Add a new module to extract strings from executables

src/execlookup.rs

@@ -0,0 +1,67 @@
+// SPDX-FileCopyrightText: 2024 Joshua Goins <josh@redstrate.com>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+use std::fs;
+
+fn from_u16(from: &mut [u16]) -> &[u8] {
+    #[cfg(target_endian = "little")]
+    from.iter_mut().for_each(|word| *word = word.to_be());
+
+    let ptr: *const u8 = from.as_ptr().cast();
+    let len = from.len().checked_mul(2).unwrap();
+
+    unsafe { std::slice::from_raw_parts(ptr, len) }
+}
+
+fn find_needle(installer_file: &Vec<u8>, needle: &str) -> Option<String> {
+    let mut needle: Vec<u16> = needle.encode_utf16().collect();
+    let bytes = from_u16(&mut needle);
+
+    let Some(position) = installer_file
+        .windows(bytes.len())
+        .position(|window| window == bytes) else {
+        return None;
+    };
+
+    let mut position = position.unwrap();
+
+    let parse_char_at_position = |position: usize| {
+        let upper = installer_file[position];
+        let lower = installer_file[position + 1];
+
+        let result = char::decode_utf16([((upper as u16) << 8) | lower as u16])
+            .map(|r| r.map_err(|e| e.unpaired_surrogate()))
+            .collect::<Vec<_>>();
+
+        result[0]
+    };
+
+    let mut string: String = String::new();
+
+    let mut last_char = parse_char_at_position(position);
+    while last_char.is_ok() && last_char.unwrap() != '\0' {
+        string.push(last_char.unwrap());
+
+        position += 2;
+        last_char = parse_char_at_position(position);
+    }
+
+    Some(string)
+}
+
+/// Extract the frontier URL from ffxivlauncher.exe
+pub fn extract_frontier_url(launcher_path: &str) -> Option<String> {
+    let installer_file = fs::read(launcher_path).unwrap();
+
+    // Old Frontier URL format
+    if let Some(url) = find_needle(&installer_file, "https://frontier.ffxiv.com") {
+        return Some(url);
+    }
+
+    // New Frontier URL format
+    if let Some(url) = find_needle(&installer_file, "https://launcher.finalfantasyxiv.com") {
+        return Some(url);
+    }
+
+    None
+}

src/lib.rs

@@ -116,6 +116,9 @@ pub mod lgb;
 #[cfg(feature = "visual_data")]
 pub mod tera;
 
+/// Reading data from executables
+pub mod execlookup;
+
 mod common_file_operations;
 
 /// Reading word dictionaries, such as the vulgar word list.