diff -r 000000000000 -r 4f2f89ce4247 JavaScriptCore/wtf/text/StringHash.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/JavaScriptCore/wtf/text/StringHash.h	Fri Sep 17 09:02:29 2010 +0300
@@ -0,0 +1,268 @@
+/*
+ * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved
+ * Copyright (C) Research In Motion Limited 2009. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef StringHash_h
+#define StringHash_h
+
+#include "AtomicString.h"
+#include "WTFString.h"
+#include <wtf/HashTraits.h>
+#include <wtf/StringHashFunctions.h>
+#include <wtf/unicode/Unicode.h>
+
+// FIXME: This is a temporary layering violation while we move string code to WTF.
+// Landing the file moves in one patch, will follow on with patches to change the namespaces.
+namespace WebCore {
+
+    // The hash() functions on StringHash and CaseFoldingHash do not support
+    // null strings. get(), contains(), and add() on HashMap<String,..., StringHash>
+    // cause a null-pointer dereference when passed null strings.
+
+    // FIXME: We should really figure out a way to put the computeHash function that's
+    // currently a member function of StringImpl into this file so we can be a little
+    // closer to having all the nearly-identical hash functions in one place.
+
+    struct StringHash {
+        static unsigned hash(StringImpl* key) { return key->hash(); }
+        static bool equal(const StringImpl* a, const StringImpl* b)
+        {
+            if (a == b)
+                return true;
+            if (!a || !b)
+                return false;
+
+            unsigned aLength = a->length();
+            unsigned bLength = b->length();
+            if (aLength != bLength)
+                return false;
+
+            // FIXME: perhaps we should have a more abstract macro that indicates when
+            // going 4 bytes at a time is unsafe
+#if CPU(ARM) || CPU(SH4)
+            const UChar* aChars = a->characters();
+            const UChar* bChars = b->characters();
+            for (unsigned i = 0; i != aLength; ++i) {
+                if (*aChars++ != *bChars++)
+                    return false;
+            }
+            return true;
+#else
+            /* Do it 4-bytes-at-a-time on architectures where it's safe */
+            const uint32_t* aChars = reinterpret_cast<const uint32_t*>(a->characters());
+            const uint32_t* bChars = reinterpret_cast<const uint32_t*>(b->characters());
+
+            unsigned halfLength = aLength >> 1;
+            for (unsigned i = 0; i != halfLength; ++i)
+                if (*aChars++ != *bChars++)
+                    return false;
+
+            if (aLength & 1 && *reinterpret_cast<const uint16_t*>(aChars) != *reinterpret_cast<const uint16_t*>(bChars))
+                return false;
+
+            return true;
+#endif
+        }
+
+        static unsigned hash(const RefPtr<StringImpl>& key) { return key->hash(); }
+        static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
+        {
+            return equal(a.get(), b.get());
+        }
+
+        static unsigned hash(const String& key) { return key.impl()->hash(); }
+        static bool equal(const String& a, const String& b)
+        {
+            return equal(a.impl(), b.impl());
+        }
+
+        static const bool safeToCompareToEmptyOrDeleted = false;
+    };
+
+    class CaseFoldingHash {
+    public:
+        // Paul Hsieh's SuperFastHash
+        // http://www.azillionmonkeys.com/qed/hash.html
+        static unsigned hash(const UChar* data, unsigned length)
+        {
+            unsigned l = length;
+            const UChar* s = data;
+            uint32_t hash = WTF::stringHashingStartValue;
+            uint32_t tmp;
+            
+            int rem = l & 1;
+            l >>= 1;
+            
+            // Main loop.
+            for (; l > 0; l--) {
+                hash += WTF::Unicode::foldCase(s[0]);
+                tmp = (WTF::Unicode::foldCase(s[1]) << 11) ^ hash;
+                hash = (hash << 16) ^ tmp;
+                s += 2;
+                hash += hash >> 11;
+            }
+            
+            // Handle end case.
+            if (rem) {
+                hash += WTF::Unicode::foldCase(s[0]);
+                hash ^= hash << 11;
+                hash += hash >> 17;
+            }
+            
+            // Force "avalanching" of final 127 bits.
+            hash ^= hash << 3;
+            hash += hash >> 5;
+            hash ^= hash << 2;
+            hash += hash >> 15;
+            hash ^= hash << 10;
+            
+            // This avoids ever returning a hash code of 0, since that is used to
+            // signal "hash not computed yet", using a value that is likely to be
+            // effectively the same as 0 when the low bits are masked.
