutable_values.into(),
                                Some(mutable_bitmap.into()),
                            )
                        })
                    }
                    (Some(values), Some(offsets)) => Right(unsafe {
                        MutableUtf8Array::new_unchecked(
                            self.data_type,
                            offsets,
                            values,
                            Some(mutable_bitmap),
                        )
                    }),
                },
            }
        } else {
            match (
                self.values.get_mut().map(std::mem::take),
                self.offsets.get_mut(),
            ) {
                (None, None) => Left(unsafe {
                    Utf8Array::new_unchecked(self.data_type, self.offsets, self.values, None)
                }),
                (None, Some(offsets)) => Left(unsafe {
                    Utf8Array::new_unchecked(self.data_type, offsets.into(), self.values, None)
                }),
                (Some(values), None) => Left(unsafe {
                    Utf8Array::new_unchecked(self.data_type, self.offsets, values.into(), None)
                }),
                (Some(values), Some(offsets)) => Right(unsafe {
                    MutableUtf8Array::new_unchecked(self.data_type, offsets, values, None)
                }),
            }
        }
    }

pub fn shared_count_strong(&self) -> usize

Get the strong count of underlying Arc data buffer.

pub fn shared_count_weak(&self) -> usize

Get the weak count of underlying Arc data buffer.

Methods from Deref<Target = [T]>

pub fn flatten(&self) -> &[T]

🔬This is a nightly-only experimental API. (slice_flatten)

Takes a &[[T; N]], and flattens it to a &[T].

Panics

This panics if the length of the resulting slice would overflow a usize.

This is only possible when flattening a slice of arrays of zero-sized types, and thus tends to be irrelevant in practice. If size_of::<T>() > 0, this will never panic.

Examples

#![feature(slice_flatten)]

assert_eq!([[1, 2, 3], [4, 5, 6]].flatten(), &[1, 2, 3, 4, 5, 6]);

assert_eq!(
    [[1, 2, 3], [4, 5, 6]].flatten(),
    [[1, 2], [3, 4], [5, 6]].flatten(),
);

let slice_of_empty_arrays: &[[i32; 0]] = &[[], [], [], [], []];
assert!(slice_of_empty_arrays.flatten().is_empty());

let empty_slice_of_arrays: &[[u32; 10]] = &[];
assert!(empty_slice_of_arrays.flatten().is_empty());

pub fn len(&self) -> usize

Returns the number of elements in the slice.

Examples

let a = [1, 2, 3];
assert_eq!(a.len(), 3);

pub fn is_empty(&self) -> bool

Returns true if the slice has a length of 0.

Examples

let a = [1, 2, 3];
assert!(!a.is_empty());

pub fn first(&self) -> Option<&T>

Returns the first element of the slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&10), v.first());

let w: &[i32] = &[];
assert_eq!(None, w.first());

pub fn split_first(&self) -> Option<(&T, &[T])>

Returns the first and all the rest of the elements of the slice, or None if it is empty.

Examples

let x = &[0, 1, 2];

if let Some((first, elements)) = x.split_first() {
    assert_eq!(first, &0);
    assert_eq!(elements, &[1, 2]);
}

pub fn split_last(&self) -> Option<(&T, &[T])>

Returns the last and all the rest of the elements of the slice, or None if it is empty.

Examples

let x = &[0, 1, 2];

if let Some((last, elements)) = x.split_last() {
    assert_eq!(last, &2);
    assert_eq!(elements, &[0, 1]);
}

pub fn last(&self) -> Option<&T>

Returns the last element of the slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&30), v.last());

let w: &[i32] = &[];
assert_eq!(None, w.last());

pub fn get<I>(&self, index: I) -> Option<&<I as SliceIndex<[T]>>::Output>where
    I: SliceIndex<[T]>,

Returns a reference to an element or subslice depending on the type of index.

• If given a position, returns a reference to the element at that position or None if out of bounds.
• If given a range, returns the subslice corresponding to that range, or None if out of bounds.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(Some(&[10, 40][..]), v.get(0..2));
assert_eq!(None, v.get(3));
assert_eq!(None, v.get(0..4));

pub unsafe fn get_unchecked<I>(
    &self,
    index: I
) -> &<I as SliceIndex<[T]>>::Outputwhere
    I: SliceIndex<[T]>,

Returns a reference to an element or subslice, without doing bounds checking.

