idx-decoder 0.0.2

An IDX file format decoder



An IDX file format decoding library. (Currently WIP)

The main type is IDXDecoder. It implements Iterator whose Item correspond to items of file format.

Type parameters

IDXDecoder takes three type parameters.

  • R: Reader from which data is taken. Can be file, network stream etc.

  • T: Type of items produced by Iterator. E.g. U8, I16, F32.

    All possible types can be found in types module

  • D: Type-level integer of dimensions. Must be less than 256.

    If it's less than 128 use nalgebra's U* types. For value >=128 use typenum's consts.


For one-dimensional decoder returns simply items.

For more dimensions, output is a Vec of values containing a single item.

E.g. a 3-dimensional decoder where items are of size 4x4 will return Vecs of length 16.

First dimension of decoder corresponds to amount of items left.


Currently decoder only implements Iterator for 1 and 3 dimensions. It's simply because I didn't implement other.

Crate also assumes that items are stored in big endian way, just like sizes.

If you found a bug or the crate is missing some functionality, add an issue or send a pull request.


let file = std::fs::File::open("data.idx")?;
let decode = idx_decoder::IDXDecoder::<_, idx_decoder::types::U8, nalgebra::U1>::new(file)?;
for item in decode {
    println!("Item: {}", item);


This crate is implemented according to file format found at

License: MIT