From 407048d0037c8d6d26c7e3fe2384e974212f124e Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Wed, 18 Dec 2024 07:46:26 +0100
Subject: Add the readrom binary
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The readrom binary is similar to `readelf` from Linux and it will allow
to display information from an NES/Famicom ROM file. For now the
information being shown is just the header, but in the future we might
also include disassembling parts of the code, or retrieving the "CHARS"
section for a given ROM file, and similar.

In order to implement the header parsing part a new library has been
introduced, simply named "header" which abstracts everything away so you
just need to call `Header::try_from("my bytes")` to fetch the actual
information.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 crates/nasm/src/main.rs    |  2 +-
 crates/readrom/Cargo.toml  | 12 ++++++++++
 crates/readrom/src/main.rs | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 crates/readrom/Cargo.toml
 create mode 100644 crates/readrom/src/main.rs

(limited to 'crates')

diff --git a/crates/nasm/src/main.rs b/crates/nasm/src/main.rs
index 9ad710b..105a995 100644
--- a/crates/nasm/src/main.rs
+++ b/crates/nasm/src/main.rs
@@ -5,7 +5,7 @@ use std::io::{self, Read, Write};
 use xixanta::assembler::Assembler;
 use xixanta::mapping::{Mapping, EMPTY, NROM, NROM65};
 
-/// Assembler for the 6502 microprocessor that targets the NES.
+/// Assembler for the 6502 microprocessor that targets the NES/Famicom.
 #[derive(ClapParser, Debug)]
 #[command(version, about, long_about = None)]
 struct Args {
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(())
+}
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