1 files changed, 93 insertions, 0 deletions
diff --git a/src/load_program.rs b/src/load_program.rs
new file mode 100644
index 0000000..0473207
--- /dev/null
+++ b/src/load_program.rs
@@ -0,0 +1,93 @@
+use crate::*;
+
+use std::io::Read;
+
+
+pub struct Program {
+    pub bytecode: Vec<u8>,
+    pub path: Option<PathBuf>,
+}
+
+impl Program {
+    fn path(&self) -> String {
+        match &self.path {
+            Some(path) => path.as_os_str().to_string_lossy().to_string(),
+            None => String::from("<unknown>"),
+        }
+    }
+}
+
+
+/// Load program from path or standard input.
+pub fn load_program(path: Option<&PathBuf>) -> Program {
+    if let Some(path) = path {
+        if let Ok(program) = load_program_from_file(path) {
+            let length = program.bytecode.len();
+            let path = program.path();
+            info!("Loaded program from {path:?} ({length} bytes)");
+            return program;
+        } else if let Some(program) = load_program_from_bedrock_path(path) {
+            let length = program.bytecode.len();
+            let path = program.path();
+            info!("Loaded program from {path:?} ({length} bytes)");
+            return program;
+        } else {
+            fatal!("Could not read program from {path:?}");
+        }
+    } else {
+        info!("Reading program from standard input...");
+        if let Ok(program) = load_program_from_stdin() {
+            let length = program.bytecode.len();
+            info!("Loaded program from standard input ({length} bytes)");
+            return program;
+        } else {
+            fatal!("Could not read program from standard input");
+        }
+    }
+}
+
+/// Attempt to load program from a directory in the BEDROCK_PATH environment variable.
+fn load_program_from_bedrock_path(path: &Path) -> Option<Program> {
+    // Only if the path can be treated as a file name.
+    if path.is_relative() && path.components().count() == 1 {
+        for base_path in std::env::var("BEDROCK_PATH").ok()?.split(':') {
+            let mut base_path = PathBuf::from(base_path);
+            if !base_path.is_absolute() { continue; }
+            base_path.push(path);
+            info!("Attempting to load program from {base_path:?}");
+            if let Ok(program) = load_program_from_file(&base_path) {
+                return Some(program);
+            }
+            if path.extension().is_some() { continue; }
+            base_path.set_extension("br");
+            info!("Attempting to load program from {base_path:?}");
+            if let Ok(program) = load_program_from_file(&base_path) {
+                return Some(program);
+            }
+        }
+    }
+    return None;
+}
+
+/// Attempt to load program from a specific file path.
+fn load_program_from_file(path: &Path) -> Result<Program, std::io::Error> {
+    // Canonicalize paths so that symbolic links to program files resolve to
+    // the real program directory, which could contain a symbols file.
+    let path = match path.canonicalize() {
+        Ok(canonical) => canonical,
+        Err(_) => path.to_path_buf(),
+    };
+    load_program_from_readable_source(std::fs::File::open(&path)?, Some(&path))
+}
+
+/// Attempt to load program from standard input.
+fn load_program_from_stdin() -> Result<Program, std::io::Error> {
+    load_program_from_readable_source(std::io::stdin(), None)
+}
+
+/// Attempt to load program from a source that implements std::io::Read.
+fn load_program_from_readable_source(source: impl Read, path: Option<&Path>) -> Result<Program, std::io::Error> {
+    let mut bytecode = Vec::<u8>::new();
+    source.take(65536).read_to_end(&mut bytecode)?;
+    return Ok(Program { bytecode, path: path.map(|p| p.to_path_buf()) });
+}