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fix: minimize the precision loss when dumping double to string #712

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merged 7 commits into from
Jan 29, 2024
Merged

fix: minimize the precision loss when dumping double to string #712

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6130f2e
fix: minimize the precision loss when dumping double to string
junekhan Oct 25, 2023
8bb7cf1
fix: abandon one-time macro
junekhan Jan 21, 2024
543fa7a
fix: replace hard-coded buffer size, replace `sprintf` with `snprintf`
junekhan Jan 22, 2024
f1894c5
fix: replace `DECIMAL_DIG` with `DBL_DECIMAL_DIG`
junekhan Jan 23, 2024
75d7811
Update json.h changed to C++11 DECIMAL_DIGIT
gittiver Jan 23, 2024
69b17cc
added cfloat include
gittiver Jan 23, 2024
5ba4b39
fix: identify float and double as different numeral types, and approa…
junekhan Jan 24, 2024
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5 changes: 3 additions & 2 deletions include/crow/json.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1851,10 +1851,11 @@ namespace crow
} f_state;
char outbuf[128];
#ifdef _MSC_VER
sprintf_s(outbuf, sizeof(outbuf), "%f", v.num.d);
#define MSC_COMPATIBLE_SPRINTF(BUFFER_PTR, FORMAT_PTR, VALUE) sprintf_s((BUFFER_PTR), 128, (FORMAT_PTR), DBL_DECIMAL_DIG, (VALUE))
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#else
snprintf(outbuf, sizeof(outbuf), "%f", v.num.d);
#define MSC_COMPATIBLE_SPRINTF(BUFFER_PTR, FORMAT_PTR, VALUE) sprintf((BUFFER_PTR), (FORMAT_PTR), DECIMAL_DIG, (VALUE))
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#endif
MSC_COMPATIBLE_SPRINTF(outbuf, "%.*g", v.num.d);
char *p = &outbuf[0], *o = nullptr; // o is the position of the first trailing 0
f_state = start;
while (*p != '\0')
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6 changes: 4 additions & 2 deletions tests/unittest.cpp
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Expand Up @@ -1038,11 +1038,13 @@ TEST_CASE("json::wvalue::wvalue(float)")

TEST_CASE("json::wvalue::wvalue(double)")
{
double d = 4.2;
double d = 0.036303908355795146;
json::wvalue value = d;

CHECK(value.t() == json::type::Number);
CHECK(value.dump() == "4.2");
auto dumped_value = value.dump();
CROW_LOG_DEBUG << dumped_value;
CHECK(std::abs(utility::lexical_cast<double>(dumped_value) - d) < numeric_limits<double>::epsilon());
} // json::wvalue::wvalue(double)

TEST_CASE("json::wvalue::wvalue(char const*)")
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