2 files changed, 67 insertions, 0 deletions
diff --git a/crates/readrom/Cargo.toml b/crates/readrom/Cargo.toml
new file mode 100644
index 0000000..98a5106
--- /dev/null
+++ b/crates/readrom/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "readrom"
+version = "1.0.0"
+rust-version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[dependencies]
+anyhow = "^1"
+clap = { version = "^4", features = ["derive"] }
+header.workspace = true
diff --git a/crates/readrom/src/main.rs b/crates/readrom/src/main.rs
new file mode 100644
index 0000000..56e60e0
--- /dev/null
+++ b/crates/readrom/src/main.rs
@@ -0,0 +1,55 @@
+use anyhow::{bail, Result};
+use clap::Parser as ClapParser;
+use header::{Header, Kind};
+use std::fs::File;
+use std::io::{ErrorKind, Read};
+
+/// Display information about NES/Famicom ROM files.
+#[derive(ClapParser, Debug)]
+#[command(version, about, long_about = None)]
+struct Args {
+    /// NES/Famicom ROM file from which to display information.
+    file: String,
+}
+
+fn print_header(header: &Header) {
+    println!("Header:");
+
+    match header.kind {
+        Kind::INes => println!("  Kind:\t\tiNES"),
+        Kind::Nes20 => println!("  Kind:\t\tNES 2.0"),
+    }
+
+    println!(
+        "  PRG ROM size:\t{} bytes ({}KB)",
+        header.prg_rom_size * 16 * 1024,
+        header.prg_rom_size * 16
+    );
+    println!(
+        "  CHR ROM size:\t{} bytes ({}KB)",
+        header.chr_rom_size * 8 * 1024,
+        header.chr_rom_size * 8
+    );
+    println!("  Mapper:\t{}", header.mapper);
+}
+
+fn main() -> Result<()> {
+    let args = Args::parse();
+    let mut input = File::open(args.file)?;
+
+    let mut buf = vec![0u8; 0x10];
+    if let Err(e) = input.read_exact(&mut buf) {
+        match e.kind() {
+            ErrorKind::UnexpectedEof => bail!("malformed ROM file."),
+            _ => return Err(e.into()),
+        }
+    }
+
+    let header = match Header::try_from(buf.as_slice()) {
+        Ok(h) => h,
+        Err(e) => bail!("{}.", e),
+    };
+    print_header(&header);
+
+    Ok(())
+}