boot: Add freestanding find_handles

uefi/src/boot.rs

@@ -18,6 +18,9 @@ use core::{mem, slice};
 use uefi::{table, Char16, Error, Event, Guid, Handle, Result, Status, StatusExt};
 use uefi_raw::table::boot::InterfaceType;
 
+#[cfg(feature = "alloc")]
+use {alloc::vec::Vec, uefi::ResultExt};
+
 #[cfg(doc)]
 use {
  crate::proto::device_path::LoadedImageDevicePath, crate::proto::loaded_image::LoadedImage,
@@ -741,6 +744,47 @@ pub fn locate_handle_buffer(search_ty: SearchType) -> Result<HandleBuffer> {
  })
 }
 
+/// Returns all the handles implementing a certain protocol.
+///
+/// # Errors
+///
+/// * [`Status::NOT_FOUND`]: no matching handles.
+#[cfg(feature = "alloc")]
+pub fn find_handles<P: ProtocolPointer + ?Sized>() -> Result<Vec<Handle>> {
+ // Search by protocol.
+ let search_type = SearchType::from_proto::<P>();
+
+ // Determine how much we need to allocate.
+ let num_handles = match locate_handle(search_type, &mut []) {
+ Err(err) => {
+ if err.status() == Status::BUFFER_TOO_SMALL {
+ err.data().expect("error data is missing")
+ } else {
+ return Err(err.to_err_without_payload());
+ }
+ }
+ // This should never happen: if no handles match the search then a
+ // `NOT_FOUND` error should be returned.
+ Ok(_) => panic!("locate_handle should not return success with empty buffer"),
+ };
+
+ // Allocate a large enough buffer without pointless initialization.
+ let mut handles = Vec::with_capacity(num_handles);
+
+ // Perform the search.
+ let num_handles = locate_handle(search_type, handles.spare_capacity_mut())
+ .discard_errdata()?
+ .len();
+
+ // Mark the returned number of elements as initialized.
+ unsafe {
+ handles.set_len(num_handles);
+ }
+
+ // Emit output, with warnings
+ Ok(handles)
+}
+
 /// Find an arbitrary handle that supports a particular [`Protocol`]. Returns
 /// [`NOT_FOUND`] if no handles support the protocol.
 ///