content: /*
   * Copyright (C) 2012 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.android.gallery3d.exif;
  
  import java.nio.charset.Charset;
  import java.text.SimpleDateFormat;
  import java.util.Arrays;
  import java.util.Date;
  
  /**
   * This class stores information of an EXIF tag. For more information about
   * defined EXIF tags, please read the Jeita EXIF 2.2 standard. Tags should be
   * instantiated using {@link ExifInterface#buildTag}.
   *
   * @see ExifInterface
   */
  public class ExifTag {
      /**
       * The BYTE type in the EXIF standard. An 8-bit unsigned integer.
       */
      public static final short TYPE_UNSIGNED_BYTE = 1;
      /**
       * The ASCII type in the EXIF standard. An 8-bit byte containing one 7-bit
       * ASCII code. The final byte is terminated with NULL.
       */
      public static final short TYPE_ASCII = 2;
      /**
       * The SHORT type in the EXIF standard. A 16-bit (2-byte) unsigned integer
       */
      public static final short TYPE_UNSIGNED_SHORT = 3;
      /**
       * The LONG type in the EXIF standard. A 32-bit (4-byte) unsigned integer
       */
      public static final short TYPE_UNSIGNED_LONG = 4;
      /**
       * The RATIONAL type of EXIF standard. It consists of two LONGs. The first
       * one is the numerator and the second one expresses the denominator.
       */
      public static final short TYPE_UNSIGNED_RATIONAL = 5;
      /**
       * The UNDEFINED type in the EXIF standard. An 8-bit byte that can take any
       * value depending on the field definition.
       */
      public static final short TYPE_UNDEFINED = 7;
      /**
       * The SLONG type in the EXIF standard. A 32-bit (4-byte) signed integer
       * (2's complement notation).
       */
      public static final short TYPE_LONG = 9;
      /**
       * The SRATIONAL type of EXIF standard. It consists of two SLONGs. The first
       * one is the numerator and the second one is the denominator.
       */
      public static final short TYPE_RATIONAL = 10;
  
      private static Charset US_ASCII = Charset.forName("US-ASCII");
      private static final int TYPE_TO_SIZE_MAP[] = new int[11];
      private static final int UNSIGNED_SHORT_MAX = 65535;
      private static final long UNSIGNED_LONG_MAX = 4294967295L;
      private static final long LONG_MAX = Integer.MAX_VALUE;
      private static final long LONG_MIN = Integer.MIN_VALUE;
  
      static {
          TYPE_TO_SIZE_MAP[TYPE_UNSIGNED_BYTE] = 1;
          TYPE_TO_SIZE_MAP[TYPE_ASCII] = 1;
          TYPE_TO_SIZE_MAP[TYPE_UNSIGNED_SHORT] = 2;
          TYPE_TO_SIZE_MAP[TYPE_UNSIGNED_LONG] = 4;
          TYPE_TO_SIZE_MAP[TYPE_UNSIGNED_RATIONAL] = 8;
          TYPE_TO_SIZE_MAP[TYPE_UNDEFINED] = 1;
          TYPE_TO_SIZE_MAP[TYPE_LONG] = 4;
          TYPE_TO_SIZE_MAP[TYPE_RATIONAL] = 8;
      }
  
      static final int SIZE_UNDEFINED = 0;
  
      // Exif TagId
      private final short mTagId;
      // Exif Tag Type
      private final short mDataType;
      // If tag has defined count
      private boolean mHasDefinedDefaultComponentCount;
      // Actual data count in tag (should be number of elements in value array)
      private int mComponentCountActual;
      // The ifd that this tag should be put in
      private int mIfd;
      // The value (array of elements of type Tag Type)
      private Object mValue;
      // Value offset in exif header.
      private int mOffset;
  
      private static final SimpleDateFormat TIME_FORMAT = new SimpleDateFormat("yyyy:MM:dd kk:mm:ss");
  
      /**
       * Returns true if the given IFD is a valid IFD.
       */
      public static boolean isValidIfd(int ifdId) {
          return ifdId == IfdId.TYPE_IFD_0 || ifdId == IfdId.TYPE_IFD_1
                  || ifdId == IfdId.TYPE_IFD_EXIF || ifdId == IfdId.TYPE_IFD_INTEROPERABILITY
                  || ifdId == IfdId.TYPE_IFD_GPS;
      }
  
