refactor: align platform crate boundaries

senbei-metadata/src/android/method_tokens.rs

@@ -2,10 +2,11 @@
 
 use serde::Serialize;
 
+use crate::common::MAGIC;
+
 /// Seed embedded in the current `libil2cpp` module `0x0C`.
 pub const DEFAULT_METHOD_TOKEN_SEED: u32 = 0xa6fa_e968;
 
-const MAGIC: u32 = 0xfab1_1baf;
 const SUPPORTED_V29: u32 = 29;
 const SUPPORTED_V31: u32 = 31;
 const HDR_METHODS: usize = 0x30;

senbei-metadata/src/common.rs

@@ -0,0 +1,12 @@
+//! Shared IL2CPP metadata header primitives.
+
+/// IL2CPP global-metadata sanity magic.
+pub(crate) const MAGIC: u32 = 0xFAB1_1BAF;
+
+/// Cheap check used by both platform scanners before opening a full metadata
+/// file.
+#[must_use]
+pub fn is_metadata(data: &[u8]) -> bool {
+    data.get(0..4)
+        .is_some_and(|bytes| u32::from_le_bytes([bytes[0], bytes[1], bytes[2], bytes[3]]) == MAGIC)
+}

senbei-metadata/src/lib.rs

@@ -1,6 +1,9 @@
 //! Unity il2cpp metadata restoration.
 
 pub mod android;
+mod common;
+mod structural;
 pub mod windows;
 
-pub use windows::*;
+pub use common::is_metadata;
+pub use structural::*;

senbei-metadata/src/structural.rs

@@ -27,8 +27,7 @@
 //! metadata (its tokens already equal `local_index + 1`), so it is safe to run on
 //! any il2cpp game — `remapped == 0` then reports that nothing changed.
 
-/// il2cpp `global-metadata.dat` sanity magic (`Il2CppGlobalMetadataHeader.sanity`).
-const MAGIC: u32 = 0xFAB1_1BAF;
+use crate::common::MAGIC;
 
 /// Metadata format version this de-obfuscator understands. The struct strides
 /// and header field offsets below are specific to it; other versions are left

senbei-metadata/src/windows/mod.rs

@@ -1,5 +1,3 @@
-//! Windows metadata restoration.
+//! Compatibility namespace for the shared structural metadata transform.
 
-mod metadata;
-
-pub use metadata::*;
+pub use crate::structural::*;