iter.rs - source
Description: Source of the Rust file `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/nalgebra-0.32.1/src/base/iter.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Matrix iterators.

    // only enables the `doc_cfg` feature when
    // the `docsrs` configuration attribute is defined
    #![cfg_attr(docsrs, feature(doc_cfg))]

    use core::fmt::Debug;
    use core::ops::Range;
    use std::iter::FusedIterator;
    use std::marker::PhantomData;
    use std::mem;

    use crate::base::dimension::{Dim, U1};
    use crate::base::storage::{RawStorage, RawStorageMut};
    use crate::base::{Matrix, MatrixView, MatrixViewMut, Scalar};

    macro_rules! iterator {
        (struct $Name:ident for $Storage:ident.$ptr: ident -> $Ptr:ty, $Ref:ty, $SRef: ty) => {
            /// An iterator through a dense matrix with arbitrary strides matrix.
            #[derive(Debug)]
            pub struct $Name<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> {
                ptr: $Ptr,
                inner_ptr: $Ptr,
                inner_end: $Ptr,
                size: usize, // We can't use an end pointer here because a stride might be zero.
                strides: (S::RStride, S::CStride),
                _phantoms: PhantomData<($Ref, R, C, S)>,
            }

            // TODO: we need to specialize for the case where the matrix storage is owned (in which
            // case the iterator is trivial because it does not have any stride).
            impl<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> $Name<'a, T, R, C, S> {
                /// Creates a new iterator for the given matrix storage.
                pub fn new(storage: $SRef) -> $Name<'a, T, R, C, S> {
                    let shape = storage.shape();
                    let strides = storage.strides();
                    let inner_offset = shape.0.value() * strides.0.value();
                    let size = shape.0.value() * shape.1.value();
                    let ptr = storage.$ptr();

                    // If we have a size of 0, 'ptr' must be
                    // dangling. Howver, 'inner_offset' might
                    // not be zero if only one dimension is zero, so
                    // we don't want to call 'offset'.
                    // This pointer will never actually get used
                    // if our size is '0', so it's fine to use
                    // 'ptr' for both the start and end.
                    let inner_end = if size == 0 {
                        ptr
                    } else {
                        // Safety:
                        // If 'size' is non-zero, we know that 'ptr'
                        // is not dangling, and 'inner_offset' must lie
                        // within the allocation
                        unsafe { ptr.add(inner_offset) }
                    };

                    $Name {
                        ptr,
                        inner_ptr: ptr,
                        inner_end,
                        size: shape.0.value() * shape.1.value(),
                        strides,
                        _phantoms: PhantomData,
                    }
                }
            }

            impl<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> Iterator for $Name<'a, T, R, C, S> {
                type Item = $Ref;

                #[inline]
                fn next(&mut self) -> Option<$Ref> {
                    unsafe {
                        if self.size == 0 {
                            None
                        } else {
                            self.size -= 1;

                            // Jump to the next outer dimension if needed.
                            if self.ptr == self.inner_end {
                                let stride = self.strides.1.value() as isize;
                                // This might go past the end of the allocation,
                                // depending on the value of 'size'. We use
                                // `wrapping_offset` to avoid UB
                                self.inner_end = self.ptr.wrapping_offset(stride);
                                // This will always be in bounds, since
                                // we're going to dereference it
                                self.ptr = self.inner_ptr.offset(stride);
                                self.inner_ptr = self.ptr;
                            }

                            // Go to the next element.
                            let old = self.ptr;

                            // Don't offset `self.ptr` for the last element,
                            // as this will be out of bounds. Iteration is done
                            // at this point (the next call to `next` will return `None`)
                            // so this is not observable.
                            if self.size != 0 {
                                let stride = self.strides.0.value();
                                self.ptr = self.ptr.add(stride);
                            }

                            // We want either `& *last` or `&mut *last` here, depending
                            // on the mutability of `$Ref`.
                            #[allow(clippy::transmute_ptr_to_ref)]
                            Some(mem::transmute(old))
                        }
                    }
                }

                #[inline]
                fn size_hint(&self) -> (usize, Option<usize>) {
                    (self.size, Some(self.size))
                }

                #[inline]
                fn count(self) -> usize {
                    self.size_hint().0
                }
            }

            impl<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> DoubleEndedIterator
                for $Name<'a, T, R, C, S>
            {
                #[inline]
                fn next_back(&mut self) -> Option<$Ref> {
                    unsafe {
                        if self.size == 0 {
                            None
                        } else {
                            // Pre-decrement `size` such that it now counts to the
                            // element we want to return.
                            self.size -= 1;