      /**
       * Returns true if a given type is a valid tag type.
       */
      public static boolean isValidType(short type) {
          return type == TYPE_UNSIGNED_BYTE || type == TYPE_ASCII ||
                  type == TYPE_UNSIGNED_SHORT || type == TYPE_UNSIGNED_LONG ||
                  type == TYPE_UNSIGNED_RATIONAL || type == TYPE_UNDEFINED ||
                  type == TYPE_LONG || type == TYPE_RATIONAL;
      }
  
      // Use builtTag in ExifInterface instead of constructor.
      ExifTag(short tagId, short type, int componentCount, int ifd,
              boolean hasDefinedComponentCount) {
          mTagId = tagId;
          mDataType = type;
          mComponentCountActual = componentCount;
          mHasDefinedDefaultComponentCount = hasDefinedComponentCount;
          mIfd = ifd;
          mValue = null;
      }
  
      /**
       * Gets the element size of the given data type in bytes.
       *
       * @see #TYPE_ASCII
       * @see #TYPE_LONG
       * @see #TYPE_RATIONAL
       * @see #TYPE_UNDEFINED
       * @see #TYPE_UNSIGNED_BYTE
       * @see #TYPE_UNSIGNED_LONG
       * @see #TYPE_UNSIGNED_RATIONAL
       * @see #TYPE_UNSIGNED_SHORT
       */
      public static int getElementSize(short type) {
          return TYPE_TO_SIZE_MAP[type];
      }
  
      /**
       * Returns the ID of the IFD this tag belongs to.
       *
       * @see IfdId#TYPE_IFD_0
       * @see IfdId#TYPE_IFD_1
       * @see IfdId#TYPE_IFD_EXIF
       * @see IfdId#TYPE_IFD_GPS
       * @see IfdId#TYPE_IFD_INTEROPERABILITY
       */
      public int getIfd() {
          return mIfd;
      }
  
      protected void setIfd(int ifdId) {
          mIfd = ifdId;
      }
  
      /**
       * Gets the TID of this tag.
       */
      public short getTagId() {
          return mTagId;
      }
  
      /**
       * Gets the data type of this tag
       *
       * @see #TYPE_ASCII
       * @see #TYPE_LONG
       * @see #TYPE_RATIONAL
       * @see #TYPE_UNDEFINED
       * @see #TYPE_UNSIGNED_BYTE
       * @see #TYPE_UNSIGNED_LONG
       * @see #TYPE_UNSIGNED_RATIONAL
       * @see #TYPE_UNSIGNED_SHORT
       */
      public short getDataType() {
          return mDataType;
      }
  
      /**
       * Gets the total data size in bytes of the value of this tag.
       */
      public int getDataSize() {
          return getComponentCount() * getElementSize(getDataType());
      }
  
      /**
       * Gets the component count of this tag.
       */
  
      // TODO: fix integer overflows with this
      public int getComponentCount() {
          return mComponentCountActual;
      }
  
      /**
       * Sets the component count of this tag. Call this function before
       * setValue() if the length of value does not match the component count.
       */
      protected void forceSetComponentCount(int count) {
          mComponentCountActual = count;
      }
  
      /**
       * Returns true if this ExifTag contains value; otherwise, this tag will
       * contain an offset value that is determined when the tag is written.
       */
      public boolean hasValue() {
          return mValue != null;
      }
  
      /**
       * Sets integer values into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_SHORT}. This method will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_SHORT},
       * {@link #TYPE_UNSIGNED_LONG}, or {@link #TYPE_LONG}.</li>
       * <li>The value overflows.</li>
       * <li>The value.length does NOT match the component count in the definition
       * for this tag.</li>
       * </ul>
       */
      public boolean setValue(int[] value) {
          if (checkBadComponentCount(value.length)) {
              return false;
          }
          if (mDataType != TYPE_UNSIGNED_SHORT && mDataType != TYPE_LONG &&
                  mDataType != TYPE_UNSIGNED_LONG) {
              return false;
          }
          if (mDataType == TYPE_UNSIGNED_SHORT && checkOverflowForUnsignedShort(value)) {
              return false;
          } else if (mDataType == TYPE_UNSIGNED_LONG && checkOverflowForUnsignedLong(value)) {
              return false;
          }
  
          long[] data = new long[value.length];
          for (int i = 0; i < value.length; i++) {
              data[i] = value[i];
          }
          mValue = data;
          mComponentCountActual = value.length;
          return true;
      }
  
