univalue: Avoid unnecessary roundtrip through double for numbers

JSON makes no distinction between numbers and reals, and our code
doesn't need to do so either.

This removes VREAL, as well as its specific post-processing in
`UniValue::write`. Non-monetary amounts do not need to be forcibly
formatted with 8 decimals, so the extra roundtrip was unnecessary
(and potentially loses precision).

qa/rpc-tests/rest.py

@@ -14,6 +14,7 @@ from struct import *
 import binascii
 import json
 import StringIO
+import decimal
 
 try:
     import http.client as httplib
@@ -243,7 +244,7 @@ class RESTTest (BitcoinTestFramework):
         response_header_json = http_get_call(url.hostname, url.port, '/rest/headers/1/'+bb_hash+self.FORMAT_SEPARATOR+"json", "", True)
         assert_equal(response_header_json.status, 200)
         response_header_json_str = response_header_json.read()
-        json_obj = json.loads(response_header_json_str)
+        json_obj = json.loads(response_header_json_str, parse_float=decimal.Decimal)
         assert_equal(len(json_obj), 1) #ensure that there is one header in the json response
         assert_equal(json_obj[0]['hash'], bb_hash) #request/response hash should be the same
 

src/rpcserver.cpp

@@ -120,7 +120,7 @@ void RPCTypeCheckObj(const UniValue& o,
 
 CAmount AmountFromValue(const UniValue& value)
 {
-    if (!value.isReal() && !value.isNum())
+    if (!value.isNum())
         throw JSONRPCError(RPC_TYPE_ERROR, "Amount is not a number");
     CAmount amount;
     if (!ParseFixedPoint(value.getValStr(), 8, &amount))

src/test/univalue_tests.cpp

@@ -49,7 +49,7 @@ BOOST_AUTO_TEST_CASE(univalue_constructor)
 
     double vd = -7.21;
     UniValue v7(vd);
-    BOOST_CHECK(v7.isReal());
+    BOOST_CHECK(v7.isNum());
     BOOST_CHECK_EQUAL(v7.getValStr(), "-7.21");
 
     string vs("yawn");
@@ -127,7 +127,7 @@ BOOST_AUTO_TEST_CASE(univalue_set)
     BOOST_CHECK_EQUAL(v.getValStr(), "zum");
 
     BOOST_CHECK(v.setFloat(-1.01));
-    BOOST_CHECK(v.isReal());
+    BOOST_CHECK(v.isNum());
     BOOST_CHECK_EQUAL(v.getValStr(), "-1.01");
 
     BOOST_CHECK(v.setInt((int)1023));
@@ -272,7 +272,7 @@ BOOST_AUTO_TEST_CASE(univalue_object)
     objTypes["distance"] = UniValue::VNUM;
     objTypes["time"] = UniValue::VNUM;
     objTypes["calories"] = UniValue::VNUM;
-    objTypes["temperature"] = UniValue::VREAL;
+    objTypes["temperature"] = UniValue::VNUM;
     objTypes["cat1"] = UniValue::VNUM;
     objTypes["cat2"] = UniValue::VNUM;
     BOOST_CHECK(obj.checkObject(objTypes));

src/univalue/univalue.cpp

@@ -86,7 +86,7 @@ bool UniValue::setFloat(double val)
     oss << std::setprecision(16) << val;
 
     bool ret = setNumStr(oss.str());
-    typ = VREAL;
+    typ = VNUM;
     return ret;
 }
 
@@ -210,7 +210,6 @@ const char *uvTypeName(UniValue::VType t)
     case UniValue::VARR: return "array";
     case UniValue::VSTR: return "string";
     case UniValue::VNUM: return "number";
-    case UniValue::VREAL: return "number";
     }
 
     // not reached
@@ -280,7 +279,7 @@ int64_t UniValue::get_int64() const
 
 double UniValue::get_real() const
 {
-    if (typ != VREAL && typ != VNUM)
+    if (typ != VNUM)
         throw std::runtime_error("JSON value is not a number as expected");
     double retval;
     if (!ParseDouble(getValStr(), &retval))

src/univalue/univalue.h

@@ -16,7 +16,7 @@
 
 class UniValue {
 public:
-    enum VType { VNULL, VOBJ, VARR, VSTR, VNUM, VREAL, VBOOL, };
+    enum VType { VNULL, VOBJ, VARR, VSTR, VNUM, VBOOL, };
 
     UniValue() { typ = VNULL; }
     UniValue(UniValue::VType initialType, const std::string& initialStr = "") {
@@ -78,7 +78,6 @@ public:
     bool isBool() const { return (typ == VBOOL); }
     bool isStr() const { return (typ == VSTR); }
     bool isNum() const { return (typ == VNUM); }
-    bool isReal() const { return (typ == VREAL); }
     bool isArray() const { return (typ == VARR); }
     bool isObject() const { return (typ == VOBJ); }
 

src/univalue/univalue_write.cpp

@@ -61,13 +61,6 @@ string UniValue::write(unsigned int prettyIndent,
     case VSTR:
         s += "\"" + json_escape(val) + "\"";
         break;
-    case VREAL:
-        {
-            std::stringstream ss;
-            ss << std::showpoint << std::fixed << std::setprecision(8) << get_real();
-            s += ss.str();
-        }
-        break;
     case VNUM:
         s += val;
         break;