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diff --git a/src/libs/xpcom18a4/xpcom/ds/nsCheapSets.h b/src/libs/xpcom18a4/xpcom/ds/nsCheapSets.h
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+++ b/src/libs/xpcom18a4/xpcom/ds/nsCheapSets.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (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.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either of the GNU General Public License Version 2 or later (the "GPL"),
+ * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef __nsCheapSets_h__
+#define __nsCheapSets_h__
+
+#include "nsHashSets.h"
+
+/**
+ * A string set that takes up minimal size when there are 0 or 1 strings in the
+ * set.  Use for cases where sizes of 0 and 1 are even slightly common.
+ */
+class NS_COM nsCheapStringSet {
+public:
+  nsCheapStringSet() : mValOrHash(nsnull)
+  {
+  }
+  ~nsCheapStringSet();
+
+  /**
+   * Put a string into the set
+   * @param aVal the value to put in
+   */
+  nsresult Put(const nsAString& aVal);
+
+  /**
+   * Remove a string from the set
+   * @param aVal the string to remove
+   */
+  void Remove(const nsAString& aVal);
+
+  /**
+   * Check if the set contains a particular string
+   * @param aVal the string to check for
+   * @return whether the string is in the set
+   */
+  PRBool Contains(const nsAString& aVal)
+  {
+    nsStringHashSet* set = GetHash();
+    // Check the value from the hash if the hash is there
+    if (set) {
+      return set->Contains(aVal);
+    }
+
+    // Check whether the value is equal to the string if the string is there
+    nsAString* str = GetStr();
+    return str && str->Equals(aVal);
+  }
+
+private:
+  typedef PRUint64 PtrBits;
+
+  /** Get the hash pointer (or null if we're not a hash) */
+  nsStringHashSet* GetHash()
+  {
+    return (PtrBits(mValOrHash) & 0x1) ? nsnull : (nsStringHashSet*)mValOrHash;
+  }
+  /** Find out whether it is a string */
+  nsAString* GetStr()
+  {
+    return (PtrBits(mValOrHash) & 0x1)
+           ? (nsAString*)(PtrBits(mValOrHash) & ~0x1)
+           : nsnull;
+  }
+  /** Set the single string */
+  nsresult SetStr(const nsAString& aVal)
+  {
+    nsString* str = new nsString(aVal);
+    if (!str) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    mValOrHash = (nsAString*)(PtrBits(str) | 0x1);
+    return NS_OK;
+  }
+  /** Initialize the hash */
+  nsresult InitHash(nsStringHashSet** aSet);
+
+private:
+  /** A hash or string ptr, depending on the lower bit (0=hash, 1=string) */
+  void* mValOrHash;
+};
+
+
+/**
+ * An integer set that takes up only 4 bytes when there are 0 or 1 integers
+ * in the set.  Use for cases where sizes of 0 and 1 are even slightly common.
+ */
+class NS_COM nsCheapInt32Set {
+public:
+  nsCheapInt32Set() : mValOrHash(nsnull)
+  {
+  }
+  ~nsCheapInt32Set();
+
+  /**
+   * Put an int into the set
+   */
+  nsresult Put(PRInt32 aVal);
+ 
+  /**
+   * Remove a int from the set
+   * @param aVal the int to remove
+   */
+  void Remove(PRInt32 aVal);
+
+  /**
+   * Check if the set contains a particular int
+   * @param aVal the int to check for
+   * @return whether the int is in the set
+   */
+  PRBool Contains(PRInt32 aVal)
+  {
+    nsInt32HashSet* set = GetHash();
+    if (set) {
+      return set->Contains(aVal);
+    }
+    if (IsInt()) {
+      return GetInt() == aVal;
+    }
+    return PR_FALSE;
+  }
+
+private:
+  typedef PRUint64 PtrBits;
+
+  /** Get the hash pointer (or null if we're not a hash) */
+  nsInt32HashSet* GetHash()
+  {
+    return PtrBits(mValOrHash) & 0x1 ? nsnull : (nsInt32HashSet*)mValOrHash;
+  }
+  /** Find out whether it is an integer */
+  PRBool IsInt()
+  {
+    return !!(PtrBits(mValOrHash) & 0x1);
+  }
+  /** Get the single integer */
+  PRInt32 GetInt()
+  {
+    return PtrBits(mValOrHash) >> 1;
+  }
+  /** Set the single integer */
+  void SetInt(PRInt32 aInt)
+  {
+    mValOrHash = (void*)(uintptr_t)((aInt << 1) | 0x1);
+  }
+  /** Create the hash and initialize */
+  nsresult InitHash(nsInt32HashSet** aSet);
+
+private:
+  /** A hash or int, depending on the lower bit (0=hash, 1=int) */
+  void* mValOrHash;
+};
+
+
+/**
+ * XXX We may want an nsCheapVoidSet and nsCheapCStringSet at some point
+ */
+
+
+#endif