fix exponential notation parsing (#857)

src/coders/BasicParser.inl

@@ -22,9 +22,26 @@ namespace {
     }
 
     inline double power(double base, int64_t power) {
+        if (power == 0) {
+            return 1.0;
+        }
+
+        uint64_t exp;
+        if (power < 0) {
+            base = 1.0 / base;
+            exp = static_cast<uint64_t>(-(power + 1)) + 1;
+        } else {
+            exp = static_cast<uint64_t>(power);
+        }
+
         double result = 1.0;
-        for (int64_t i = 0; i < power; i++) {
-            result *= base;
+
+        while (exp > 0) {
+            if (exp & 1)
+                result *= base;
+
+            base *= base;
+            exp >>= 1;
         }
         return result;
     }

test/coders/json.cpp

@@ -8,6 +8,8 @@ TEST(JSON, EncodeDecode) {
     const int bytesSize = 20;
     const int year = 2019;
     const float score = 3.141592;
+    const double distance = 1.23e45;
+    const double epsilon = 1e-6;
     const bool visible = true;
     dv::objects::Bytes srcBytes(bytesSize);
     for (int i = 0; i < bytesSize; i ++) {
@@ -20,6 +22,8 @@ TEST(JSON, EncodeDecode) {
         object["name"] = name;
         object["year"] = year;
         object["score"] = score;
+        object["distance"] = distance;
+        object["epsilon"] = epsilon;
         object["visible"] = visible;
         object["data"] = srcBytes;
 
@@ -30,6 +34,8 @@ TEST(JSON, EncodeDecode) {
         EXPECT_EQ(object["name"].asString(), name);
         EXPECT_EQ(object["year"].asInteger(), year);
         EXPECT_FLOAT_EQ(object["score"].asNumber(), score);
+        EXPECT_DOUBLE_EQ(object["distance"].asNumber(), distance);
+        EXPECT_DOUBLE_EQ(object["epsilon"].asNumber(), epsilon);
         EXPECT_EQ(object["visible"].asBoolean(), visible);
         auto b64string = object["data"].asString();