rom-scanner-hashing

name	rom-scanner-hashing
description	Use this skill when implementing ROM scanning and CRC hashing logic for matching local files against the GameBase64 database.
version	1.0.0
author	64Box
tags	["rom-scanner","crc32","rust","tauri","zip"]

ROM Scanner & CRC Hashing

When to Use This Skill

• When writing Rust backend commands to scan a user's local directories for games.
• When implementing CRC32 hashing to match local files against the Games database.
• When linking discovered .zip, .d64, .t64, .tap, or .crt files to metadata.

1. Memory Management & Streaming

Never load entire files or large file sets into RAM at once.

• Do not use std::fs::read(path) or std::fs::read_to_string(path) for scanner hashing.
• Use std::fs::File, std::io::BufReader, and crc32fast to hash uncompressed files in chunks.

use crc32fast::Hasher;
use std::fs::File;
use std::io::{BufRead, BufReader};

let file = File::open(path)?;
let mut reader = BufReader::new(file);
let mut hasher = Hasher::new();
let mut buffer = [0; 8192];

while let Ok(count) = reader.read(&mut buffer) {
    if count == 0 { break; }
    hasher.update(&buffer[..count]);
}
let crc = hasher.finalize();

2. Zip File Optimization

Most official GameBase64 collection files are zipped.

• Do not extract and hash the archive contents just to find CRC.
• Read CRC32 directly from the zip central directory with a crate such as zip or async_zip.

3. Database Matching & Formatting

• Format CRC output as a padded 8-character hexadecimal string.
• Match with case-insensitive queries such as:

SELECT GA_Id, Name FROM Games WHERE CRC = ? COLLATE NOCASE

4. UI Non-Blocking & IPC Progress

• Run scanning work asynchronously with tokio::task::spawn_blocking or tauri::async_runtime.
• Emit progress events over Tauri IPC so the frontend can keep the UI responsive.

Example event payload:

tauri::Window::emit("scan-progress", { "scanned": 1500, "total": 30000, "current_file": "Commando.zip" })