Serialise doubles into more human friendly XML and JSON

BREAKING-CHANGES.txt

@@ -4,6 +4,30 @@ JUCE breaking changes
 Develop
 =======
 
+Change
+------
+The formatting of floating point numbers written to XML and JSON files has
+changed.
+
+Note that there is no change in precision - the XML and JSON files containing
+the new format numbers will parse in exactly the same way, it is only the
+string representation that has changed.
+
+Possible Issues
+---------------
+If you rely upon exactly reproducing XML or JSON files then the new files may
+be different.
+
+Workaround
+----------
+Update any reference XML or JSON files to use the new format.
+
+Rationale
+---------
+The new format retains full precision, provides a human friendly representation
+of values near 1, and uses scientific notation for small and large numbers.
+This prevents needless file size bloat from numbers like 0.00000000000000001.
+
 
 Version 5.4.3
 =============

modules/juce_core/containers/juce_Variant.cpp

@@ -175,7 +175,7 @@ public:
     int toInt (const ValueUnion& data) const noexcept override       { return (int) data.doubleValue; }
     int64 toInt64 (const ValueUnion& data) const noexcept override   { return (int64) data.doubleValue; }
     double toDouble (const ValueUnion& data) const noexcept override { return data.doubleValue; }
-    String toString (const ValueUnion& data) const override          { return minimiseLengthOfFloatString (String (data.doubleValue, 15, true)); }
+    String toString (const ValueUnion& data) const override          { return serialiseDouble (data.doubleValue); }
     bool toBool (const ValueUnion& data) const noexcept override     { return data.doubleValue != 0.0; }
     bool isDouble() const noexcept override                          { return true; }
     bool isComparable() const noexcept override                      { return true; }

modules/juce_core/javascript/juce_JSON.cpp

@@ -352,8 +352,7 @@ struct JSONFormatter
 
             if (juce_isfinite (d))
             {
-                String doubleString (d, maximumDecimalPlaces, true);
+                out << serialiseDouble (d);
-                out << minimiseLengthOfFloatString (doubleString);
             }
             else
             {
@@ -664,12 +663,17 @@ public:
             tests[1] = "1";
             tests[1.1] = "1.1";
             tests[1.01] = "1.01";
-            tests[0.76378] = "7.6378e-1";
+            tests[0.76378] = "0.76378";
-            tests[-10] = "-1e1";
+            tests[-10] = "-10";
-            tests[10.01] = "1.001e1";
+            tests[10.01] = "10.01";
-            tests[0.0123] = "1.23e-2";
+            tests[0.0123] = "0.0123";
             tests[-3.7e-27] = "-3.7e-27";
             tests[1e+40] = "1e40";
+            tests[-12345678901234567.0] = "-1.234567890123457e16";
+            tests[192000] = "192000";
+            tests[1234567] = "1.234567e6";
+            tests[0.00006] = "0.00006";
+            tests[0.000006] = "6e-6";
 
             for (auto& test : tests)
                 expectEquals (JSON::toString (test.first), test.second);

modules/juce_core/text/juce_String.cpp

@@ -2258,6 +2258,48 @@ static String minimiseLengthOfFloatString (const String& input)
     return input;
 }
 
