/*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.util;
  
  import io.netty.util.internal.EmptyArrays;
  import io.netty.util.internal.InternalThreadLocalMap;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.PlatformDependent;
  
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetEncoder;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  import java.util.regex.Pattern;
  import java.util.regex.PatternSyntaxException;
  
  import static io.netty.util.internal.MathUtil.isOutOfBounds;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  /**
   * A string which has been encoded into a character encoding whose character always takes a single byte, similarly to
   * ASCII. It internally keeps its content in a byte array unlike {@link String}, which uses a character array, for
   * reduced memory footprint and faster data transfer from/to byte-based data structures such as a byte array and
   * {@link ByteBuffer}. It is often used in conjunction with {@code Headers} that require a {@link CharSequence}.
   * <p>
   * This class was designed to provide an immutable array of bytes, and caches some internal state based upon the value
   * of this array. However underlying access to this byte array is provided via not copying the array on construction or
   * {@link #array()}. If any changes are made to the underlying byte array it is the user's responsibility to call
   * {@link #arrayChanged()} so the state of this class can be reset.
   */
  public final class AsciiString implements CharSequence, Comparable<CharSequence> {
      public static final AsciiString EMPTY_STRING = cached("");
      private static final char MAX_CHAR_VALUE = 255;
  
      public static final int INDEX_NOT_FOUND = -1;
  
      /**
       * If this value is modified outside the constructor then call {@link #arrayChanged()}.
       */
      private final byte[] value;
      /**
       * Offset into {@link #value} that all operations should use when acting upon {@link #value}.
       */
      private final int offset;
      /**
       * Length in bytes for {@link #value} that we care about. This is independent from {@code value.length}
       * because we may be looking at a subsection of the array.
       */
      private final int length;
      /**
       * The hash code is cached after it is first computed. It can be reset with {@link #arrayChanged()}.
       */
      private int hash;
      /**
       * Used to cache the {@link #toString()} value.
       */
      private String string;
  
      /**
       * Initialize this byte string based upon a byte array. A copy will be made.
       */
      public AsciiString(byte[] value) {
          this(value, true);
      }
  
      /**
       * Initialize this byte string based upon a byte array.
       * {@code copy} determines if a copy is made or the array is shared.
       */
      public AsciiString(byte[] value, boolean copy) {
          this(value, 0, value.length, copy);
      }
  
      /**
       * Construct a new instance from a {@code byte[]} array.
       * @param copy {@code true} then a copy of the memory will be made. {@code false} the underlying memory
       * will be shared.
       */
      public AsciiString(byte[] value, int start, int length, boolean copy) {
          if (copy) {
              final byte[] rangedCopy = new byte[length];
              System.arraycopy(value, start, rangedCopy, 0, rangedCopy.length);
              this.value = rangedCopy;
             this.offset = 0;
         } else {
             if (isOutOfBounds(start, length, value.length)) {
                 throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= start + length(" +
                         length + ") <= " + "value.length(" + value.length + ')');
             }
             this.value = value;
             this.offset = start;
         }
         this.length = length;
     }
 
     /**
      * Create a copy of the underlying storage from {@code value}.
      * The copy will start at {@link ByteBuffer#position()} and copy {@link ByteBuffer#remaining()} bytes.
      */
     public AsciiString(ByteBuffer value) {
         this(value, true);
     }
 
     /**
      * Initialize an instance based upon the underlying storage from {@code value}.
      * There is a potential to share the underlying array storage if {@link ByteBuffer#hasArray()} is {@code true}.
      * if {@code copy} is {@code true} a copy will be made of the memory.
      * if {@code copy} is {@code false} the underlying storage will be shared, if possible.
      */
     public AsciiString(ByteBuffer value, boolean copy) {
         this(value, value.position(), value.remaining(), copy);
     }
 
     /**
      * Initialize an {@link AsciiString} based upon the underlying storage from {@code value}.
      * There is a potential to share the underlying array storage if {@link ByteBuffer#hasArray()} is {@code true}.
      * if {@code copy} is {@code true} a copy will be made of the memory.
      * if {@code copy} is {@code false} the underlying storage will be shared, if possible.
      */
     public AsciiString(ByteBuffer value, int start, int length, boolean copy) {
         if (isOutOfBounds(start, length, value.capacity())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= start + length(" + length
                             + ") <= " + "value.capacity(" + value.capacity() + ')');
         }
 
         if (value.hasArray()) {
             if (copy) {
                 final int bufferOffset = value.arrayOffset() + start;
                 this.value = Arrays.copyOfRange(value.array(), bufferOffset, bufferOffset + length);
                 offset = 0;
             } else {
                 this.value = value.array();
                 this.offset = start;
             }
         } else {
             this.value = PlatformDependent.allocateUninitializedArray(length);
             int oldPos = value.position();
             value.get(this.value, 0, length);
             value.position(oldPos);
             this.offset = 0;
         }
         this.length = length;
     }
 
     /**
      * Create a copy of {@code value} into this instance assuming ASCII encoding.
      */
     public AsciiString(char[] value) {
         this(value, 0, value.length);
     }
 
     /**
      * Create a copy of {@code value} into this instance assuming ASCII encoding.
      * The copy will start at index {@code start} and copy {@code length} bytes.
      */
     public AsciiString(char[] value, int start, int length) {
         if (isOutOfBounds(start, length, value.length)) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= start + length(" + length
                             + ") <= " + "value.length(" + value.length + ')');
         }
 
         this.value = PlatformDependent.allocateUninitializedArray(length);
         for (int i = 0, j = start; i < length; i++, j++) {
             this.value[i] = c2b(value[j]);
         }
         this.offset = 0;
         this.length = length;
     }
 
     /**
      * Create a copy of {@code value} into this instance using the encoding type of {@code charset}.
      */
     public AsciiString(char[] value, Charset charset) {
         this(value, charset, 0, value.length);
     }
 
     /**
      * Create a copy of {@code value} into a this instance using the encoding type of {@code charset}.
      * The copy will start at index {@code start} and copy {@code length} bytes.
      */
     public AsciiString(char[] value, Charset charset, int start, int length) {
         CharBuffer cbuf = CharBuffer.wrap(value, start, length);
         CharsetEncoder encoder = CharsetUtil.encoder(charset);
         ByteBuffer nativeBuffer = ByteBuffer.allocate((int) (encoder.maxBytesPerChar() * length));
         encoder.encode(cbuf, nativeBuffer, true);
         final int bufferOffset = nativeBuffer.arrayOffset();
         this.value = Arrays.copyOfRange(nativeBuffer.array(), bufferOffset, bufferOffset + nativeBuffer.position());
         this.offset = 0;
         this.length =  this.value.length;
     }
 
     /**
      * Create a copy of {@code value} into this instance assuming ASCII encoding.
      */
     public AsciiString(CharSequence value) {
         this(value, 0, value.length());
     }
 
