content: /*
   * Copyright (C) 2016 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.google.android.exoplayer2.util;
  
  import com.google.android.exoplayer2.C;
  import java.nio.ByteBuffer;
  import java.nio.charset.Charset;
  
  /**
   * Wraps a byte array, providing a set of methods for parsing data from it. Numerical values are
   * parsed with the assumption that their constituent bytes are in big endian order.
   */
  public final class ParsableByteArray {
  
    public byte[] data;
  
    private int position;
    private int limit;
  
    /**
     * Creates a new instance that initially has no backing data.
     */
    public ParsableByteArray() {}
  
    /**
     * Creates a new instance with {@code limit} bytes and sets the limit.
     *
     * @param limit The limit to set.
     */
    public ParsableByteArray(int limit) {
      this.data = new byte[limit];
      this.limit = limit;
    }
  
    /**
     * Creates a new instance wrapping {@code data}, and sets the limit to {@code data.length}.
     *
     * @param data The array to wrap.
     */
    public ParsableByteArray(byte[] data) {
      this.data = data;
      limit = data.length;
    }
  
    /**
     * Creates a new instance that wraps an existing array.
     *
     * @param data The data to wrap.
     * @param limit The limit to set.
     */
    public ParsableByteArray(byte[] data, int limit) {
      this.data = data;
      this.limit = limit;
    }
  
    /**
     * Resets the position to zero and the limit to the specified value. If the limit exceeds the
     * capacity, {@code data} is replaced with a new array of sufficient size.
     *
     * @param limit The limit to set.
     */
    public void reset(int limit) {
      reset(capacity() < limit ? new byte[limit] : data, limit);
    }
  
    /**
     * Updates the instance to wrap {@code data}, and resets the position to zero.
     *
     * @param data The array to wrap.
     * @param limit The limit to set.
     */
    public void reset(byte[] data, int limit) {
      this.data = data;
      this.limit = limit;
      position = 0;
    }
  
    /**
     * Sets the position and limit to zero.
     */
    public void reset() {
      position = 0;
      limit = 0;
    }
  
    /**
     * Returns the number of bytes yet to be read.
     */
    public int bytesLeft() {
      return limit - position;
    }
  
    /**
     * Returns the limit.
     */
    public int limit() {
      return limit;
    }
  
    /**
     * Sets the limit.
     *
     * @param limit The limit to set.
     */
    public void setLimit(int limit) {
      Assertions.checkArgument(limit >= 0 && limit <= data.length);
      this.limit = limit;
    }
  
    /**
     * Returns the current offset in the array, in bytes.
     */
    public int getPosition() {
      return position;
    }
  
    /**
     * Returns the capacity of the array, which may be larger than the limit.
     */
    public int capacity() {
      return data == null ? 0 : data.length;
    }
  
    /**
     * Sets the reading offset in the array.
     *
     * @param position Byte offset in the array from which to read.
     * @throws IllegalArgumentException Thrown if the new position is neither in nor at the end of the
     *     array.
     */
    public void setPosition(int position) {
      // It is fine for position to be at the end of the array.
      Assertions.checkArgument(position >= 0 && position <= limit);
      this.position = position;
    }
  
    /**
     * Moves the reading offset by {@code bytes}.
     *
     * @param bytes The number of bytes to skip.
     * @throws IllegalArgumentException Thrown if the new position is neither in nor at the end of the
     *     array.
     */
    public void skipBytes(int bytes) {
      setPosition(position + bytes);
    }
  
    /**
     * Reads the next {@code length} bytes into {@code bitArray}, and resets the position of
     * {@code bitArray} to zero.
     *
     * @param bitArray The {@link ParsableBitArray} into which the bytes should be read.
     * @param length The number of bytes to write.
     */
    public void readBytes(ParsableBitArray bitArray, int length) {
      readBytes(bitArray.data, 0, length);
      bitArray.setPosition(0);
    }
  
    /**
     * Reads the next {@code length} bytes into {@code buffer} at {@code offset}.
     *
     * @see System#arraycopy(Object, int, Object, int, int)
     * @param buffer The array into which the read data should be written.
     * @param offset The offset in {@code buffer} at which the read data should be written.
     * @param length The number of bytes to read.
     */
    public void readBytes(byte[] buffer, int offset, int length) {
      System.arraycopy(data, position, buffer, offset, length);
      position += length;
    }
  
    /**
     * Reads the next {@code length} bytes into {@code buffer}.
     *
     * @see ByteBuffer#put(byte[], int, int)
     * @param buffer The {@link ByteBuffer} into which the read data should be written.
     * @param length The number of bytes to read.
     */
    public void readBytes(ByteBuffer buffer, int length) {
      buffer.put(data, position, length);
      position += length;
    }
  
    /**
     * Peeks at the next byte as an unsigned value.
     */
    public int peekUnsignedByte() {
      return (data[position] & 0xFF);
    }
  
    /**
     * Peeks at the next char.
     */
    public char peekChar() {
      return (char) ((data[position] & 0xFF) << 8
          | (data[position + 1] & 0xFF));
    }
  
