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Support u128/i128 in runtime interface
#4703
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This implements support for `u128`/`i128` as parameters/return value in runtime interfaces. As we can not pass them as identity, as for the other primitives types, we pass them as an pointer to an `[u8; 16]` array.
pepyakin
suggested changes
Jan 21, 2020
| let data = context.read_memory(Pointer::new(arg), 16)?; | ||
| let mut res = [0u8; 16]; | ||
| res.copy_from_slice(&data); | ||
| Ok(unsafe { mem::transmute::<[u8; 16], $type>(res) }) |
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- I wonder if this is safe? The alignment of u128 might be 16 and I am not sure sure if we can say anything regarding this about
res. - Does it assume that wasm and host have the same endianness?
I think this can be swapped with u128::from_le_bytes here instead of transmute?
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- What? Why can we not say the same about
res? It is as well 16 bytes. (Looking at the rust source code forfrom_le_bytesit does exactly the same transmute) - Yes it assumes it. Please don't start again this xD As it is no primitive type, I probably also need to call
to_le_byteson the host?
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But good catches! I searched yesterday evening for *_let_bytes, but failed for some reason 🤷♀️
pepyakin
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Jan 22, 2020
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This implements support for
u128/i128as parameters/return value inruntime interfaces. As we can not pass them as identity, as for the
other primitives types, we pass them as an pointer to an
[u8; 16]array.