Fix #509 by checking Nan/Inf when writing a double

include/rapidjson/internal/ieee754.h

@@ -40,6 +40,7 @@ public:
 
     bool IsNan() const { return (u_ & kExponentMask) == kExponentMask && Significand() != 0; }
     bool IsInf() const { return (u_ & kExponentMask) == kExponentMask && Significand() == 0; }
+    bool IsNanOrInf() const { return (u_ & kExponentMask) == kExponentMask; }
     bool IsNormal() const { return (u_ & kExponentMask) != 0 || Significand() == 0; }
     bool IsZero() const { return (u_ & (kExponentMask | kSignificandMask)) == 0; }
 

include/rapidjson/writer.h

@@ -235,6 +235,9 @@ protected:
     }
 
     bool WriteDouble(double d) {
+        if (internal::Double(d).IsNanOrInf())
+            return false;
+        
         char buffer[25];
         char* end = internal::dtoa(d, buffer);
         for (char* p = buffer; p != end; ++p)
@@ -381,6 +384,9 @@ inline bool Writer<StringBuffer>::WriteUint64(uint64_t u) {
 
 template<>
 inline bool Writer<StringBuffer>::WriteDouble(double d) {
+    if (internal::Double(d).IsNanOrInf())
+        return false;
+    
     char *buffer = os_->Push(25);
     char* end = internal::dtoa(d, buffer);
     os_->Pop(static_cast<size_t>(25 - (end - buffer)));

test/unittest/writertest.cpp

@@ -375,3 +375,27 @@ TEST(Writer, InvalidEventSequence) {
         EXPECT_FALSE(writer.IsComplete());
     }
 }
+
+double zero = 0.0;	// Use global variable to prevent compiler warning
+
+TEST(Writer, NaN) {
+    double nan = zero / zero;
+    EXPECT_TRUE(internal::Double(nan).IsNan());
+    StringBuffer buffer;
+    Writer<StringBuffer> writer(buffer);
+    EXPECT_FALSE(writer.Double(nan));
+}
+
+TEST(Writer, Inf) {
+    double inf = 1.0 / zero;
+    EXPECT_TRUE(internal::Double(inf).IsInf());
+    StringBuffer buffer;
+    {
+        Writer<StringBuffer> writer(buffer);
+        EXPECT_FALSE(writer.Double(inf));
+    }
+    {
+        Writer<StringBuffer> writer(buffer);
+        EXPECT_FALSE(writer.Double(-inf));
+    }
+}