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https://github.com/italicsjenga/vello.git
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WGSL: Allow imports anywhere (#196)
This means we support imports not at the start of a line.
This commit is contained in:
Daniel McNab
GitHub
parent
3831b58dea
commit
1b84071d33
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@ -41,25 +41,44 @@ pub fn preprocess(
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) -> String {
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let mut output = String::with_capacity(input.len());
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let mut stack = vec![];
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'all_lines: for (line_number, mut line) in input.lines().enumerate() {
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loop {
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if line.is_empty() {
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break;
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}
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let hash_index = line.find('#');
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let comment_index = line.find("//");
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let hash_index = match (hash_index, comment_index) {
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(Some(hash_index), None) => hash_index,
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(Some(hash_index), Some(comment_index)) if hash_index < comment_index => hash_index,
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// Add this line to the output - all directives are commented out or there are no directives
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_ => break,
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};
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let directive_start = &line[hash_index + '#'.len_utf8()..];
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let directive_len = directive_start
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// The first character which can't be part of the directive name marks the end of the directive
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// In practise this should always be whitespace, but in theory a 'unit' directive
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// could be added
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.find(|c: char| !c.is_alphanumeric())
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.unwrap_or(directive_start.len());
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let directive = &directive_start[..directive_len];
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let directive_is_at_start = line.trim_start().starts_with('#');
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for (line_number, line) in input.lines().enumerate() {
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let trimmed = line.trim();
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if trimmed.starts_with("#") {
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let trimmed = &trimmed[1..];
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let val_idx = trimmed
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.chars()
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.take_while(|char| char.is_alphanumeric())
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.map(char::len_utf8)
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.sum();
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let arg = trimmed[val_idx..].trim();
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match &trimmed[..val_idx] {
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x @ ("ifdef" | "ifndef") => {
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let exists = defines.contains(arg);
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let mode = x == "ifdef";
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match directive {
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if_item @ ("ifdef" | "ifndef" | "else" | "endif") if !directive_is_at_start => {
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eprintln!("#{if_item} directives must be the first non_whitespace items on their line, ignoring (line {line_number})");
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break;
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}
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def_test @ ("ifdef" | "ifndef") => {
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let def = directive_start[directive_len..].trim();
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let exists = defines.contains(def);
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let mode = def_test == "ifdef";
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stack.push(StackItem {
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active: mode == exists,
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else_passed: false,
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});
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// Don't add this line to the output; instead process the next line
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continue 'all_lines;
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}
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"else" => {
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let item = stack.last_mut();
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@ -71,29 +90,62 @@ pub fn preprocess(
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item.active = !item.active;
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}
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}
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let remainder = directive_start[directive_len..].trim();
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if !remainder.is_empty() {
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eprintln!("#else directives don't take an argument. `{remainder}` will not be in output (line {line_number})");
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}
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// Don't add this line to the output; it should be empty (see warning above)
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continue 'all_lines;
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}
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"endif" => {
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if let None = stack.pop() {
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eprintln!("Mismatched endif (line {line_number})");
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}
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let remainder = directive_start[directive_len..].trim();
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if !remainder.is_empty() {
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eprintln!("#endif directives don't take an argument. `{remainder}` will not be in output (line {line_number})");
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}
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// Don't add this line to the output; it should be empty (see warning above)
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continue 'all_lines;
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}
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"import" => {
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let import = imports.get(arg);
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if let Some(import) = import {
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output.push_str(&preprocess(import, defines, imports));
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output.push_str(&line[..hash_index]);
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let directive_end = &directive_start[directive_len..];
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let import_name_start = if let Some(import_name_start) =
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directive_end.find(|c: char| !c.is_whitespace())
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{
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import_name_start
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} else {
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eprintln!("Unkown import `{arg}` (line {line_number})");
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eprintln!("#import needs a non_whitespace argument (line {line_number})");
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continue 'all_lines;
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};
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let import_name_start = &directive_end[import_name_start..];
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let import_name_end_index = import_name_start
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// The first character which can't be part of the import name marks the end of the import
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.find(|c: char| !(c == '_' || c.is_alphanumeric()))
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.unwrap_or(import_name_start.len());
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let import_name = &import_name_start[..import_name_end_index];
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line = &import_name_start[import_name_end_index..];
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let import = imports.get(import_name);
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if let Some(import) = import {
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// In theory, we can cache this until the top item of the stack changes
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// However, in practise there will only ever be at most 2 stack items, so it's reasonable to just recompute it every time
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if stack.iter().all(|item| item.active) {
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output.push_str(&preprocess(import, defines, imports));
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}
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} else {
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eprintln!("Unknown import `{import_name}` (line {line_number})");
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}
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continue;
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}
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val => {
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eprintln!("Unknown preprocessor directive `{val}` (line {line_number})")
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eprintln!("Unknown preprocessor directive `{val}` (line {line_number})");
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}
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}
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} else {
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if stack.last().map(|x| x.active).unwrap_or(true) {
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output.push_str(line);
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output.push('\n');
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}
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}
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if stack.iter().all(|item| item.active) {
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output.push_str(line);
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output.push('\n');
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}
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}
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output
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