For a safe alternative see get.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used.

Examples

let x = &[1, 2, 4];

unsafe {
    assert_eq!(x.get_unchecked(1), &2);
}

pub fn as_ptr(&self) -> *const T

Returns a raw pointer to the slice’s buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

The caller must also ensure that the memory the pointer (non-transitively) points to is never written to (except inside an UnsafeCell) using this pointer or any pointer derived from it. If you need to mutate the contents of the slice, use as_mut_ptr.

Modifying the container referenced by this slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

Examples

let x = &[1, 2, 4];
let x_ptr = x.as_ptr();

unsafe {
    for i in 0..x.len() {
        assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
    }
}

pub fn as_ptr_range(&self) -> Range<*const T>

Returns the two raw pointers spanning the slice.

The returned range is half-open, which means that the end pointer points one past the last element of the slice. This way, an empty slice is represented by two equal pointers, and the difference between the two pointers represents the size of the slice.

See as_ptr for warnings on using these pointers. The end pointer requires extra caution, as it does not point to a valid element in the slice.

This function is useful for interacting with foreign interfaces which use two pointers to refer to a range of elements in memory, as is common in C++.

It can also be useful to check if a pointer to an element refers to an element of this slice:

let a = [1, 2, 3];
let x = &a[1] as *const _;
let y = &5 as *const _;

assert!(a.as_ptr_range().contains(&x));
assert!(!a.as_ptr_range().contains(&y));

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the slice.

The iterator yields all items from start to end.

Examples

let x = &[1, 2, 4];
let mut iterator = x.iter();

assert_eq!(iterator.next(), Some(&1));
assert_eq!(iterator.next(), Some(&2));
assert_eq!(iterator.next(), Some(&4));
assert_eq!(iterator.next(), None);

pub fn windows(&self, size: usize) -> Windows<'_, T>

Returns an iterator over all contiguous windows of length size. The windows overlap. If the slice is shorter than size, the iterator returns no values.

Panics

Panics if size is 0.

Examples

let slice = ['r', 'u', 's', 't'];
let mut iter = slice.windows(2);
assert_eq!(iter.next().unwrap(), &['r', 'u']);
assert_eq!(iter.next().unwrap(), &['u', 's']);
assert_eq!(iter.next().unwrap(), &['s', 't']);
assert!(iter.next().is_none());

If the slice is shorter than size:

let slice = ['f', 'o', 'o'];
let mut iter = slice.windows(4);
assert!(iter.next().is_none());

pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T>

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last chunk will not have length chunk_size.

See chunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and rchunks for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert_eq!(iter.next().unwrap(), &['m']);
assert!(iter.next().is_none());

pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T>

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks.

See chunks for a variant of this iterator that also returns the remainder as a smaller chunk, and rchunks_exact for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks_exact(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['m']);

pub unsafe fn as_chunks_unchecked<const N: usize>(&self) -> &[[T; N]]

🔬This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.

Safety

This may only be called when

• The slice splits exactly into N-element chunks (aka self.len() % N == 0).
• N != 0.

Examples

#![feature(slice_as_chunks)]
let slice: &[char] = &['l', 'o', 'r', 'e', 'm', '!'];
let chunks: &[[char; 1]] =
    // SAFETY: 1-element chunks never have remainder
    unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l'], ['o'], ['r'], ['e'], ['m'], ['!']]);
let chunks: &[[char; 3]] =
    // SAFETY: The slice length (6) is a multiple of 3
    unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l', 'o', 'r'], ['e', 'm', '!']]);

// These would be unsound:
// let chunks: &[[_; 5]] = slice.as_chunks_unchecked() // The slice length is not a multiple of 5
// let chunks: &[[_; 0]] = slice.as_chunks_unchecked() // Zero-length chunks are never allowed

pub fn as_chunks<const N: usize>(&self) -> (&[[T; N]], &[T])

🔬This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the beginning of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples

#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (chunks, remainder) = slice.as_chunks();
assert_eq!(chunks, &[['l', 'o'], ['r', 'e']]);
assert_eq!(remainder, &['m']);

pub fn as_rchunks<const N: usize>(&self) -> (&[T], &[[T; N]])

🔬This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the end of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples

#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (remainder, chunks) = slice.as_rchunks();
assert_eq!(remainder, &['l']);
assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);

pub fn array_chunks<const N: usize>(&self) -> ArrayChunks<'_, T, N>

🔬This is a nightly-only experimental API. (array_chunks)

Returns an iterator over N elements of the slice at a time, starting at the beginning of the slice.

