Add CRC32 check for PAT section

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131294029

library/src/main/java/com/google/android/exoplayer2/extractor/ts/TsExtractor.java

@@ -272,10 +272,17 @@ public final class TsExtractor implements Extractor {
         int pointerField = data.readUnsignedByte();
         data.skipBytes(pointerField);
       }
-
       data.readBytes(patScratch, 3);
       patScratch.skipBits(12); // table_id (8), section_syntax_indicator (1), '0' (1), reserved (2)
       int sectionLength = patScratch.readBits(12);
+
+      int crcStart = data.getPosition() - 3;
+      int crcEnd = data.getPosition() + sectionLength;
+      if (Util.crc(data.data, crcStart, crcEnd, 0xffffffff) != 0) {
+        // CRC Invalid. The section gets discarded.
+        return;
+      }
+
       // transport_stream_id (16), reserved (2), version_number (5), current_next_indicator (1),
       // section_number (8), last_section_number (8)
       data.skipBytes(5);
@@ -292,8 +299,6 @@ public final class TsExtractor implements Extractor {
           tsPayloadReaders.put(pid, new PmtReader());
         }
       }
-
-      // Skip CRC_32.
     }
 
   }

library/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -868,6 +868,24 @@ public final class Util {
   }
 
   /**
+   * Returns the result of updating a CRC with the specified bytes in a "most significant bit first"
+   * order.
+   *
+   * @param bytes Array containing the bytes to update the crc value with.
+   * @param start The index to the first byte in the byte range to update the crc with.
+   * @param end The index after the last byte in the byte range to update the crc with.
+   * @param initialValue The initial value for the crc calculation.
+   * @return The result of updating the initial value with the specified bytes.
+   */
+  public static int crc(byte[] bytes, int start, int end, int initialValue) {
+    for (int i = start; i < end; i++) {
+      initialValue = (initialValue << 8)
+          ^ CRC32_BYTES_MSBF[((initialValue >>> 24) ^ (bytes[i] & 0xFF)) & 0xFF];
+    }
+    return initialValue;
+  }
+
+  /**
    * Returns the SHA-1 digest of {@code input} as a hex string.
    *
    * @param input The string whose SHA-1 digest is required.
@@ -883,4 +901,48 @@ public final class Util {
     }
   }
 
