Meta/Fuzzers: Extract common audio fuzzing code

Apart from the class used audio fuzzers have identical behavior: Create
a memory stream from the fuzzer input and pass this to the loader, then
try to load audio until an error occurs. Since the loader plugins need
to have the same static create() function anyways for LibAudio itself,
we can unify the fuzzer implementations and reduce code duplication.

Meta/Lagom/Fuzzers/AudioFuzzerCommon.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
+ * Copyright (c) 2023, kleines Filmröllchen <filmroellchen@serenityos.org>
+ * Copyright (c) 2021-2023, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Concepts.h>
+#include <AK/MemoryStream.h>
+#include <LibAudio/Loader.h>
+#include <stddef.h>
+#include <stdint.h>
+
+template<typename LoaderPluginType>
+requires(IsBaseOf<Audio::LoaderPlugin, LoaderPluginType>)
+int fuzz_audio_loader(uint8_t const* data, size_t size)
+{
+    auto const bytes = ReadonlyBytes { data, size };
+    auto stream = try_make<FixedMemoryStream>(bytes).release_value();
+    auto audio_or_error = LoaderPluginType::create(move(stream));
+
+    if (audio_or_error.is_error())
+        return 0;
+
+    auto audio = audio_or_error.release_value();
+
+    for (;;) {
+        auto samples = audio->load_chunks(4 * KiB);
+        if (samples.is_error())
+            return 0;
+        if (samples.value().size() == 0)
+            break;
+    }
+
+    return 0;
+}