preprocess: add preprocessor module with include resolver

.idea/src.iml

@@ -2,6 +2,7 @@
 <module type="CPP_MODULE" version="4">
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/librashader-preprocess/src" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/librashader-presets/src" isTestSource="false" />
       <excludeFolder url="file://$MODULE_DIR$/target" />
     </content>

Cargo.lock

@@ -8,6 +8,14 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2c676a478f63e9fa2dd5368a42f28bba0d6c560b775f38583c8bbaa7fcd67c9c"
 
+[[package]]
+name = "librashader-preprocess"
+version = "0.1.0"
+dependencies = [
+ "librashader-presets",
+ "thiserror",
+]
+
 [[package]]
 name = "librashader-presets"
 version = "0.1.0"

Cargo.toml

@@ -1,4 +1,5 @@
 [workspace]
 members = [
-    "librashader-presets"
+    "librashader-presets",
+    "librashader-preprocess"
 ]

librashader-preprocess/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "librashader-preprocess"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+thiserror = "1.0.37"
+librashader-presets = { path = "../librashader-presets" }

librashader-preprocess/src/error.rs

@@ -0,0 +1,14 @@
+use std::path::PathBuf;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum PreprocessError {
+    #[error("the version header was missing")]
+    MissingVersionHeader,
+    #[error("the file was not found during resolution")]
+    IOError(PathBuf, std::io::Error),
+    #[error("unexpected end of file")]
+    UnexpectedEof,
+    #[error("unexpected end of line")]
+    UnexpectedEol(usize),
+}

librashader-preprocess/src/include.rs

@@ -0,0 +1,90 @@
+use std::fs::File;
+use std::io::Read;
+use std::str::Lines;
+use std::path::Path;
+use crate::PreprocessError;
+
+const GL_GOOGLE_CPP_STYLE_LINE_DIRECTIVE: &'static str = "#extension GL_GOOGLE_CPP_STYLE_LINE_DIRECTIVE : require";
+
+trait PushLine {
+    fn push_line(&mut self, str: &str);
+}
+
+impl PushLine for String {
+    fn push_line(&mut self, str: &str) {
+        self.push_str(str);
+        self.push('\n');
+    }
+}
+
+fn read_file(path: impl AsRef<Path>) -> Result<String, PreprocessError> {
+    let path = path.as_ref();
+    let mut source = String::new();
+    File::open(path).and_then(|mut f| f.read_to_string(&mut source))
+        .map_err(|e| PreprocessError::IOError(path.to_path_buf(), e))?;
+    Ok(source)
+}
+
+pub fn read_source(path: impl AsRef<Path>) -> Result<String, PreprocessError> {
+    let path = path.as_ref();
+    let source = read_file(path)?;
+    let mut output = String::new();
+
+    let source = source.trim();
+    let mut lines = source.lines();
+
+    if let Some(header) = lines.next() {
+        if !header.starts_with("#version ") {
+            return Err(PreprocessError::MissingVersionHeader)
+        }
+        output.push_line(header);
+    } else {
+        return Err(PreprocessError::UnexpectedEof)
+    }
+
+    output.push_line(GL_GOOGLE_CPP_STYLE_LINE_DIRECTIVE);
+    mark_line(2, path.file_name().and_then(|f| f.to_str()).unwrap_or(""), &mut output);
+    preprocess(lines, path, &mut output)?;
+
+    Ok(output)
+}
+
+fn mark_line(line_no: usize, comment: &str, output: &mut String) {
+    output.push_line(&format!("#line {} \"{}\"", line_no, comment))
+}
+
+fn preprocess(lines: Lines, file_name: impl AsRef<Path>, output: &mut String) -> Result<(), PreprocessError> {
+    let file_name = file_name.as_ref();
+    let include_path = file_name.parent().unwrap();
+    let file_name = file_name.file_name().and_then(|f| f.to_str()).unwrap_or("");
+
+    for (line_no, line) in lines.enumerate() {
+        if line.starts_with("#include ") {
+            let include_file = line["#include ".len()..].trim().trim_matches('"');
+            if include_file.is_empty() {
+                return Err(PreprocessError::UnexpectedEol(line_no))
+            }
+
+            let mut include_path = include_path.to_path_buf();
+            include_path.push(include_file);
+
+            let source = read_file(&include_path)?;
+            let source = source.trim();
+            let lines = source.lines();
+
+            let include_file = include_path.file_name().and_then(|f| f.to_str()).unwrap_or("");
+            mark_line(1, include_file, output);
+            preprocess(lines, include_path, output)?;
+            mark_line(line_no + 1, file_name, output);
+            continue;
+        }
+        if line.starts_with("#endif") || line.starts_with("#pragma") {
+            output.push_line(line);
+            mark_line(line_no + 2, file_name, output);
+            continue;
+        }
+
+        output.push_line(line)
+    }
+    Ok(())
+}

librashader-preprocess/src/lib.rs

@@ -0,0 +1,15 @@
+mod error;
+mod include;
+
+pub use error::*;
+
+
+#[cfg(test)]
+mod test {
+    use crate::include::read_source;
+    #[test]
+    pub fn preprocess_file() {
+        let result = read_source("../test/slang-shaders/blurs/shaders/royale/blur3x3-last-pass.slang").unwrap();
+        eprintln!("{result}")
+    }
+}