+  /**
+   * Allows the CRC calculation to be done byte by byte instead of bit per bit being the order
+   * "most significant bit first".
+   */
+  private static final int[] CRC32_BYTES_MSBF = {
+      0X00000000, 0X04C11DB7, 0X09823B6E, 0X0D4326D9, 0X130476DC, 0X17C56B6B, 0X1A864DB2,
+      0X1E475005, 0X2608EDB8, 0X22C9F00F, 0X2F8AD6D6, 0X2B4BCB61, 0X350C9B64, 0X31CD86D3,
+      0X3C8EA00A, 0X384FBDBD, 0X4C11DB70, 0X48D0C6C7, 0X4593E01E, 0X4152FDA9, 0X5F15ADAC,
+      0X5BD4B01B, 0X569796C2, 0X52568B75, 0X6A1936C8, 0X6ED82B7F, 0X639B0DA6, 0X675A1011,
+      0X791D4014, 0X7DDC5DA3, 0X709F7B7A, 0X745E66CD, 0X9823B6E0, 0X9CE2AB57, 0X91A18D8E,
+      0X95609039, 0X8B27C03C, 0X8FE6DD8B, 0X82A5FB52, 0X8664E6E5, 0XBE2B5B58, 0XBAEA46EF,
+      0XB7A96036, 0XB3687D81, 0XAD2F2D84, 0XA9EE3033, 0XA4AD16EA, 0XA06C0B5D, 0XD4326D90,
+      0XD0F37027, 0XDDB056FE, 0XD9714B49, 0XC7361B4C, 0XC3F706FB, 0XCEB42022, 0XCA753D95,
+      0XF23A8028, 0XF6FB9D9F, 0XFBB8BB46, 0XFF79A6F1, 0XE13EF6F4, 0XE5FFEB43, 0XE8BCCD9A,
+      0XEC7DD02D, 0X34867077, 0X30476DC0, 0X3D044B19, 0X39C556AE, 0X278206AB, 0X23431B1C,
+      0X2E003DC5, 0X2AC12072, 0X128E9DCF, 0X164F8078, 0X1B0CA6A1, 0X1FCDBB16, 0X018AEB13,
+      0X054BF6A4, 0X0808D07D, 0X0CC9CDCA, 0X7897AB07, 0X7C56B6B0, 0X71159069, 0X75D48DDE,
+      0X6B93DDDB, 0X6F52C06C, 0X6211E6B5, 0X66D0FB02, 0X5E9F46BF, 0X5A5E5B08, 0X571D7DD1,
+      0X53DC6066, 0X4D9B3063, 0X495A2DD4, 0X44190B0D, 0X40D816BA, 0XACA5C697, 0XA864DB20,
+      0XA527FDF9, 0XA1E6E04E, 0XBFA1B04B, 0XBB60ADFC, 0XB6238B25, 0XB2E29692, 0X8AAD2B2F,
+      0X8E6C3698, 0X832F1041, 0X87EE0DF6, 0X99A95DF3, 0X9D684044, 0X902B669D, 0X94EA7B2A,
+      0XE0B41DE7, 0XE4750050, 0XE9362689, 0XEDF73B3E, 0XF3B06B3B, 0XF771768C, 0XFA325055,
+      0XFEF34DE2, 0XC6BCF05F, 0XC27DEDE8, 0XCF3ECB31, 0XCBFFD686, 0XD5B88683, 0XD1799B34,
+      0XDC3ABDED, 0XD8FBA05A, 0X690CE0EE, 0X6DCDFD59, 0X608EDB80, 0X644FC637, 0X7A089632,
+      0X7EC98B85, 0X738AAD5C, 0X774BB0EB, 0X4F040D56, 0X4BC510E1, 0X46863638, 0X42472B8F,
+      0X5C007B8A, 0X58C1663D, 0X558240E4, 0X51435D53, 0X251D3B9E, 0X21DC2629, 0X2C9F00F0,
+      0X285E1D47, 0X36194D42, 0X32D850F5, 0X3F9B762C, 0X3B5A6B9B, 0X0315D626, 0X07D4CB91,
+      0X0A97ED48, 0X0E56F0FF, 0X1011A0FA, 0X14D0BD4D, 0X19939B94, 0X1D528623, 0XF12F560E,
+      0XF5EE4BB9, 0XF8AD6D60, 0XFC6C70D7, 0XE22B20D2, 0XE6EA3D65, 0XEBA91BBC, 0XEF68060B,
+      0XD727BBB6, 0XD3E6A601, 0XDEA580D8, 0XDA649D6F, 0XC423CD6A, 0XC0E2D0DD, 0XCDA1F604,
+      0XC960EBB3, 0XBD3E8D7E, 0XB9FF90C9, 0XB4BCB610, 0XB07DABA7, 0XAE3AFBA2, 0XAAFBE615,
+      0XA7B8C0CC, 0XA379DD7B, 0X9B3660C6, 0X9FF77D71, 0X92B45BA8, 0X9675461F, 0X8832161A,
+      0X8CF30BAD, 0X81B02D74, 0X857130C3, 0X5D8A9099, 0X594B8D2E, 0X5408ABF7, 0X50C9B640,
+      0X4E8EE645, 0X4A4FFBF2, 0X470CDD2B, 0X43CDC09C, 0X7B827D21, 0X7F436096, 0X7200464F,
+      0X76C15BF8, 0X68860BFD, 0X6C47164A, 0X61043093, 0X65C52D24, 0X119B4BE9, 0X155A565E,
+      0X18197087, 0X1CD86D30, 0X029F3D35, 0X065E2082, 0X0B1D065B, 0X0FDC1BEC, 0X3793A651,
+      0X3352BBE6, 0X3E119D3F, 0X3AD08088, 0X2497D08D, 0X2056CD3A, 0X2D15EBE3, 0X29D4F654,
+      0XC5A92679, 0XC1683BCE, 0XCC2B1D17, 0XC8EA00A0, 0XD6AD50A5, 0XD26C4D12, 0XDF2F6BCB,
+      0XDBEE767C, 0XE3A1CBC1, 0XE760D676, 0XEA23F0AF, 0XEEE2ED18, 0XF0A5BD1D, 0XF464A0AA,
+      0XF9278673, 0XFDE69BC4, 0X89B8FD09, 0X8D79E0BE, 0X803AC667, 0X84FBDBD0, 0X9ABC8BD5,
+      0X9E7D9662, 0X933EB0BB, 0X97FFAD0C, 0XAFB010B1, 0XAB710D06, 0XA6322BDF, 0XA2F33668,
+      0XBCB4666D, 0XB8757BDA, 0XB5365D03, 0XB1F740B4
+  };
+
 }