feat: add folder-based Android unpack workflow

senbei-android-engine/src/lib.rs

@@ -0,0 +1,32 @@
+//! Pure-static Stage 1 decryption and recursive Stage 2 module extraction.
+
+mod error;
+mod extract;
+mod report;
+mod stage1;
+mod stream;
+
+pub use error::Error;
+pub use extract::{ExtractOptions, extract_stage2};
+pub use report::ExtractionReport;
+pub use stage1::{DEFAULT_CIPHER_CONSTANT, DEFAULT_OUTER_SIZE};
+
+/// Return whether `data` has the protected AArch64 Stage 1 section layout.
+///
+/// This is a cheap, read-only probe used by folder mode to distinguish the
+/// protected target from ordinary Unity libraries before invoking extraction.
+#[must_use]
+pub fn is_protected_libil2cpp(data: &[u8]) -> bool {
+    if !stage1::looks_protected(data) {
+        return false;
+    }
+    let Ok(stage1) = stage1::inspect(
+        data,
+        std::path::Path::new("<probe>"),
+        DEFAULT_OUTER_SIZE,
+        DEFAULT_CIPHER_CONSTANT,
+    ) else {
+        return false;
+    };
+    senbei_android_crypto::Module9bConfig::parse_embedded(&stage1.plaintext).is_ok()
+}