The chunks are array references and do not overlap. If N does not divide the length of the slice, then the last up to N-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

This method is the const generic equivalent of chunks_exact.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples

#![feature(array_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.array_chunks();
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['m']);

pub fn array_windows<const N: usize>(&self) -> ArrayWindows<'_, T, N>

🔬This is a nightly-only experimental API. (array_windows)

Returns an iterator over overlapping windows of N elements of a slice, starting at the beginning of the slice.

This is the const generic equivalent of windows.

If N is greater than the size of the slice, it will return no windows.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples

#![feature(array_windows)]
let slice = [0, 1, 2, 3];
let mut iter = slice.array_windows();
assert_eq!(iter.next().unwrap(), &[0, 1]);
assert_eq!(iter.next().unwrap(), &[1, 2]);
assert_eq!(iter.next().unwrap(), &[2, 3]);
assert!(iter.next().is_none());

pub fn rchunks(&self, chunk_size: usize) -> RChunks<'_, T>

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last chunk will not have length chunk_size.

See rchunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and chunks for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.rchunks(2);
assert_eq!(iter.next().unwrap(), &['e', 'm']);
assert_eq!(iter.next().unwrap(), &['o', 'r']);
assert_eq!(iter.next().unwrap(), &['l']);
assert!(iter.next().is_none());

pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, T>

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of rchunks.

See rchunks for a variant of this iterator that also returns the remainder as a smaller chunk, and chunks_exact for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.rchunks_exact(2);
assert_eq!(iter.next().unwrap(), &['e', 'm']);
assert_eq!(iter.next().unwrap(), &['o', 'r']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['l']);

pub fn group_by<F>(&self, pred: F) -> GroupBy<'_, T, F>where
    F: FnMut(&T, &T) -> bool,

🔬This is a nightly-only experimental API. (slice_group_by)

Returns an iterator over the slice producing non-overlapping runs of elements using the predicate to separate them.

The predicate is called on two elements following themselves, it means the predicate is called on slice[0] and slice[1] then on slice[1] and slice[2] and so on.

Examples

#![feature(slice_group_by)]

let slice = &[1, 1, 1, 3, 3, 2, 2, 2];

let mut iter = slice.group_by(|a, b| a == b);

assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
assert_eq!(iter.next(), Some(&[3, 3][..]));
assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
assert_eq!(iter.next(), None);

This method can be used to extract the sorted subslices:

#![feature(slice_group_by)]

let slice = &[1, 1, 2, 3, 2, 3, 2, 3, 4];

let mut iter = slice.group_by(|a, b| a <= b);

assert_eq!(iter.next(), Some(&[1, 1, 2, 3][..]));
assert_eq!(iter.next(), Some(&[2, 3][..]));
assert_eq!(iter.next(), Some(&[2, 3, 4][..]));
assert_eq!(iter.next(), None);

pub fn split_at(&self, mid: usize) -> (&[T], &[T])

Divides one slice into two at an index.

The first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).

Panics

Panics if mid > len.

Examples

let v = [1, 2, 3, 4, 5, 6];

{
   let (left, right) = v.split_at(0);
   assert_eq!(left, []);
   assert_eq!(right, [1, 2, 3, 4, 5, 6]);
}

{
    let (left, right) = v.split_at(2);
    assert_eq!(left, [1, 2]);
    assert_eq!(right, [3, 4, 5, 6]);
}

{
    let (left, right) = v.split_at(6);
    assert_eq!(left, [1, 2, 3, 4, 5, 6]);
    assert_eq!(right, []);
}

pub unsafe fn split_at_unchecked(&self, mid: usize) -> (&[T], &[T])

🔬This is a nightly-only experimental API. (slice_split_at_unchecked)

Divides one slice into two at an index, without doing bounds checking.

The first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).

For a safe alternative see split_at.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. The caller has to ensure that 0 <= mid <= self.len().

