1 files changed, 182 insertions, 0 deletions
diff --git a/src/de/danoeh/antennapod/util/id3reader/ID3Reader.java b/src/de/danoeh/antennapod/util/id3reader/ID3Reader.java
new file mode 100644
index 000000000..8164170bf
--- /dev/null
+++ b/src/de/danoeh/antennapod/util/id3reader/ID3Reader.java
@@ -0,0 +1,182 @@
+package de.danoeh.antennapod.util.id3reader;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.PushbackInputStream;
+
+import de.danoeh.antennapod.util.id3reader.model.FrameHeader;
+import de.danoeh.antennapod.util.id3reader.model.TagHeader;
+
+/**
+ * Reads the ID3 Tag of a given file. In order to use this class, you should
+ * create a subclass of it and overwrite the onStart* - or onEnd* - methods.
+ */
+public class ID3Reader {
+	private static final int HEADER_LENGTH = 10;
+	private static final int ID3_LENGTH = 3;
+	private static final int FRAME_ID_LENGTH = 4;
+
+	protected static final int ACTION_SKIP = 1;
+	protected static final int ACTION_DONT_SKIP = 2;
+
+	protected int readerPosition;
+
+	private static final char[] LITTLE_ENDIAN_BOM = { 0xff, 0xfe };
+	private static final char[] BIG_ENDIAN_BOM = { 0xfe, 0xff };
+
+	public ID3Reader() {
+	}
+
+	public final void readInputStream(InputStream input) throws IOException,
+			ID3ReaderException {
+		int rc;
+		readerPosition = 0;
+		char[] tagHeaderSource = readBytes(input, HEADER_LENGTH);
+		TagHeader tagHeader = createTagHeader(tagHeaderSource);
+		if (tagHeader == null) {
+			onNoTagHeaderFound();
+		} else {
+			rc = onStartTagHeader(tagHeader);
+			if (rc == ACTION_SKIP) {
+				onEndTag();
+			} else {
+				while (readerPosition < tagHeader.getSize()) {
+					FrameHeader frameHeader = createFrameHeader(readBytes(
+							input, HEADER_LENGTH));
+					rc = onStartFrameHeader(frameHeader, input);
+					if (rc == ACTION_SKIP) {
+						skipBytes(input, frameHeader.getSize());
+					}
+				}
+				onEndTag();
+			}
+		}
+	}
+
+	/**
+	 * Read a certain number of bytes from the given input stream. This method
+	 * changes the readerPosition-attribute.
+	 */
+	protected char[] readBytes(InputStream input, int number)
+			throws IOException, ID3ReaderException {
+		char[] header = new char[number];
+		for (int i = 0; i < number; i++) {
+			int b = input.read();
+			readerPosition++;
+			if (b != -1) {
+				header[i] = (char) b;
+			} else {
+				throw new ID3ReaderException("Unexpected end of stream");
+			}
+		}
+		return header;
+	}
+
+	/**
+	 * Skip a certain number of bytes on the given input stream. This method
+	 * changes the readerPosition-attribute.
+	 */
+	protected void skipBytes(InputStream input, int number) throws IOException {
+		int skipped = 0;
+		while (skipped < number) {
+			skipped += input.skip(number - skipped);
+			System.out.println("Skipped = " + skipped);
+		}
+
+		readerPosition += number;
+	}
+
+	private TagHeader createTagHeader(char[] source) throws ID3ReaderException {
+		boolean hasTag = (source[0] == 0x49) && (source[1] == 0x44)
+				&& (source[2] == 0x33);
+		if (source.length != HEADER_LENGTH) {
+			throw new ID3ReaderException("Length of header must be "
+					+ HEADER_LENGTH);
+		}
+		if (hasTag) {
+			String id = null;
+			id = new String(source, 0, ID3_LENGTH);
+			char version = (char) ((source[3] << 8) | source[4]);
+			byte flags = (byte) source[5];
+			int size = (source[6] << 24) | (source[7] << 16) | (source[8] << 8)
+					| source[9];
+			return new TagHeader(id, size, version, flags);
+		} else {
+			return null;
+		}
+	}
+
+	private FrameHeader createFrameHeader(char[] source)
+			throws ID3ReaderException {
+		if (source.length != HEADER_LENGTH) {
+			throw new ID3ReaderException("Length of header must be "
+					+ HEADER_LENGTH);
+		}
+		String id = null;
+		id = new String(source, 0, FRAME_ID_LENGTH);
+		int size = (((int) source[4]) << 24) | (((int) source[5]) << 16)
+				| (((int) source[6]) << 8) | source[7];
+		char flags = (char) ((source[8] << 8) | source[9]);
+		return new FrameHeader(id, size, flags);
+	}
+
+	protected String readString(InputStream input, int max) throws IOException,
+			ID3ReaderException {
+		char[] bom = readBytes(input, 2);
+		if (bom == LITTLE_ENDIAN_BOM || bom == BIG_ENDIAN_BOM) {
+			return readUnicodeString(input, bom, max);
+		} else {
+			PushbackInputStream pi = new PushbackInputStream(input, 2);
+			pi.unread(bom[1]);
+			pi.unread(bom[0]);
+			return readISOString(pi, max);
+		}
+	}
+
+	private String readISOString(InputStream input, int max)
+			throws IOException, ID3ReaderException {
+		int bytesRead = 0;
+		StringBuilder builder = new StringBuilder();
+		char c;
+		while (++bytesRead <= max && (c = (char) input.read()) > 0) {
+			builder.append(c);
+		}
+		return builder.toString();
+	}
+
+	private String readUnicodeString(InputStream input, char[] bom, int max)
+			throws IOException, ID3ReaderException {
+		StringBuffer builder = new StringBuffer();
+		char c1 = (char) input.read();
+		char c2 = (char) input.read();
+		int bytesRead = 2;
+		while ((c1 > 0 && c2 > 0) && ++bytesRead <= max) {
+
+			builder.append(c1);
+			c1 = c2;
+			c2 = (char) input.read();
+		}
+		if (bom == LITTLE_ENDIAN_BOM) {
+			builder.reverse();
+		}
+		return builder.toString();
+	}
+
+	public int onStartTagHeader(TagHeader header) {
+		return ACTION_SKIP;
+	}
+
+	public int onStartFrameHeader(FrameHeader header, InputStream input)
+			throws IOException, ID3ReaderException {
+		return ACTION_SKIP;
+	}
+
+	public void onEndTag() {
+
+	}
+
+	public void onNoTagHeaderFound() {
+
+	}
+
+}