more refactoring

xtask/src/main.rs

@@ -0,0 +1,83 @@
+use std::{env, error::Error, fmt, path::{Path, PathBuf}, process::ExitCode};
+
+mod mkimg;
+
+fn main() -> ExitCode {
+    match xtask() {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(err) => {
+            eprintln!("{}", err);
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn xtask() -> Result<(), XtaskError> {
+    let mut args = env::args_os().skip(1);
+
+    let task = args
+        .next()
+        .ok_or_else(|| XtaskError::with_message("no task provided".to_owned()))?;
+
+    let task = task.to_str().ok_or_else(|| {
+        XtaskError::with_message(format!("invalid utf-8 \"{}\"", task.to_string_lossy()))
+    })?;
+
+    let manifest_dir = PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").ok_or_else(|| {
+        XtaskError::with_message("CARGO_MANIFEST_DIR not set".to_owned())
+    })?);
+
+    let workspace_dir = manifest_dir.parent().ok_or_else(|| {
+        XtaskError::with_message("invalid CARGO_MANIFEST_DIR".to_owned())
+    })?;
+
+    let ctx = Context {
+        workspace: workspace_dir,
+    };
+
+    match task {
+        "mkimg" => mkimg::mkimg_bios_gpt(ctx),
+        _ => Err(XtaskError::with_message(format!("unknown task \"{}\"", task))),
+    }
+}
+
+struct Context<'a> {
+    workspace: &'a Path,
+}
+
+#[derive(Debug)]
+struct XtaskError {
+    message: String,
+    parent: Option<Box<dyn Error>>,
+}
+
+impl XtaskError {
+    fn with_message(message: String) -> Self {
+        Self {
+            message,
+            parent: None,
+        }
+    }
+
+    fn wrap_with_message<E>(err: E, message: String) -> Self
+    where
+        E: Error + 'static,
+    {
+        Self {
+            message,
+            parent: Some(Box::new(err)),
+        }
+    }
+}
+
+impl fmt::Display for XtaskError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.message)?;
+        if let Some(parent) = &self.parent {
+            write!(f, ": {}", parent)?;
+        }
+        Ok(())
+    }
+}
+
+impl Error for XtaskError {}

xtask/src/mkimg.rs

@@ -0,0 +1,32 @@
+use crate::{Context, XtaskError};
+
+const BLOCK_SIZE: u64 = 512;
+const PARTITION_ENTRY_SIZE: u64 = 128;
+
+const ATTR_REQUIRED: u64 = 1 >> 0;
+const ATTR_NO_BLOCK_IO_PROTO: u64 = 1 >> 1;
+const ATTR_LEGACY_BIOS_BOOTABLE: u64 = 1 >> 2;
+
+// LBA 0: MBR
+// LBA 1: partition header
+// LBA 2..33: partition table entries
+// LBA 34..n: usable blocks
+// LBA -33..-2: partition table entries (dup)
+// LBA -1: partition header (dup)
+
+struct Partition {
+    type_guid: [u8; 16],
+    part_guid: [u8; 16],
+    lba_start: u64,
+    lba_end: u64,
+    attr: u64,
+    name: String,
+}
+
+
+
+pub fn mkimg_bios_gpt(ctx: Context) -> Result<(), XtaskError> {
+    println!("dir={}", ctx.workspace.to_string_lossy());
+
+    Ok(())
+}