Allow the description of the "physical" value

[gbonnefille]

Currently, PDL allows to extract data as raw integers or enum.

Sometimes, the encoded data represent physical values. In such situation, once extracted, the raw value should be converted into a physical value. For example, a float or, more advanced, a timestamp.

Is there any solution to extend the generated struct with such conversions?

Or perhaps adding this directly in the PDL description?

[hchataing]

In theory you can extend PDL native types with custom declarations, but the exact details have not been fully flattened out yet.
There are two distinct custom field declarations:

little_endian_declarations

// With explicit fixed width
custom_field CustomType1 : 32 "custom_type_1"

// With implicit width
custom_field CustomType2 "custom_type_2"

This is how the rust generator currently handles both:

1. In the case of fixed width types, the generator produces a struct type with backing integer of the smallest fitting size: pub struct CustomType1(u32);

2. In the case of variable width types, the generator 'assumes' the presence of the type CustomField2 in context, with the following trait derivation: impl pdl_runtime::Packet for CustomField2.

On both cases the string is ignored. Very sketchy, but that's we have for lack of better solution until we add something to specify the external type for various output languages.

For your specific situation, what you might do is this:

1. Declare the floating point type as a custom field with fixed width custom_field Float32 : 32 "float32"
2. Implement a conversion operator to extract the value as f32: impl TryInto<f32> for Float32

[gbonnefille]

I had success with

    impl From<f32> for Float32 {
        fn from(value: f32) -> Self {
            let store = value.to_bits();
            CCSDS_Float(store)
        }
    }

    impl Into<f32> for Float32 {
        fn into(self) -> f32 {
            f32::from_bits(self.0)
        }
    }