implement first draft of a file_descriptor_table and open_file_description

1 files changed, 81 insertions, 0 deletions

diff --git a/kernel/filesystem/src/file_descriptor_table.cpp b/kernel/filesystem/src/file_descriptor_table.cpp
new file mode 100644
index 0000000..0c79431
--- /dev/null
+++ b/kernel/filesystem/src/file_descriptor_table.cpp
@@ -0,0 +1,81 @@
+#include "filesystem/file_descriptor_table.hpp"
+
+#include "kapi/system.hpp"
+
+#include "filesystem/open_file_description.hpp"
+
+#include <algorithm>
+#include <cstddef>
+#include <optional>
+
+namespace filesystem
+{
+  namespace
+  {
+    constinit auto static global_file_descriptor_table = std::optional<file_descriptor_table>{};
+  }  // namespace
+
+  auto file_descriptor_table::init() -> void
+  {
+    if (global_file_descriptor_table)
+    {
+      kapi::system::panic("[FILESYSTEM] File descriptor table has already been initialized.");
+    }
+
+    global_file_descriptor_table.emplace(file_descriptor_table{});
+  }
+
+  auto file_descriptor_table::get() -> file_descriptor_table &
+  {
+    if (!global_file_descriptor_table)
+    {
+      kapi::system::panic("[FILESYSTEM] File descriptor table has not been initialized.");
+    }
+
+    return *global_file_descriptor_table;
+  }
+
+  auto file_descriptor_table::add_file(open_file_description & f) -> int
+  {
+    auto it = std::ranges::find(m_open_files, nullptr);
+    if (it != m_open_files.end())
+    {
+      *it = &f;
+      return static_cast<int>(it - m_open_files.begin());
+    }
+
+    return -1;
+  }
+
+  auto file_descriptor_table::get_file(int fd) -> open_file_description &
+  {
+    if (fd < 0)
+    {
+      kapi::system::panic("[FILESYSTEM] get_file called with negative descriptor.");
+    }
+
+    auto const index = static_cast<size_t>(fd);
+    if (index >= m_open_files.size() || m_open_files[index] == nullptr)
+    {
+      kapi::system::panic("[FILESYSTEM] get_file called with invalid descriptor.");
+    }
+
+    return *m_open_files[index];
+  }
+
+  auto file_descriptor_table::remove_file(int fd) -> void
+  {
+    if (fd < 0)
+    {
+      kapi::system::panic("[FILESYSTEM] remove_file called with negative descriptor.");
+    }
+
+    auto const index = static_cast<size_t>(fd);
+    if (index >= m_open_files.size())
+    {
+      kapi::system::panic("[FILESYSTEM] remove_file called with out-of-range descriptor.");
+    }
+
+    m_open_files[index] = nullptr;
+  }
+}  // namespace filesystem
\ No newline at end of file