    /**
     * Reads the next byte as an unsigned value.
     */
    public int readUnsignedByte() {
      return (data[position++] & 0xFF);
    }
  
    /**
     * Reads the next two bytes as an unsigned value.
     */
    public int readUnsignedShort() {
      return (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF);
    }
  
    /**
     * Reads the next two bytes as an unsigned value.
     */
    public int readLittleEndianUnsignedShort() {
      return (data[position++] & 0xFF) | (data[position++] & 0xFF) << 8;
    }
  
    /**
     * Reads the next two bytes as a signed value.
     */
    public short readShort() {
      return (short) ((data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF));
    }
  
    /**
     * Reads the next two bytes as a signed value.
     */
    public short readLittleEndianShort() {
      return (short) ((data[position++] & 0xFF) | (data[position++] & 0xFF) << 8);
    }
  
    /**
     * Reads the next three bytes as an unsigned value.
     */
    public int readUnsignedInt24() {
      return (data[position++] & 0xFF) << 16
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF);
    }
  
    /**
     * Reads the next three bytes as a signed value.
     */
    public int readInt24() {
      return ((data[position++] & 0xFF) << 24) >> 8
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF);
    }
  
    /**
     * Reads the next three bytes as a signed value in little endian order.
     */
    public int readLittleEndianInt24() {
      return (data[position++] & 0xFF)
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF) << 16;
    }
  
    /**
     * Reads the next three bytes as an unsigned value in little endian order.
     */
    public int readLittleEndianUnsignedInt24() {
      return (data[position++] & 0xFF)
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF) << 16;
    }
  
    /**
     * Reads the next four bytes as an unsigned value.
     */
    public long readUnsignedInt() {
      return (data[position++] & 0xFFL) << 24
          | (data[position++] & 0xFFL) << 16
          | (data[position++] & 0xFFL) << 8
          | (data[position++] & 0xFFL);
    }
  
    /**
     * Reads the next four bytes as an unsigned value in little endian order.
     */
    public long readLittleEndianUnsignedInt() {
      return (data[position++] & 0xFFL)
          | (data[position++] & 0xFFL) << 8
          | (data[position++] & 0xFFL) << 16
          | (data[position++] & 0xFFL) << 24;
    }
  
    /**
     * Reads the next four bytes as a signed value
     */
    public int readInt() {
      return (data[position++] & 0xFF) << 24
          | (data[position++] & 0xFF) << 16
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF);
    }
  
    /**
     * Reads the next four bytes as a signed value in little endian order.
     */
    public int readLittleEndianInt() {
      return (data[position++] & 0xFF)
          | (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF) << 16
          | (data[position++] & 0xFF) << 24;
    }
  
    /**
     * Reads the next eight bytes as a signed value.
     */
    public long readLong() {
      return (data[position++] & 0xFFL) << 56
          | (data[position++] & 0xFFL) << 48
          | (data[position++] & 0xFFL) << 40
          | (data[position++] & 0xFFL) << 32
          | (data[position++] & 0xFFL) << 24
          | (data[position++] & 0xFFL) << 16
          | (data[position++] & 0xFFL) << 8
          | (data[position++] & 0xFFL);
    }
  
    /**
     * Reads the next eight bytes as a signed value in little endian order.
     */
    public long readLittleEndianLong() {
      return (data[position++] & 0xFFL)
          | (data[position++] & 0xFFL) << 8
          | (data[position++] & 0xFFL) << 16
          | (data[position++] & 0xFFL) << 24
          | (data[position++] & 0xFFL) << 32
          | (data[position++] & 0xFFL) << 40
          | (data[position++] & 0xFFL) << 48
          | (data[position++] & 0xFFL) << 56;
    }
  
    /**
     * Reads the next four bytes, returning the integer portion of the fixed point 16.16 integer.
     */
    public int readUnsignedFixedPoint1616() {
      int result = (data[position++] & 0xFF) << 8
          | (data[position++] & 0xFF);
      position += 2; // Skip the non-integer portion.
      return result;
    }
  
    /**
     * Reads a Synchsafe integer.
     * <p>
     * Synchsafe integers keep the highest bit of every byte zeroed. A 32 bit synchsafe integer can
     * store 28 bits of information.
     *
     * @return The parsed value.
     */
    public int readSynchSafeInt() {
      int b1 = readUnsignedByte();
      int b2 = readUnsignedByte();
      int b3 = readUnsignedByte();
      int b4 = readUnsignedByte();
      return (b1 << 21) | (b2 << 14) | (b3 << 7) | b4;
    }
  
    /**
     * Reads the next four bytes as an unsigned integer into an integer, if the top bit is a zero.
     *
     * @throws IllegalStateException Thrown if the top bit of the input data is set.
     */
    public int readUnsignedIntToInt() {
      int result = readInt();
      if (result < 0) {
        throw new IllegalStateException("Top bit not zero: " + result);
      }
      return result;
    }
  
