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mirror of https://github.com/qpdf/qpdf.git synced 2024-10-31 19:02:30 +00:00

Add new private class JSON::Writer

Create a simple utility class for writing JSON to a pipeline.
This commit is contained in:
m-holger 2024-02-09 13:03:53 +00:00
parent b1b789df42
commit 9e90007a4a
3 changed files with 134 additions and 4 deletions

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@ -290,8 +290,11 @@ class JSON
QPDF_DLL QPDF_DLL
qpdf_offset_t getEnd() const; qpdf_offset_t getEnd() const;
// The following class does not form part of the public API and is for internal use only.
class Writer;
private: private:
static std::string encode_string(std::string const& utf8);
static void writeClose(Pipeline* p, bool first, size_t depth, char const* delimeter); static void writeClose(Pipeline* p, bool first, size_t depth, char const* delimeter);
enum value_type_e { enum value_type_e {

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@ -1,5 +1,7 @@
#include <qpdf/JSON.hh> #include <qpdf/JSON.hh>
#include <qpdf/JSON_writer.hh>
#include <qpdf/BufferInputSource.hh> #include <qpdf/BufferInputSource.hh>
#include <qpdf/Pl_Base64.hh> #include <qpdf/Pl_Base64.hh>
#include <qpdf/Pl_Concatenate.hh> #include <qpdf/Pl_Concatenate.hh>
@ -119,7 +121,7 @@ JSON::JSON_array::write(Pipeline* p, size_t depth) const
JSON::JSON_string::JSON_string(std::string const& utf8) : JSON::JSON_string::JSON_string(std::string const& utf8) :
JSON_value(vt_string), JSON_value(vt_string),
utf8(utf8), utf8(utf8),
encoded(encode_string(utf8)) encoded(Writer::encode_string(utf8))
{ {
} }
@ -211,7 +213,7 @@ JSON::unparse() const
} }
std::string std::string
JSON::encode_string(std::string const& str) JSON::Writer::encode_string(std::string const& str)
{ {
static auto constexpr hexchars = "0123456789abcdef"; static auto constexpr hexchars = "0123456789abcdef";
@ -279,7 +281,7 @@ JSON
JSON::addDictionaryMember(std::string const& key, JSON const& val) JSON::addDictionaryMember(std::string const& key, JSON const& val)
{ {
if (auto* obj = m ? dynamic_cast<JSON_dictionary*>(m->value.get()) : nullptr) { if (auto* obj = m ? dynamic_cast<JSON_dictionary*>(m->value.get()) : nullptr) {
return obj->members[encode_string(key)] = val.m ? val : makeNull(); return obj->members[Writer::encode_string(key)] = val.m ? val : makeNull();
} else { } else {
throw std::runtime_error("JSON::addDictionaryMember called on non-dictionary"); throw std::runtime_error("JSON::addDictionaryMember called on non-dictionary");
} }

125
libqpdf/qpdf/JSON_writer.hh Normal file
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@ -0,0 +1,125 @@
#ifndef JSON_WRITER_HH
#define JSON_WRITER_HH
#include <qpdf/JSON.hh>
#include <qpdf/Pipeline.hh>
#include <string_view>
// Writer is a small utility class to aid writing JSON to a pipeline. Methods are designed to allow
// chaining of calls.
//
// Some uses of the class have a significant performance impact. The class is intended purely for
// internal use to allow it to be adapted as needed to maintain performance.
class JSON::Writer
{
public:
Writer(Pipeline* p, size_t depth) :
p(p),
indent(2 * depth)
{
}
Writer&
write(char const* data, size_t len)
{
p->write(reinterpret_cast<unsigned char const*>(data), len);
return *this;
}
Writer&
writeNext()
{
auto n = indent;
if (first) {
first = false;
write(&spaces[1], n % n_spaces + 1);
} else {
write(&spaces[0], n % n_spaces + 2);
}
while (n >= n_spaces) {
write(&spaces[2], n_spaces);
n -= n_spaces;
}
return *this;
}
Writer&
writeStart(char const& c)
{
write(&c, 1);
first = true;
indent += 2;
return *this;
}
Writer&
writeEnd(char const& c)
{
if (indent > 1) {
indent -= 2;
}
if (!first) {
first = true;
writeNext();
}
first = false;
write(&c, 1);
return *this;
}
Writer&
operator<<(std::string_view sv)
{
p->write(reinterpret_cast<unsigned char const*>(sv.data()), sv.size());
return *this;
}
Writer&
operator<<(char const* s)
{
*this << std::string_view{s};
return *this;
}
Writer&
operator<<(bool val)
{
*this << (val ? "true" : "false");
return *this;
}
Writer&
operator<<(int val)
{
*this << std::to_string(val);
return *this;
}
Writer&
operator<<(size_t val)
{
*this << std::to_string(val);
return *this;
}
Writer&
operator<<(JSON&& j)
{
j.write(p, indent / 2);
return *this;
}
static std::string encode_string(std::string const& utf8);
private:
Pipeline* p;
bool first{true};
size_t indent;
static constexpr std::string_view spaces =
",\n ";
static constexpr auto n_spaces = spaces.size() - 2;
};
#endif // JSON_WRITER_HH