From 18d80c9159424014f204fb1b2545405eeea9221f Mon Sep 17 00:00:00 2001
From: Marcel Braun <marcel.braun@ost.ch>
Date: Sat, 30 May 2026 10:10:15 +0200
Subject: Implement ext2 inode write

---
 kernel/kernel/filesystem/ext2/inode.cpp       | 41 +++++++++++++++++++++++++--
 kernel/kernel/filesystem/ext2/inode.tests.cpp | 15 ----------
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/kernel/kernel/filesystem/ext2/inode.cpp b/kernel/kernel/filesystem/ext2/inode.cpp
index 6dadbec5..e873d446 100644
--- a/kernel/kernel/filesystem/ext2/inode.cpp
+++ b/kernel/kernel/filesystem/ext2/inode.cpp
@@ -76,10 +76,45 @@ namespace kernel::filesystem::ext2
     return bytes_read;
   }
 
-  auto inode::write(void const *, size_t, size_t) -> kstd::result<size_t>
+  auto inode::write(void const * buffer, size_t offset, size_t size) -> kstd::result<size_t>
   {
-    kapi::system::panic("[EXT2] inode::write is not implemented yet");
-    return 0;
+    auto const max_writable = this->size() - offset;
+    auto const requested_size = std::min(size, max_writable);
+
+    auto block_index = offset / m_filesystem->block_size();
+    auto in_block_offset = offset % m_filesystem->block_size();
+
+    auto bytes_written = 0uz;
+
+    while (bytes_written < requested_size)
+    {
+      auto const block_number = m_filesystem->map_inode_block_index_to_global_block_number(block_index, m_data);
+      // TODO BA-FS26 if blocknumber == 0 --> handle sparse file
+      if (!block_number)
+      {
+        kstd::failure(block_number.error());
+      }
+
+      auto const bytes_to_write =
+          std::min(requested_size - bytes_written, m_filesystem->block_size() - in_block_offset);
+
+      auto const block_start_offset = block_number.value() * m_filesystem->block_size();
+      auto const write_offset = block_start_offset + in_block_offset;
+
+      auto const write_result = m_filesystem->backing_inode()->write(
+          static_cast<uint8_t const *>(buffer) + bytes_written, write_offset, bytes_to_write);
+      if (!write_result)
+      {
+        return kstd::failure(write_result.error());
+      }
+
+      bytes_written += write_result.value();
+
+      block_index++;
+      in_block_offset = 0;  // After the first block, we always start at the beginning of the block
+    }
+
+    return bytes_written;
   }
 
   [[nodiscard]] auto inode::data() const -> inode_data const &
diff --git a/kernel/kernel/filesystem/ext2/inode.tests.cpp b/kernel/kernel/filesystem/ext2/inode.tests.cpp
index 496e7c4f..7041f886 100644
--- a/kernel/kernel/filesystem/ext2/inode.tests.cpp
+++ b/kernel/kernel/filesystem/ext2/inode.tests.cpp
@@ -277,21 +277,6 @@ SCENARIO("Ext2 inode read across block boundaries", "[filesystem][ext2][inode]")
   }
 }
 
-SCENARIO("Ext2 inode write is not implemented", "[filesystem][ext2][inode]")
-{
-  GIVEN("an ext2 inode")
-  {
-    auto fs = kernel::filesystem::ext2::filesystem{};
-    auto inode = kernel::filesystem::ext2::inode{&fs, kernel::filesystem::ext2::inode_data{}};
-
-    THEN("writing to the inode panics")
-    {
-      auto buffer = kstd::vector<std::byte>(32, std::byte{0x00});
-      REQUIRE_THROWS_AS(inode.write(buffer.data(), 0, buffer.size()), kernel::tests::cpu::halt);
-    }
-  }
-}
-
 SCENARIO("Ext2 inode get_size() correctly returns size depending on revision level", "[filesystem][ext2][inode]")
 {
   auto const block_size = 1024uz;
-- 
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