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|
use std::collections::HashMap;
use super::{
Result,
lexer::{Token, TokenKind},
util::{SpanParserError, TokenError},
};
use TokenKind as K;
#[derive(Clone, Debug)]
struct Macro<'s> {
contents: Vec<Token<'s>>,
args: Vec<(usize, usize)>,
num_args: usize,
}
struct PreProcessor<'s> {
idx: usize,
tokens: Vec<Token<'s>>,
macros: HashMap<&'s str, Macro<'s>>,
}
impl<'s> PreProcessor<'s> {
fn new(tokens: Vec<Token<'s>>) -> Self {
let macros = HashMap::new();
Self {
idx: 0,
tokens,
macros,
}
}
fn next(&mut self) -> Token<'s> {
if self.idx >= self.tokens.len() {
Token {
span: self.tokens[self.idx - 1].span,
content: "",
kind: K::Eof,
}
} else {
self.idx += 1;
self.tokens[self.idx - 1]
}
}
fn expect(&mut self, kind: TokenKind) -> Result<Token<'s>> {
let token = self.next();
if token.kind == kind {
Ok(token)
} else {
token.token_err(format!("expected {kind}, got {}", token.kind))
}
}
fn parse_int(&mut self) -> Result<usize> {
let token = self.expect(K::Integer)?;
token.content.parse().span_err(token.span)
}
fn read_macro(&mut self) -> Result<Macro<'s>> {
let mut nest_counter = 0;
let mut contents = vec![];
let mut args = vec![];
let mut num_args = 0;
loop {
let token = self.next();
match token.kind {
K::Argument => {
let num = self.parse_int()?;
args.push((num, contents.len()));
num_args = num_args.max(num);
}
K::MacroDefine => {
nest_counter += 1;
contents.push(token);
}
K::MacroEnd => {
if nest_counter > 0 {
nest_counter -= 1;
contents.push(token);
} else {
break;
}
}
K::Eof => return token.token_err("macro definition was not closed"),
_ => contents.push(token),
}
}
args.sort_by(|(_, l), (_, r)| l.cmp(r).reverse());
Ok(Macro {
contents,
args,
num_args,
})
}
fn read_macros(&mut self) -> Result<Vec<Token<'s>>> {
let mut buffer = vec![];
self.idx = 0;
loop {
let token = self.next();
if token.kind == K::Eof {
break;
}
if token.kind != K::MacroDefine {
buffer.push(token);
continue;
}
let name = self.expect(K::Identifier)?.content;
let content = self.read_macro()?;
self.macros.insert(name, content);
}
Ok(buffer)
}
fn pass(&mut self) -> Result<Vec<Token<'s>>> {
let mut buffer = self.read_macros()?;
let mut idx = 0;
loop {
if idx >= buffer.len() {
break;
}
let token = buffer[idx];
if token.kind != K::Identifier {
idx += 1;
continue;
}
// TODO: remove clone
let Some(mac) = self.macros.get(token.content).cloned() else {
idx += 1;
continue;
};
let mut args = vec![];
for n in 1..=mac.num_args {
let arg = buffer[idx + n];
if matches!(arg.kind, K::Eof | K::LineSeparator) {
return arg.token_err("missing macro argument");
}
args.push(arg);
}
let mut content = mac.contents;
for (n, idx) in mac.args {
// this works since mac.args is stored by idx descending
content.insert(idx, args[n - 1]);
}
let len = content.len();
buffer.splice(idx..=(idx + mac.num_args), content);
idx += len + 1;
}
Ok(buffer)
}
fn process(&mut self) -> Result<Vec<Token<'s>>> {
loop {
let result = self.pass()?;
if self.tokens == result {
return Ok(result);
}
self.tokens = result;
}
}
}
pub fn process(tokens: Vec<Token<'_>>) -> Result<Vec<Token<'_>>> {
PreProcessor::new(tokens).process()
}
|
