From 9c602f2cf8fd87f55adc31c085e469e72b7cbbfa Mon Sep 17 00:00:00 2001
From: "marcel.braun" <marcel.braun@ost.ch>
Date: Sun, 29 Mar 2026 20:49:03 +0200
Subject: Move block device offset and size-to-blocks calculation to
 block_device_utils

---
 kernel/src/devices/block_device_utils.cpp | 103 ++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 kernel/src/devices/block_device_utils.cpp

(limited to 'kernel/src/devices')

diff --git a/kernel/src/devices/block_device_utils.cpp b/kernel/src/devices/block_device_utils.cpp
new file mode 100644
index 0000000..9d3af1b
--- /dev/null
+++ b/kernel/src/devices/block_device_utils.cpp
@@ -0,0 +1,103 @@
+#include "kernel/devices/block_device_utils.hpp"
+
+#include "kapi/system.hpp"
+
+#include "kernel/devices/block_device.hpp"
+#include "kernel/devices/device.hpp"
+
+#include <kstd/cstring>
+#include <kstd/memory>
+#include <kstd/vector>
+
+#include <algorithm>
+#include <cstddef>
+
+namespace devices::block_device_utils
+{
+
+  using block_op = void (*)(size_t idx, size_t off, size_t len, size_t done, devices::block_device * device,
+                            std::byte * scratch, void * buffer);
+
+  auto process_blocks(kstd::shared_ptr<devices::device> const & device, size_t offset, size_t size, void * buffer,
+                      block_op op) -> size_t
+  {
+    if (buffer == nullptr)
+    {
+      kapi::system::panic("[FILESYSTEM] device_file::process_blocks called with null buffer.");
+    }
+
+    if (size == 0)
+    {
+      return 0;
+    }
+
+    auto * block_dev = static_cast<devices::block_device *>(device.get());
+    if (block_dev == nullptr)
+    {
+      kapi::system::panic("[FILESYSTEM] device_file: expected block_device.");
+    }
+
+    size_t const block_size = block_dev->block_size();
+    size_t const capacity = block_dev->capacity();
+
+    if (offset >= capacity)
+      return 0;
+    size_t const total_to_process = std::min(size, capacity - offset);
+
+    kstd::vector<std::byte> scratch_buffer{block_size};
+    auto processed = 0uz;
+
+    while (processed < total_to_process)
+    {
+      size_t const absolute_offset = offset + processed;
+      size_t const block_index = absolute_offset / block_size;
+      size_t const in_block_offset = absolute_offset % block_size;
+      size_t const chunk_size = std::min(total_to_process - processed, block_size - in_block_offset);
+
+      op(block_index, in_block_offset, chunk_size, processed, block_dev, scratch_buffer.data(), buffer);
+
+      processed += chunk_size;
+    }
+
+    return processed;
+  }
+
+  auto read(kstd::shared_ptr<devices::device> const & device, void * buffer, size_t offset, size_t size) -> size_t
+  {
+    return process_blocks(device, offset, size, buffer,
+                          [](size_t idx, size_t off, size_t len, size_t done, devices::block_device * device,
+                             std::byte * scratch, void * buffer) {
+                            auto * out = static_cast<std::byte *>(buffer);
+                            if (off == 0 && len == device->block_size())
+                            {
+                              device->read_block(idx, out + done);
+                            }
+                            else
+                            {
+                              device->read_block(idx, scratch);
+                              kstd::libc::memcpy(out + done, scratch + off, len);
+                            }
+                          });
+  }
+
+  auto write(kstd::shared_ptr<devices::device> const & device, void const * buffer, size_t offset, size_t size)
+      -> size_t
+  {
+    return process_blocks(device, offset, size, const_cast<void *>(buffer),
+                          [](size_t idx, size_t off, size_t len, size_t done, devices::block_device * device,
+                             std::byte * scratch, void * buffer) {
+                            auto const * in = static_cast<std::byte const *>(buffer);
+                            if (off == 0 && len == device->block_size())
+                            {
+                              device->write_block(idx, in + done);
+                            }
+                            else
+                            {
+                              device->read_block(idx, scratch);
+                              kstd::libc::memcpy(scratch + off, in + done, len);
+                              device->write_block(idx, scratch);
+                            }
+                          });
+  }
+
+}  // namespace devices::block_device_utils
\ No newline at end of file
-- 
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