77 lines
2.2 KiB
Rust
77 lines
2.2 KiB
Rust
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use std::{
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io::{Error, ErrorKind},
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marker::PhantomData,
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};
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use crate::HaskellSize;
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/*******************************************************************************
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Main class definition
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*******************************************************************************/
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const ERROR_NOT_ALL_BYTES_READ: &str = "Not all bytes read";
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pub trait FromHaskell<Tag>: Sized {
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/// Deserialize data sent from Haskell
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///
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/// This is the analogue of `BorshDeserialize::deserialize`.
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//
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/// See `ToHaskell` for a detailed discussion of the `tag` argument.
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fn from_haskell(buf: &mut &[u8], tag: PhantomData<Tag>) -> Result<Self, Error>;
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fn from_haskell_slice(slice: &[u8], tag: PhantomData<Tag>) -> Result<Self, Error> {
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let mut slice_mut = slice;
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let result = Self::from_haskell(&mut slice_mut, tag)?;
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if !slice_mut.is_empty() {
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return Err(Error::new(ErrorKind::InvalidData, ERROR_NOT_ALL_BYTES_READ));
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}
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Ok(result)
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}
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}
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/*******************************************************************************
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Derived functionality
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See comments in `to_haskell` for why these functions do not live inside the
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trait.
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*******************************************************************************/
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/// Marshall value with variable-sized encoding
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pub fn marshall_from_haskell_var<Tag, T>(inp: *const u8, len: usize, tag: PhantomData<Tag>) -> T
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where
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T: FromHaskell<Tag>,
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{
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let mut vec: Vec<u8> = vec![0; len];
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unsafe {
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std::ptr::copy(inp, vec.as_mut_ptr(), len);
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}
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match T::from_haskell_slice(vec.as_ref(), tag) {
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Ok(t) => t,
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Err(e) => panic!("{}", e),
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}
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}
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/// Marshall value with fixed-size encoding
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///
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/// The `len` argument here is only to verify that the Haskell-side and
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/// Rust-side agree on the size of the encoding.
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pub fn marshall_from_haskell_fixed<Tag, T>(
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inp: *const u8,
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inp_len: usize,
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tag: PhantomData<Tag>,
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) -> T
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where
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T: FromHaskell<Tag> + HaskellSize<Tag>,
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{
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let expected_len = T::haskell_size(tag);
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if inp_len != expected_len {
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panic!(
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"expected buffer of size {}, but got {}",
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expected_len, inp_len
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)
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} else {
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marshall_from_haskell_var(inp, inp_len, tag)
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}
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}
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