1 files changed, 125 insertions, 0 deletions
diff --git a/libqpdf/qpdf/JSON_writer.hh b/libqpdf/qpdf/JSON_writer.hh
new file mode 100644
index 00000000..6d870b88
--- /dev/null
+++ b/libqpdf/qpdf/JSON_writer.hh
@@ -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