40 lines
1.2 KiB
Rust
40 lines
1.2 KiB
Rust
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// © 2023 John Breaux
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//! A [JumpTarget] contains the [pc-relative offset](Number) or [Identifier]
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//! for a [Jump instruction encoding](Encoding::Jump)
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use super::*;
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/// The target of a [Jump](Encoding::Jump)
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
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pub struct JumpTarget(Number);
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impl JumpTarget {
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pub fn word(&self) -> u16 { u16::from(self.0) & 0x3ff }
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}
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impl Parsable for JumpTarget {
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/// - Identifier
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/// - Number
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/// - Negative
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/// - Number
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fn parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Self, Error>
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where T: crate::TokenStream<'text> {
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// Try to parse a number
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let target = Number::parse(p, stream)?;
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match target.into() {
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i if i % 2 != 0 => Err(Error::JumpedOdd(i).context(stream.context()))?,
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i if (-1024..=1022).contains(&(i - 2)) => Ok(Self((target - 2) >> 1)),
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i => Err(Error::JumpedTooFar(i).context(stream.context()))?,
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}
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}
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}
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impl From<JumpTarget> for u16 {
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fn from(value: JumpTarget) -> Self { value.0.into() }
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}
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impl Display for JumpTarget {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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write!(f, "{}", (1 + isize::from(self.0)) << 1)
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}
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}
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