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⚡ micro-optimizations for dump()
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All ‘<<‘ calls have been replaced by write()/put() calls. The
indentation strings needs not to be resized. Cachegrind measures 1%
performance improvement.
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@nlohmann
nlohmann committed Feb 27, 2017
1 parent b1441f3 commit 0f04e42
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Showing 2 changed files with 132 additions and 52 deletions.
92 changes: 66 additions & 26 deletions src/json.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8420,47 +8420,69 @@ class basic_json
{
if (m_value.object->empty())
{
o << "{}";
o.write("{}", 2);
return;
}

if (pretty_print)
{
o << "{\n";
o.write("{\n", 2);

// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
string_t indent_string = string_t(new_indent, ' ');

// first n-1 elements
auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{
o << indent_string << '\"' << escape_string(i->first) << "\": ";
o.write(indent_string.c_str(), new_indent);
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\": ", 3);
i->second.dump(o, true, indent_step, new_indent);
o << ",\n";
o.write(",\n", 2);
}

o << indent_string << '\"' << escape_string(i->first) << "\": ";
// last element
assert(i != m_value.object->cend());
o.write(indent_string.c_str(), new_indent);
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\": ", 3);
i->second.dump(o, true, indent_step, new_indent);

indent_string.resize(current_indent);
o << '\n' << indent_string << '}';
o.put('\n');
o.write(indent_string.c_str(), current_indent);
o.put('}');
}
else
{
o << '{';
o.put('{');

// first n-1 elements
auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{
o << '\"' << escape_string(i->first) << "\":";
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\":", 2);
i->second.dump(o, false, indent_step, current_indent);
o << ',';
o.put(',');
}

o << '\"' << escape_string(i->first) << "\":";
// last element
assert(i != m_value.object->cend());
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\":", 2);
i->second.dump(o, false, indent_step, current_indent);
o << '}';

o.put('}');
}

return;
Expand All @@ -8470,57 +8492,75 @@ class basic_json
{
if (m_value.array->empty())
{
o << "[]";
o.write("[]", 2);
return;
}

if (pretty_print)
{
o << "[\n";
o.write("[\n", 2);

// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
string_t indent_string = string_t(new_indent, ' ');

// first n-1 elements
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
o << indent_string;
o.write(indent_string.c_str(), new_indent);
i->dump(o, true, indent_step, new_indent);
o << ",\n";
o.write(",\n", 2);
}

o << indent_string;
// last element
assert(not m_value.array->empty());
o.write(indent_string.c_str(), new_indent);
m_value.array->back().dump(o, true, indent_step, new_indent);

indent_string.resize(current_indent);
o << '\n' << indent_string << ']';
o.put('\n');
o.write(indent_string.c_str(), current_indent);
o.put(']');
}
else
{
o << '[';
o.put('[');

// first n-1 elements
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
i->dump(o, false, indent_step, current_indent);
o << ',';
o.put(',');
}

// last element
assert(not m_value.array->empty());
m_value.array->back().dump(o, false, indent_step, current_indent);
o << ']';

o.put(']');
}

return;
}

case value_t::string:
{
o << '\"' << escape_string(*m_value.string) << '\"';
o.put('\"');
const auto s = escape_string(*m_value.string);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.put('\"');
return;
}

case value_t::boolean:
{
o << (m_value.boolean ? "true" : "false");
if (m_value.boolean)
{
o.write("true", 4);
}
else
{
o.write("false", 5);
}
return;
}

Expand All @@ -8544,13 +8584,13 @@ class basic_json

case value_t::discarded:
{
o << "<discarded>";
o.write("<discarded>", 11);
return;
}

case value_t::null:
{
o << "null";
o.write("null", 4);
return;
}
}
Expand Down
92 changes: 66 additions & 26 deletions src/json.hpp.re2c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8420,47 +8420,69 @@ class basic_json
{
if (m_value.object->empty())
{
o << "{}";
o.write("{}", 2);
return;
}

if (pretty_print)
{
o << "{\n";
o.write("{\n", 2);

// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
string_t indent_string = string_t(new_indent, ' ');

// first n-1 elements
auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{
o << indent_string << '\"' << escape_string(i->first) << "\": ";
o.write(indent_string.c_str(), new_indent);
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\": ", 3);
i->second.dump(o, true, indent_step, new_indent);
o << ",\n";
o.write(",\n", 2);
}

o << indent_string << '\"' << escape_string(i->first) << "\": ";
// last element
assert(i != m_value.object->cend());
o.write(indent_string.c_str(), new_indent);
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\": ", 3);
i->second.dump(o, true, indent_step, new_indent);

indent_string.resize(current_indent);
o << '\n' << indent_string << '}';
o.put('\n');
o.write(indent_string.c_str(), current_indent);
o.put('}');
}
else
{
o << '{';
o.put('{');

// first n-1 elements
auto i = m_value.object->cbegin();
for (size_t cnt = 0; cnt < m_value.object->size() - 1; ++cnt, ++i)
{
o << '\"' << escape_string(i->first) << "\":";
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\":", 2);
i->second.dump(o, false, indent_step, current_indent);
o << ',';
o.put(',');
}

o << '\"' << escape_string(i->first) << "\":";
// last element
assert(i != m_value.object->cend());
o.put('\"');
const auto s = escape_string(i->first);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.write("\":", 2);
i->second.dump(o, false, indent_step, current_indent);
o << '}';

o.put('}');
}

return;
Expand All @@ -8470,57 +8492,75 @@ class basic_json
{
if (m_value.array->empty())
{
o << "[]";
o.write("[]", 2);
return;
}

if (pretty_print)
{
o << "[\n";
o.write("[\n", 2);

// variable to hold indentation for recursive calls
const auto new_indent = current_indent + indent_step;
string_t indent_string = string_t(new_indent, ' ');

// first n-1 elements
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
o << indent_string;
o.write(indent_string.c_str(), new_indent);
i->dump(o, true, indent_step, new_indent);
o << ",\n";
o.write(",\n", 2);
}

o << indent_string;
// last element
assert(not m_value.array->empty());
o.write(indent_string.c_str(), new_indent);
m_value.array->back().dump(o, true, indent_step, new_indent);

indent_string.resize(current_indent);
o << '\n' << indent_string << ']';
o.put('\n');
o.write(indent_string.c_str(), current_indent);
o.put(']');
}
else
{
o << '[';
o.put('[');

// first n-1 elements
for (auto i = m_value.array->cbegin(); i != m_value.array->cend() - 1; ++i)
{
i->dump(o, false, indent_step, current_indent);
o << ',';
o.put(',');
}

// last element
assert(not m_value.array->empty());
m_value.array->back().dump(o, false, indent_step, current_indent);
o << ']';

o.put(']');
}

return;
}

case value_t::string:
{
o << '\"' << escape_string(*m_value.string) << '\"';
o.put('\"');
const auto s = escape_string(*m_value.string);
o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
o.put('\"');
return;
}

case value_t::boolean:
{
o << (m_value.boolean ? "true" : "false");
if (m_value.boolean)
{
o.write("true", 4);
}
else
{
o.write("false", 5);
}
return;
}

Expand All @@ -8544,13 +8584,13 @@ class basic_json

case value_t::discarded:
{
o << "<discarded>";
o.write("<discarded>", 11);
return;
}

case value_t::null:
{
o << "null";
o.write("null", 4);
return;
}
}
Expand Down

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