      /**
       * Sets integer value into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_SHORT}, or {@link #TYPE_LONG}. This method
       * will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_SHORT},
       * {@link #TYPE_UNSIGNED_LONG}, or {@link #TYPE_LONG}.</li>
       * <li>The value overflows.</li>
       * <li>The component count in the definition of this tag is not 1.</li>
       * </ul>
       */
      public boolean setValue(int value) {
          return setValue(new int[] {
                  value
          });
      }
  
      /**
       * Sets long values into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_LONG}. This method will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_LONG}.</li>
       * <li>The value overflows.</li>
       * <li>The value.length does NOT match the component count in the definition
       * for this tag.</li>
       * </ul>
       */
      public boolean setValue(long[] value) {
          if (checkBadComponentCount(value.length) || mDataType != TYPE_UNSIGNED_LONG) {
              return false;
          }
          if (checkOverflowForUnsignedLong(value)) {
              return false;
          }
          mValue = value;
          mComponentCountActual = value.length;
          return true;
      }
  
      /**
       * Sets long values into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_LONG}. This method will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_LONG}.</li>
       * <li>The value overflows.</li>
       * <li>The component count in the definition for this tag is not 1.</li>
       * </ul>
       */
      public boolean setValue(long value) {
          return setValue(new long[] {
                  value
          });
      }
  
      /**
       * Sets a string value into this tag. This method should be used for tags of
       * type {@link #TYPE_ASCII}. The string is converted to an ASCII string.
       * Characters that cannot be converted are replaced with '?'. The length of
       * the string must be equal to either (component count -1) or (component
       * count). The final byte will be set to the string null terminator '\0',
       * overwriting the last character in the string if the value.length is equal
       * to the component count. This method will fail if:
       * <ul>
       * <li>The data type is not {@link #TYPE_ASCII} or {@link #TYPE_UNDEFINED}.</li>
       * <li>The length of the string is not equal to (component count -1) or
       * (component count) in the definition for this tag.</li>
       * </ul>
       */
      public boolean setValue(String value) {
          if (mDataType != TYPE_ASCII && mDataType != TYPE_UNDEFINED) {
              return false;
          }
  
          byte[] buf = value.getBytes(US_ASCII);
          byte[] finalBuf = buf;
          if (buf.length > 0) {
              finalBuf = (buf[buf.length - 1] == 0 || mDataType == TYPE_UNDEFINED) ? buf : Arrays
                  .copyOf(buf, buf.length + 1);
          } else if (mDataType == TYPE_ASCII && mComponentCountActual == 1) {
              finalBuf = new byte[] { 0 };
          }
          int count = finalBuf.length;
          if (checkBadComponentCount(count)) {
              return false;
          }
          mComponentCountActual = count;
          mValue = finalBuf;
          return true;
      }
  
      /**
       * Sets Rational values into this tag. This method should be used for tags
       * of type {@link #TYPE_UNSIGNED_RATIONAL}, or {@link #TYPE_RATIONAL}. This
       * method will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_RATIONAL}
       * or {@link #TYPE_RATIONAL}.</li>
       * <li>The value overflows.</li>
       * <li>The value.length does NOT match the component count in the definition
       * for this tag.</li>
       * </ul>
       *
       * @see Rational
       */
      public boolean setValue(Rational[] value) {
          if (checkBadComponentCount(value.length)) {
              return false;
          }
          if (mDataType != TYPE_UNSIGNED_RATIONAL && mDataType != TYPE_RATIONAL) {
              return false;
          }
          if (mDataType == TYPE_UNSIGNED_RATIONAL && checkOverflowForUnsignedRational(value)) {
              return false;
          } else if (mDataType == TYPE_RATIONAL && checkOverflowForRational(value)) {
              return false;
          }
  
          mValue = value;
          mComponentCountActual = value.length;
          return true;
      }
  