+            hash |= !hash << 31;
+            
+            return hash;
+        }
+
+        static unsigned hash(StringImpl* str)
+        {
+            return hash(str->characters(), str->length());
+        }
+        
+        static unsigned hash(const char* str, unsigned length)
+        {
+            // This hash is designed to work on 16-bit chunks at a time. But since the normal case
+            // (above) is to hash UTF-16 characters, we just treat the 8-bit chars as if they
+            // were 16-bit chunks, which will give matching results.
+
+            unsigned l = length;
+            const char* s = str;
+            uint32_t hash = WTF::stringHashingStartValue;
+            uint32_t tmp;
+            
+            int rem = l & 1;
+            l >>= 1;
+            
+            // Main loop
+            for (; l > 0; l--) {
+                hash += WTF::Unicode::foldCase(s[0]);
+                tmp = (WTF::Unicode::foldCase(s[1]) << 11) ^ hash;
+                hash = (hash << 16) ^ tmp;
+                s += 2;
+                hash += hash >> 11;
+            }
+            
+            // Handle end case
+            if (rem) {
+                hash += WTF::Unicode::foldCase(s[0]);
+                hash ^= hash << 11;
+                hash += hash >> 17;
+            }
+            
+            // Force "avalanching" of final 127 bits
+            hash ^= hash << 3;
+            hash += hash >> 5;
+            hash ^= hash << 2;
+            hash += hash >> 15;
+            hash ^= hash << 10;
+            
+            // this avoids ever returning a hash code of 0, since that is used to
+            // signal "hash not computed yet", using a value that is likely to be
+            // effectively the same as 0 when the low bits are masked
+            hash |= !hash << 31;
+            
+            return hash;
+        }
+        
+        static bool equal(const StringImpl* a, const StringImpl* b)
+        {
+            if (a == b)
+                return true;
+            if (!a || !b)
+                return false;
+            unsigned length = a->length();
+            if (length != b->length())
+                return false;
+            return WTF::Unicode::umemcasecmp(a->characters(), b->characters(), length) == 0;
+        }
+
+        static unsigned hash(const RefPtr<StringImpl>& key) 
+        {
+            return hash(key.get());
+        }
+
+        static bool equal(const RefPtr<StringImpl>& a, const RefPtr<StringImpl>& b)
+        {
+            return equal(a.get(), b.get());
+        }
+
+        static unsigned hash(const String& key)
+        {
+            return hash(key.impl());
+        }
+        static unsigned hash(const AtomicString& key)
+        {
+            return hash(key.impl());
+        }
+        static bool equal(const String& a, const String& b)
+        {
+            return equal(a.impl(), b.impl());
+        }
+        static bool equal(const AtomicString& a, const AtomicString& b)
+        {
+            return (a == b) || equal(a.impl(), b.impl());
+        }
+
+        static const bool safeToCompareToEmptyOrDeleted = false;
+    };
+
+    // This hash can be used in cases where the key is a hash of a string, but we don't
+    // want to store the string. It's not really specific to string hashing, but all our
+    // current uses of it are for strings.
+    struct AlreadyHashed : IntHash<unsigned> {
+        static unsigned hash(unsigned key) { return key; }
+
+        // To use a hash value as a key for a hash table, we need to eliminate the
+        // "deleted" value, which is negative one. That could be done by changing
+        // the string hash function to never generate negative one, but this works
+        // and is still relatively efficient.
+        static unsigned avoidDeletedValue(unsigned hash)
+        {
+            ASSERT(hash);
+            unsigned newHash = hash | (!(hash + 1) << 31);
+            ASSERT(newHash);
+            ASSERT(newHash != 0xFFFFFFFF);
+            return newHash;
+        }
+    };
+
+}
+
+namespace WTF {
+
+    template<> struct HashTraits<WebCore::String> : GenericHashTraits<WebCore::String> {
+        static const bool emptyValueIsZero = true;
+        static void constructDeletedValue(WebCore::String& slot) { new (&slot) WebCore::String(HashTableDeletedValue); }
+        static bool isDeletedValue(const WebCore::String& slot) { return slot.isHashTableDeletedValue(); }
+    };
+
+}
+
+#endif