     /**
      * Create a copy of {@code value} into this instance assuming ASCII encoding.
      * The copy will start at index {@code start} and copy {@code length} bytes.
      */
     public AsciiString(CharSequence value, int start, int length) {
         if (isOutOfBounds(start, length, value.length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= start + length(" + length
                             + ") <= " + "value.length(" + value.length() + ')');
         }
 
         this.value = PlatformDependent.allocateUninitializedArray(length);
         for (int i = 0, j = start; i < length; i++, j++) {
             this.value[i] = c2b(value.charAt(j));
         }
         this.offset = 0;
         this.length = length;
     }
 
     /**
      * Create a copy of {@code value} into this instance using the encoding type of {@code charset}.
      */
     public AsciiString(CharSequence value, Charset charset) {
         this(value, charset, 0, value.length());
     }
 
     /**
      * Create a copy of {@code value} into this instance using the encoding type of {@code charset}.
      * The copy will start at index {@code start} and copy {@code length} bytes.
      */
     public AsciiString(CharSequence value, Charset charset, int start, int length) {
         CharBuffer cbuf = CharBuffer.wrap(value, start, start + length);
         CharsetEncoder encoder = CharsetUtil.encoder(charset);
         ByteBuffer nativeBuffer = ByteBuffer.allocate((int) (encoder.maxBytesPerChar() * length));
         encoder.encode(cbuf, nativeBuffer, true);
         final int offset = nativeBuffer.arrayOffset();
         this.value = Arrays.copyOfRange(nativeBuffer.array(), offset, offset + nativeBuffer.position());
         this.offset = 0;
         this.length = this.value.length;
     }
 
     /**
      * Iterates over the readable bytes of this buffer with the specified {@code processor} in ascending order.
      *
      * @return {@code -1} if the processor iterated to or beyond the end of the readable bytes.
      *         The last-visited index If the {@link ByteProcessor#process(byte)} returned {@code false}.
      */
     public int forEachByte(ByteProcessor visitor) throws Exception {
         return forEachByte0(0, length(), visitor);
     }
 
     /**
      * Iterates over the specified area of this buffer with the specified {@code processor} in ascending order.
      * (i.e. {@code index}, {@code (index + 1)},  .. {@code (index + length - 1)}).
      *
      * @return {@code -1} if the processor iterated to or beyond the end of the specified area.
      *         The last-visited index If the {@link ByteProcessor#process(byte)} returned {@code false}.
      */
     public int forEachByte(int index, int length, ByteProcessor visitor) throws Exception {
         if (isOutOfBounds(index, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= index(" + index + ") <= start + length(" + length
                     + ") <= " + "length(" + length() + ')');
         }
         return forEachByte0(index, length, visitor);
     }
 
     private int forEachByte0(int index, int length, ByteProcessor visitor) throws Exception {
         final int len = offset + index + length;
         for (int i = offset + index; i < len; ++i) {
             if (!visitor.process(value[i])) {
                 return i - offset;
             }
         }
         return -1;
     }
 
     /**
      * Iterates over the readable bytes of this buffer with the specified {@code processor} in descending order.
      *
      * @return {@code -1} if the processor iterated to or beyond the beginning of the readable bytes.
      *         The last-visited index If the {@link ByteProcessor#process(byte)} returned {@code false}.
      */
     public int forEachByteDesc(ByteProcessor visitor) throws Exception {
         return forEachByteDesc0(0, length(), visitor);
     }
 
     /**
      * Iterates over the specified area of this buffer with the specified {@code processor} in descending order.
      * (i.e. {@code (index + length - 1)}, {@code (index + length - 2)}, ... {@code index}).
      *
      * @return {@code -1} if the processor iterated to or beyond the beginning of the specified area.
      *         The last-visited index If the {@link ByteProcessor#process(byte)} returned {@code false}.
      */
     public int forEachByteDesc(int index, int length, ByteProcessor visitor) throws Exception {
         if (isOutOfBounds(index, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= index(" + index + ") <= start + length(" + length
                     + ") <= " + "length(" + length() + ')');
         }
         return forEachByteDesc0(index, length, visitor);
     }
 
     private int forEachByteDesc0(int index, int length, ByteProcessor visitor) throws Exception {
         final int end = offset + index;
         for (int i = offset + index + length - 1; i >= end; --i) {
             if (!visitor.process(value[i])) {
                 return i - offset;
             }
         }
         return -1;
     }
 
     public byte byteAt(int index) {
         // We must do a range check here to enforce the access does not go outside our sub region of the array.
         // We rely on the array access itself to pick up the array out of bounds conditions
         if (index < 0 || index >= length) {
             throw new IndexOutOfBoundsException("index: " + index + " must be in the range [0," + length + ")");
         }
         // Try to use unsafe to avoid double checking the index bounds
         if (PlatformDependent.hasUnsafe()) {
             return PlatformDependent.getByte(value, index + offset);
         }
         return value[index + offset];
     }
 
     /**
      * Determine if this instance has 0 length.
      */
     public boolean isEmpty() {
         return length == 0;
     }
 
     /**
      * The length in bytes of this instance.
      */
     @Override
     public int length() {
         return length;
     }
 
     /**
      * During normal use cases the {@link AsciiString} should be immutable, but if the underlying array is shared,
      * and changes then this needs to be called.
      */
     public void arrayChanged() {
         string = null;
         hash = 0;
     }
 
     /**
      * This gives direct access to the underlying storage array.
      * The {@link #toByteArray()} should be preferred over this method.
      * If the return value is changed then {@link #arrayChanged()} must be called.
      * @see #arrayOffset()
      * @see #isEntireArrayUsed()
      */
     public byte[] array() {
         return value;
     }
 
     /**
      * The offset into {@link #array()} for which data for this ByteString begins.
      * @see #array()
      * @see #isEntireArrayUsed()
      */
     public int arrayOffset() {
         return offset;
     }
 
     /**
      * Determine if the storage represented by {@link #array()} is entirely used.
      * @see #array()
      */
     public boolean isEntireArrayUsed() {
         return offset == 0 && length == value.length;
     }
 
     /**
      * Converts this string to a byte array.
      */
     public byte[] toByteArray() {
         return toByteArray(0, length());
     }
 
     /**
      * Converts a subset of this string to a byte array.
      * The subset is defined by the range [{@code start}, {@code end}).
      */
     public byte[] toByteArray(int start, int end) {
         return Arrays.copyOfRange(value, start + offset, end + offset);
     }
 
     /**
      * Copies the content of this string to a byte array.
      *
      * @param srcIdx the starting offset of characters to copy.
      * @param dst the destination byte array.
      * @param dstIdx the starting offset in the destination byte array.
      * @param length the number of characters to copy.
      */
     public void copy(int srcIdx, byte[] dst, int dstIdx, int length) {
         if (isOutOfBounds(srcIdx, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= srcIdx(" + srcIdx + ") <= srcIdx + length("
                             + length + ") <= srcLen(" + length() + ')');
         }
 
         System.arraycopy(value, srcIdx + offset, checkNotNull(dst, "dst"), dstIdx, length);
     }
 
     @Override
     public char charAt(int index) {
         return b2c(byteAt(index));
     }
 
     /**
      * Determines if this {@code String} contains the sequence of characters in the {@code CharSequence} passed.
      *
      * @param cs the character sequence to search for.
      * @return {@code true} if the sequence of characters are contained in this string, otherwise {@code false}.
      */
     public boolean contains(CharSequence cs) {
         return indexOf(cs) >= 0;
     }
 
