Better #1665

dbms/src/IO/ReadHelpers.h

@@ -354,7 +354,7 @@ void tryReadIntTextUnsafe(T & x, ReadBuffer & buf)
 template <bool throw_exception, typename ExcepFun, typename NoExcepFun, typename... Args>
 bool exceptionPolicySelector(ExcepFun && excep_f, NoExcepFun && no_excep_f, Args &&... args)
 {
-    if (throw_exception)
+    if constexpr (throw_exception)
     {
         excep_f(std::forward<Args>(args)...);
         return true;
@@ -374,7 +374,7 @@ void assertNaN(ReadBuffer & buf);
 
 /// Rough: not exactly nearest machine representable number is returned.
 /// Some garbage may be successfully parsed, examples: '.' parsed as 0; 123Inf parsed as inf.
-template <typename T, typename ReturnType, char point_symbol = '.'>
+template <typename T, typename ReturnType>
 ReturnType readFloatTextImpl(T & x, ReadBuffer & buf)
 {
     static constexpr bool throw_exception = std::is_same_v<ReturnType, void>;
@@ -401,7 +401,7 @@ ReturnType readFloatTextImpl(T & x, ReadBuffer & buf)
             case '-':
                 negative = true;
                 break;
-            case point_symbol:
+            case '.':
                 after_point = true;
                 break;
             case '0':

dbms/src/IO/WriteHelpers.h

@@ -99,29 +99,26 @@ inline void writeBoolText(bool x, WriteBuffer & buf)
 }
 
 
-inline void writeFloatText(double x, WriteBuffer & buf)
+template <typename T>
+inline void writeFloatText(T x, WriteBuffer & buf)
 {
-    DoubleConverter<false>::BufferType buffer;
-    double_conversion::StringBuilder builder{buffer, sizeof(buffer)};
+    static_assert(std::is_same_v<T, double> || std::is_same_v<T, float>, "Argument for writeFloatText must be float or double");
 
-    const auto result = DoubleConverter<false>::instance().ToShortest(x, &builder);
+    using Converter = DoubleConverter<false>;
 
-    if (!result)
-        throw Exception("Cannot print double number", ErrorCodes::CANNOT_PRINT_FLOAT_OR_DOUBLE_NUMBER);
-
-    buf.write(buffer, builder.position());
-}
-
-inline void writeFloatText(float x, WriteBuffer & buf)
-{
-    DoubleConverter<false>::BufferType buffer;
+    Converter::BufferType buffer;
     double_conversion::StringBuilder builder{buffer, sizeof(buffer)};
 
-    const auto result = DoubleConverter<false>::instance().ToShortestSingle(x, &builder);
+    bool result = false;
+    if constexpr (std::is_same_v<T, double>)
+        result = Converter::instance().ToShortest(x, &builder);
+    else
+        result = Converter::instance().ToShortestSingle(x, &builder);
 
     if (!result)
-        throw Exception("Cannot print float number", ErrorCodes::CANNOT_PRINT_FLOAT_OR_DOUBLE_NUMBER);
+        throw Exception("Cannot print floating point number", ErrorCodes::CANNOT_PRINT_FLOAT_OR_DOUBLE_NUMBER);
 
+    /// TODO Excessive copy. Use optimistic path if buffer have enough bytes.
     buf.write(buffer, builder.position());
 }