Changeset 2769 in webkit for trunk/JavaScriptCore/kjs/ustring.cpp

Timestamp:

Nov 19, 2002, 5:23:02 PM (23 years ago)

Author:

darin

Message:

• another step towards atomic identifiers; storing hash in the string rep. gives about a 1.5% speedup in the JavaScript iBench

• kjs/ustring.h: Add a hash field to UString::Rep.
• kjs/ustring.cpp: (UString::Rep::create): Set hash to uninitialized value. (UString::Rep::destroy): Do the deleting in her, and call Identifier if needed. (UString::Rep::computeHash): Added. (UString::append): Set hash to 0 when modifying the string in place. (UString::operator=): Ditto.

• kjs/property_map.cpp: Use the hash from UString.

• kjs/identifier.h: Added aboutToDestroyUStringRep.
• kjs/identifier.cpp: (Identifier::aboutToDestroyUStringRep): Added.

File:

• trunk/JavaScriptCore/kjs/ustring.cpp (modified) (5 diffs)

trunk/JavaScriptCore/kjs/ustring.cpp

@@ -37 +37 @@
 #include "ustring.h"
 #include "operations.h"
+#include "identifier.h"
 #include <math.h>
 
@@ -115 +116 @@
 
 UChar UChar::null((char)0);
-UString::Rep UString::Rep::null = { 0, 0, 0, 1 };
-UString::Rep UString::Rep::empty = { 0, 0, 0, 1 };
+UString::Rep UString::Rep::null = { 0, 0, 0, 1, 1 };
+UString::Rep UString::Rep::empty = { 0, 0, 0, 1, 1 };
 UString UString::null;
 const int normalStatBufferSize = 4096;
@@ -163 +164 @@
   r->capacity = l;
   r->rc = 1;
+  r->_hash = 0;
 
   return r;
+}
+
+void UString::Rep::destroy()
+{
+  if (capacity == capacityForIdentifier)
+    Identifier::aboutToDestroyUStringRep(this);
+  delete [] dat;
+  delete this;
+}
+
+void UString::Rep::computeHash() const
+{
+    int length = len;
+    int prefixLength = length < 8 ? length : 8;
+    int suffixPosition = length < 16 ? 8 : length - 8;
+
+    unsigned h = length;
+    for (int i = 0; i < prefixLength; i++)
+        h = 127 * h + dat[i].unicode();
+    for (int i = suffixPosition; i < length; i++)
+        h = 127 * h + dat[i].unicode();
+    if (h == 0)
+        h = 0x80000000;
+    _hash = h;
 }
 
@@ -329 +355 @@
     memcpy(rep->dat+l, t.data(), tLen * sizeof(UChar));
     rep->len = newLen;
+    rep->_hash = 0;
     return *this;
   }
@@ -389 +416 @@
   int l = c ? strlen(c) : 0;
   UChar *d;
-  if (rep->rc == 1 && l < rep->capacity) {
+  if (rep->rc == 1 && l <= rep->capacity) {
     d = rep->dat;
+    rep->_hash = 0;
   } else {
     release();