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use crate::{
containers::{Ptr, SharedList},
Token,
};
/// Enum of what token rewriter should do with a token.
#[derive(Debug)]
#[repr(C)]
pub enum RewriteAction {
/// Means "drop the token", i.e. don't return it to a parser
Drop,
/// Means "keep the token", i.e. return it to a parser
Keep,
}
/// Enum of what token rewriter should do with the state of the lexer
#[derive(Debug)]
#[repr(C)]
pub enum LexStateAction {
/// Means "set the state to X"
Set(i32),
/// Means "keep the state unchanged"
Keep,
}
/// Output of the token rewriter
#[derive(Debug)]
#[repr(C)]
pub struct TokenRewriterResult {
/// Rewritten token. Can be input token if no rewriting expected
pub rewritten_token: Ptr<Token>,
/// Action to be applied on a token (keep or drop)
pub token_action: RewriteAction,
/// Action to be applied on lexer's state (keep as is or change)
pub lex_state_action: LexStateAction,
}
/// Token rewriter function
pub type TokenRewriterFn = dyn Fn(Ptr<Token>, SharedList<u8>) -> TokenRewriterResult;
/// Token rewriter struct, can be used to rewrite tokens on the fly
pub struct TokenRewriter {
f: Option<Box<TokenRewriterFn>>,
}
impl TokenRewriter {
/// Constructs a rewriter based on a given function
pub fn new(f: Box<TokenRewriterFn>) -> Self {
Self { f: Some(f) }
}
/// Constructs a no-op token rewriter that has no side effect. Default value.
pub fn none() -> Self {
Self { f: None }
}
/// Returns an optional reference to a function that rewrite tokens
pub fn as_option(&self) -> Option<&TokenRewriterFn> {
if let Some(f) = &self.f {
Some(&**f)
} else {
None
}
}
}
impl std::fmt::Debug for TokenRewriter {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("TokenRewriter")
.field("f", &self.as_option().map(|_| "function"))
.finish()
}
}