Remove run-time calculation of hash constants in pdfium.

fpdfsdk/src/javascript/global.cpp

Index: fpdfsdk/src/javascript/global.cpp
diff --git a/fpdfsdk/src/javascript/global.cpp b/fpdfsdk/src/javascript/global.cpp
index 04f9ef9da37938666db05320615de5e1b4bbad3b..85eb3619b84ff65534f9168e500cb39a0b11346d 100644
--- a/fpdfsdk/src/javascript/global.cpp
+++ b/fpdfsdk/src/javascript/global.cpp
@@ -16,14 +16,71 @@
 
 /* ---------------------------- 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()