Trait ndarray_npy::ViewNpyExt [−][src]
Expand description
Extension trait for creating an ArrayView
from a buffer containing an
.npy
file.
The primary use-case for this is viewing a memory-mapped .npy
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 readonly memory-mapped file as an
ArrayView
.
This example uses the memmap2
crate
because that appears to be the best-maintained memory-mapping crate at the
moment, but view_npy
takes a &[u8]
instead of a file so that you can
use the memory-mapping crate you’re most comfortable with.
use memmap2::Mmap;
use ndarray::ArrayView2;
use ndarray_npy::ViewNpyExt;
use std::fs::File;
let file = File::open("resources/array.npy")?;
let mmap = unsafe { Mmap::map(&file)? };
let view = ArrayView2::<i32>::view_npy(&mmap)?;