      /**
       * Sets a Rational value into this tag. This method should be used for tags
       * of type {@link #TYPE_UNSIGNED_RATIONAL}, or {@link #TYPE_RATIONAL}. This
       * method will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_RATIONAL}
       * or {@link #TYPE_RATIONAL}.</li>
       * <li>The value overflows.</li>
       * <li>The component count in the definition for this tag is not 1.</li>
       * </ul>
       *
       * @see Rational
       */
      public boolean setValue(Rational value) {
          return setValue(new Rational[] {
                  value
          });
      }
  
      /**
       * Sets byte values into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_BYTE} or {@link #TYPE_UNDEFINED}. This method
       * will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_BYTE} or
       * {@link #TYPE_UNDEFINED} .</li>
       * <li>The length does NOT match the component count in the definition for
       * this tag.</li>
       * </ul>
       */
      public boolean setValue(byte[] value, int offset, int length) {
          if (checkBadComponentCount(length)) {
              return false;
          }
          if (mDataType != TYPE_UNSIGNED_BYTE && mDataType != TYPE_UNDEFINED) {
              return false;
          }
          mValue = new byte[length];
          System.arraycopy(value, offset, mValue, 0, length);
          mComponentCountActual = length;
          return true;
      }
  
      /**
       * Equivalent to setValue(value, 0, value.length).
       */
      public boolean setValue(byte[] value) {
          return setValue(value, 0, value.length);
      }
  
      /**
       * Sets byte value into this tag. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_BYTE} or {@link #TYPE_UNDEFINED}. This method
       * will fail if:
       * <ul>
       * <li>The component type of this tag is not {@link #TYPE_UNSIGNED_BYTE} or
       * {@link #TYPE_UNDEFINED} .</li>
       * <li>The component count in the definition for this tag is not 1.</li>
       * </ul>
       */
      public boolean setValue(byte value) {
          return setValue(new byte[] {
                  value
          });
      }
  
      /**
       * Sets the value for this tag using an appropriate setValue method for the
       * given object. This method will fail if:
       * <ul>
       * <li>The corresponding setValue method for the class of the object passed
       * in would fail.</li>
       * <li>There is no obvious way to cast the object passed in into an EXIF tag
       * type.</li>
       * </ul>
       */
      public boolean setValue(Object obj) {
          if (obj == null) {
              return false;
          } else if (obj instanceof Short) {
              return setValue(((Short) obj).shortValue() & 0x0ffff);
          } else if (obj instanceof String) {
              return setValue((String) obj);
          } else if (obj instanceof int[]) {
              return setValue((int[]) obj);
          } else if (obj instanceof long[]) {
              return setValue((long[]) obj);
          } else if (obj instanceof Rational) {
              return setValue((Rational) obj);
          } else if (obj instanceof Rational[]) {
              return setValue((Rational[]) obj);
          } else if (obj instanceof byte[]) {
              return setValue((byte[]) obj);
          } else if (obj instanceof Integer) {
              return setValue(((Integer) obj).intValue());
          } else if (obj instanceof Long) {
              return setValue(((Long) obj).longValue());
          } else if (obj instanceof Byte) {
              return setValue(((Byte) obj).byteValue());
          } else if (obj instanceof Short[]) {
              // Nulls in this array are treated as zeroes.
              Short[] arr = (Short[]) obj;
              int[] fin = new int[arr.length];
              for (int i = 0; i < arr.length; i++) {
                  fin[i] = (arr[i] == null) ? 0 : arr[i].shortValue() & 0x0ffff;
              }
              return setValue(fin);
          } else if (obj instanceof Integer[]) {
              // Nulls in this array are treated as zeroes.
              Integer[] arr = (Integer[]) obj;
              int[] fin = new int[arr.length];
              for (int i = 0; i < arr.length; i++) {
                  fin[i] = (arr[i] == null) ? 0 : arr[i].intValue();
              }
              return setValue(fin);
          } else if (obj instanceof Long[]) {
              // Nulls in this array are treated as zeroes.
              Long[] arr = (Long[]) obj;
              long[] fin = new long[arr.length];
              for (int i = 0; i < arr.length; i++) {
                  fin[i] = (arr[i] == null) ? 0 : arr[i].longValue();
              }
              return setValue(fin);
          } else if (obj instanceof Byte[]) {
              // Nulls in this array are treated as zeroes.
              Byte[] arr = (Byte[]) obj;
              byte[] fin = new byte[arr.length];
              for (int i = 0; i < arr.length; i++) {
                  fin[i] = (arr[i] == null) ? 0 : arr[i].byteValue();
              }
              return setValue(fin);
          } else {
              return false;
          }
      }
  
