From 82c8a4c16e3af3d62d7211e741b051da900de79c Mon Sep 17 00:00:00 2001
From: Lukas Oesch <lukasoesch20@gmail.com>
Date: Fri, 3 Apr 2026 10:16:36 +0200
Subject: first lookup draft

---
 kernel/src/filesystem/ext2/filesystem.cpp | 48 ++++++++++++++++++++++++++++++-
 kernel/src/main.cpp                       |  2 ++
 2 files changed, 49 insertions(+), 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index 31dc6f2..82fcba9 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -5,11 +5,13 @@
 #include "kernel/devices/block_device_utils.hpp"
 #include "kernel/filesystem/ext2/block_group_descriptor.hpp"
 #include "kernel/filesystem/ext2/inode.hpp"
+#include "kernel/filesystem/ext2/linked_directory_entry.hpp"
 #include "kernel/filesystem/ext2/superblock.hpp"
 #include "kernel/filesystem/filesystem.hpp"
 #include "kernel/filesystem/inode.hpp"
 
 #include <kstd/memory>
+#include <kstd/string>
 #include <kstd/vector>
 
 #include <cstddef>
@@ -24,6 +26,7 @@ namespace kernel::filesystem::ext2
     constexpr uint16_t MAGIC_NUMBER = 0xEF53;
 
     constexpr uint32_t ROOT_INODE_NUMBER = 2;
+    constexpr size_t DIRECT_BLOCK_COUNT = 12;
 
     // Mode bits
     constexpr uint16_t S_IFMT = 0xF000;
@@ -67,9 +70,52 @@ namespace kernel::filesystem::ext2
     return 0;
   }
 
-  auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & /*parent*/, std::string_view name)
+  auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
       -> kstd::shared_ptr<kernel::filesystem::inode>
   {
+    if (!parent || !parent->is_directory())
+    {
+      return nullptr;
+    }
+
+    auto * ext2_parent = static_cast<inode *>(parent.get());
+    if (!ext2_parent)
+    {
+      return nullptr;
+    }
+
+    auto const block_size = get_block_size();
+    auto const & inode_data = ext2_parent->m_data;
+    kstd::vector<uint8_t> buffer(block_size);
+
+    for (size_t i = 0; i < DIRECT_BLOCK_COUNT && inode_data.block[i] != 0; ++i)
+    {
+      kernel::devices::block_device_utils::read(m_device, buffer.data(), inode_data.block[i] * block_size, block_size);
+
+      size_t offset = 0;
+      while (offset < block_size)
+      {
+        auto * entry = reinterpret_cast<linked_directory_entry const *>(buffer.data() + offset);
+        if (entry->inode == 0)
+          break;
+
+        // Stop if the directory entry is malformed to avoid overruns/loops.
+        // if (entry->rec_len < sizeof(linked_directory_entry) || offset + entry->rec_len > block_size)
+        // {
+        //   break;
+        // }
+
+        std::string_view entry_name(reinterpret_cast<char const *>(entry->name.data()), entry->name_len);
+        if (entry_name == name)
+        {
+          return read_inode(entry->inode);
+        }
+
+        offset += entry->rec_len;
+      }
+    }
+
+    return nullptr;
     // TODO BA-FS26 implement ext2 directory traversal and inode loading
     if (name == "dev")
     {
diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index 8df6767..258c28b 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -117,6 +117,8 @@ auto test_file_lookup() -> void
   auto vfs = kernel::filesystem::vfs::get();
   auto storage_mgmt = kernel::devices::storage::management::get();
 
+  auto ofd_hello = vfs.open("/hello.txt");
+
   auto ofd1 = vfs.open("/a/b/c");
   auto ofd2 = vfs.open("/dev/ram0");
   auto ofd3 = vfs.open("/a/d/e");
-- 
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