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⚡ micro-optimizations for dump()

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Added separate code paths for normal output and pritty-printed output.
This allowed to remove most of the ifs along the way. Benchmarks and
cachegrind suggest a 10% performance improvement.
This commit is contained in:
Niels Lohmann 2017-02-26 16:55:54 +01:00
parent ae155c4734
commit bd0326cbc1
No known key found for this signature in database
GPG key ID: 7F3CEA63AE251B69
2 changed files with 108 additions and 84 deletions
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92
src/json.hpp
View file

@ -8414,9 +8414,6 @@ class basic_json
const unsigned int indent_step,
const unsigned int current_indent = 0) const
{
// variable to hold indentation for recursive calls
unsigned int new_indent = current_indent;
switch (m_type)
{
case value_t::object:
@ -8427,35 +8424,43 @@ class basic_json
return;
}
o << "{";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
}
o << "{\n";
// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' ');
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
{
if (i != m_value.object->cbegin())
{
o << (pretty_print ? ",\n" : ",");
o << ",\n";
}
o << string_t(new_indent, ' ') << "\""
<< escape_string(i->first) << "\":"
<< (pretty_print ? " " : "");
i->second.dump(o, pretty_print, indent_step, new_indent);
o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent);
}
// decrease indentation
if (pretty_print)
o << '\n' << string_t(current_indent, ' ') + '}';
}
else
{
new_indent -= indent_step;
o << "\n";
o << '{';
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
{
if (i != m_value.object->cbegin())
{
o << ',';
}
o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent);
}
o << '}';
}
o << string_t(new_indent, ' ') + "}";
return;
}
@ -8467,39 +8472,46 @@ class basic_json
return;
}
o << "[";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
o << "[\n";
// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' ');
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
o << indent_string;
i->dump(o, true, indent_step, new_indent);
o << ",\n";
}
for (auto i = m_value.array->cbegin(); i != m_value.array->cend(); ++i)
{
if (i != m_value.array->cbegin())
{
o << (pretty_print ? ",\n" : ",");
o << indent_string;
assert(not m_value.array->empty());
m_value.array->back().dump(o, true, indent_step, new_indent);
o << '\n' << string_t(current_indent, ' ') << ']';
}
o << string_t(new_indent, ' ');
i->dump(o, pretty_print, indent_step, new_indent);
else
{
o << '[';
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
i->dump(o, false, indent_step, current_indent);
o << ',';
}
assert(not m_value.array->empty());
m_value.array->back().dump(o, false, indent_step, current_indent);
o << ']';
}
// decrease indentation
if (pretty_print)
{
new_indent -= indent_step;
o << "\n";
}
o << string_t(new_indent, ' ') << "]";
return;
}
case value_t::string:
{
o << string_t("\"") << escape_string(*m_value.string) << "\"";
o << '\"' << escape_string(*m_value.string) << '\"';
return;
}

92
src/json.hpp.re2c
View file

@ -8414,9 +8414,6 @@ class basic_json
const unsigned int indent_step,
const unsigned int current_indent = 0) const
{
// variable to hold indentation for recursive calls
unsigned int new_indent = current_indent;
switch (m_type)
{
case value_t::object:
@ -8427,35 +8424,43 @@ class basic_json
return;
}
o << "{";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
}
o << "{\n";
// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' ');
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
{
if (i != m_value.object->cbegin())
{
o << (pretty_print ? ",\n" : ",");
o << ",\n";
}
o << string_t(new_indent, ' ') << "\""
<< escape_string(i->first) << "\":"
<< (pretty_print ? " " : "");
i->second.dump(o, pretty_print, indent_step, new_indent);
o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent);
}
// decrease indentation
if (pretty_print)
o << '\n' << string_t(current_indent, ' ') + '}';
}
else
{
new_indent -= indent_step;
o << "\n";
o << '{';
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
{
if (i != m_value.object->cbegin())
{
o << ',';
}
o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent);
}
o << '}';
}
o << string_t(new_indent, ' ') + "}";
return;
}
@ -8467,39 +8472,46 @@ class basic_json
return;
}
o << "[";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
o << "[\n";
// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' ');
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
o << indent_string;
i->dump(o, true, indent_step, new_indent);
o << ",\n";
}
for (auto i = m_value.array->cbegin(); i != m_value.array->cend(); ++i)
{
if (i != m_value.array->cbegin())
{
o << (pretty_print ? ",\n" : ",");
o << indent_string;
assert(not m_value.array->empty());
m_value.array->back().dump(o, true, indent_step, new_indent);
o << '\n' << string_t(current_indent, ' ') << ']';
}
o << string_t(new_indent, ' ');
i->dump(o, pretty_print, indent_step, new_indent);
else
{
o << '[';
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
i->dump(o, false, indent_step, current_indent);
o << ',';
}
assert(not m_value.array->empty());
m_value.array->back().dump(o, false, indent_step, current_indent);
o << ']';
}
// decrease indentation
if (pretty_print)
{
new_indent -= indent_step;
o << "\n";
}
o << string_t(new_indent, ' ') << "]";
return;
}
case value_t::string:
{
o << string_t("\"") << escape_string(*m_value.string) << "\"";
o << '\"' << escape_string(*m_value.string) << '\"';
return;
}