      /**
       * Sets a timestamp to this tag. The method converts the timestamp with the
       * format of "yyyy:MM:dd kk:mm:ss" and calls {@link #setValue(String)}. This
       * method will fail if the data type is not {@link #TYPE_ASCII} or the
       * component count of this tag is not 20 or undefined.
       *
       * @param time the number of milliseconds since Jan. 1, 1970 GMT
       * @return true on success
       */
      public boolean setTimeValue(long time) {
          // synchronized on TIME_FORMAT as SimpleDateFormat is not thread safe
          synchronized (TIME_FORMAT) {
              return setValue(TIME_FORMAT.format(new Date(time)));
          }
      }
  
      /**
       * Gets the value as a String. This method should be used for tags of type
       * {@link #TYPE_ASCII}.
       *
       * @return the value as a String, or null if the tag's value does not exist
       *         or cannot be converted to a String.
       */
      public String getValueAsString() {
          if (mValue == null) {
              return null;
          } else if (mValue instanceof String) {
              return (String) mValue;
          } else if (mValue instanceof byte[]) {
              return new String((byte[]) mValue, US_ASCII);
          }
          return null;
      }
  
      /**
       * Gets the value as a String. This method should be used for tags of type
       * {@link #TYPE_ASCII}.
       *
       * @param defaultValue the String to return if the tag's value does not
       *            exist or cannot be converted to a String.
       * @return the tag's value as a String, or the defaultValue.
       */
      public String getValueAsString(String defaultValue) {
          String s = getValueAsString();
          if (s == null) {
              return defaultValue;
          }
          return s;
      }
  
      /**
       * Gets the value as a byte array. This method should be used for tags of
       * type {@link #TYPE_UNDEFINED} or {@link #TYPE_UNSIGNED_BYTE}.
       *
       * @return the value as a byte array, or null if the tag's value does not
       *         exist or cannot be converted to a byte array.
       */
      public byte[] getValueAsBytes() {
          if (mValue instanceof byte[]) {
              return (byte[]) mValue;
          }
          return null;
      }
  
      /**
       * Gets the value as a byte. If there are more than 1 bytes in this value,
       * gets the first byte. This method should be used for tags of type
       * {@link #TYPE_UNDEFINED} or {@link #TYPE_UNSIGNED_BYTE}.
       *
       * @param defaultValue the byte to return if tag's value does not exist or
       *            cannot be converted to a byte.
       * @return the tag's value as a byte, or the defaultValue.
       */
      public byte getValueAsByte(byte defaultValue) {
          byte[] b = getValueAsBytes();
          if (b == null || b.length < 1) {
              return defaultValue;
          }
          return b[0];
      }
  
      /**
       * Gets the value as an array of Rationals. This method should be used for
       * tags of type {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}.
       *
       * @return the value as as an array of Rationals, or null if the tag's value
       *         does not exist or cannot be converted to an array of Rationals.
       */
      public Rational[] getValueAsRationals() {
          if (mValue instanceof Rational[]) {
              return (Rational[]) mValue;
          }
          return null;
      }
  
      /**
       * Gets the value as a Rational. If there are more than 1 Rationals in this
       * value, gets the first one. This method should be used for tags of type
       * {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}.
       *
       * @param defaultValue the Rational to return if tag's value does not exist
       *            or cannot be converted to a Rational.
       * @return the tag's value as a Rational, or the defaultValue.
       */
      public Rational getValueAsRational(Rational defaultValue) {
          Rational[] r = getValueAsRationals();
          if (r == null || r.length < 1) {
              return defaultValue;
          }
          return r[0];
      }
  
