pack double and float in a more size efficient way

check also for nan and numeric limits

Author: GeorgFritze

include/msgpack/v1/pack.hpp

@@ -1138,11 +1138,18 @@ inline packer<Stream>& packer<Stream>::pack_unsigned_long_long(unsigned long lon
 template <typename Stream>
 inline packer<Stream>& packer<Stream>::pack_float(float d)
 {
-    if (d == int64_t(d))
-    {
-        pack_imp_int64(int64_t(d));
-        return *this;
+    if (d == d) { // check for nan 
+        // compare d to limits::max() to avoid undefined behaviour
+        if (d >= 0 && d <= std::numeric_limits<uint64_t>::max() && d == uint64_t(d)) {
+            pack_imp_uint64(uint64_t(d));
+            return *this;
+        
+        } else if (d >= std::numeric_limits<int64_t>::min() && d == int64_t(d)) {
+            pack_imp_int64(int64_t(d));
+            return *this;
+        }
     }
+
     union { float f; uint32_t i; } mem;
     mem.f = d;
     char buf[5];
@@ -1154,10 +1161,16 @@ inline packer<Stream>& packer<Stream>::pack_float(float d)
 template <typename Stream>
 inline packer<Stream>& packer<Stream>::pack_double(double d)
 {
-    if (d == int64_t(d))
-    {
-        pack_imp_int64(int64_t(d));
-        return *this;
+    if (d == d) { // check for nan 
+        // compare d to limits::max() to avoid undefined behaviour
+        if (d >= 0 && d <= std::numeric_limits<uint64_t>::max() && d == uint64_t(d)) {
+            pack_imp_uint64(uint64_t(d));
+            return *this;
+        
+        } else if (d >= std::numeric_limits<int64_t>::min() && d == int64_t(d)) {
+            pack_imp_int64(int64_t(d));
+            return *this;
+        }
     }
 
     union { double f; uint64_t i; } mem;