     /**
      * Compares the specified string to this string using the ASCII values of the characters. Returns 0 if the strings
      * contain the same characters in the same order. Returns a negative integer if the first non-equal character in
      * this string has an ASCII value which is less than the ASCII value of the character at the same position in the
      * specified string, or if this string is a prefix of the specified string. Returns a positive integer if the first
      * non-equal character in this string has a ASCII value which is greater than the ASCII value of the character at
      * the same position in the specified string, or if the specified string is a prefix of this string.
      *
      * @param string the string to compare.
      * @return 0 if the strings are equal, a negative integer if this string is before the specified string, or a
      *         positive integer if this string is after the specified string.
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     @Override
     public int compareTo(CharSequence string) {
         if (this == string) {
             return 0;
         }
 
         int result;
         int length1 = length();
         int length2 = string.length();
         int minLength = Math.min(length1, length2);
         for (int i = 0, j = arrayOffset(); i < minLength; i++, j++) {
             result = b2c(value[j]) - string.charAt(i);
             if (result != 0) {
                 return result;
             }
         }
 
         return length1 - length2;
     }
 
     /**
      * Concatenates this string and the specified string.
      *
      * @param string the string to concatenate
      * @return a new string which is the concatenation of this string and the specified string.
      */
     public AsciiString concat(CharSequence string) {
         int thisLen = length();
         int thatLen = string.length();
         if (thatLen == 0) {
             return this;
         }
 
         if (string instanceof AsciiString) {
             AsciiString that = (AsciiString) string;
             if (isEmpty()) {
                 return that;
             }
 
             byte[] newValue = PlatformDependent.allocateUninitializedArray(thisLen + thatLen);
             System.arraycopy(value, arrayOffset(), newValue, 0, thisLen);
             System.arraycopy(that.value, that.arrayOffset(), newValue, thisLen, thatLen);
             return new AsciiString(newValue, false);
         }
 
         if (isEmpty()) {
             return new AsciiString(string);
         }
 
         byte[] newValue = PlatformDependent.allocateUninitializedArray(thisLen + thatLen);
         System.arraycopy(value, arrayOffset(), newValue, 0, thisLen);
         for (int i = thisLen, j = 0; i < newValue.length; i++, j++) {
             newValue[i] = c2b(string.charAt(j));
         }
 
         return new AsciiString(newValue, false);
     }
 
     /**
      * Compares the specified string to this string to determine if the specified string is a suffix.
      *
      * @param suffix the suffix to look for.
      * @return {@code true} if the specified string is a suffix of this string, {@code false} otherwise.
      * @throws NullPointerException if {@code suffix} is {@code null}.
      */
     public boolean endsWith(CharSequence suffix) {
         int suffixLen = suffix.length();
         return regionMatches(length() - suffixLen, suffix, 0, suffixLen);
     }
 
     /**
      * Compares the specified string to this string ignoring the case of the characters and returns true if they are
      * equal.
      *
      * @param string the string to compare.
      * @return {@code true} if the specified string is equal to this string, {@code false} otherwise.
      */
     public boolean contentEqualsIgnoreCase(CharSequence string) {
         if (this == string) {
             return true;
         }
 
         if (string == null || string.length() != length()) {
             return false;
         }
 
         if (string instanceof AsciiString) {
             AsciiString other = (AsciiString) string;
             byte[] value = this.value;
             if (offset == 0 && other.offset == 0 && length == value.length) {
                 byte[] otherValue = other.value;
                 for (int i = 0; i < value.length; ++i) {
                     if (!equalsIgnoreCase(value[i], otherValue[i])) {
                         return false;
                     }
                 }
                 return true;
             }
             return misalignedEqualsIgnoreCase(other);
         }
 
         byte[] value = this.value;
         for (int i = offset, j = 0; j < string.length(); ++i, ++j) {
             if (!equalsIgnoreCase(b2c(value[i]), string.charAt(j))) {
                 return false;
             }
         }
         return true;
     }
 
     private boolean misalignedEqualsIgnoreCase(AsciiString other) {
         byte[] value = this.value;
         byte[] otherValue = other.value;
         for (int i = offset, j = other.offset, end = offset + length; i < end; ++i, ++j) {
             if (!equalsIgnoreCase(value[i], otherValue[j])) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Copies the characters in this string to a character array.
      *
      * @return a character array containing the characters of this string.
      */
     public char[] toCharArray() {
         return toCharArray(0, length());
     }
 
     /**
      * Copies the characters in this string to a character array.
      *
      * @return a character array containing the characters of this string.
      */
     public char[] toCharArray(int start, int end) {
         int length = end - start;
         if (length == 0) {
             return EmptyArrays.EMPTY_CHARS;
         }
 
         if (isOutOfBounds(start, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= srcIdx + length("
                             + length + ") <= srcLen(" + length() + ')');
         }
 
         final char[] buffer = new char[length];
         for (int i = 0, j = start + arrayOffset(); i < length; i++, j++) {
             buffer[i] = b2c(value[j]);
         }
         return buffer;
     }
 
     /**
      * Copied the content of this string to a character array.
      *
      * @param srcIdx the starting offset of characters to copy.
      * @param dst the destination character array.
      * @param dstIdx the starting offset in the destination byte array.
      * @param length the number of characters to copy.
      */
     public void copy(int srcIdx, char[] dst, int dstIdx, int length) {
         ObjectUtil.checkNotNull(dst, "dst");
 
         if (isOutOfBounds(srcIdx, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= srcIdx(" + srcIdx + ") <= srcIdx + length("
                             + length + ") <= srcLen(" + length() + ')');
         }
 
         final int dstEnd = dstIdx + length;
         for (int i = dstIdx, j = srcIdx + arrayOffset(); i < dstEnd; i++, j++) {
             dst[i] = b2c(value[j]);
         }
     }
 
     /**
      * Copies a range of characters into a new string.
      * @param start the offset of the first character (inclusive).
      * @return a new string containing the characters from start to the end of the string.
      * @throws IndexOutOfBoundsException if {@code start < 0} or {@code start > length()}.
      */
     public AsciiString subSequence(int start) {
         return subSequence(start, length());
     }
 
     /**
      * Copies a range of characters into a new string.
      * @param start the offset of the first character (inclusive).
      * @param end The index to stop at (exclusive).
      * @return a new string containing the characters from start to the end of the string.
      * @throws IndexOutOfBoundsException if {@code start < 0} or {@code start > length()}.
      */
     @Override
     public AsciiString subSequence(int start, int end) {
        return subSequence(start, end, true);
     }
 
