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|
use crate::*;
use std::collections::HashMap;
pub fn parse_bytecode(tokens: Vec<Tracked<IntermediateToken>>, width: Option<u32>) -> Result<Vec<Segment>, Vec<Tracked<BytecodeError>>> {
BytecodeParser::new(width).parse(tokens)
}
pub struct BytecodeParser {
width: Option<u32>,
addresses: HashMap<String, Tracked<usize>>,
address: usize,
segment_address: usize,
segment_source: Option<SourceSpan>,
segments: Vec<Segment>,
words: Vec<Tracked<Word>>,
errors: Vec<Tracked<BytecodeError>>,
}
impl BytecodeParser {
pub fn new(width: Option<u32>) -> Self {
Self {
width,
addresses: HashMap::new(),
address: 0,
segment_address: 0,
segment_source: None,
segments: Vec::new(),
words: Vec::new(),
errors: Vec::new(),
}
}
pub fn parse(mut self, tokens: Vec<Tracked<IntermediateToken>>) -> Result<Vec<Segment>, Vec<Tracked<BytecodeError>>> {
// Calculate all label addresses ahead of time.
let mut address = 0;
for token in &tokens {
let source = &token.source;
match &token.value {
IntermediateToken::LabelDefinition(name) => {
let tracked = Tracked::from(address, source.clone());
if let Some(_) = self.addresses.insert(name.clone(), tracked) {
unreachable!("Uncaught duplicate label definition '{name}'");
}
}
IntermediateToken::Word(_) => {
address += 1;
}
IntermediateToken::PinnedAddress(pinned) => {
address = pinned.value;
}
}
}
for token in &tokens {
let source = &token.source;
match &token.value {
IntermediateToken::Word(word) => {
let word = self.evaluate_word(word, source);
// Check that the word width fits the provided width.
if let Some(width) = self.width {
if word.width != width {
let error = BytecodeError::IncorrectWidth(width, word.width);
self.errors.push(Tracked::from(error, source.clone()));
}
}
self.words.push(word);
self.address += 1;
}
IntermediateToken::PinnedAddress(address) => {
let current = self.address;
let pinned = address.value;
if current > pinned {
let error = BytecodeError::PinnedAddressBacktrack(pinned, current);
self.errors.push(Tracked::from(error, address.source.clone()));
} else {
let words = std::mem::take(&mut self.words);
if !words.is_empty() {
let address = self.segment_address;
let source = std::mem::take(&mut self.segment_source);
let segment = Segment { address, source, words };
self.segments.push(segment);
}
self.segment_source = Some(address.source.clone());
self.address = pinned;
self.segment_address = pinned;
}
}
IntermediateToken::LabelDefinition(_) => (),
}
}
// Finish final segment.
let words = std::mem::take(&mut self.words);
if !words.is_empty() {
let address = self.segment_address;
let source = std::mem::take(&mut self.segment_source);
let segment = Segment { address, source, words };
self.segments.push(segment);
}
match self.errors.is_empty() {
true => Ok(self.segments),
false => Err(self.errors),
}
}
fn evaluate_expression(&mut self, expression: &IntermediateExpression, source: &SourceSpan) -> isize {
let mut stack = ExpressionStack::new();
for token in &expression.tokens {
let source = &token.source;
match &token.value {
IntermediateExpressionToken::Integer(integer) => match integer {
IntermediateInteger::Integer(value) => {
stack.push(*value);
}
IntermediateInteger::Expression(expression) => {
stack.push(self.evaluate_expression(expression, source));
}
IntermediateInteger::LabelReference(name) => {
stack.push(self.evaluate_label_reference(name));
}
}
IntermediateExpressionToken::Operator(operator) => {
if let Err(err) = stack.apply(*operator, source) {
let error = BytecodeError::StackError(err);
self.errors.push(Tracked::from(error, source.clone()))
}
}
}
}
match stack.pull_result() {
Ok(value) => value,
Err(err) => {
let error = BytecodeError::StackError(Tracked::from(err, source.clone()));
self.errors.push(Tracked::from(error, source.clone()));
0
}
}
}
fn evaluate_label_reference(&mut self, name: &Tracked<String>) -> isize {
if let Some(address) = self.addresses.get(&name.to_string()) {
address.value as isize
} else {
unreachable!("Uncaught unresolved label reference '{name}'")
}
}
fn evaluate_word(&mut self, word: &IntermediateWord, source: &SourceSpan) -> Tracked<Word> {
let mut word_value = word.value;
for field in &word.fields {
let field_source = &field.value.value.source;
let field_value = match &field.value.value.value {
IntermediateInteger::Expression(expression) => {
self.evaluate_expression(expression, source)
}
IntermediateInteger::LabelReference(name) => {
self.evaluate_label_reference(name)
}
IntermediateInteger::Integer(value) => {
*value
}
};
let value_width = match field_value.cmp(&0) {
std::cmp::Ordering::Less => (-field_value).ilog2() + 1,
std::cmp::Ordering::Equal => 0,
std::cmp::Ordering::Greater => field_value.ilog2() + 1,
};
if field.width < value_width {
let error = BytecodeError::ValueTooWide(field.width, value_width);
self.errors.push(Tracked::from(error, field_source.clone()));
} else {
let mask = 2_usize.pow(field.width as u32) - 1;
let clamped_value = (field_value as usize) & mask;
word_value |= (clamped_value << field.shift) as usize;
}
}
let word = Word { width: word.width, value: word_value };
return Tracked::from(word, source.clone());
}
}
|
