[THRIFT-3636] Double precision is not fully preserved in C++ TJSONProtocol

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9.3
• Fix Version/s: 0.10.0
• Component/s: C++ - Library

Environment

Linux Mac Windows

• Assignee: WangYaofu
• Reporter: WangYaofu
• Created: 15/Feb/16 02:36
• Updated: 19/Feb/16 02:17
• Resolved: 17/Feb/16 15:01

Description

The precision is 15 bits after dot of format casting from double to string in Thrift-cpp-library- json-protocol.
But the expected precision is 16 bits after dot in Thrift-json-protocol.

The solution:
To Change code 'str.precision(std::numeric_limits<double>::digits10 + 1);' to 'str.precision(std::numeric_limits<double>::digits10 + 2);'
in function doubeToString file TJSONProtocol.cpp at line 524,
e.g:
before:
In C++ TJsonProtocol.cpp:
double a = 1.12345678906666663;
string astr = doubleToString(a);
double b = stringToDouble(astr);
the result as below:
a = 1.1234567890666667
astr = "1.123456789066667"
b = 1.1234567890666669
after changing:
the result as below:
a = 1.1234567890666667
astr = "1.1234567890666667"
b = 1.1234567890666667
This result is expected.