Replace lower_into_buffer and try_lift_from_buffer with a trait #972
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bendk
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rfk
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Jun 23, 2021
uniffi/src/lib.rs
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| } | ||
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| fn try_read(buf: &mut &[u8]) -> Result<Self> { | ||
| T::try_read(buf) |
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Stylistically, you're using all three of T::method, ViaFfi::method and <T as ViaFfi>::method in calls here, it may be worth consolidating to a single one for consistency. (I personally like RustBufferViaFfi::method as the most explicit option, but don't feel strongly about the details).
rfk
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Jun 23, 2021
| /// For complex types were it's too fiddly or too unsafe to convert them into a special-purpose | ||
| /// C-compatible value, you can use this helper function to implement `lower()` in terms of `write()` | ||
| /// and pass the value as a serialized buffer of bytes. | ||
| pub fn lower_into_buffer<T: ViaFfi>(value: T) -> RustBuffer { |
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I guess technically this is a breaking change, swapping some pub functions for a pub trait, and as such should be called out in the changelog.
mhammond
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Jun 24, 2021
uniffi/src/lib.rs
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| @@ -364,6 +338,44 @@ unsafe impl ViaFfi for String { | |||
| } | |||
| } | |||
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| /// A helper trait to implement lowering/lifting using a `RustBuffer` | |||
| /// | |||
| /// For complex types were it's too fiddly or too unsafe to convert them into a special-purpose | |||
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typo - "where" (that typo already existed :)
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The main motivation is to eliminate the possibility of calling
`try_lift_from_buffer()` on a `RustBuffer` that wasn't created with
`lower_into_buffer()`. For example, this code seems reasonable, but it
totally fails:
```
let buf: RustBuffer = ViaFfi::lower("Test".to_string());
assert_eq!(try_lift_from_buffer::<String>(buf).unwrap(), "Test")
```
This is because Strings have an asymmetry between `lower()` and
`write()`. `write()` needs to write out the string length, but
`lower()` can optimize to avoid that and just use `RustBuffer.len`.
It also reduces some boilerplate code, which is nice too.
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I'm not totally sure about this one, but it seems like it could be an improvement. What do you all think?
The main motivation is to eliminate the possibility of calling
try_lift_from_buffer()on aRustBufferthat wasn't created withlower_into_buffer(). For example, this code seems reasonable, but ittotally fails:
This is because Strings have an asymmetry between
lower()andwrite().write()needs to write out the string length, butlower()can optimize to avoid that and just useRustBuffer.len.It also reduces some boilerplate code, which is nice too.