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   /*
    * Copyright 2013 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:
    *
    *   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 org.jboss.netty.handler.codec.spdy;
  
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.Map.Entry;
  
  
  public class DefaultSpdyHeaders extends SpdyHeaders {
  
      private static final int BUCKET_SIZE = 17;
  
      private static int hash(String name) {
          int h = 0;
          for (int i = name.length() - 1; i >= 0; i --) {
              char c = name.charAt(i);
              if (c >= 'A' && c <= 'Z') {
                  c += 32;
              }
              h = 31 * h + c;
          }
  
          if (h > 0) {
              return h;
          } else if (h == Integer.MIN_VALUE) {
              return Integer.MAX_VALUE;
          } else {
              return -h;
          }
      }
  
      private static boolean eq(String name1, String name2) {
          int nameLen = name1.length();
          if (nameLen != name2.length()) {
              return false;
          }
  
          for (int i = nameLen - 1; i >= 0; i --) {
              char c1 = name1.charAt(i);
              char c2 = name2.charAt(i);
              if (c1 != c2) {
                  if (c1 >= 'A' && c1 <= 'Z') {
                      c1 += 32;
                  }
                  if (c2 >= 'A' && c2 <= 'Z') {
                      c2 += 32;
                  }
                  if (c1 != c2) {
                      return false;
                  }
              }
          }
          return true;
      }
  
      private static int index(int hash) {
          return hash % BUCKET_SIZE;
      }
  
      private final HeaderEntry[] entries = new HeaderEntry[BUCKET_SIZE];
      private final HeaderEntry head = new HeaderEntry(-1, null, null);
  
      DefaultSpdyHeaders() {
          head.before = head.after = head;
      }
  
      @Override
      public SpdyHeaders add(final String name, final Object value) {
          String lowerCaseName = name.toLowerCase();
          SpdyCodecUtil.validateHeaderName(lowerCaseName);
          String strVal = toString(value);
          SpdyCodecUtil.validateHeaderValue(strVal);
          int h = hash(lowerCaseName);
          int i = index(h);
          add0(h, i, lowerCaseName, strVal);
          return this;
      }
  
      private void add0(int h, int i, final String name, final String value) {
          // Update the hash table.
         HeaderEntry e = entries[i];
         HeaderEntry newEntry;
         entries[i] = newEntry = new HeaderEntry(h, name, value);
         newEntry.next = e;
 
         // Update the linked list.
         newEntry.addBefore(head);
     }
 
     @Override
     public SpdyHeaders remove(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
         String lowerCaseName = name.toLowerCase();
         int h = hash(lowerCaseName);
         int i = index(h);
         remove0(h, i, lowerCaseName);
         return this;
     }
 
     private void remove0(int h, int i, String name) {
         HeaderEntry e = entries[i];
         if (e == null) {
             return;
         }
 
         for (;;) {
             if (e.hash == h && eq(name, e.key)) {
                 e.remove();
                 HeaderEntry next = e.next;
                 if (next != null) {
                     entries[i] = next;
                     e = next;
                 } else {
                     entries[i] = null;
                     return;
                 }
             } else {
                 break;
             }
         }
 
         for (;;) {
             HeaderEntry next = e.next;
             if (next == null) {
                 break;
             }
             if (next.hash == h && eq(name, next.key)) {
                 e.next = next.next;
                 next.remove();
             } else {
                 e = next;
             }
         }
     }
 
     @Override
     public SpdyHeaders set(final String name, final Object value) {
         String lowerCaseName = name.toLowerCase();
         SpdyCodecUtil.validateHeaderName(lowerCaseName);
         String strVal = toString(value);
         SpdyCodecUtil.validateHeaderValue(strVal);
         int h = hash(lowerCaseName);
         int i = index(h);
         remove0(h, i, lowerCaseName);
         add0(h, i, lowerCaseName, strVal);
         return this;
     }
 
     @Override
     public SpdyHeaders set(final String name, final Iterable<?> values) {
         if (values == null) {
             throw new NullPointerException("values");
         }
 
