[jira] [Created] (THRIFT-3636) The precision is 15 bits after dot of casting from double to string in Thrift-cpp-library- json-protocol.

["WangYaofu (JIRA)" <ji...@apache.org>]

WangYaofu created THRIFT-3636:
---------------------------------

             Summary: The precision is 15 bits after dot of casting from double to string in Thrift-cpp-library- json-protocol.
                 Key: THRIFT-3636
                 URL: https://issues.apache.org/jira/browse/THRIFT-3636
             Project: Thrift
          Issue Type: Bug
          Components: C++ - Library
    Affects Versions: 0.9.3
         Environment: Linux Max Windows
            Reporter: WangYaofu
            Assignee: WangYaofu
             Fix For: 0.9.4


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.



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