                            // Fetch strides
                            let inner_stride = self.strides.0.value();
                            let outer_stride = self.strides.1.value();

                            // Compute number of rows
                            // Division should be exact
                            let inner_raw_size = self.inner_end.offset_from(self.inner_ptr) as usize;
                            let inner_size = inner_raw_size / inner_stride;

                            // Compute rows and cols remaining
                            let outer_remaining = self.size / inner_size;
                            let inner_remaining = self.size % inner_size;

                            // Compute pointer to last element
                            let last = self
                                .ptr
                                .add((outer_remaining * outer_stride + inner_remaining * inner_stride));

                            // We want either `& *last` or `&mut *last` here, depending
                            // on the mutability of `$Ref`.
                            #[allow(clippy::transmute_ptr_to_ref)]
                            Some(mem::transmute(last))
                        }
                    }
                }
            }

            impl<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> ExactSizeIterator
                for $Name<'a, T, R, C, S>
            {
                #[inline]
                fn len(&self) -> usize {
                    self.size
                }
            }

            impl<'a, T, R: Dim, C: Dim, S: 'a + $Storage<T, R, C>> FusedIterator
                for $Name<'a, T, R, C, S>
            {
            }
        };
    }

    iterator!(struct MatrixIter for RawStorage.ptr -> *const T, &'a T, &'a S);
    iterator!(struct MatrixIterMut for RawStorageMut.ptr_mut -> *mut T, &'a mut T, &'a mut S);

    /*
     *
     * Row iterators.
     *
     */
    #[derive(Clone, Debug)]
    /// An iterator through the rows of a matrix.
    pub struct RowIter<'a, T, R: Dim, C: Dim, S: RawStorage<T, R, C>> {
        mat: &'a Matrix<T, R, C, S>,
        curr: usize,
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> RowIter<'a, T, R, C, S> {
        pub(crate) fn new(mat: &'a Matrix<T, R, C, S>) -> Self {
            RowIter { mat, curr: 0 }
        }
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> Iterator for RowIter<'a, T, R, C, S> {
        type Item = MatrixView<'a, T, U1, C, S::RStride, S::CStride>;

        #[inline]
        fn next(&mut self) -> Option<Self::Item> {
            if self.curr < self.mat.nrows() {
                let res = self.mat.row(self.curr);
                self.curr += 1;
                Some(res)
            } else {
                None
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            (
                self.mat.nrows() - self.curr,
                Some(self.mat.nrows() - self.curr),
            )
        }

        #[inline]
        fn count(self) -> usize {
            self.mat.nrows() - self.curr
        }
    }

    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> ExactSizeIterator
        for RowIter<'a, T, R, C, S>
    {
        #[inline]
        fn len(&self) -> usize {
            self.mat.nrows() - self.curr
        }
    }

    /// An iterator through the mutable rows of a matrix.
    #[derive(Debug)]
    pub struct RowIterMut<'a, T, R: Dim, C: Dim, S: RawStorageMut<T, R, C>> {
        mat: *mut Matrix<T, R, C, S>,
        curr: usize,
        phantom: PhantomData<&'a mut Matrix<T, R, C, S>>,
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> RowIterMut<'a, T, R, C, S> {
        pub(crate) fn new(mat: &'a mut Matrix<T, R, C, S>) -> Self {
            RowIterMut {
                mat,
                curr: 0,
                phantom: PhantomData,
            }
        }

        fn nrows(&self) -> usize {
            unsafe { (*self.mat).nrows() }
        }
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Iterator
        for RowIterMut<'a, T, R, C, S>
    {
        type Item = MatrixViewMut<'a, T, U1, C, S::RStride, S::CStride>;

        #[inline]
        fn next(&mut self) -> Option<Self::Item> {
            if self.curr < self.nrows() {
                let res = unsafe { (*self.mat).row_mut(self.curr) };
                self.curr += 1;
                Some(res)
            } else {
                None
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            (self.nrows() - self.curr, Some(self.nrows() - self.curr))
        }

        #[inline]
        fn count(self) -> usize {
            self.nrows() - self.curr
        }
    }

    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> ExactSizeIterator
        for RowIterMut<'a, T, R, C, S>
    {
        #[inline]
        fn len(&self) -> usize {
            self.nrows() - self.curr
        }
    }