Examples

#![feature(slice_split_at_unchecked)]

let v = [1, 2, 3, 4, 5, 6];

unsafe {
   let (left, right) = v.split_at_unchecked(0);
   assert_eq!(left, []);
   assert_eq!(right, [1, 2, 3, 4, 5, 6]);
}

unsafe {
    let (left, right) = v.split_at_unchecked(2);
    assert_eq!(left, [1, 2]);
    assert_eq!(right, [3, 4, 5, 6]);
}

unsafe {
    let (left, right) = v.split_at_unchecked(6);
    assert_eq!(left, [1, 2, 3, 4, 5, 6]);
    assert_eq!(right, []);
}

pub fn split_array_ref<const N: usize>(&self) -> (&[T; N], &[T])

🔬This is a nightly-only experimental API. (split_array)

Divides one slice into an array and a remainder slice at an index.

The array will contain all indices from [0, N) (excluding the index N itself) and the slice will contain all indices from [N, len) (excluding the index len itself).

Panics

Panics if N > len.

Examples

#![feature(split_array)]

let v = &[1, 2, 3, 4, 5, 6][..];

{
   let (left, right) = v.split_array_ref::<0>();
   assert_eq!(left, &[]);
   assert_eq!(right, [1, 2, 3, 4, 5, 6]);
}

{
    let (left, right) = v.split_array_ref::<2>();
    assert_eq!(left, &[1, 2]);
    assert_eq!(right, [3, 4, 5, 6]);
}

{
    let (left, right) = v.split_array_ref::<6>();
    assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
    assert_eq!(right, []);
}

pub fn rsplit_array_ref<const N: usize>(&self) -> (&[T], &[T; N])

🔬This is a nightly-only experimental API. (split_array)

Divides one slice into an array and a remainder slice at an index from the end.

The slice will contain all indices from [0, len - N) (excluding the index len - N itself) and the array will contain all indices from [len - N, len) (excluding the index len itself).

Panics

Panics if N > len.

Examples

#![feature(split_array)]

let v = &[1, 2, 3, 4, 5, 6][..];

{
   let (left, right) = v.rsplit_array_ref::<0>();
   assert_eq!(left, [1, 2, 3, 4, 5, 6]);
   assert_eq!(right, &[]);
}

{
    let (left, right) = v.rsplit_array_ref::<2>();
    assert_eq!(left, [1, 2, 3, 4]);
    assert_eq!(right, &[5, 6]);
}

{
    let (left, right) = v.rsplit_array_ref::<6>();
    assert_eq!(left, []);
    assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
}

pub fn split<F>(&self, pred: F) -> Split<'_, T, F>where
    F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred. The matched element is not contained in the subslices.

Examples

let slice = [10, 40, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the first element is matched, an empty slice will be the first item returned by the iterator. Similarly, if the last element in the slice is matched, an empty slice will be the last item returned by the iterator:

let slice = [10, 40, 33];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[]);
assert!(iter.next().is_none());

If two matched elements are directly adjacent, an empty slice will be present between them:

let slice = [10, 6, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10]);
assert_eq!(iter.next().unwrap(), &[]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

pub fn split_inclusive<F>(&self, pred: F) -> SplitInclusive<'_, T, F>where
    F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred. The matched element is contained in the end of the previous subslice as a terminator.

Examples

let slice = [10, 40, 33, 20];
let mut iter = slice.split_inclusive(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the last element of the slice is matched, that element will be considered the terminator of the preceding slice. That slice will be the last item returned by the iterator.

let slice = [3, 10, 40, 33];
let mut iter = slice.split_inclusive(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[3]);
assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
assert!(iter.next().is_none());

pub fn rsplit<F>(&self, pred: F) -> RSplit<'_, T, F>where
    F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.

Examples

let slice = [11, 22, 33, 0, 44, 55];
let mut iter = slice.rsplit(|num| *num == 0);

assert_eq!(iter.next().unwrap(), &[44, 55]);
assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
assert_eq!(iter.next(), None);

As with split(), if the first or last element is matched, an empty slice will be the first (or last) item returned by the iterator.

let v = &[0, 1, 1, 2, 3, 5, 8];
let mut it = v.rsplit(|n| *n % 2 == 0);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next().unwrap(), &[3, 5]);
assert_eq!(it.next().unwrap(), &[1, 1]);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next(), None);

pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<'_, T, F>where
    F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once by numbers divisible by 3 (i.e., [10, 40], [20, 60, 50]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.splitn(2, |num| *num % 3 == 0) {
    println!("{group:?}");
}

pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<'_, T, F>where
    F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once, starting from the end, by numbers divisible by 3 (i.e., [50], [10, 40, 30, 20]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.rsplitn(2, |num| *num % 3 == 0) {
    println!("{group:?}");
}

pub fn contains(&self, x: &T) -> boolwhere
    T: PartialEq<T>,

Returns true if the slice contains an element with the given value.