         String lowerCaseName = name.toLowerCase();
         SpdyCodecUtil.validateHeaderName(lowerCaseName);
 
         int h = hash(lowerCaseName);
         int i = index(h);
 
         remove0(h, i, lowerCaseName);
         for (Object v: values) {
             if (v == null) {
                 break;
             }
             String strVal = toString(v);
             SpdyCodecUtil.validateHeaderValue(strVal);
             add0(h, i, lowerCaseName, strVal);
         }
         return this;
     }
 
     @Override
     public SpdyHeaders clear() {
         for (int i = 0; i < entries.length; i ++) {
             entries[i] = null;
         }
         head.before = head.after = head;
         return this;
     }
 
     @Override
     public String get(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
 
         int h = hash(name);
         int i = index(h);
         HeaderEntry e = entries[i];
         while (e != null) {
             if (e.hash == h && eq(name, e.key)) {
                 return e.value;
             }
 
             e = e.next;
         }
         return null;
     }
 
     @Override
     public List<String> getAll(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
 
         LinkedList<String> values = new LinkedList<String>();
 
         int h = hash(name);
         int i = index(h);
         HeaderEntry e = entries[i];
         while (e != null) {
             if (e.hash == h && eq(name, e.key)) {
                 values.addFirst(e.value);
             }
             e = e.next;
         }
         return values;
     }
 
     @Override
     public List<Map.Entry<String, String>> entries() {
         List<Map.Entry<String, String>> all =
                 new LinkedList<Map.Entry<String, String>>();
 
         HeaderEntry e = head.after;
         while (e != head) {
             all.add(e);
             e = e.after;
         }
         return all;
     }
 
     @Override
     public Iterator<Map.Entry<String, String>> iterator() {
         return new HeaderIterator();
     }
 
     @Override
     public boolean contains(String name) {
         return get(name) != null;
     }
 
     @Override
     public Set<String> names() {
         Set<String> names = new TreeSet<String>();
 
         HeaderEntry e = head.after;
         while (e != head) {
             names.add(e.key);
             e = e.after;
         }
         return names;
     }
 
     @Override
     public SpdyHeaders add(String name, Iterable<?> values) {
         SpdyCodecUtil.validateHeaderValue(name);
         int h = hash(name);
         int i = index(h);
         for (Object v: values) {
             String vstr = toString(v);
             SpdyCodecUtil.validateHeaderValue(vstr);
             add0(h, i, name, vstr);
         }
         return this;
     }
 
     @Override
     public boolean isEmpty() {
         return head == head.after;
     }
 
     private static String toString(Object value) {
         if (value == null) {
             return null;
         }
         return value.toString();
     }
 
     private final class HeaderIterator implements Iterator<Map.Entry<String, String>> {
 
         private HeaderEntry current = head;
 
         @Override
         public boolean hasNext() {
             return current.after != head;
         }
 
         @Override
         public Entry<String, String> next() {
             current = current.after;
 
             if (current == head) {
                 throw new NoSuchElementException();
             }
 
             return current;
         }
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException();
         }
     }
 
     private static final class HeaderEntry implements Map.Entry<String, String> {
         final int hash;
         final String key;
         String value;
         HeaderEntry next;
         HeaderEntry before, after;
 
         HeaderEntry(int hash, String key, String value) {
             this.hash = hash;
             this.key = key;
             this.value = value;
         }
 
         void remove() {
             before.after = after;
             after.before = before;
         }
 
         void addBefore(HeaderEntry e) {
             after  = e;
             before = e.before;
             before.after = this;
             after.before = this;
         }
 
         @Override
         public String getKey() {
             return key;
         }
 
         @Override
         public String getValue() {
             return value;
         }
 
         @Override
         public String setValue(String value) {
             if (value == null) {
                 throw new NullPointerException("value");
             }
             SpdyCodecUtil.validateHeaderValue(value);
             String oldValue = this.value;
             this.value = value;
             return oldValue;
         }
 
         @Override
         public String toString() {
             return key + '=' + value;
         }
     }
 }