    /*
     * Column iterators.
     *
     */
    #[derive(Clone, Debug)]
    /// An iterator through the columns of a matrix.
    pub struct ColumnIter<'a, T, R: Dim, C: Dim, S: RawStorage<T, R, C>> {
        mat: &'a Matrix<T, R, C, S>,
        range: Range<usize>,
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> ColumnIter<'a, T, R, C, S> {
        /// a new column iterator covering all columns of the matrix
        pub(crate) fn new(mat: &'a Matrix<T, R, C, S>) -> Self {
            ColumnIter {
                mat,
                range: 0..mat.ncols(),
            }
        }

        pub(crate) fn split_at(self, index: usize) -> (Self, Self) {
            // SAFETY: this makes sur the generated ranges are valid.
            let split_pos = (self.range.start + index).min(self.range.end);

            let left_iter = ColumnIter {
                mat: self.mat,
                range: self.range.start..split_pos,
            };

            let right_iter = ColumnIter {
                mat: self.mat,
                range: split_pos..self.range.end,
            };

            (left_iter, right_iter)
        }
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> Iterator for ColumnIter<'a, T, R, C, S> {
        type Item = MatrixView<'a, T, R, U1, S::RStride, S::CStride>;

        #[inline]
        fn next(&mut self) -> Option<Self::Item> {
            debug_assert!(self.range.start <= self.range.end);
            if self.range.start < self.range.end {
                let res = self.mat.column(self.range.start);
                self.range.start += 1;
                Some(res)
            } else {
                None
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            let hint = self.range.len();
            (hint, Some(hint))
        }

        #[inline]
        fn count(self) -> usize {
            self.range.len()
        }
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> DoubleEndedIterator
        for ColumnIter<'a, T, R, C, S>
    {
        fn next_back(&mut self) -> Option<Self::Item> {
            debug_assert!(self.range.start <= self.range.end);
            if !self.range.is_empty() {
                self.range.end -= 1;
                debug_assert!(self.range.end < self.mat.ncols());
                debug_assert!(self.range.end >= self.range.start);
                Some(self.mat.column(self.range.end))
            } else {
                None
            }
        }
    }

    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> ExactSizeIterator
        for ColumnIter<'a, T, R, C, S>
    {
        #[inline]
        fn len(&self) -> usize {
            self.range.end - self.range.start
        }
    }

    /// An iterator through the mutable columns of a matrix.
    #[derive(Debug)]
    pub struct ColumnIterMut<'a, T, R: Dim, C: Dim, S: RawStorageMut<T, R, C>> {
        mat: *mut Matrix<T, R, C, S>,
        range: Range<usize>,
        phantom: PhantomData<&'a mut Matrix<T, R, C, S>>,
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> ColumnIterMut<'a, T, R, C, S> {
        pub(crate) fn new(mat: &'a mut Matrix<T, R, C, S>) -> Self {
            let range = 0..mat.ncols();
            ColumnIterMut {
                mat,
                range,
                phantom: Default::default(),
            }
        }

        pub(crate) fn split_at(self, index: usize) -> (Self, Self) {
            // SAFETY: this makes sur the generated ranges are valid.
            let split_pos = (self.range.start + index).min(self.range.end);

            let left_iter = ColumnIterMut {
                mat: self.mat,
                range: self.range.start..split_pos,
                phantom: Default::default(),
            };

            let right_iter = ColumnIterMut {
                mat: self.mat,
                range: split_pos..self.range.end,
                phantom: Default::default(),
            };

            (left_iter, right_iter)
        }

        fn ncols(&self) -> usize {
            unsafe { (*self.mat).ncols() }
        }
    }

    impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Iterator
        for ColumnIterMut<'a, T, R, C, S>
    {
        type Item = MatrixViewMut<'a, T, R, U1, S::RStride, S::CStride>;

        #[inline]
        fn next(&'_ mut self) -> Option<Self::Item> {
            debug_assert!(self.range.start <= self.range.end);
            if self.range.start < self.range.end {
                let res = unsafe { (*self.mat).column_mut(self.range.start) };
                self.range.start += 1;
                Some(res)
            } else {
                None
            }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            let hint = self.range.len();
            (hint, Some(hint))
        }

        #[inline]
        fn count(self) -> usize {
            self.range.len()
        }
    }

    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> ExactSizeIterator
        for ColumnIterMut<'a, T, R, C, S>
    {
        #[inline]
        fn len(&self) -> usize {
            self.range.len()
        }
    }

    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> DoubleEndedIterator
        for ColumnIterMut<'a, T, R, C, S>
    {
        fn next_back(&mut self) -> Option<Self::Item> {
            debug_assert!(self.range.start <= self.range.end);
            if !self.range.is_empty() {
                self.range.end -= 1;
                debug_assert!(self.range.end < self.ncols());
                debug_assert!(self.range.end >= self.range.start);
                Some(unsafe { (*self.mat).column_mut(self.range.end) })
            } else {
                None
            }
        }
    }