better jar handling; get native files from manifest instead of iterator over every file in the jar

src/yugecin/opsudance/utils/ManifestWrapper.java

@@ -0,0 +1,54 @@
+/*
+ * opsu!dance - fork of opsu! with cursordance auto
+ * Copyright (C) 2017 yugecin
+ *
+ * opsu!dance is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * opsu!dance is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with opsu!dance.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package yugecin.opsudance.utils;
+
+import yugecin.opsudance.core.NotNull;
+import yugecin.opsudance.core.Nullable;
+
+import java.util.jar.Attributes;
+import java.util.jar.Manifest;
+
+public class ManifestWrapper {
+
+	@Nullable
+	public final Manifest manifest;
+
+	public ManifestWrapper(@Nullable Manifest manifest) {
+		this.manifest = manifest;
+	}
+
+	/**
+	 * @param attribute attribute in jarfile or null for default attributes
+	 */
+	public String valueOrDefault(@Nullable String attribute, @NotNull String key, @Nullable String dfault) {
+		if (manifest == null) {
+			return dfault;
+		}
+		Attributes attributes =
+			attribute == null ? manifest.getMainAttributes() : manifest.getAttributes(attribute);
+		if (attributes == null) {
+			return dfault;
+		}
+		String val = attributes.getValue(key);
+		if (val == null) {
+			return dfault;
+		}
+		return val;
+	}
+
+}

src/yugecin/opsudance/utils/SyntacticSugar.java

@@ -0,0 +1,34 @@
+/*
+ * opsu!dance - fork of opsu! with cursordance auto
+ * Copyright (C) 2017 yugecin
+ *
+ * opsu!dance is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * opsu!dance is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with opsu!dance.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package yugecin.opsudance.utils;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+public class SyntacticSugar {
+
+	/**
+	 * close the closeable and swallow exceptions, if any
+	 */
+	public static void closeAndSwallow(Closeable closable) {
+		try {
+			closable.close();
+		} catch (IOException ignored) {}
+	}
+
+}