From 4a2d4fb3ab38a64c4b10832f5a6318b7240829cc Mon Sep 17 00:00:00 2001
From: Marcel Braun <marcel.braun@ost.ch>
Date: Mon, 6 Apr 2026 11:40:12 +0200
Subject: Implement read data in ext2 inode

---
 .../include/kernel/filesystem/ext2/filesystem.hpp  |  5 ++--
 kernel/include/kernel/filesystem/filesystem.hpp    |  1 +
 kernel/src/filesystem/ext2/inode.cpp               | 33 ++++++++++++++++++++--
 kernel/src/filesystem/filesystem.cpp               |  5 ++++
 4 files changed, 39 insertions(+), 5 deletions(-)

(limited to 'kernel')

diff --git a/kernel/include/kernel/filesystem/ext2/filesystem.hpp b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
index 9761903..762f590 100644
--- a/kernel/include/kernel/filesystem/ext2/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
@@ -24,12 +24,13 @@ namespace kernel::filesystem::ext2
     auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
         -> kstd::shared_ptr<kernel::filesystem::inode> override;
 
+    auto get_block_size() -> size_t;
+    auto map_inode_block_index_to_global_block_number(uint32_t inode_block_index, inode_data data) -> uint32_t;
+
   private:
     auto read_inode(uint32_t inode_number) -> kstd::shared_ptr<kernel::filesystem::ext2::inode>;
-    auto map_inode_block_index_to_global_block_number(uint32_t inode_block_index, inode_data data) -> uint32_t;
     auto read_block_number_at_index(uint32_t block_number, uint32_t index) -> uint32_t;
 
-    auto get_block_size() -> size_t;
     auto get_inode_size() -> size_t;
     auto get_inode_block_count(inode_data const & data) -> uint32_t;
 
diff --git a/kernel/include/kernel/filesystem/filesystem.hpp b/kernel/include/kernel/filesystem/filesystem.hpp
index 1c45377..0f9de9f 100644
--- a/kernel/include/kernel/filesystem/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/filesystem.hpp
@@ -22,6 +22,7 @@ namespace kernel::filesystem
     virtual auto lookup(kstd::shared_ptr<inode> const & parent, std::string_view name) -> kstd::shared_ptr<inode> = 0;
 
     [[nodiscard]] auto root_inode() const -> kstd::shared_ptr<inode> const &;
+    [[nodiscard]] auto device() const -> kstd::shared_ptr<kapi::devices::device> const &;
 
   protected:
     kstd::shared_ptr<inode> m_root_inode{};
diff --git a/kernel/src/filesystem/ext2/inode.cpp b/kernel/src/filesystem/ext2/inode.cpp
index 4d36e66..7f4cf69 100644
--- a/kernel/src/filesystem/ext2/inode.cpp
+++ b/kernel/src/filesystem/ext2/inode.cpp
@@ -2,9 +2,13 @@
 
 #include "kapi/system.hpp"
 
+#include "kernel/devices/block_device_utils.hpp"
+#include "kernel/filesystem/ext2/filesystem.hpp"
 #include "kernel/filesystem/inode.hpp"
 
+#include <algorithm>
 #include <cstddef>
+#include <cstdint>
 
 namespace kernel::filesystem::ext2
 {
@@ -18,10 +22,33 @@ namespace kernel::filesystem::ext2
     }
   }
 
-  auto inode::read(void * /*buffer*/, size_t /*offset*/, size_t /*size*/) const -> size_t
+  auto inode::read(void * buffer, size_t offset, size_t size) const -> size_t
   {
-    // TODO BA-FS26 implement
-    return 0;
+    auto block_index = offset / m_filesystem->get_block_size();
+    auto in_block_offset = offset % m_filesystem->get_block_size();
+
+    auto bytes_read = 0uz;
+
+    while (bytes_read < size)
+    {
+      auto const block_number = m_filesystem->map_inode_block_index_to_global_block_number(block_index, m_data);
+      if (block_number == 0)  // TODO BA-FS26 really correct?
+      {
+        break;
+      }
+
+      auto const block_start_offset = block_number * m_filesystem->get_block_size();
+      auto const read_offset = block_start_offset + in_block_offset;
+      auto const bytes_to_read = std::min(size - bytes_read, m_filesystem->get_block_size() - in_block_offset);
+
+      bytes_read += kernel::devices::block_device_utils::read(
+          m_filesystem->device(), static_cast<uint8_t *>(buffer) + bytes_read, read_offset, bytes_to_read);
+
+      block_index++;
+      in_block_offset = 0;  // After the first block, we always start at the beginning of the block
+    }
+
+    return bytes_read;
   }
 
   auto inode::write(void const * /*buffer*/, size_t /*offset*/, size_t /*size*/) -> size_t
diff --git a/kernel/src/filesystem/filesystem.cpp b/kernel/src/filesystem/filesystem.cpp
index a06eb80..26c57b6 100644
--- a/kernel/src/filesystem/filesystem.cpp
+++ b/kernel/src/filesystem/filesystem.cpp
@@ -49,4 +49,9 @@ namespace kernel::filesystem
   {
     return m_root_inode;
   }
+
+  auto filesystem::device() const -> kstd::shared_ptr<kapi::devices::device> const &
+  {
+    return m_device;
+  }
 }  // namespace kernel::filesystem
\ No newline at end of file
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