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<const wchar_t A = 0, const wchar_t B = 0, const wchar_t C = 0,

[Tom Sepez, 2015/01/02 17:59:08]

Do we allow variadic templates from c++11x?  Does that help with your max arity
issue?

[brucedawson, 2015/01/02 19:56:17]

We do allow variadic templates, they are used in base\tuple.h. They do solve the
max-arity issue, but it's not clear to me whether this is progress or not.

+  const wchar_t D = 0, const wchar_t E = 0, const wchar_t F = 0,
+  const wchar_t G = 0, const wchar_t H = 0, const wchar_t I = 0>
+struct cHash

[Tom Sepez, 2015/01/02 17:59:08]

Nit: struct/class name should start with uppercase.  Maybe a better name here?

[brucedawson, 2015/01/02 19:56:17]

Yep.

+{
+    template<const wchar_t X, unsigned hash = 0>
+    struct HashCalc
+    {
+        enum : unsigned { value = (X == 0)

[Tom Sepez, 2015/01/02 17:59:08]

can we do this with static const int value instead?  Is that cleaner?

[brucedawson, 2015/01/02 19:56:17]

Yes, static const int is cleaner.

+          ? hash
+          : (hash * 1313llu + X) & 0xFFFFFFFF };
+    };
+
+    enum { value = HashCalc<I,HashCalc<H,HashCalc<G,HashCalc<F,HashCalc<E,
+      HashCalc<D,HashCalc<C,HashCalc<B,HashCalc<A>::value>::value>::value
+      >::value>::value>::value>::value>::value>::value };
+};
+
+extern const unsigned int JSCONST_nStringHash =
+  cHash<'s','t','r','i','n','g'>::value;
+extern const unsigned int JSCONST_nNumberHash =
+  cHash<'n','u','m','b','e','r'>::value;
+extern const unsigned int JSCONST_nBoolHash =
+  cHash<'b','o','o','l','e','a','n'>::value;
+extern const unsigned int JSCONST_nDateHash =
+  cHash<'d','a','t','e'>::value;
+extern const unsigned int JSCONST_nObjectHash =
+  cHash<'o','b','j','e','c','t'>::value;
+extern const unsigned int JSCONST_nFXobjHash =
+  cHash<'f','x','o','b','j'>::value;
+extern const unsigned int JSCONST_nNullHash =
+  cHash<'n','u','l','l'>::value;
+extern const unsigned int JSCONST_nUndefHash =
+  cHash<'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;
 }