The functions `into_{signed,positive,negative}` used to be implemented
on the `FormattedValue` trait for convenience. This was wrong for the
following reasons:
- They aren't specific to `FormattedValue`s: they can also be
implemented for regular unsigned integers such as `u64`, `usize` or
`u32`.
- They were implemented for `format::Undefined` and all variants of
`GenericFormattedValue`, some of which are already signed.
This commit introduces the new trait `UnsignedIntoSigned`, which makes
it possible to fix both of the above problems.
Users can build a `Signed` from an `Undefined`, an `i64`, `isize` or
`i32` thanks to the `From` trait implementations.
The trait FormattedValue was only implemented on types which
could implement the full range of values for a Format. In order
to declare a function which could take both the intrinsic type
of any Format (e.g. `ClockTime`) as well the full range of values
(e.g. `Option<ClockTime>`), the argument was declared:
```rust
impl Into<GenericFormattedValue>,
```
This commit implements `FormattedValue` for any type representing
a format. E.g.: both `ClockTime` and `Option<ClockTime>` will now
implement `FormattedValue`. The trait `FormattedValueFullRange`
is implemented on types which can be built from any raw value.
These changes are intended to help for the implementation of a
means to enforce format conformity at compilation time for
functions with multiple formatted value arguments.
The following signatures were found to be incorrect and are fixed:
- `message::StepDone`: forced the type for `amount` and `duration`
to be of the same type, when `duration` is expected to be of the
`Time` format.
- `query::Convert::set`: the two arguments were forced to the same
type, so potentialy the same format, unless a
`GenericFormattedValue` was used.
See https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1059
They can actually be shared with multiple threads at the same time
safely as all functions requiring an immutable reference are
thread-safe.
OTOH TypeFind can't be shared safely between different threads as not
all implementations of the TypeFind struct are thread-safe.
FormatValue is now renamed to GenericFormattedValue and the API slightly
changed. In addition there is now a FormattedValue trait, and a
SpecificFormattedValue trait plus types for Bytes, Buffers and the
existing ClockTime.
This allows to create functions like
Pad::query_duration<F: SpecificFormattedValue>() -> Option<F>
and doesn't require the caller to unwrap the generic value anymore,
which is completely unneeded in these cases.
In addition, Segment became FormattedSegment<T> with API to
upcast/downcast between the specific formatted values and the generic
formatted value. This greatly simplifies usage of Segments.