+static String serialiseDouble (double input)
+{
+    auto absInput = std::abs (input);
+
+    if (absInput >= 1.0e6 || absInput <= 1.0e-5)
+        return minimiseLengthOfFloatString ({ input, 15, true });
+
+    int intInput = (int) input;
+
+    if ((double) intInput == input)
+        return minimiseLengthOfFloatString ({ input, 1 });
+
+    auto numberOfDecimalPlaces = [absInput]
+    {
+        if (absInput < 1.0)
+        {
+            if (absInput >= 1.0e-3)
+            {
+                if (absInput >= 1.0e-1) return 16;
+                if (absInput >= 1.0e-2) return 17;
+                return 18;
+            }
+
+            if (absInput >= 1.0e-4) return 19;
+            return 20;
+        }
+
+        if (absInput < 1.0e3)
+        {
+            if (absInput < 1.0e1) return 15;
+            if (absInput < 1.0e2) return 14;
+            return 13;
+        }
+
+        if (absInput < 1.0e4) return 12;
+        if (absInput < 1.0e5) return 11;
+        return 10;
+    }();
+
+    return minimiseLengthOfFloatString (String (input, numberOfDecimalPlaces));
+}
+
 //==============================================================================
 //==============================================================================
 #if JUCE_UNIT_TESTS
@@ -2851,6 +2893,34 @@ public:
                     expectEquals (minimiseLengthOfFloatString (String (test.first, 15, true)), test.second);
             }
         }
+
+        {
+            beginTest ("Serialisation");
+
+            std::map <double, String> tests;
+            tests[1234567890123456.7] = "1.234567890123457e15";
+            tests[12345678.901234567] = "1.234567890123457e7";
+            tests[1234567.8901234567] = "1.234567890123457e6";
+            tests[123456.78901234567] = "123456.7890123457";
+            tests[12345.678901234567] = "12345.67890123457";
+            tests[1234.5678901234567] = "1234.567890123457";
+            tests[123.45678901234567] = "123.4567890123457";
+            tests[12.345678901234567] = "12.34567890123457";
+            tests[1.2345678901234567] = "1.234567890123457";
+            tests[0.12345678901234567] = "0.1234567890123457";
+            tests[0.012345678901234567] = "0.01234567890123457";
+            tests[0.0012345678901234567] = "0.001234567890123457";
+            tests[0.00012345678901234567] = "0.0001234567890123457";
+            tests[0.000012345678901234567] = "0.00001234567890123457";
+            tests[0.0000012345678901234567] = "1.234567890123457e-6";
+            tests[0.00000012345678901234567] = "1.234567890123457e-7";
+
+            for (auto& test : tests)
+            {
+                expectEquals (serialiseDouble (test.first), test.second);
+                expectEquals (serialiseDouble (-test.first), "-" + test.second);
+            }
+        }
     }
 };
 

modules/juce_core/xml/juce_XmlElement.cpp

@@ -580,8 +580,7 @@ void XmlElement::setAttribute (const Identifier& attributeName, const int number
 
 void XmlElement::setAttribute (const Identifier& attributeName, const double number)
 {
-    String doubleString (number, 15, true);
+    setAttribute (attributeName, serialiseDouble (number));
-    setAttribute (attributeName, minimiseLengthOfFloatString (doubleString));
 }
 
 void XmlElement::removeAttribute (const Identifier& attributeName) noexcept
@@ -946,12 +945,17 @@ public:
             tests[1] = "1";
             tests[1.1] = "1.1";
             tests[1.01] = "1.01";
-            tests[0.76378] = "7.6378e-1";
+            tests[0.76378] = "0.76378";
-            tests[-10] = "-1e1";
+            tests[-10] = "-10";
-            tests[10.01] = "1.001e1";
+            tests[10.01] = "10.01";
-            tests[0.0123] = "1.23e-2";
+            tests[0.0123] = "0.0123";
             tests[-3.7e-27] = "-3.7e-27";
             tests[1e+40] = "1e40";
+            tests[-12345678901234567.0] = "-1.234567890123457e16";
+            tests[192000] = "192000";
+            tests[1234567] = "1.234567e6";
+            tests[0.00006] = "0.00006";
+            tests[0.000006] = "6e-6";
 
             for (auto& test : tests)
             {

modules/juce_data_structures/values/juce_ValueTree.cpp

@@ -1198,12 +1198,17 @@ public:
             tests[1] = "1";
             tests[1.1] = "1.1";
             tests[1.01] = "1.01";
-            tests[0.76378] = "7.6378e-1";
+            tests[0.76378] = "0.76378";
-            tests[-10] = "-1e1";
+            tests[-10] = "-10";
-            tests[10.01] = "1.001e1";
+            tests[10.01] = "10.01";
-            tests[0.0123] = "1.23e-2";
+            tests[0.0123] = "0.0123";
             tests[-3.7e-27] = "-3.7e-27";
             tests[1e+40] = "1e40";
+            tests[-12345678901234567.0] = "-1.234567890123457e16";
+            tests[192000] = "192000";
+            tests[1234567] = "1.234567e6";
+            tests[0.00006] = "0.00006";
+            tests[0.000006] = "6e-6";
 
             for (auto& test : tests)
             {