Trait ViewMutNpyExt

pub trait ViewMutNpyExt<'a>: Sized {
    // Required method
    fn view_mut_npy(buf: &'a mut [u8]) -> Result<Self, ViewNpyError>;
}

Extension trait for creating an ArrayViewMut from a mutable buffer containing an .npy file.

The primary use-case for this is modifying a memory-mapped .npy file. Modifying the elements in the view will modify the file. Modifying the shape/strides of the view will not modify the shape/strides of the array in the file.

Notes:

• For types for which not all bit patterns are valid, such as bool, the implementation iterates over all of the elements when creating the view to ensure they have a valid bit pattern.

• The data in the buffer must be properly aligned for the element type. Typically, this should not be a concern for memory-mapped files (unless an option like MAP_FIXED is used), since memory mappings are usually aligned to a page boundary, and the .npy format has padding such that the header size is a multiple of 64 bytes.

Example

This is an example of opening a writable memory-mapped file as an ArrayViewMut. Changes to the data in the view will modify the underlying file.

This example uses the memmap2 crate because that appears to be the best-maintained memory-mapping crate at the moment, but view_mut_npy takes a &mut [u8] instead of a file so that you can use the memory-mapping crate you’re most comfortable with.

use memmap2::MmapMut;
use ndarray::ArrayViewMut2;
use ndarray_npy::ViewMutNpyExt;
use std::fs;

let file = fs::OpenOptions::new()
    .read(true)
    .write(true)
    .open("resources/array.npy")?;
let mut mmap = unsafe { MmapMut::map_mut(&file)? };
let view_mut = ArrayViewMut2::<i32>::view_mut_npy(&mut mmap)?;

Required Methods

fn view_mut_npy(buf: &'a mut [u8]) -> Result<Self, ViewNpyError>

Creates an ArrayViewMut from a mutable buffer containing an .npy file.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<'a, A, D> ViewMutNpyExt<'a> for ArrayViewMut<'a, A, D>

where A: ViewMutElement, D: Dimension,

fn view_mut_npy(buf: &'a mut [u8]) -> Result<Self, ViewNpyError>

Implementors