This operation is O(n).

Note that if you have a sorted slice, binary_search may be faster.

Examples

let v = [10, 40, 30];
assert!(v.contains(&30));
assert!(!v.contains(&50));

If you do not have a &T, but some other value that you can compare with one (for example, String implements PartialEq<str>), you can use iter().any:

let v = [String::from("hello"), String::from("world")]; // slice of `String`
assert!(v.iter().any(|e| e == "hello")); // search with `&str`
assert!(!v.iter().any(|e| e == "hi"));

pub fn starts_with(&self, needle: &[T]) -> boolwhere
    T: PartialEq<T>,

Returns true if needle is a prefix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.starts_with(&[10]));
assert!(v.starts_with(&[10, 40]));
assert!(!v.starts_with(&[50]));
assert!(!v.starts_with(&[10, 50]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.starts_with(&[]));
let v: &[u8] = &[];
assert!(v.starts_with(&[]));

pub fn ends_with(&self, needle: &[T]) -> boolwhere
    T: PartialEq<T>,

Returns true if needle is a suffix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.ends_with(&[30]));
assert!(v.ends_with(&[40, 30]));
assert!(!v.ends_with(&[50]));
assert!(!v.ends_with(&[50, 30]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.ends_with(&[]));
let v: &[u8] = &[];
assert!(v.ends_with(&[]));

pub fn strip_prefix<P>(&self, prefix: &P) -> Option<&[T]>where
    P: SlicePattern<Item = T> + ?Sized,
    T: PartialEq<T>,

Returns a subslice with the prefix removed.

If the slice starts with prefix, returns the subslice after the prefix, wrapped in Some. If prefix is empty, simply returns the original slice.

If the slice does not start with prefix, returns None.

Examples

let v = &[10, 40, 30];
assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..]));
assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..]));
assert_eq!(v.strip_prefix(&[50]), None);
assert_eq!(v.strip_prefix(&[10, 50]), None);

let prefix : &str = "he";
assert_eq!(b"hello".strip_prefix(prefix.as_bytes()),
           Some(b"llo".as_ref()));

pub fn strip_suffix<P>(&self, suffix: &P) -> Option<&[T]>where
    P: SlicePattern<Item = T> + ?Sized,
    T: PartialEq<T>,

Returns a subslice with the suffix removed.

If the slice ends with suffix, returns the subslice before the suffix, wrapped in Some. If suffix is empty, simply returns the original slice.

If the slice does not end with suffix, returns None.

Examples

let v = &[10, 40, 30];
assert_eq!(v.strip_suffix(&[30]), Some(&[10, 40][..]));
assert_eq!(v.strip_suffix(&[40, 30]), Some(&[10][..]));
assert_eq!(v.strip_suffix(&[50]), None);
assert_eq!(v.strip_suffix(&[50, 30]), None);

pub fn binary_search(&self, x: &T) -> Result<usize, usize>where
    T: Ord,

Binary searches this slice for a given element. This behaves similarly to contains if this slice is sorted.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search_by, binary_search_by_key, and partition_point.

Examples

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

assert_eq!(s.binary_search(&13),  Ok(9));
assert_eq!(s.binary_search(&4),   Err(7));
assert_eq!(s.binary_search(&100), Err(13));
let r = s.binary_search(&1);
assert!(match r { Ok(1..=4) => true, _ => false, });

If you want to find that whole range of matching items, rather than an arbitrary matching one, that can be done using partition_point:

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

let low = s.partition_point(|x| x < &1);
assert_eq!(low, 1);
let high = s.partition_point(|x| x <= &1);
assert_eq!(high, 5);
let r = s.binary_search(&1);
assert!((low..high).contains(&r.unwrap()));

assert!(s[..low].iter().all(|&x| x < 1));
assert!(s[low..high].iter().all(|&x| x == 1));
assert!(s[high..].iter().all(|&x| x > 1));

// For something not found, the "range" of equal items is empty
assert_eq!(s.partition_point(|x| x < &11), 9);
assert_eq!(s.partition_point(|x| x <= &11), 9);
assert_eq!(s.binary_search(&11), Err(9));

If you want to insert an item to a sorted vector, while maintaining sort order, consider using partition_point:

let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
let num = 42;
let idx = s.partition_point(|&x| x < num);
// The above is equivalent to `let idx = s.binary_search(&num).unwrap_or_else(|x| x);`
s.insert(idx, num);
assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);

pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>where
    F: FnMut(&'a T) -> Ordering,

Binary searches this slice with a comparator function. This behaves similarly to contains if this slice is sorted.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is Less, Equal or Greater the desired target.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search, binary_search_by_key, and partition_point.

