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⚡ micro-optimizations for dump()

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Indentation string is recycled to avoid allocations. Comma-separation
in objects does not need an if any more. Cachegrind measures 1%
performance improvement.
This commit is contained in:
Niels Lohmann 2017-02-26 20:58:00 +01:00
parent bd0326cbc1
commit b1441f3485
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GPG key ID: 7F3CEA63AE251B69
2 changed files with 34 additions and 28 deletions
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31
src/json.hpp
View file

@ -8430,34 +8430,36 @@ class basic_json
// variable to hold indentation for recursive calls // variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step; const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' '); string_t indent_string = string_t(new_indent, ' ');
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i) auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{ {
if (i != m_value.object->cbegin())
{
o << ",\n";
}
o << indent_string << '\"' << escape_string(i->first) << "\": "; o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent); i->second.dump(o, true, indent_step, new_indent);
o << ",\n";
} }
o << '\n' << string_t(current_indent, ' ') + '}'; o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent);
indent_string.resize(current_indent);
o << '\n' << indent_string << '}';
} }
else else
{ {
o << '{'; o << '{';
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i) auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{ {
if (i != m_value.object->cbegin())
{
o << ',';
}
o << '\"' << escape_string(i->first) << "\":"; o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent); i->second.dump(o, false, indent_step, current_indent);
o << ',';
} }
o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent);
o << '}'; o << '}';
} }
@ -8478,7 +8480,7 @@ class basic_json
// variable to hold indentation for recursive calls // variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step; const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' '); string_t indent_string = string_t(new_indent, ' ');
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i) for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{ {
@ -8491,7 +8493,8 @@ class basic_json
assert(not m_value.array->empty()); assert(not m_value.array->empty());
m_value.array->back().dump(o, true, indent_step, new_indent); m_value.array->back().dump(o, true, indent_step, new_indent);
o << '\n' << string_t(current_indent, ' ') << ']'; indent_string.resize(current_indent);
o << '\n' << indent_string << ']';
} }
else else
{ {

31
src/json.hpp.re2c
View file

@ -8430,34 +8430,36 @@ class basic_json
// variable to hold indentation for recursive calls // variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step; const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' '); string_t indent_string = string_t(new_indent, ' ');
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i) auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{ {
if (i != m_value.object->cbegin())
{
o << ",\n";
}
o << indent_string << '\"' << escape_string(i->first) << "\": "; o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent); i->second.dump(o, true, indent_step, new_indent);
o << ",\n";
} }
o << '\n' << string_t(current_indent, ' ') + '}'; o << indent_string << '\"' << escape_string(i->first) << "\": ";
i->second.dump(o, true, indent_step, new_indent);
indent_string.resize(current_indent);
o << '\n' << indent_string << '}';
} }
else else
{ {
o << '{'; o << '{';
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i) auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{ {
if (i != m_value.object->cbegin())
{
o << ',';
}
o << '\"' << escape_string(i->first) << "\":"; o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent); i->second.dump(o, false, indent_step, current_indent);
o << ',';
} }
o << '\"' << escape_string(i->first) << "\":";
i->second.dump(o, false, indent_step, current_indent);
o << '}'; o << '}';
} }
@ -8478,7 +8480,7 @@ class basic_json
// variable to hold indentation for recursive calls // variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step; const auto new_indent = current_indent + indent_step;
const std::string indent_string = string_t(new_indent, ' '); string_t indent_string = string_t(new_indent, ' ');
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i) for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{ {
@ -8491,7 +8493,8 @@ class basic_json
assert(not m_value.array->empty()); assert(not m_value.array->empty());
m_value.array->back().dump(o, true, indent_step, new_indent); m_value.array->back().dump(o, true, indent_step, new_indent);
o << '\n' << string_t(current_indent, ' ') << ']'; indent_string.resize(current_indent);
o << '\n' << indent_string << ']';
} }
else else
{ {