      /**
       * Gets the value as a Rational. If there are more than 1 Rationals in this
       * value, gets the first one. This method should be used for tags of type
       * {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}.
       *
       * @param defaultValue the numerator of the Rational to return if tag's
       *            value does not exist or cannot be converted to a Rational (the
       *            denominator will be 1).
       * @return the tag's value as a Rational, or the defaultValue.
       */
      public Rational getValueAsRational(long defaultValue) {
          Rational defaultVal = new Rational(defaultValue, 1);
          return getValueAsRational(defaultVal);
      }
  
      /**
       * Gets the value as an array of ints. This method should be used for tags
       * of type {@link #TYPE_UNSIGNED_SHORT}, {@link #TYPE_UNSIGNED_LONG}.
       *
       * @return the value as as an array of ints, or null if the tag's value does
       *         not exist or cannot be converted to an array of ints.
       */
      public int[] getValueAsInts() {
          if (mValue == null) {
              return null;
          } else if (mValue instanceof long[]) {
              long[] val = (long[]) mValue;
              int[] arr = new int[val.length];
              for (int i = 0; i < val.length; i++) {
                  arr[i] = (int) val[i]; // Truncates
              }
              return arr;
          }
          return null;
      }
  
      /**
       * Gets the value as an int. If there are more than 1 ints in this value,
       * gets the first one. This method should be used for tags of type
       * {@link #TYPE_UNSIGNED_SHORT}, {@link #TYPE_UNSIGNED_LONG}.
       *
       * @param defaultValue the int to return if tag's value does not exist or
       *            cannot be converted to an int.
       * @return the tag's value as a int, or the defaultValue.
       */
      public int getValueAsInt(int defaultValue) {
          int[] i = getValueAsInts();
          if (i == null || i.length < 1) {
              return defaultValue;
          }
          return i[0];
      }
  
      /**
       * Gets the value as an array of longs. This method should be used for tags
       * of type {@link #TYPE_UNSIGNED_LONG}.
       *
       * @return the value as as an array of longs, or null if the tag's value
       *         does not exist or cannot be converted to an array of longs.
       */
      public long[] getValueAsLongs() {
          if (mValue instanceof long[]) {
              return (long[]) mValue;
          }
          return null;
      }
  
      /**
       * Gets the value or null if none exists. If there are more than 1 longs in
       * this value, gets the first one. This method should be used for tags of
       * type {@link #TYPE_UNSIGNED_LONG}.
       *
       * @param defaultValue the long to return if tag's value does not exist or
       *            cannot be converted to a long.
       * @return the tag's value as a long, or the defaultValue.
       */
      public long getValueAsLong(long defaultValue) {
          long[] l = getValueAsLongs();
          if (l == null || l.length < 1) {
              return defaultValue;
          }
          return l[0];
      }
  
      /**
       * Gets the tag's value or null if none exists.
       */
      public Object getValue() {
          return mValue;
      }
  
      /**
       * Gets a long representation of the value.
       *
       * @param defaultValue value to return if there is no value or value is a
       *            rational with a denominator of 0.
       * @return the tag's value as a long, or defaultValue if no representation
       *         exists.
       */
      public long forceGetValueAsLong(long defaultValue) {
          long[] l = getValueAsLongs();
          if (l != null && l.length >= 1) {
              return l[0];
          }
          byte[] b = getValueAsBytes();
          if (b != null && b.length >= 1) {
              return b[0];
          }
          Rational[] r = getValueAsRationals();
          if (r != null && r.length >= 1 && r[0].getDenominator() != 0) {
              return (long) r[0].toDouble();
          }
          return defaultValue;
      }
  