     /**
      * Either copy or share a subset of underlying sub-sequence of bytes.
      * @param start the offset of the first character (inclusive).
      * @param end The index to stop at (exclusive).
      * @param copy If {@code true} then a copy of the underlying storage will be made.
      * If {@code false} then the underlying storage will be shared.
      * @return a new string containing the characters from start to the end of the string.
      * @throws IndexOutOfBoundsException if {@code start < 0} or {@code start > length()}.
      */
     public AsciiString subSequence(int start, int end, boolean copy) {
         if (isOutOfBounds(start, end - start, length())) {
             throw new IndexOutOfBoundsException("expected: 0 <= start(" + start + ") <= end (" + end + ") <= length("
                             + length() + ')');
         }
 
         if (start == 0 && end == length()) {
             return this;
         }
 
         if (end == start) {
             return EMPTY_STRING;
         }
 
         return new AsciiString(value, start + offset, end - start, copy);
     }
 
     /**
      * Searches in this string for the first index of the specified string. The search for the string starts at the
      * beginning and moves towards the end of this string.
      *
      * @param string the string to find.
      * @return the index of the first character of the specified string in this string, -1 if the specified string is
      *         not a substring.
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     public int indexOf(CharSequence string) {
         return indexOf(string, 0);
     }
 
     /**
      * Searches in this string for the index of the specified string. The search for the string starts at the specified
      * offset and moves towards the end of this string.
      *
      * @param subString the string to find.
      * @param start the starting offset.
      * @return the index of the first character of the specified string in this string, -1 if the specified string is
      *         not a substring.
      * @throws NullPointerException if {@code subString} is {@code null}.
      */
     public int indexOf(CharSequence subString, int start) {
         final int subCount = subString.length();
         if (start < 0) {
             start = 0;
         }
         if (subCount <= 0) {
             return start < length ? start : length;
         }
         if (subCount > length - start) {
             return INDEX_NOT_FOUND;
         }
 
         final char firstChar = subString.charAt(0);
         if (firstChar > MAX_CHAR_VALUE) {
             return INDEX_NOT_FOUND;
         }
         final byte firstCharAsByte = c2b0(firstChar);
         final int len = offset + length - subCount;
         for (int i = start + offset; i <= len; ++i) {
             if (value[i] == firstCharAsByte) {
                 int o1 = i, o2 = 0;
                 while (++o2 < subCount && b2c(value[++o1]) == subString.charAt(o2)) {
                     // Intentionally empty
                 }
                 if (o2 == subCount) {
                     return i - offset;
                 }
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     /**
      * Searches in this string for the index of the specified char {@code ch}.
      * The search for the char starts at the specified offset {@code start} and moves towards the end of this string.
      *
      * @param ch the char to find.
      * @param start the starting offset.
      * @return the index of the first occurrence of the specified char {@code ch} in this string,
      * -1 if found no occurrence.
      */
     public int indexOf(char ch, int start) {
         if (ch > MAX_CHAR_VALUE) {
             return INDEX_NOT_FOUND;
         }
 
         if (start < 0) {
             start = 0;
         }
 
         final byte chAsByte = c2b0(ch);
         final int len = offset + length;
         for (int i = start + offset; i < len; ++i) {
             if (value[i] == chAsByte) {
                 return i - offset;
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     /**
      * Searches in this string for the last index of the specified string. The search for the string starts at the end
      * and moves towards the beginning of this string.
      *
      * @param string the string to find.
      * @return the index of the first character of the specified string in this string, -1 if the specified string is
      *         not a substring.
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     public int lastIndexOf(CharSequence string) {
         // Use count instead of count - 1 so lastIndexOf("") answers count
         return lastIndexOf(string, length);
     }
 
     /**
      * Searches in this string for the index of the specified string. The search for the string starts at the specified
      * offset and moves towards the beginning of this string.
      *
      * @param subString the string to find.
      * @param start the starting offset.
      * @return the index of the first character of the specified string in this string , -1 if the specified string is
      *         not a substring.
      * @throws NullPointerException if {@code subString} is {@code null}.
      */
     public int lastIndexOf(CharSequence subString, int start) {
         final int subCount = subString.length();
         start = Math.min(start, length - subCount);
         if (start < 0) {
             return INDEX_NOT_FOUND;
         }
         if (subCount == 0) {
             return start;
         }
 
         final char firstChar = subString.charAt(0);
         if (firstChar > MAX_CHAR_VALUE) {
             return INDEX_NOT_FOUND;
         }
         final byte firstCharAsByte = c2b0(firstChar);
         for (int i = offset + start; i >= offset; --i) {
             if (value[i] == firstCharAsByte) {
                 int o1 = i, o2 = 0;
                 while (++o2 < subCount && b2c(value[++o1]) == subString.charAt(o2)) {
                     // Intentionally empty
                 }
                 if (o2 == subCount) {
                     return i - offset;
                 }
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     /**
      * Compares the specified string to this string and compares the specified range of characters to determine if they
      * are the same.
      *
      * @param thisStart the starting offset in this string.
      * @param string the string to compare.
      * @param start the starting offset in the specified string.
      * @param length the number of characters to compare.
      * @return {@code true} if the ranges of characters are equal, {@code false} otherwise
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     public boolean regionMatches(int thisStart, CharSequence string, int start, int length) {
         ObjectUtil.checkNotNull(string, "string");
 
         if (start < 0 || string.length() - start < length) {
             return false;
         }
 
         final int thisLen = length();
         if (thisStart < 0 || thisLen - thisStart < length) {
             return false;
         }
 
         if (length <= 0) {
             return true;
         }
 
         if (string instanceof AsciiString) {
             final AsciiString asciiString = (AsciiString) string;
             return PlatformDependent.equals(value, thisStart + offset, asciiString.value,
                                             start + asciiString.offset, length);
         }
         final int thatEnd = start + length;
         for (int i = start, j = thisStart + arrayOffset(); i < thatEnd; i++, j++) {
             if (b2c(value[j]) != string.charAt(i)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Compares the specified string to this string and compares the specified range of characters to determine if they
      * are the same. When ignoreCase is true, the case of the characters is ignored during the comparison.
      *
      * @param ignoreCase specifies if case should be ignored.
      * @param thisStart the starting offset in this string.
      * @param string the string to compare.
      * @param start the starting offset in the specified string.
      * @param length the number of characters to compare.
      * @return {@code true} if the ranges of characters are equal, {@code false} otherwise.
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     public boolean regionMatches(boolean ignoreCase, int thisStart, CharSequence string, int start, int length) {
         if (!ignoreCase) {
             return regionMatches(thisStart, string, start, length);
         }
 
         ObjectUtil.checkNotNull(string, "string");
 
         final int thisLen = length();
         if (thisStart < 0 || length > thisLen - thisStart) {
             return false;
         }
         if (start < 0 || length > string.length() - start) {
             return false;
         }
 
         thisStart += arrayOffset();
         final int thisEnd = thisStart + length;
         if (string instanceof AsciiString) {
             final AsciiString asciiString = (AsciiString) string;
             final byte[] value = this.value;
             final byte[] otherValue = asciiString.value;
             start += asciiString.offset;
             while (thisStart < thisEnd) {
                 if (!equalsIgnoreCase(value[thisStart++], otherValue[start++])) {
                     return false;
                 }
             }
             return true;
         }
         while (thisStart < thisEnd) {
             if (!equalsIgnoreCase(b2c(value[thisStart++]), string.charAt(start++))) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Copies this string replacing occurrences of the specified character with another character.
      *
      * @param oldChar the character to replace.
      * @param newChar the replacement character.
      * @return a new string with occurrences of oldChar replaced by newChar.
      */
     public AsciiString replace(char oldChar, char newChar) {
         if (oldChar > MAX_CHAR_VALUE) {
             return this;
         }
 
         final byte oldCharAsByte = c2b0(oldChar);
         final byte newCharAsByte = c2b(newChar);
         final int len = offset + length;
         for (int i = offset; i < len; ++i) {
             if (value[i] == oldCharAsByte) {
                 byte[] buffer = PlatformDependent.allocateUninitializedArray(length());
                 System.arraycopy(value, offset, buffer, 0, i - offset);
                 buffer[i - offset] = newCharAsByte;
                 ++i;
                 for (; i < len; ++i) {
                     byte oldValue = value[i];
                     buffer[i - offset] = oldValue != oldCharAsByte ? oldValue : newCharAsByte;
                 }
                 return new AsciiString(buffer, false);
             }
         }
         return this;
     }
 