    /**
     * Reads the next four bytes as a little endian unsigned integer into an integer, if the top bit
     * is a zero.
     *
     * @throws IllegalStateException Thrown if the top bit of the input data is set.
     */
    public int readLittleEndianUnsignedIntToInt() {
      int result = readLittleEndianInt();
      if (result < 0) {
        throw new IllegalStateException("Top bit not zero: " + result);
      }
      return result;
    }
  
    /**
     * Reads the next eight bytes as an unsigned long into a long, if the top bit is a zero.
     *
     * @throws IllegalStateException Thrown if the top bit of the input data is set.
     */
    public long readUnsignedLongToLong() {
      long result = readLong();
      if (result < 0) {
        throw new IllegalStateException("Top bit not zero: " + result);
      }
      return result;
    }
  
    /**
     * Reads the next four bytes as a 32-bit floating point value.
     */
    public float readFloat() {
      return Float.intBitsToFloat(readInt());
    }
  
    /**
     * Reads the next eight bytes as a 64-bit floating point value.
     */
    public double readDouble() {
      return Double.longBitsToDouble(readLong());
    }
  
    /**
     * Reads the next {@code length} bytes as UTF-8 characters.
     *
     * @param length The number of bytes to read.
     * @return The string encoded by the bytes.
     */
    public String readString(int length) {
      return readString(length, Charset.forName(C.UTF8_NAME));
    }
  
    /**
     * Reads the next {@code length} bytes as characters in the specified {@link Charset}.
     *
     * @param length The number of bytes to read.
     * @param charset The character set of the encoded characters.
     * @return The string encoded by the bytes in the specified character set.
     */
    public String readString(int length, Charset charset) {
      String result = new String(data, position, length, charset);
      position += length;
      return result;
    }
  
    /**
     * Reads the next {@code length} bytes as UTF-8 characters. A terminating NUL byte is discarded,
     * if present.
     *
     * @param length The number of bytes to read.
     * @return The string, not including any terminating NUL byte.
     */
    public String readNullTerminatedString(int length) {
      if (length == 0) {
        return "";
      }
      int stringLength = length;
      int lastIndex = position + length - 1;
      if (lastIndex < limit && data[lastIndex] == 0) {
        stringLength--;
      }
      String result = new String(data, position, stringLength);
      position += length;
      return result;
    }
  
    /**
     * Reads up to the next NUL byte (or the limit) as UTF-8 characters.
     *
     * @return The string not including any terminating NUL byte, or null if the end of the data has
     *     already been reached.
     */
    public String readNullTerminatedString() {
      if (bytesLeft() == 0) {
        return null;
      }
      int stringLimit = position;
      while (stringLimit < limit && data[stringLimit] != 0) {
        stringLimit++;
      }
      String string = new String(data, position, stringLimit - position);
      position = stringLimit;
      if (position < limit) {
        position++;
      }
      return string;
    }
  
    /**
     * Reads a line of text.
     * <p>
     * A line is considered to be terminated by any one of a carriage return ('\r'), a line feed
     * ('\n'), or a carriage return followed immediately by a line feed ('\r\n'). The system's default
     * charset (UTF-8) is used.
     *
     * @return The line not including any line-termination characters, or null if the end of the data
     *     has already been reached.
     */
    public String readLine() {
      if (bytesLeft() == 0) {
        return null;
      }
      int lineLimit = position;
      while (lineLimit < limit && !Util.isLinebreak(data[lineLimit])) {
        lineLimit++;
      }
      if (lineLimit - position >= 3 && data[position] == (byte) 0xEF
          && data[position + 1] == (byte) 0xBB && data[position + 2] == (byte) 0xBF) {
        // There's a byte order mark at the start of the line. Discard it.
        position += 3;
      }
      String line = new String(data, position, lineLimit - position);
      position = lineLimit;
      if (position == limit) {
        return line;
      }
      if (data[position] == '\r') {
        position++;
        if (position == limit) {
          return line;
        }
      }
      if (data[position] == '\n') {
        position++;
      }
      return line;
    }
  
    /**
     * Reads a long value encoded by UTF-8 encoding
     *
     * @throws NumberFormatException if there is a problem with decoding
     * @return Decoded long value
     */
    public long readUtf8EncodedLong() {
      int length = 0;
      long value = data[position];
      // find the high most 0 bit
      for (int j = 7; j >= 0; j--) {
        if ((value & (1 << j)) == 0) {
          if (j < 6) {
            value &= (1 << j) - 1;
            length = 7 - j;
          } else if (j == 7) {
            length = 1;
          }
          break;
        }
      }
      if (length == 0) {
        throw new NumberFormatException("Invalid UTF-8 sequence first byte: " + value);
      }
      for (int i = 1; i < length; i++) {
        int x = data[position + i];
        if ((x & 0xC0) != 0x80) { // if the high most 0 bit not 7th
          throw new NumberFormatException("Invalid UTF-8 sequence continuation byte: " + value);
        }
        value = (value << 6) | (x & 0x3F);
      }
      position += length;
      return value;
    }
  
  }
  