      /**
       * Gets a string representation of the value.
       */
      public String forceGetValueAsString() {
          if (mValue == null) {
              return "";
          } else if (mValue instanceof byte[]) {
              if (mDataType == TYPE_ASCII) {
                  return new String((byte[]) mValue, US_ASCII);
              } else {
                  return Arrays.toString((byte[]) mValue);
              }
          } else if (mValue instanceof long[]) {
              if (((long[]) mValue).length == 1) {
                  return String.valueOf(((long[]) mValue)[0]);
              } else {
                  return Arrays.toString((long[]) mValue);
              }
          } else if (mValue instanceof Object[]) {
              if (((Object[]) mValue).length == 1) {
                  Object val = ((Object[]) mValue)[0];
                  if (val == null) {
                      return "";
                  } else {
                      return val.toString();
                  }
              } else {
                  return Arrays.toString((Object[]) mValue);
              }
          } else {
              return mValue.toString();
          }
      }
  
      /**
       * Gets the value for type {@link #TYPE_ASCII}, {@link #TYPE_LONG},
       * {@link #TYPE_UNDEFINED}, {@link #TYPE_UNSIGNED_BYTE},
       * {@link #TYPE_UNSIGNED_LONG}, or {@link #TYPE_UNSIGNED_SHORT}. For
       * {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}, call
       * {@link #getRational(int)} instead.
       *
       * @exception IllegalArgumentException if the data type is
       *                {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}.
       */
      protected long getValueAt(int index) {
          if (mValue instanceof long[]) {
              return ((long[]) mValue)[index];
          } else if (mValue instanceof byte[]) {
              return ((byte[]) mValue)[index];
          }
          throw new IllegalArgumentException("Cannot get integer value from "
                  + convertTypeToString(mDataType));
      }
  
      /**
       * Gets the {@link #TYPE_ASCII} data.
       *
       * @exception IllegalArgumentException If the type is NOT
       *                {@link #TYPE_ASCII}.
       */
      protected String getString() {
          if (mDataType != TYPE_ASCII) {
              throw new IllegalArgumentException("Cannot get ASCII value from "
                      + convertTypeToString(mDataType));
          }
          return new String((byte[]) mValue, US_ASCII);
      }
  
      /*
       * Get the converted ascii byte. Used by ExifOutputStream.
       */
      protected byte[] getStringByte() {
          return (byte[]) mValue;
      }
  
      /**
       * Gets the {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL} data.
       *
       * @exception IllegalArgumentException If the type is NOT
       *                {@link #TYPE_RATIONAL} or {@link #TYPE_UNSIGNED_RATIONAL}.
       */
      protected Rational getRational(int index) {
          if ((mDataType != TYPE_RATIONAL) && (mDataType != TYPE_UNSIGNED_RATIONAL)) {
              throw new IllegalArgumentException("Cannot get RATIONAL value from "
                      + convertTypeToString(mDataType));
          }
          return ((Rational[]) mValue)[index];
      }
  
      /**
       * Equivalent to getBytes(buffer, 0, buffer.length).
       */
      protected void getBytes(byte[] buf) {
          getBytes(buf, 0, buf.length);
      }
  
      /**
       * Gets the {@link #TYPE_UNDEFINED} or {@link #TYPE_UNSIGNED_BYTE} data.
       *
       * @param buf the byte array in which to store the bytes read.
       * @param offset the initial position in buffer to store the bytes.
       * @param length the maximum number of bytes to store in buffer. If length >
       *            component count, only the valid bytes will be stored.
       * @exception IllegalArgumentException If the type is NOT
       *                {@link #TYPE_UNDEFINED} or {@link #TYPE_UNSIGNED_BYTE}.
       */
      protected void getBytes(byte[] buf, int offset, int length) {
          if ((mDataType != TYPE_UNDEFINED) && (mDataType != TYPE_UNSIGNED_BYTE)) {
              throw new IllegalArgumentException("Cannot get BYTE value from "
                      + convertTypeToString(mDataType));
          }
          System.arraycopy(mValue, 0, buf, offset,
                  (length > mComponentCountActual) ? mComponentCountActual : length);
      }
  
      /**
       * Gets the offset of this tag. This is only valid if this data size > 4 and
       * contains an offset to the location of the actual value.
       */
      protected int getOffset() {
          return mOffset;
      }
  