     /**
      * Compares the specified string to this string to determine if the specified string is a prefix.
      *
      * @param prefix the string to look for.
      * @return {@code true} if the specified string is a prefix of this string, {@code false} otherwise
      * @throws NullPointerException if {@code prefix} is {@code null}.
      */
     public boolean startsWith(CharSequence prefix) {
         return startsWith(prefix, 0);
     }
 
     /**
      * Compares the specified string to this string, starting at the specified offset, to determine if the specified
      * string is a prefix.
      *
      * @param prefix the string to look for.
      * @param start the starting offset.
      * @return {@code true} if the specified string occurs in this string at the specified offset, {@code false}
      *         otherwise.
      * @throws NullPointerException if {@code prefix} is {@code null}.
      */
     public boolean startsWith(CharSequence prefix, int start) {
         return regionMatches(start, prefix, 0, prefix.length());
     }
 
     /**
      * Converts the characters in this string to lowercase, using the default Locale.
      *
      * @return a new string containing the lowercase characters equivalent to the characters in this string.
      */
     public AsciiString toLowerCase() {
         return AsciiStringUtil.toLowerCase(this);
     }
 
     /**
      * Converts the characters in this string to uppercase, using the default Locale.
      *
      * @return a new string containing the uppercase characters equivalent to the characters in this string.
      */
     public AsciiString toUpperCase() {
         return AsciiStringUtil.toUpperCase(this);
     }
 
     /**
      * Copies this string removing white space characters from the beginning and end of the string, and tries not to
      * copy if possible.
      *
      * @param c The {@link CharSequence} to trim.
      * @return a new string with characters {@code <= \\u0020} removed from the beginning and the end.
      */
     public static CharSequence trim(CharSequence c) {
         if (c instanceof AsciiString) {
             return ((AsciiString) c).trim();
         }
         if (c instanceof String) {
             return ((String) c).trim();
         }
         int start = 0, last = c.length() - 1;
         int end = last;
         while (start <= end && c.charAt(start) <= ' ') {
             start++;
         }
         while (end >= start && c.charAt(end) <= ' ') {
             end--;
         }
         if (start == 0 && end == last) {
             return c;
         }
         return c.subSequence(start, end);
     }
 
     /**
      * Duplicates this string removing white space characters from the beginning and end of the
      * string, without copying.
      *
      * @return a new string with characters {@code <= \\u0020} removed from the beginning and the end.
      */
     public AsciiString trim() {
         int start = arrayOffset(), last = arrayOffset() + length() - 1;
         int end = last;
         while (start <= end && value[start] <= ' ') {
             start++;
         }
         while (end >= start && value[end] <= ' ') {
             end--;
         }
         if (start == 0 && end == last) {
             return this;
         }
         return new AsciiString(value, start, end - start + 1, false);
     }
 
     /**
      * Compares a {@code CharSequence} to this {@code String} to determine if their contents are equal.
      *
      * @param a the character sequence to compare to.
      * @return {@code true} if equal, otherwise {@code false}
      */
     public boolean contentEquals(CharSequence a) {
         if (this == a) {
             return true;
         }
 
         if (a == null || a.length() != length()) {
             return false;
         }
         if (a instanceof AsciiString) {
             return equals(a);
         }
 
         for (int i = arrayOffset(), j = 0; j < a.length(); ++i, ++j) {
             if (b2c(value[i]) != a.charAt(j)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Determines whether this string matches a given regular expression.
      *
      * @param expr the regular expression to be matched.
      * @return {@code true} if the expression matches, otherwise {@code false}.
      * @throws PatternSyntaxException if the syntax of the supplied regular expression is not valid.
      * @throws NullPointerException if {@code expr} is {@code null}.
      */
     public boolean matches(String expr) {
         return Pattern.matches(expr, this);
     }
 
     /**
      * Splits this string using the supplied regular expression {@code expr}. The parameter {@code max} controls the
      * behavior how many times the pattern is applied to the string.
      *
      * @param expr the regular expression used to divide the string.
      * @param max the number of entries in the resulting array.
      * @return an array of Strings created by separating the string along matches of the regular expression.
      * @throws NullPointerException if {@code expr} is {@code null}.
      * @throws PatternSyntaxException if the syntax of the supplied regular expression is not valid.
      * @see Pattern#split(CharSequence, int)
      */
     public AsciiString[] split(String expr, int max) {
         return toAsciiStringArray(Pattern.compile(expr).split(this, max));
     }
 
     /**
      * Splits the specified {@link String} with the specified delimiter..
      */
     public AsciiString[] split(char delim) {
         final List<AsciiString> res = InternalThreadLocalMap.get().arrayList();
 
         int start = 0;
         final int length = length();
         for (int i = start; i < length; i++) {
             if (charAt(i) == delim) {
                 if (start == i) {
                     res.add(EMPTY_STRING);
                 } else {
                     res.add(new AsciiString(value, start + arrayOffset(), i - start, false));
                 }
                 start = i + 1;
             }
         }
 
         if (start == 0) { // If no delimiter was found in the value
             res.add(this);
         } else {
             if (start != length) {
                 // Add the last element if it's not empty.
                 res.add(new AsciiString(value, start + arrayOffset(), length - start, false));
             } else {
                 // Truncate trailing empty elements.
                 for (int i = res.size() - 1; i >= 0; i--) {
                     if (res.get(i).isEmpty()) {
                         res.remove(i);
                     } else {
                         break;
                     }
                 }
             }
         }
 
         return res.toArray(EmptyArrays.EMPTY_ASCII_STRINGS);
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * Provides a case-insensitive hash code for Ascii like byte strings.
      */
     @Override
     public int hashCode() {
         int h = hash;
         if (h == 0) {
             h = PlatformDependent.hashCodeAscii(value, offset, length);
             hash = h;
         }
         return h;
     }
 
     @Override
     public boolean equals(Object obj) {
         if (obj == null || obj.getClass() != AsciiString.class) {
             return false;
         }
         if (this == obj) {
             return true;
         }
 
         AsciiString other = (AsciiString) obj;
         return length() == other.length() &&
                hashCode() == other.hashCode() &&
                PlatformDependent.equals(array(), arrayOffset(), other.array(), other.arrayOffset(), length());
     }
 
     /**
      * Translates the entire byte string to a {@link String}.
      * @see #toString(int)
      */
     @Override
     public String toString() {
         String cache = string;
         if (cache == null) {
             cache = toString(0);
             string = cache;
         }
         return cache;
     }
 
