tsfoster/elm-bytes-extra

Helpers for working with elm/bytes

elm-bytes-extra's Issues

Add decoder to decode with offset

slice is a great function to extract chunks out of a Bytes sequence. However, it would be very practical if one could have a quick way of decoding with offsets(where there's no easy access to Bytes). That's why I am proposing this offset Decoder as a combinator for a Decoder.

Example Implementation

-- in the Bytes.Extra.Decode module
withOffset : Int -> Decoder a -> Decoder a
withOffset offset decoder =
    Bytes.Decode.bytes (max 0 offset) |> andThen (\_ -> decoder)

-- can then be used like this
import Bytes.Decode exposing (float64)
import Bytes.Decode.Extra exposing (withOffset)

withOffset 8 float64 -- will first skip 8 bytes and then decode a 64 bit-float 

Concrete use case
I am currently trying to decode buffer data out of buffers in GLTF data (3d model format). In many cases the data is not densely packed, so it is necessary to skip some bytes while decoding to get to the later data.

PS: Thanks for this useful package. <3