Add input stream that identifies its content.

diff --git a/src/main/java/net/pterodactylus/sonitus/io/IdentifyingInputStream.java b/src/main/java/net/pterodactylus/sonitus/io/IdentifyingInputStream.java
new file mode 100644 (file)
index 0000000..537c9a4
--- /dev/null
+++ b/src/main/java/net/pterodactylus/sonitus/io/IdentifyingInputStream.java
@@ -0,0 +1,96 @@
+/*
+ * Sonitus - IdentifyingStream.java - Copyright © 2013 David Roden
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pterodactylus.sonitus.io;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import net.pterodactylus.sonitus.data.Format;
+
+import com.google.common.base.Optional;
+
+/**
+ * Wrapper around an {@link InputStream} that identifies the {@link Format} of
+ * the wrapped stream.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class IdentifyingInputStream extends FilterInputStream {
+
+       /** The identified format. */
+       private final Format format;
+
+       /**
+        * Creates a new identifying input stream.
+        *
+        * @param inputStream
+        *              The input stream to wrap
+        * @param format
+        *              The format of the stream
+        */
+       private IdentifyingInputStream(InputStream inputStream, Format format) {
+               super(inputStream);
+               this.format = format;
+       }
+
+       //
+       // ACCESSORS
+       //
+
+       /**
+        * Returns the identified format.
+        *
+        * @return The identified format
+        */
+       public Format format() {
+               return format;
+       }
+
+       //
+       // STATIC METHODS
+       //
+
+       /**
+        * Tries to identify the given input stream.
+        *
+        * @param inputStream
+        *              The input stream to identify
+        * @return An identifying input stream that delivers the original stream and
+        *         the format it detected, or {@link com.google.common.base.Optional#absent()}
+        *         if no format could be identified
+        * @throws IOException
+        *              if an I/O error occurs
+        */
+       public static Optional<IdentifyingInputStream> create(InputStream inputStream) throws IOException {
+
+               /* remember everything we read here. */
+               RememberingInputStream rememberingInputStream = new RememberingInputStream(inputStream);
+
+               /* try Ogg Vorbis first. */
+               try {
+                       Format format = OggVorbisIdentifier.identify(rememberingInputStream);
+                       return Optional.of(new IdentifyingInputStream(rememberingInputStream.remembered(), format));
+               } catch (IdentifierException ie1) {
+                       rememberingInputStream = new RememberingInputStream(rememberingInputStream.remembered());
+               }
+
+               return Optional.absent();
+       }
+
+}