     /**
      * Translates the entire byte string to a {@link String} using the {@code charset} encoding.
      * @see #toString(int, int)
      */
     public String toString(int start) {
         return toString(start, length());
     }
 
     /**
      * Translates the [{@code start}, {@code end}) range of this byte string to a {@link String}.
      */
     public String toString(int start, int end) {
         int length = end - start;
         if (length == 0) {
             return "";
         }
 
         if (isOutOfBounds(start, length, length())) {
             throw new IndexOutOfBoundsException("expected: " + "0 <= start(" + start + ") <= srcIdx + length("
                             + length + ") <= srcLen(" + length() + ')');
         }
 
         @SuppressWarnings("deprecation")
         final String str = new String(value, 0, start + offset, length);
         return str;
     }
 
     public boolean parseBoolean() {
         return length >= 1 && value[offset] != 0;
     }
 
     public char parseChar() {
         return parseChar(0);
     }
 
     public char parseChar(int start) {
         if (start + 1 >= length()) {
             throw new IndexOutOfBoundsException("2 bytes required to convert to character. index " +
                     start + " would go out of bounds.");
         }
         final int startWithOffset = start + offset;
         return (char) ((b2c(value[startWithOffset]) << 8) | b2c(value[startWithOffset + 1]));
     }
 
     public short parseShort() {
         return parseShort(0, length(), 10);
     }
 
     public short parseShort(int radix) {
         return parseShort(0, length(), radix);
     }
 
     public short parseShort(int start, int end) {
         return parseShort(start, end, 10);
     }
 
     public short parseShort(int start, int end, int radix) {
         int intValue = parseInt(start, end, radix);
         short result = (short) intValue;
         if (result != intValue) {
             throw new NumberFormatException(subSequence(start, end, false).toString());
         }
         return result;
     }
 
     public int parseInt() {
         return parseInt(0, length(), 10);
     }
 
     public int parseInt(int radix) {
         return parseInt(0, length(), radix);
     }
 
     public int parseInt(int start, int end) {
         return parseInt(start, end, 10);
     }
 
     public int parseInt(int start, int end, int radix) {
         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
             throw new NumberFormatException();
         }
 
         if (start == end) {
             throw new NumberFormatException();
         }
 
         int i = start;
         boolean negative = byteAt(i) == '-';
         if (negative && ++i == end) {
             throw new NumberFormatException(subSequence(start, end, false).toString());
         }
 
         return parseInt(i, end, radix, negative);
     }
 
     private int parseInt(int start, int end, int radix, boolean negative) {
         int max = Integer.MIN_VALUE / radix;
         int result = 0;
         int currOffset = start;
         while (currOffset < end) {
             int digit = Character.digit((char) (value[currOffset++ + offset] & 0xFF), radix);
             if (digit == -1) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             if (max > result) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             int next = result * radix - digit;
             if (next > result) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             result = next;
         }
         if (!negative) {
             result = -result;
             if (result < 0) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
         }
         return result;
     }
 
     public long parseLong() {
         return parseLong(0, length(), 10);
     }
 
     public long parseLong(int radix) {
         return parseLong(0, length(), radix);
     }
 
     public long parseLong(int start, int end) {
         return parseLong(start, end, 10);
     }
 
     public long parseLong(int start, int end, int radix) {
         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
             throw new NumberFormatException();
         }
 
         if (start == end) {
             throw new NumberFormatException();
         }
 
         int i = start;
         boolean negative = byteAt(i) == '-';
         if (negative && ++i == end) {
             throw new NumberFormatException(subSequence(start, end, false).toString());
         }
 
         return parseLong(i, end, radix, negative);
     }
 
     private long parseLong(int start, int end, int radix, boolean negative) {
         long max = Long.MIN_VALUE / radix;
         long result = 0;
         int currOffset = start;
         while (currOffset < end) {
             int digit = Character.digit((char) (value[currOffset++ + offset] & 0xFF), radix);
             if (digit == -1) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             if (max > result) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             long next = result * radix - digit;
             if (next > result) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
             result = next;
         }
         if (!negative) {
             result = -result;
             if (result < 0) {
                 throw new NumberFormatException(subSequence(start, end, false).toString());
             }
         }
         return result;
     }
 
     public float parseFloat() {
         return parseFloat(0, length());
     }
 
     public float parseFloat(int start, int end) {
         return Float.parseFloat(toString(start, end));
     }
 
     public double parseDouble() {
         return parseDouble(0, length());
     }
 
     public double parseDouble(int start, int end) {
         return Double.parseDouble(toString(start, end));
     }
 
     public static final HashingStrategy<CharSequence> CASE_INSENSITIVE_HASHER =
             new HashingStrategy<CharSequence>() {
         @Override
         public int hashCode(CharSequence o) {
             return AsciiString.hashCode(o);
         }
 
         @Override
         public boolean equals(CharSequence a, CharSequence b) {
             return AsciiString.contentEqualsIgnoreCase(a, b);
         }
     };
 
     public static final HashingStrategy<CharSequence> CASE_SENSITIVE_HASHER =
             new HashingStrategy<CharSequence>() {
         @Override
         public int hashCode(CharSequence o) {
             return AsciiString.hashCode(o);
         }
 
         @Override
         public boolean equals(CharSequence a, CharSequence b) {
             return AsciiString.contentEquals(a, b);
         }
     };
 
     /**
      * Returns an {@link AsciiString} containing the given character sequence. If the given string is already a
      * {@link AsciiString}, just returns the same instance.
      */
     public static AsciiString of(CharSequence string) {
         return string instanceof AsciiString ? (AsciiString) string : new AsciiString(string);
     }
 
     /**
      * Returns an {@link AsciiString} containing the given string and retains/caches the input
      * string for later use in {@link #toString()}.
      * Used for the constants (which already stored in the JVM's string table) and in cases
      * where the guaranteed use of the {@link #toString()} method.
      */
     public static AsciiString cached(String string) {
         AsciiString asciiString = new AsciiString(string);
         asciiString.string = string;
         return asciiString;
     }
 
     /**
      * Returns the case-insensitive hash code of the specified string. Note that this method uses the same hashing
      * algorithm with {@link #hashCode()} so that you can put both {@link AsciiString}s and arbitrary
      * {@link CharSequence}s into the same headers.
      */
     public static int hashCode(CharSequence value) {
         if (value == null) {
             return 0;
         }
         if (value instanceof AsciiString) {
             return value.hashCode();
         }
 
         return PlatformDependent.hashCodeAscii(value);
     }
 
     /**
      * Determine if {@code a} contains {@code b} in a case sensitive manner.
      */
     public static boolean contains(CharSequence a, CharSequence b) {
         return contains(a, b, DefaultCharEqualityComparator.INSTANCE);
     }
 
     /**
      * Determine if {@code a} contains {@code b} in a case insensitive manner.
      */
     public static boolean containsIgnoreCase(CharSequence a, CharSequence b) {
         return contains(a, b, AsciiCaseInsensitiveCharEqualityComparator.INSTANCE);
     }
 