Examples

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

let seek = 13;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
let seek = 4;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
let seek = 100;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
let seek = 1;
let r = s.binary_search_by(|probe| probe.cmp(&seek));
assert!(match r { Ok(1..=4) => true, _ => false, });

pub fn binary_search_by_key<'a, B, F>(
    &'a self,
    b: &B,
    f: F
) -> Result<usize, usize>where
    F: FnMut(&'a T) -> B,
    B: Ord,

Binary searches this slice with a key extraction function. This behaves similarly to contains if this slice is sorted.

Assumes that the slice is sorted by the key, for instance with sort_by_key using the same key extraction function.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search, binary_search_by, and partition_point.

Examples

Looks up a series of four elements in a slice of pairs sorted by their second elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
         (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
         (1, 21), (2, 34), (4, 55)];

assert_eq!(s.binary_search_by_key(&13, |&(a, b)| b),  Ok(9));
assert_eq!(s.binary_search_by_key(&4, |&(a, b)| b),   Err(7));
assert_eq!(s.binary_search_by_key(&100, |&(a, b)| b), Err(13));
let r = s.binary_search_by_key(&1, |&(a, b)| b);
assert!(match r { Ok(1..=4) => true, _ => false, });

pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T])

Transmute the slice to a slice of another type, ensuring alignment of the types is maintained.

This method splits the slice into three distinct slices: prefix, correctly aligned middle slice of a new type, and the suffix slice. How exactly the slice is split up is not specified; the middle part may be smaller than necessary. However, if this fails to return a maximal middle part, that is because code is running in a context where performance does not matter, such as a sanitizer attempting to find alignment bugs. Regular code running in a default (debug or release) execution will return a maximal middle part.

This method has no purpose when either input element T or output element U are zero-sized and will return the original slice without splitting anything.

Safety

This method is essentially a transmute with respect to the elements in the returned middle slice, so all the usual caveats pertaining to transmute::<T, U> also apply here.

Examples

Basic usage:

unsafe {
    let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
    let (prefix, shorts, suffix) = bytes.align_to::<u16>();
    // less_efficient_algorithm_for_bytes(prefix);
    // more_efficient_algorithm_for_aligned_shorts(shorts);
    // less_efficient_algorithm_for_bytes(suffix);
}

pub fn as_simd<const LANES: usize>(&self) -> (&[T], &[Simd<T, LANES>], &[T])where
    Simd<T, LANES>: AsRef<[T; LANES]>,
    T: SimdElement,
    LaneCount<LANES>: SupportedLaneCount,

🔬This is a nightly-only experimental API. (portable_simd)

Split a slice into a prefix, a middle of aligned SIMD types, and a suffix.

This is a safe wrapper around slice::align_to, so has the same weak postconditions as that method. You’re only assured that self.len() == prefix.len() + middle.len() * LANES + suffix.len().

Notably, all of the following are possible:

• prefix.len() >= LANES.
• middle.is_empty() despite self.len() >= 3 * LANES.
• suffix.len() >= LANES.

That said, this is a safe method, so if you’re only writing safe code, then this can at most cause incorrect logic, not unsoundness.

Panics

This will panic if the size of the SIMD type is different from LANES times that of the scalar.

At the time of writing, the trait restrictions on Simd<T, LANES> keeps that from ever happening, as only power-of-two numbers of lanes are supported. It’s possible that, in the future, those restrictions might be lifted in a way that would make it possible to see panics from this method for something like LANES == 3.

