Support running/profiling ISX files

src/emulator/shrooms_vb_util.rs

@@ -0,0 +1,33 @@
+use std::ffi::c_void;
+
+#[unsafe(no_mangle)]
+unsafe fn vbu_realloc_shim(ptr: *mut c_void, new_size: usize) -> *mut c_void {
+    if !ptr.is_null() {
+        // not supporting proper realloc because it needs bookkeeping and it's unnecessary
+        return std::ptr::null_mut();
+    }
+    let allocation = vec![0u8; new_size].into_boxed_slice();
+    Box::into_raw(allocation).cast()
+}
+
+#[link(name = "vb")]
+unsafe extern "C" {
+    #[link_name = "vbuFromISX"]
+    fn vbu_from_isx(bytes: *const c_void, length: usize, rom_length: *mut usize) -> *mut c_void;
+}
+
+pub fn rom_from_isx(bytes: &[u8]) -> Option<Vec<u8>> {
+    if !bytes.starts_with(b"ISX") {
+        return None;
+    }
+    let mut rom_length = 0;
+    let raw_rom =
+        unsafe { vbu_from_isx(bytes.as_ptr().cast(), bytes.len(), &mut rom_length) };
+    if raw_rom.is_null() {
+        return None;
+    }
+    // SAFETY: the rom was allocated by vbu_realloc_shim, which created it from a Vec<u8>.
+    let rom =
+        unsafe { Vec::from_raw_parts(raw_rom.cast(), rom_length, rom_length) };
+    Some(rom)
+}