65 lines
2.0 KiB
Rust
65 lines
2.0 KiB
Rust
#![doc(hidden)]
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//! A horrifying hack to Serde-serialize [IOValue] instances to Preserves *as themselves*.
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//!
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//! Frankly I think this portion of the codebase might not survive for long. I can't think of a
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//! better way of achieving this, but the drawbacks of having this functionality are *severe*.
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//!
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//! See <https://gitlab.com/preserves/preserves/-/issues/42>.
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use super::repr::IOValue;
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pub static MAGIC: &str = "$____Preserves_Serde_Magic";
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struct IOValueVisitor;
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impl<'de> serde::de::Visitor<'de> for IOValueVisitor {
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type Value = IOValue;
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fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
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write!(formatter, "a magic encoding of an embedded Preserves Value")
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}
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fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
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where
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E: serde::de::Error,
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{
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let b = unsafe { Box::from_raw(v as *mut IOValue) };
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Ok(*b)
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}
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}
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#[inline(always)]
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pub fn output_value<S: serde::Serializer>(serializer: S, v: IOValue) -> Result<S::Ok, S::Error> {
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serializer.serialize_newtype_struct(MAGIC, &(Box::into_raw(Box::new(v)) as u64))
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}
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#[inline(always)]
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pub fn input_value<'de, D: serde::Deserializer<'de>>(deserializer: D) -> Result<IOValue, D::Error> {
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deserializer.deserialize_newtype_struct(MAGIC, IOValueVisitor)
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}
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//---------------------------------------------------------------------------
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#[inline]
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pub fn receive_output_value<T: ?Sized>(name: &'static str, magic_value: &T) -> Option<IOValue> {
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if name == MAGIC {
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let b =
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unsafe { Box::from_raw(*((magic_value as *const T) as *const u64) as *mut IOValue) };
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let v: IOValue = *b;
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Some(v)
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} else {
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None
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}
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}
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#[inline]
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pub fn transmit_input_value<F>(name: &'static str, f: F) -> Result<Option<u64>, crate::error::Error>
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where
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F: FnOnce() -> Result<IOValue, crate::error::Error>,
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{
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if name == MAGIC {
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let b: Box<IOValue> = Box::new(f()?);
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Ok(Some(Box::into_raw(b) as u64))
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} else {
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Ok(None)
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}
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}
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