Examples

#![feature(portable_simd)]
use core::simd::SimdFloat;

let short = &[1, 2, 3];
let (prefix, middle, suffix) = short.as_simd::<4>();
assert_eq!(middle, []); // Not enough elements for anything in the middle

// They might be split in any possible way between prefix and suffix
let it = prefix.iter().chain(suffix).copied();
assert_eq!(it.collect::<Vec<_>>(), vec![1, 2, 3]);

fn basic_simd_sum(x: &[f32]) -> f32 {
    use std::ops::Add;
    use std::simd::f32x4;
    let (prefix, middle, suffix) = x.as_simd();
    let sums = f32x4::from_array([
        prefix.iter().copied().sum(),
        0.0,
        0.0,
        suffix.iter().copied().sum(),
    ]);
    let sums = middle.iter().copied().fold(sums, f32x4::add);
    sums.reduce_sum()
}

let numbers: Vec<f32> = (1..101).map(|x| x as _).collect();
assert_eq!(basic_simd_sum(&numbers[1..99]), 4949.0);

pub fn is_sorted(&self) -> boolwhere
    T: PartialOrd<T>,

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted.

That is, for each element a and its following element b, a <= b must hold. If the slice yields exactly zero or one element, true is returned.

Note that if Self::Item is only PartialOrd, but not Ord, the above definition implies that this function returns false if any two consecutive items are not comparable.

Examples

#![feature(is_sorted)]
let empty: [i32; 0] = [];

assert!([1, 2, 2, 9].is_sorted());
assert!(![1, 3, 2, 4].is_sorted());
assert!([0].is_sorted());
assert!(empty.is_sorted());
assert!(![0.0, 1.0, f32::NAN].is_sorted());

pub fn is_sorted_by<'a, F>(&'a self, compare: F) -> boolwhere
    F: FnMut(&'a T, &'a T) -> Option<Ordering>,

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted using the given comparator function.

Instead of using PartialOrd::partial_cmp, this function uses the given compare function to determine the ordering of two elements. Apart from that, it’s equivalent to is_sorted; see its documentation for more information.

pub fn is_sorted_by_key<'a, F, K>(&'a self, f: F) -> boolwhere
    F: FnMut(&'a T) -> K,
    K: PartialOrd<K>,

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted using the given key extraction function.

Instead of comparing the slice’s elements directly, this function compares the keys of the elements, as determined by f. Apart from that, it’s equivalent to is_sorted; see its documentation for more information.

Examples

#![feature(is_sorted)]

assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len()));
assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));

pub fn partition_point<P>(&self, pred: P) -> usizewhere
    P: FnMut(&T) -> bool,

Returns the index of the partition point according to the given predicate (the index of the first element of the second partition).

The slice is assumed to be partitioned according to the given predicate. This means that all elements for which the predicate returns true are at the start of the slice and all elements for which the predicate returns false are at the end. For example, [7, 15, 3, 5, 4, 12, 6] is partitioned under the predicate x % 2 != 0 (all odd numbers are at the start, all even at the end).

If this slice is not partitioned, the returned result is unspecified and meaningless, as this method performs a kind of binary search.

See also binary_search, binary_search_by, and binary_search_by_key.

Examples

let v = [1, 2, 3, 3, 5, 6, 7];
let i = v.partition_point(|&x| x < 5);

assert_eq!(i, 4);
assert!(v[..i].iter().all(|&x| x < 5));
assert!(v[i..].iter().all(|&x| !(x < 5)));

If all elements of the slice match the predicate, including if the slice is empty, then the length of the slice will be returned:

let a = [2, 4, 8];
assert_eq!(a.partition_point(|x| x < &100), a.len());
let a: [i32; 0] = [];
assert_eq!(a.partition_point(|x| x < &100), 0);

If you want to insert an item to a sorted vector, while maintaining sort order:

let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
let num = 42;
let idx = s.partition_point(|&x| x < num);
s.insert(idx, num);
assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);

pub fn is_ascii(&self) -> bool

Checks if all bytes in this slice are within the ASCII range.

pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool

Checks that two slices are an ASCII case-insensitive match.

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

pub fn escape_ascii(&self) -> EscapeAscii<'_>

Returns an iterator that produces an escaped version of this slice, treating it as an ASCII string.

