implement read_inode

1 files changed, 27 insertions, 8 deletions

diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index 96c1589..d650e97 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -21,7 +21,9 @@ namespace kernel::filesystem::ext2
   namespace
   {
     constexpr size_t SUPERBLOCK_OFFSET = 1024;
-    constexpr uint16_t EXT2_MAGIC = 0xEF53;
+    constexpr uint16_t MAGIC_NUMBER = 0xEF53;
+
+    constexpr uint32_t ROOT_INODE_NUMBER = 2;
 
     // Mode bits
     // constexpr uint16_t S_IFMT = 0xF000;
@@ -44,7 +46,7 @@ namespace kernel::filesystem::ext2
 
     kernel::devices::block_device_utils::read(m_device, &m_superblock, SUPERBLOCK_OFFSET, sizeof(m_superblock));
 
-    if (m_superblock.magic != EXT2_MAGIC)
+    if (m_superblock.magic != MAGIC_NUMBER)
     {
       return -1;
     }
@@ -60,12 +62,7 @@ namespace kernel::filesystem::ext2
                                               block_group_descriptor_table_offset,
                                               num_block_groups * sizeof(block_group_descriptor));
 
-    // TODO BA-FS26 load proper root inode from ext2 metadata
-    // m_root_inode = inode{inode_kind::directory};
-
-    // TODO BA-FS26 implement
-    m_root_inode = kstd::make_shared<inode>();
-    // devices::block_device_utils::read(device, nullptr, 0, 0);  // TODO BA-FS26 just for testing
+    m_root_inode = read_inode(ROOT_INODE_NUMBER);
     return 0;
   }
 
@@ -82,6 +79,28 @@ namespace kernel::filesystem::ext2
     return kstd::make_shared<inode>();
   }
 
+  auto filesystem::read_inode(uint32_t inode_number) -> kstd::shared_ptr<inode>
+  {
+    auto const block_size = get_block_size();
+    auto const inodes_per_group = m_superblock.inodes_per_group;
+    auto const block_group_index = (inode_number - 1) / inodes_per_group;
+    auto const inode_index_within_group = (inode_number - 1) % inodes_per_group;
+
+    if (block_group_index >= m_block_group_descriptors.size())
+    {
+      return nullptr;
+    }
+
+    auto const & block_group_descriptor = m_block_group_descriptors.at(block_group_index);
+    auto const inode_table_start_block = block_group_descriptor.inode_table;
+    auto const inode_table_offset = static_cast<size_t>(inode_table_start_block) * block_size;
+    auto const inode_offset = inode_table_offset + inode_index_within_group * get_inode_size();
+
+    auto new_inode = kstd::make_shared<inode>();
+    kernel::devices::block_device_utils::read(m_device, &new_inode->m_data, inode_offset, sizeof(inode_data));
+    return new_inode;
+  }
+
   auto filesystem::get_block_size() -> size_t
   {
     return 1024U << m_superblock.log_block_size;