      /**
       * Sets the offset of this tag.
       */
      protected void setOffset(int offset) {
          mOffset = offset;
      }
  
      protected void setHasDefinedCount(boolean d) {
          mHasDefinedDefaultComponentCount = d;
      }
  
      protected boolean hasDefinedCount() {
          return mHasDefinedDefaultComponentCount;
      }
  
      private boolean checkBadComponentCount(int count) {
          if (mHasDefinedDefaultComponentCount && (mComponentCountActual != count)) {
              return true;
          }
          return false;
      }
  
      private static String convertTypeToString(short type) {
          switch (type) {
              case TYPE_UNSIGNED_BYTE:
                  return "UNSIGNED_BYTE";
              case TYPE_ASCII:
                  return "ASCII";
              case TYPE_UNSIGNED_SHORT:
                  return "UNSIGNED_SHORT";
              case TYPE_UNSIGNED_LONG:
                  return "UNSIGNED_LONG";
              case TYPE_UNSIGNED_RATIONAL:
                  return "UNSIGNED_RATIONAL";
              case TYPE_UNDEFINED:
                  return "UNDEFINED";
              case TYPE_LONG:
                  return "LONG";
              case TYPE_RATIONAL:
                  return "RATIONAL";
              default:
                  return "";
          }
      }
  
      private boolean checkOverflowForUnsignedShort(int[] value) {
          for (int v : value) {
              if (v > UNSIGNED_SHORT_MAX || v < 0) {
                  return true;
              }
          }
          return false;
      }
  
      private boolean checkOverflowForUnsignedLong(long[] value) {
          for (long v : value) {
              if (v < 0 || v > UNSIGNED_LONG_MAX) {
                  return true;
              }
          }
          return false;
      }
  
      private boolean checkOverflowForUnsignedLong(int[] value) {
          for (int v : value) {
              if (v < 0) {
                  return true;
              }
          }
          return false;
      }
  
      private boolean checkOverflowForUnsignedRational(Rational[] value) {
          for (Rational v : value) {
              if (v.getNumerator() < 0 || v.getDenominator() < 0
                      || v.getNumerator() > UNSIGNED_LONG_MAX
                      || v.getDenominator() > UNSIGNED_LONG_MAX) {
                  return true;
              }
          }
          return false;
      }
  
      private boolean checkOverflowForRational(Rational[] value) {
          for (Rational v : value) {
              if (v.getNumerator() < LONG_MIN || v.getDenominator() < LONG_MIN
                      || v.getNumerator() > LONG_MAX
                      || v.getDenominator() > LONG_MAX) {
                  return true;
              }
          }
          return false;
      }
  
      @Override
      public boolean equals(Object obj) {
          if (obj == null) {
              return false;
          }
          if (obj instanceof ExifTag) {
              ExifTag tag = (ExifTag) obj;
              if (tag.mTagId != this.mTagId
                      || tag.mComponentCountActual != this.mComponentCountActual
                      || tag.mDataType != this.mDataType) {
                  return false;
              }
              if (mValue != null) {
                  if (tag.mValue == null) {
                      return false;
                  } else if (mValue instanceof long[]) {
                      if (!(tag.mValue instanceof long[])) {
                          return false;
                      }
                      return Arrays.equals((long[]) mValue, (long[]) tag.mValue);
                  } else if (mValue instanceof Rational[]) {
                      if (!(tag.mValue instanceof Rational[])) {
                          return false;
                      }
                      return Arrays.equals((Rational[]) mValue, (Rational[]) tag.mValue);
                  } else if (mValue instanceof byte[]) {
                      if (!(tag.mValue instanceof byte[])) {
                          return false;
                      }
                      return Arrays.equals((byte[]) mValue, (byte[]) tag.mValue);
                  } else {
                      return mValue.equals(tag.mValue);
                  }
              } else {
                  return tag.mValue == null;
              }
          }
          return false;
      }
  
      @Override
      public String toString() {
          return String.format("tag id: %04X\n", mTagId) + "ifd id: " + mIfd + "\ntype: "
                  + convertTypeToString(mDataType) + "\ncount: " + mComponentCountActual
                  + "\noffset: " + mOffset + "\nvalue: " + forceGetValueAsString() + "\n";
      }
  
  }
  