Examples

let s = b"0\t\r\n'\"\\\x9d";
let escaped = s.escape_ascii().to_string();
assert_eq!(escaped, "0\\t\\r\\n\\'\\\"\\\\\\x9d");

pub fn trim_ascii_start(&self) -> &[u8]

🔬This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with leading ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

#![feature(byte_slice_trim_ascii)]

assert_eq!(b" \t hello world\n".trim_ascii_start(), b"hello world\n");
assert_eq!(b"  ".trim_ascii_start(), b"");
assert_eq!(b"".trim_ascii_start(), b"");

pub fn trim_ascii_end(&self) -> &[u8]

🔬This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with trailing ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

#![feature(byte_slice_trim_ascii)]

assert_eq!(b"\r hello world\n ".trim_ascii_end(), b"\r hello world");
assert_eq!(b"  ".trim_ascii_end(), b"");
assert_eq!(b"".trim_ascii_end(), b"");

pub fn trim_ascii(&self) -> &[u8]

🔬This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with leading and trailing ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

#![feature(byte_slice_trim_ascii)]

assert_eq!(b"\r hello world\n ".trim_ascii(), b"hello world");
assert_eq!(b"  ".trim_ascii(), b"");
assert_eq!(b"".trim_ascii(), b"");

pub fn to_vec(&self) -> Vec<T, Global> where
    T: Clone,

Copies self into a new Vec.

Examples

let s = [10, 40, 30];
let x = s.to_vec();
// Here, `s` and `x` can be modified independently.

pub fn to_vec_in<A>(&self, alloc: A) -> Vec<T, A> where
    A: Allocator,
    T: Clone,

🔬This is a nightly-only experimental API. (allocator_api)

Copies self into a new Vec with an allocator.

Examples

#![feature(allocator_api)]

use std::alloc::System;

let s = [10, 40, 30];
let x = s.to_vec_in(System);
// Here, `s` and `x` can be modified independently.

pub fn repeat(&self, n: usize) -> Vec<T, Global> where
    T: Copy,

Creates a vector by copying a slice n times.

Panics

This function will panic if the capacity would overflow.

Examples

Basic usage:

assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);

A panic upon overflow:

// this will panic at runtime
b"0123456789abcdef".repeat(usize::MAX);

pub fn concat<Item>(&self) -> <[T] as Concat<Item>>::Output where
    [T]: Concat<Item>,
    Item: ?Sized,

Flattens a slice of T into a single value Self::Output.

Examples

assert_eq!(["hello", "world"].concat(), "helloworld");
assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);

pub fn join<Separator>(&self, sep: Separator) -> <[T] as Join<Separator>>::Output where
    [T]: Join<Separator>,

Flattens a slice of T into a single value Self::Output, placing a given separator between each.

Examples

assert_eq!(["hello", "world"].join(" "), "hello world");
assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);
assert_eq!([[1, 2], [3, 4]].join(&[0, 0][..]), [1, 2, 0, 0, 3, 4]);

pub fn connect<Separator>(
    &self,
    sep: Separator
) -> <[T] as Join<Separator>>::Output where
    [T]: Join<Separator>,

👎Deprecated since 1.3.0: renamed to join

Flattens a slice of T into a single value Self::Output, placing a given separator between each.

Examples

assert_eq!(["hello", "world"].connect(" "), "hello world");
assert_eq!([[1, 2], [3, 4]].connect(&0), [1, 2, 0, 3, 4]);

pub fn to_ascii_uppercase(&self) -> Vec<u8, Global>

Returns a vector containing a copy of this slice where each byte is mapped to its ASCII upper case equivalent.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

pub fn to_ascii_lowercase(&self) -> Vec<u8, Global>

Returns a vector containing a copy of this slice where each byte is mapped to its ASCII lower case equivalent.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

Trait Implementations

impl<T: Clone> Clone for Buffer<T>

fn clone(&self) -> Buffer<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Buffer<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Buffer<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> Deref for Buffer<T>

type Target = [T]

The resulting type after dereferencing.

fn deref(&self) -> &[T]

Dereferences the value.

impl<T> From<Vec<T, Global>> for Buffer<T>

fn from(p: Vec<T>) -> Self

Converts to this type from the input type.

impl<T> FromIterator<T> for Buffer<T>

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self

Creates a value from an iterator.

impl<T: Copy> IntoIterator for Buffer<T>

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<T: PartialEq> PartialEq<Buffer<T>> for Buffer<T>

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<O: Offset> TryFrom<Buffer<O>> for OffsetsBuffer<O>

type Error = Error

The type returned in the event of a conversion error.

fn try_from(offsets: Buffer<O>) -> Result<Self, Self::Error>

Performs the conversion.