From 1286d35767448925db9ac1d6d52855da822ce2fe Mon Sep 17 00:00:00 2001
From: Niels <niels.lohmann@gmail.com>
Date: Wed, 20 Jul 2016 20:07:45 +0200
Subject: [PATCH] make sure precision is reset on output streams during
serialization
---
src/json.hpp | 31 ++++++++++++++++++++++---------
src/json.hpp.re2c | 31 ++++++++++++++++++++++---------
test/src/unit.cpp | 22 ++++++++++++++++++++++
3 files changed, 66 insertions(+), 18 deletions(-)
diff --git a/src/json.hpp b/src/json.hpp
index fa14b0e7..29155327 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -2120,6 +2120,12 @@ class basic_json
// fix locale problems
ss.imbue(std::locale(std::locale(), new DecimalSeparator));
+ // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+ // string->float->string, string->double->string or string->long
+ // double->string; to be safe, we read this value from
+ // std::numeric_limits<number_float_t>::digits10
+ ss.precision(std::numeric_limits<double>::digits10);
+
if (indent >= 0)
{
dump(ss, true, static_cast<unsigned int>(indent));
@@ -5693,6 +5699,10 @@ class basic_json
`std::setw(4)` on @a o sets the indentation level to `4` and the
serialization result is the same as calling `dump(4)`.
+ @note During serializaion, the locale and the precision of the output
+ stream @a o are changed. The original values are restored when the
+ function returns.
+
@param[in,out] o stream to serialize to
@param[in] j JSON value to serialize
@@ -5713,14 +5723,23 @@ class basic_json
// reset width to 0 for subsequent calls to this stream
o.width(0);
+
// fix locale problems
- auto old_locale = o.imbue(std::locale(std::locale(), new DecimalSeparator));
+ const auto old_locale = o.imbue(std::locale(std::locale(), new DecimalSeparator));
+ // set precision
+
+ // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+ // string->float->string, string->double->string or string->long
+ // double->string; to be safe, we read this value from
+ // std::numeric_limits<number_float_t>::digits10
+ const auto old_preicison = o.precision(std::numeric_limits<double>::digits10);
// do the actual serialization
j.dump(o, pretty_print, static_cast<unsigned int>(indentation));
- // reset locale
+ // reset locale and precision
o.imbue(old_locale);
+ o.precision(old_preicison);
return o;
}
@@ -6184,13 +6203,7 @@ class basic_json
}
else
{
- // Otherwise 6, 15 or 16 digits of precision allows
- // round-trip IEEE 754 string->float->string,
- // string->double->string or string->long
- // double->string; to be safe, we read this value from
- // std::numeric_limits<number_float_t>::digits10
- o << std::setprecision(std::numeric_limits<double>::digits10)
- << m_value.number_float;
+ o << m_value.number_float;
}
return;
}
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index dd1bda1f..8eeedefe 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -2120,6 +2120,12 @@ class basic_json
// fix locale problems
ss.imbue(std::locale(std::locale(), new DecimalSeparator));
+ // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+ // string->float->string, string->double->string or string->long
+ // double->string; to be safe, we read this value from
+ // std::numeric_limits<number_float_t>::digits10
+ ss.precision(std::numeric_limits<double>::digits10);
+
if (indent >= 0)
{
dump(ss, true, static_cast<unsigned int>(indent));
@@ -5693,6 +5699,10 @@ class basic_json
`std::setw(4)` on @a o sets the indentation level to `4` and the
serialization result is the same as calling `dump(4)`.
+ @note During serializaion, the locale and the precision of the output
+ stream @a o are changed. The original values are restored when the
+ function returns.
+
@param[in,out] o stream to serialize to
@param[in] j JSON value to serialize
@@ -5713,14 +5723,23 @@ class basic_json
// reset width to 0 for subsequent calls to this stream
o.width(0);
+
// fix locale problems
- auto old_locale = o.imbue(std::locale(std::locale(), new DecimalSeparator));
+ const auto old_locale = o.imbue(std::locale(std::locale(), new DecimalSeparator));
+ // set precision
+
+ // 6, 15 or 16 digits of precision allows round-trip IEEE 754
+ // string->float->string, string->double->string or string->long
+ // double->string; to be safe, we read this value from
+ // std::numeric_limits<number_float_t>::digits10
+ const auto old_preicison = o.precision(std::numeric_limits<double>::digits10);
// do the actual serialization
j.dump(o, pretty_print, static_cast<unsigned int>(indentation));
- // reset locale
+ // reset locale and precision
o.imbue(old_locale);
+ o.precision(old_preicison);
return o;
}
@@ -6184,13 +6203,7 @@ class basic_json
}
else
{
- // Otherwise 6, 15 or 16 digits of precision allows
- // round-trip IEEE 754 string->float->string,
- // string->double->string or string->long
- // double->string; to be safe, we read this value from
- // std::numeric_limits<number_float_t>::digits10
- o << std::setprecision(std::numeric_limits<double>::digits10)
- << m_value.number_float;
+ o << m_value.number_float;
}
return;
}
diff --git a/test/src/unit.cpp b/test/src/unit.cpp
index a12f0529..a7ca7394 100644
--- a/test/src/unit.cpp
+++ b/test/src/unit.cpp
@@ -1685,6 +1685,28 @@ TEST_CASE("object inspection")
json j_discarded(json::value_t::discarded);
CHECK(j_discarded.dump() == "<discarded>");
}
+
+ SECTION("check that precision is reset after serialization")
+ {
+ // create stringstream and set precision
+ std::stringstream ss;
+ ss.precision(3);
+ ss << 3.141592653589793 << std::fixed;
+ CHECK(ss.str() == "3.14");
+
+ // reset stringstream
+ ss.str(std::string());
+
+ // use stringstream for JSON serialization
+ json j_number = 3.141592653589793;
+ ss << j_number;
+
+ // check that precision has been overridden during serialization
+ CHECK(ss.str() == "3.141592653589793");
+
+ // check that precision has been restored
+ CHECK(ss.precision() == 3);
+ }
}
SECTION("return the type of the object (explicit)")