From d74e79de9538329eafee46e13175c01cc68bd73d Mon Sep 17 00:00:00 2001
From: pjht <pterpstra@pterpstra.com>
Date: Tue, 19 Mar 2024 09:23:37 -0500
Subject: [PATCH] Initial commit

---
 Tupfile         |  6 ++++++
 initrd_maker.rs | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 Tupfile
 create mode 100644 initrd_maker.rs

diff --git a/Tupfile b/Tupfile
new file mode 100644
index 0000000..8a8058f
--- /dev/null
+++ b/Tupfile
@@ -0,0 +1,6 @@
+.gitignore
+
+export RUSTUP_HOME
+RUSTC_FLAGS = -C debuginfo=0 -C opt-level=3 --edition 2021 
+
+: initrd_maker.rs |> rustc $(RUSTC_FLAGS) -o %o %f |> %B
diff --git a/initrd_maker.rs b/initrd_maker.rs
new file mode 100644
index 0000000..bd3b1cc
--- /dev/null
+++ b/initrd_maker.rs
@@ -0,0 +1,50 @@
+use std::{
+    env::args,
+    fs::File,
+    io::{self, Write},
+    path::Path,
+};
+
+const BLOCK_SIZE: u32 = 512;
+const MAX_NAME_LEN: u32 = BLOCK_SIZE - 4 - 4 - 2 - 1;
+
+fn main() {
+    let mut archive = File::create("initrd").expect("Could not open initrd");
+    for file_path in args().skip(1) {
+        let file_path = Path::new(&file_path);
+        let file_name = file_path.file_name().unwrap();
+        let file_name_len = u32::try_from(file_name.len()).unwrap();
+        assert!(
+            file_name_len <= MAX_NAME_LEN,
+            "File {:?} has name longer than {} bytes",
+            file_name,
+            MAX_NAME_LEN
+        );
+        let mut file = File::open(file_path).expect("File did not exist");
+        let length = u32::try_from(file.metadata().expect("Could not get file metadata").len())
+            .expect("File size greater than 4 GiB");
+        let file_num_blocks = (length / BLOCK_SIZE) + if length % BLOCK_SIZE == 0 { 0 } else { 1 };
+        let mut header_block = Vec::new();
+        header_block.extend_from_slice(&length.to_be_bytes());
+        header_block.extend_from_slice(&file_num_blocks.to_be_bytes());
+        header_block.extend_from_slice(&file_name_len.to_be_bytes());
+        header_block.extend_from_slice(file_name.to_str().unwrap().as_bytes());
+        header_block.push(0);
+        header_block.resize(BLOCK_SIZE as usize, 0);
+        archive
+            .write_all(&header_block)
+            .expect("Could not write to initrd");
+        #[allow(clippy::cast_possible_truncation)]
+        let bytes_written = io::copy(&mut file, &mut archive)
+            .expect("Could not read from file/write to initrd") as u32;
+        if (bytes_written % BLOCK_SIZE) != 0 {
+            let bytes_padding = (BLOCK_SIZE) - (bytes_written % BLOCK_SIZE);
+            archive
+                .write_all(&vec![0; bytes_padding as usize])
+                .expect("Could not write to initrd");
+        }
+    }
+    archive
+        .write_all(&[0; BLOCK_SIZE as usize])
+        .expect("Could not write to initrd");
+}