1 files changed, 145 insertions, 0 deletions
diff --git a/kernel/kstd/print.cpp b/kernel/kstd/print.cpp
new file mode 100644
index 0000000..c7d26ba
--- /dev/null
+++ b/kernel/kstd/print.cpp
@@ -0,0 +1,145 @@
+#include "kapi/cio.hpp"
+
+#include <kstd/format>
+#include <kstd/os/print.hpp>
+#include <kstd/print>
+
+#include <array>
+#include <cstddef>
+#include <iterator>
+#include <string_view>
+
+namespace kstd::os
+{
+
+  namespace
+  {
+    struct write_buffer
+    {
+      using output_stream = kapi::cio::output_stream;
+
+      constexpr auto static size = 128uz;
+
+      write_buffer(write_buffer const &) = delete;
+      write_buffer(write_buffer &&) = delete;
+      auto operator=(write_buffer const &) -> write_buffer & = delete;
+      auto operator=(write_buffer &&) -> write_buffer & = delete;
+
+      explicit write_buffer(output_stream stream)
+          : m_stream{stream}
+      {}
+
+      ~write_buffer() noexcept
+      {
+        flush();
+      }
+
+      auto flush() noexcept -> void
+      {
+        if (m_position > 0)
+        {
+          std::string_view chunk{m_buffer.data(), m_position};
+          kapi::cio::write(m_stream, chunk);
+          m_position = 0;
+        }
+      }
+
+      auto static callback(void * object, std::string_view text) -> void
+      {
+        auto * self = static_cast<write_buffer *>(object);
+        for (char const character : text)
+        {
+          if (self->m_position >= size)
+          {
+            self->flush();
+          }
+          self->m_buffer.at(self->m_position++) = character;
+        }
+      }
+
+    private:
+      output_stream m_stream;
+      std::array<char, size> m_buffer{};
+      std::size_t m_position{};
+    };
+
+  }  // namespace
+
+  auto vprint(print_sink sink, std::string_view format, kstd::format_args args) -> void
+  {
+    auto writer = write_buffer{(sink == print_sink::stderr) ? kapi::cio::output_stream::stderr
+                                                            : kapi::cio::output_stream::stdout};
+    auto context = kstd::format_context{.writer = write_buffer::callback, .user_data = &writer};
+
+    auto current = format.begin();
+    auto end = format.end();
+    auto next_automatic_index = 0uz;
+
+    while (current != end)
+    {
+      if (*current != '{')
+      {
+        auto start = current;
+        while (current != end && *current != '{')
+        {
+          std::advance(current, 1);
+        }
+        context.push(std::string_view(start, current - start));
+        continue;
+      }
+
+      if (std::next(current) != end && *(std::next(current)) == '{')
+      {
+        context.push('{');
+        std::advance(current, 2);
+        continue;
+      }
+
+      std::advance(current, 1);
+
+      auto index = 0uz;
+      if (current != end && *current >= '0' && *current <= '9')
+      {
+        while (current != end && *current >= '0' && *current <= '9')
+        {
+          index = index * 10 + static_cast<std::size_t>(*current - '0');
+          std::advance(current, 1);
+        }
+      }
+      else
+      {
+        index = next_automatic_index++;
+      }
+
+      auto remaining_fmt = std::string_view{current, static_cast<std::size_t>(std::distance(current, end))};
+
+      auto const arg = args.get(index);
+      if (arg.format)
+      {
+        auto const after_specs = arg.format(arg.value, remaining_fmt, context);
+        auto const consumed = remaining_fmt.size() - after_specs.size();
+        std::advance(current, consumed);
+      }
+      else
+      {
+        context.push("{?}");
+        while (current != end && *current != '}')
+          std::advance(current, 1);
+      }
+
+      if (current != end && *current == '}')
+      {
+        std::advance(current, 1);
+      }
+      else
+      {
+        context.push("{fmt-err}");
+        while (current != end && *current != '}')
+          std::advance(current, 1);
+        if (current != end)
+          std::advance(current, 1);
+      }
+    }
+  }
+
+}  // namespace kstd::os