Remove run-time calculation of hash constants in pdfium.

fpdfsdk/src/javascript/global.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
  
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../include/javascript/JavaScript.h"
 #include "../../include/javascript/IJavaScript.h"
 #include "../../include/javascript/JS_Define.h"
 #include "../../include/javascript/JS_Object.h"
 #include "../../include/javascript/JS_Value.h"
 #include "../../include/javascript/JS_GlobalData.h"
 #include "../../include/javascript/global.h"
 #include "../../include/javascript/JS_EventHandler.h"
 #include "../../include/javascript/JS_Context.h"
 
 /* ---------------------------- global ---------------------------- */
 
-extern const unsigned int JSCONST_nStringHash = JS_CalcHash(VALUE_NAME_STRING,wcslen(VALUE_NAME_STRING));
-extern const unsigned int JSCONST_nNumberHash = JS_CalcHash(VALUE_NAME_NUMBER,wcslen(VALUE_NAME_NUMBER));
-extern const unsigned int JSCONST_nBoolHash = JS_CalcHash(VALUE_NAME_BOOLEAN,wcslen(VALUE_NAME_BOOLEAN));
-extern const unsigned int JSCONST_nDateHash = JS_CalcHash(VALUE_NAME_DATE,wcslen(VALUE_NAME_DATE));
-extern const unsigned int JSCONST_nObjectHash = JS_CalcHash(VALUE_NAME_OBJECT,wcslen(VALUE_NAME_OBJECT));
-extern const unsigned int JSCONST_nFXobjHash = JS_CalcHash(VALUE_NAME_FXOBJ,wcslen(VALUE_NAME_FXOBJ));
-extern const unsigned int JSCONST_nNullHash = JS_CalcHash(VALUE_NAME_NULL,wcslen(VALUE_NAME_NULL));
-extern const unsigned int JSCONST_nUndefHash = JS_CalcHash(VALUE_NAME_UNDEFINED,wcslen(VALUE_NAME_UNDEFINED));
+// Helper class for compile-time calculation of hash values in order to
+// avoid having global object initializers.
+template <unsigned acc, wchar_t... Ns>

[Tom Sepez, 2015/01/05 21:26:20]

Should this be unsigned long long acc?
[nit: ACC in uppercase to match other params?]

[brucedawson, 2015/01/05 21:52:56]

ACC looks a bit ugly, but changed for consistency. I think unsigned is correct
(see below).

+struct CHash {};

[Tom Sepez, 2015/01/05 21:26:20]

nit: do we need {} here? 

[brucedawson, 2015/01/05 21:52:55]

I guess not. Removed.

+
+template <wchar_t N>

[Tom Sepez, 2015/01/05 21:26:20]

I think in this case, the argument is <unsinged long long ACC>

[brucedawson, 2015/01/05 21:52:55]

The goal is to always pass in unsigned -- making down to unsigned ASAP. I'm
pretty sure there is no need for unsigned long long.

+struct CHash<N> { static const unsigned value = N;
+};
+
+template <unsigned acc, wchar_t N>
+struct CHash<acc, N> {
+  static const unsigned value = (acc * 1313LLU + N) & 0xFFFFFFFF;
+};
+
+template <unsigned acc, wchar_t N, wchar_t... Ns>
+struct CHash<acc, N, Ns...> {
+  static const unsigned value = CHash<CHash<acc, N>::value, Ns...>::value;
+};
+
+extern const unsigned int JSCONST_nStringHash =
+  CHash<0,'s','t','r','i','n','g'>::value;

[Tom Sepez, 2015/01/05 21:26:20]

Maybe use a helper class so that we don't have to explicitly pass 0.

[brucedawson, 2015/01/05 21:52:55]

No need for a helper class -- I just deleted the zeroes. They were added during
an investigation but are totally unneeded. Good catch.

+extern const unsigned int JSCONST_nNumberHash =
+  CHash<0,'n','u','m','b','e','r'>::value;
+extern const unsigned int JSCONST_nBoolHash =
+  CHash<0,'b','o','o','l','e','a','n'>::value;
+extern const unsigned int JSCONST_nDateHash =
+  CHash<0,'d','a','t','e'>::value;
+extern const unsigned int JSCONST_nObjectHash =
+  CHash<0,'o','b','j','e','c','t'>::value;
+extern const unsigned int JSCONST_nFXobjHash =
+  CHash<0,'f','x','o','b','j'>::value;
+extern const unsigned int JSCONST_nNullHash =
+  CHash<0,'n','u','l','l'>::value;
+extern const unsigned int JSCONST_nUndefHash =
+  CHash<0,'u','n','d','e','f','i','n','e','d'>::value;
+
+#ifdef _DEBUG
+class HashVerify
+{
+public:
+  HashVerify();
+} g_hashVerify;
+
+HashVerify::HashVerify()
+{
+  ASSERT(JSCONST_nStringHash ==
+    JS_CalcHash(VALUE_NAME_STRING,wcslen(VALUE_NAME_STRING)));
+  ASSERT(JSCONST_nNumberHash ==
+    JS_CalcHash(VALUE_NAME_NUMBER,wcslen(VALUE_NAME_NUMBER)));
+  ASSERT(JSCONST_nBoolHash ==
+    JS_CalcHash(VALUE_NAME_BOOLEAN,wcslen(VALUE_NAME_BOOLEAN)));
+  ASSERT(JSCONST_nDateHash ==
+    JS_CalcHash(VALUE_NAME_DATE,wcslen(VALUE_NAME_DATE)));
+  ASSERT(JSCONST_nObjectHash ==
+    JS_CalcHash(VALUE_NAME_OBJECT,wcslen(VALUE_NAME_OBJECT)));
+  ASSERT(JSCONST_nFXobjHash ==
+    JS_CalcHash(VALUE_NAME_FXOBJ,wcslen(VALUE_NAME_FXOBJ)));
+  ASSERT(JSCONST_nNullHash ==
+    JS_CalcHash(VALUE_NAME_NULL,wcslen(VALUE_NAME_NULL)));
+  ASSERT(JSCONST_nUndefHash ==
+    JS_CalcHash(VALUE_NAME_UNDEFINED,wcslen(VALUE_NAME_UNDEFINED)));
+}
+#endif
+
 
 BEGIN_JS_STATIC_CONST(CJS_Global)
 END_JS_STATIC_CONST()
 
 BEGIN_JS_STATIC_PROP(CJS_Global)
 END_JS_STATIC_PROP()
 
 BEGIN_JS_STATIC_METHOD(CJS_Global)
         JS_STATIC_METHOD_ENTRY(setPersistent, 2)
 END_JS_STATIC_METHOD()
@@ skipping 513 matching lines @@
                 }
                 break;
         default:
                 return FALSE;
         }       
 
         m_mapGlobal.SetAt(propname, (FX_LPVOID)pNewData);
 
         return TRUE;
 }