     /**
      * Returns {@code true} if both {@link CharSequence}'s are equals when ignore the case. This only supports 8-bit
      * ASCII.
      */
     public static boolean contentEqualsIgnoreCase(CharSequence a, CharSequence b) {
         if (a == null || b == null) {
             return a == b;
         }
 
         if (a instanceof AsciiString) {
             return ((AsciiString) a).contentEqualsIgnoreCase(b);
         }
         if (b instanceof AsciiString) {
             return ((AsciiString) b).contentEqualsIgnoreCase(a);
         }
 
         if (a.length() != b.length()) {
             return false;
         }
         for (int i = 0; i < a.length(); ++i) {
             if (!equalsIgnoreCase(a.charAt(i),  b.charAt(i))) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Determine if {@code collection} contains {@code value} and using
      * {@link #contentEqualsIgnoreCase(CharSequence, CharSequence)} to compare values.
      * @param collection The collection to look for and equivalent element as {@code value}.
      * @param value The value to look for in {@code collection}.
      * @return {@code true} if {@code collection} contains {@code value} according to
      * {@link #contentEqualsIgnoreCase(CharSequence, CharSequence)}. {@code false} otherwise.
      * @see #contentEqualsIgnoreCase(CharSequence, CharSequence)
      */
     public static boolean containsContentEqualsIgnoreCase(Collection<CharSequence> collection, CharSequence value) {
         for (CharSequence v : collection) {
             if (contentEqualsIgnoreCase(value, v)) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * Determine if {@code a} contains all of the values in {@code b} using
      * {@link #contentEqualsIgnoreCase(CharSequence, CharSequence)} to compare values.
      * @param a The collection under test.
      * @param b The values to test for.
      * @return {@code true} if {@code a} contains all of the values in {@code b} using
      * {@link #contentEqualsIgnoreCase(CharSequence, CharSequence)} to compare values. {@code false} otherwise.
      * @see #contentEqualsIgnoreCase(CharSequence, CharSequence)
      */
     public static boolean containsAllContentEqualsIgnoreCase(Collection<CharSequence> a, Collection<CharSequence> b) {
         for (CharSequence v : b) {
             if (!containsContentEqualsIgnoreCase(a, v)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Returns {@code true} if the content of both {@link CharSequence}'s are equals. This only supports 8-bit ASCII.
      */
     public static boolean contentEquals(CharSequence a, CharSequence b) {
         if (a == null || b == null) {
             return a == b;
         }
 
         if (a instanceof AsciiString) {
             return ((AsciiString) a).contentEquals(b);
         }
 
         if (b instanceof AsciiString) {
             return ((AsciiString) b).contentEquals(a);
         }
 
         if (a.length() != b.length()) {
             return false;
         }
         for (int i = 0; i <  a.length(); ++i) {
             if (a.charAt(i) != b.charAt(i)) {
                 return false;
             }
         }
         return true;
     }
 
     private static AsciiString[] toAsciiStringArray(String[] jdkResult) {
         AsciiString[] res = new AsciiString[jdkResult.length];
         for (int i = 0; i < jdkResult.length; i++) {
             res[i] = new AsciiString(jdkResult[i]);
         }
         return res;
     }
 
     private interface CharEqualityComparator {
         boolean equals(char a, char b);
     }
 
     private static final class DefaultCharEqualityComparator implements CharEqualityComparator {
         static final DefaultCharEqualityComparator INSTANCE = new DefaultCharEqualityComparator();
         private DefaultCharEqualityComparator() { }
 
         @Override
         public boolean equals(char a, char b) {
             return a == b;
         }
     }
 
     private static final class AsciiCaseInsensitiveCharEqualityComparator implements CharEqualityComparator {
         static final AsciiCaseInsensitiveCharEqualityComparator
                 INSTANCE = new AsciiCaseInsensitiveCharEqualityComparator();
         private AsciiCaseInsensitiveCharEqualityComparator() { }
 
         @Override
         public boolean equals(char a, char b) {
             return equalsIgnoreCase(a, b);
         }
     }
 
     private static final class GeneralCaseInsensitiveCharEqualityComparator implements CharEqualityComparator {
         static final GeneralCaseInsensitiveCharEqualityComparator
                 INSTANCE = new GeneralCaseInsensitiveCharEqualityComparator();
         private GeneralCaseInsensitiveCharEqualityComparator() { }
 
         @Override
         public boolean equals(char a, char b) {
             //For motivation, why we need two checks, see comment in String#regionMatches
             return Character.toUpperCase(a) == Character.toUpperCase(b) ||
                 Character.toLowerCase(a) == Character.toLowerCase(b);
         }
     }
 
     private static boolean contains(CharSequence a, CharSequence b, CharEqualityComparator cmp) {
         if (a == null || b == null || a.length() < b.length()) {
             return false;
         }
         if (b.length() == 0) {
             return true;
         }
         int bStart = 0;
         for (int i = 0; i < a.length(); ++i) {
             if (cmp.equals(b.charAt(bStart), a.charAt(i))) {
                 // If b is consumed then true.
                 if (++bStart == b.length()) {
                     return true;
                 }
             } else if (a.length() - i < b.length()) {
                 // If there are not enough characters left in a for b to be contained, then false.
                 return false;
             } else {
                 bStart = 0;
             }
         }
         return false;
     }
 
     private static boolean regionMatchesCharSequences(final CharSequence cs, final int csStart,
                                          final CharSequence string, final int start, final int length,
                                          CharEqualityComparator charEqualityComparator) {
         //general purpose implementation for CharSequences
         if (csStart < 0 || length > cs.length() - csStart) {
             return false;
         }
         if (start < 0 || length > string.length() - start) {
             return false;
         }
 
         int csIndex = csStart;
         int csEnd = csIndex + length;
         int stringIndex = start;
 
         while (csIndex < csEnd) {
             char c1 = cs.charAt(csIndex++);
             char c2 = string.charAt(stringIndex++);
 
             if (!charEqualityComparator.equals(c1, c2)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * This methods make regionMatches operation correctly for any chars in strings
      * @param cs the {@code CharSequence} to be processed
      * @param ignoreCase specifies if case should be ignored.
      * @param csStart the starting offset in the {@code cs} CharSequence
      * @param string the {@code CharSequence} to compare.
      * @param start the starting offset in the specified {@code string}.
      * @param length the number of characters to compare.
      * @return {@code true} if the ranges of characters are equal, {@code false} otherwise.
      */
     public static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int csStart,
                                         final CharSequence string, final int start, final int length) {
         if (cs == null || string == null) {
             return false;
         }
 
         if (cs instanceof String && string instanceof String) {
             return ((String) cs).regionMatches(ignoreCase, csStart, (String) string, start, length);
         }
 
         if (cs instanceof AsciiString) {
             return ((AsciiString) cs).regionMatches(ignoreCase, csStart, string, start, length);
         }
 
         return regionMatchesCharSequences(cs, csStart, string, start, length,
                                             ignoreCase ? GeneralCaseInsensitiveCharEqualityComparator.INSTANCE :
                                                     DefaultCharEqualityComparator.INSTANCE);
     }
 
