1 files changed, 101 insertions, 6 deletions

diff --git a/app/src/main/java/github/daneren2005/dsub/util/tags/LameHeader.java b/app/src/main/java/github/daneren2005/dsub/util/tags/LameHeader.java
index 720ee87f..691c7279 100644
--- a/app/src/main/java/github/daneren2005/dsub/util/tags/LameHeader.java
+++ b/app/src/main/java/github/daneren2005/dsub/util/tags/LameHeader.java
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2013 Adrian Ulrich <adrian@blinkenlights.ch>
+ * Copyright (C) 2017 Google Inc.
  *
  * 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
@@ -19,28 +20,122 @@ package github.daneren2005.dsub.util.tags;
 
 import java.io.IOException;
 import java.io.RandomAccessFile;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Enumeration;
 
 
 public class LameHeader extends Common {
-	
+
+	// Sampling rate version -> field mapping
+	private static int[][] sampleRates = {
+		{ 11025, 12000,  8000 }, // MPEG2.5 (idx = 0)
+		{     0,     0,     0 }, // reserved (idx = 1)
+		{ 22050, 24000, 16000 }, // MPEG2 (idx = 2)
+		{ 44100, 48000, 32000 }, // MPEG1 (idx = 3)
+	};
+
+	// SamplesPerFrame layer -> version mapping
+	private static int[][] samplesPerFrame = {
+		// reserved, layer3, layer2, layer1
+		{  0,        576,   1152,  384 }, // MPEG2.5
+		{  0,          0,      0,    0 }, // RESERVED
+		{  0,        576,   1152,  384 }, // MPEG2
+		{  0,       1152,   1152,  384 }, // MPEG1
+	};
+
+
 	public LameHeader() {
 	}
 	
 	public HashMap getTags(RandomAccessFile s) throws IOException {
-		return parseLameHeader(s, 0);
+		HashMap rgain = parseLameHeader(s, 0);
+		HashMap tags = parseV1Header(s, s.length()-128);
+
+		// Add replay gain info to returned object if available
+		for (String k : Arrays.asList("REPLAYGAIN_TRACK_GAIN", "REPLAYGAIN_ALBUM_GAIN")) {
+			if (rgain.containsKey(k))
+				tags.put(k, rgain.get(k));
+		}
+
+		return tags;
 	}
-	
+
+	/**
+	 * Attempts to parse ID3v1(.1) information from given RandomAccessFile
+	 *
+	 * @param s the seekable RandomAccessFile
+	 * @param offset position of the ID3v1 tag
+	 */
+	private HashMap parseV1Header(RandomAccessFile s, long offset) throws IOException {
+		HashMap tags = new HashMap();
+		byte[] tag  = new byte[3];
+		byte[] year = new byte[4];
+		byte[] str  = new byte[30];
+
+		s.seek(offset);
+		s.read(tag);
+
+		if("TAG".equals(new String(tag))) {
+			for (String name : Arrays.asList("TITLE", "ARTIST", "ALBUM")) {
+				s.read(str);
+				String value = new String(str, "ISO-8859-1").trim();
+				if (value.length() > 0)
+					addTagEntry(tags, name, value);
+			}
+
+			// year is a string for whatever reason...
+			s.read(year);
+			String y = new String(year).trim();
+			if (y.length() > 0)
+				addTagEntry(tags, "YEAR", y);
+
+			s.skipBytes(28); // skip comment field
+			s.read(tag);
+
+			if (tag[0] == 0 && tag[1] != 0) // tag[0] == 0 -> is id3v1.1 compatible
+				addTagEntry(tags, "TRACKNUMBER", String.format("%d", tag[1]));
+
+			if (tag[2] != 0)
+				addTagEntry(tags, "GENRE", String.format("%d", tag[2]));
+		}
+
+
+		return tags;
+	}
+
 	public HashMap parseLameHeader(RandomAccessFile s, long offset) throws IOException {
 		HashMap tags = new HashMap();
-		byte[] chunk = new byte[4];
+		byte[] chunk = new byte[12];
 		
 		s.seek(offset + 0x24);
 		s.read(chunk);
 		
-		String lameMark = new String(chunk, 0, chunk.length, "ISO-8859-1");
-		
+		String lameMark = new String(chunk, 0, 4, "ISO-8859-1");
+		int flags = b2u(chunk[7]);
+
+		if((flags & 0x01) !=0 ) { // header indicates that totalFrames field is present
+			int total_frames = b2be32(chunk, 8);
+			s.seek(offset);
+			s.read(chunk);
+
+			int mpeg_hdr = b2be32(chunk, 0);
+			int srate_idx = (mpeg_hdr >> 10) & 3; // sampling rate index at bit 10-11
+			int layer_idx = (mpeg_hdr >> 17) & 3; // layer index value bit 17-18
+			int ver_idx   = (mpeg_hdr >> 19) & 3; // version index value bit 19-20
+
+			// Try to calculate song duration if all indexes are sane
+			if (ver_idx < sampleRates.length && srate_idx < sampleRates[ver_idx].length && layer_idx < samplesPerFrame[ver_idx].length) {
+				int sample_rate = sampleRates[ver_idx][srate_idx];
+				int sample_pfr  = samplesPerFrame[ver_idx][layer_idx];
+				if (sample_rate > 0 && sample_pfr > 0) {
+					double duration = ((double)sample_pfr / (double)sample_rate) * total_frames;
+					tags.put("duration", (int)duration);
+				}
+			}
+
+		}
+
 		if(lameMark.equals("Info") || lameMark.equals("Xing")) {
 			s.seek(offset+0xAB);
 			s.read(chunk);