     /**
      * This is optimized version of regionMatches for string with ASCII chars only
      * @param cs the {@code CharSequence} to be processed
      * @param ignoreCase specifies if case should be ignored.
      * @param csStart the starting offset in the {@code cs} CharSequence
      * @param string the {@code CharSequence} to compare.
      * @param start the starting offset in the specified {@code string}.
      * @param length the number of characters to compare.
      * @return {@code true} if the ranges of characters are equal, {@code false} otherwise.
      */
     public static boolean regionMatchesAscii(final CharSequence cs, final boolean ignoreCase, final int csStart,
                                         final CharSequence string, final int start, final int length) {
         if (cs == null || string == null) {
             return false;
         }
 
         if (!ignoreCase && cs instanceof String && string instanceof String) {
             //we don't call regionMatches from String for ignoreCase==true. It's a general purpose method,
             //which make complex comparison in case of ignoreCase==true, which is useless for ASCII-only strings.
             //To avoid applying this complex ignore-case comparison, we will use regionMatchesCharSequences
             return ((String) cs).regionMatches(false, csStart, (String) string, start, length);
         }
 
         if (cs instanceof AsciiString) {
             return ((AsciiString) cs).regionMatches(ignoreCase, csStart, string, start, length);
         }
 
         return regionMatchesCharSequences(cs, csStart, string, start, length,
                                           ignoreCase ? AsciiCaseInsensitiveCharEqualityComparator.INSTANCE :
                                                       DefaultCharEqualityComparator.INSTANCE);
     }
 
     /**
      * <p>Case in-sensitive find of the first index within a CharSequence
      * from the specified position.</p>
      *
      * <p>A {@code null} CharSequence will return {@code -1}.
      * A negative start position is treated as zero.
      * An empty ("") search CharSequence always matches.
      * A start position greater than the string length only matches
      * an empty search CharSequence.</p>
      *
      * <pre>
      * AsciiString.indexOfIgnoreCase(null, *, *)          = -1
      * AsciiString.indexOfIgnoreCase(*, null, *)          = -1
      * AsciiString.indexOfIgnoreCase("", "", 0)           = 0
      * AsciiString.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
      * AsciiString.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
      * AsciiString.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
      * AsciiString.indexOfIgnoreCase("abc", "", 9)        = -1
      * </pre>
      *
      * @param str  the CharSequence to check, may be null
      * @param searchStr  the CharSequence to find, may be null
      * @param startPos  the start position, negative treated as zero
      * @return the first index of the search CharSequence (always &ge; startPos),
      *  -1 if no match or {@code null} string input
      */
     public static int indexOfIgnoreCase(final CharSequence str, final CharSequence searchStr, int startPos) {
         if (str == null || searchStr == null) {
             return INDEX_NOT_FOUND;
         }
         if (startPos < 0) {
             startPos = 0;
         }
         int searchStrLen = searchStr.length();
         final int endLimit = str.length() - searchStrLen + 1;
         if (startPos > endLimit) {
             return INDEX_NOT_FOUND;
         }
         if (searchStrLen == 0) {
             return startPos;
         }
         for (int i = startPos; i < endLimit; i++) {
             if (regionMatches(str, true, i, searchStr, 0, searchStrLen)) {
                 return i;
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     /**
      * <p>Case in-sensitive find of the first index within a CharSequence
      * from the specified position. This method optimized and works correctly for ASCII CharSequences only</p>
      *
      * <p>A {@code null} CharSequence will return {@code -1}.
      * A negative start position is treated as zero.
      * An empty ("") search CharSequence always matches.
      * A start position greater than the string length only matches
      * an empty search CharSequence.</p>
      *
      * <pre>
      * AsciiString.indexOfIgnoreCase(null, *, *)          = -1
      * AsciiString.indexOfIgnoreCase(*, null, *)          = -1
      * AsciiString.indexOfIgnoreCase("", "", 0)           = 0
      * AsciiString.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
      * AsciiString.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
      * AsciiString.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
      * AsciiString.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
      * AsciiString.indexOfIgnoreCase("abc", "", 9)        = -1
      * </pre>
      *
      * @param str  the CharSequence to check, may be null
      * @param searchStr  the CharSequence to find, may be null
      * @param startPos  the start position, negative treated as zero
      * @return the first index of the search CharSequence (always &ge; startPos),
      *  -1 if no match or {@code null} string input
      */
     public static int indexOfIgnoreCaseAscii(final CharSequence str, final CharSequence searchStr, int startPos) {
         if (str == null || searchStr == null) {
             return INDEX_NOT_FOUND;
         }
         if (startPos < 0) {
             startPos = 0;
         }
         int searchStrLen = searchStr.length();
         final int endLimit = str.length() - searchStrLen + 1;
         if (startPos > endLimit) {
             return INDEX_NOT_FOUND;
         }
         if (searchStrLen == 0) {
             return startPos;
         }
         for (int i = startPos; i < endLimit; i++) {
             if (regionMatchesAscii(str, true, i, searchStr, 0, searchStrLen)) {
                 return i;
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     /**
      * <p>Finds the first index in the {@code CharSequence} that matches the
      * specified character.</p>
      *
      * @param cs  the {@code CharSequence} to be processed, not null
      * @param searchChar the char to be searched for
      * @param start  the start index, negative starts at the string start
      * @return the index where the search char was found,
      * -1 if char {@code searchChar} is not found or {@code cs == null}
      */
     //-----------------------------------------------------------------------
     public static int indexOf(final CharSequence cs, final char searchChar, int start) {
         if (cs instanceof String) {
             return ((String) cs).indexOf(searchChar, start);
         } else if (cs instanceof AsciiString) {
             return ((AsciiString) cs).indexOf(searchChar, start);
         }
         if (cs == null) {
             return INDEX_NOT_FOUND;
         }
         final int sz = cs.length();
         for (int i = start < 0 ? 0 : start; i < sz; i++) {
             if (cs.charAt(i) == searchChar) {
                 return i;
             }
         }
         return INDEX_NOT_FOUND;
     }
 
     private static boolean equalsIgnoreCase(byte a, byte b) {
         return a == b || AsciiStringUtil.toLowerCase(a) == AsciiStringUtil.toLowerCase(b);
     }
 
     private static boolean equalsIgnoreCase(char a, char b) {
         return a == b || toLowerCase(a) == toLowerCase(b);
     }
 
     /**
      * If the character is uppercase - converts the character to lowercase,
      * otherwise returns the character as it is. Only for ASCII characters.
      *
      * @return lowercase ASCII character equivalent
      */
     public static char toLowerCase(char c) {
         return isUpperCase(c) ? (char) (c + 32) : c;
     }
 
     private static byte toUpperCase(byte b) {
         return AsciiStringUtil.toUpperCase(b);
     }
 
     public static boolean isUpperCase(byte value) {
         return AsciiStringUtil.isUpperCase(value);
     }
 
     public static boolean isUpperCase(char value) {
         return value >= 'A' && value <= 'Z';
     }
 
     public static byte c2b(char c) {
         return (byte) ((c > MAX_CHAR_VALUE) ? '?' : c);
     }
 
     private static byte c2b0(char c) {
         return (byte) c;
     }
 
     public static char b2c(byte b) {
         return (char) (b & 0xFF);
     }
 }