refactoring read and write block calculations

4 files changed, 52 insertions, 25 deletions

diff --git a/kernel/devices/include/devices/BlockDevice.hpp b/kernel/devices/include/devices/BlockDevice.hpp
index 65d765b..56e26d0 100644
--- a/kernel/devices/include/devices/BlockDevice.hpp
+++ b/kernel/devices/include/devices/BlockDevice.hpp
@@ -9,11 +9,24 @@ namespace devices
 {
   struct block_device : device
   {
-    block_device(size_t major, size_t minor);
+    block_device(size_t major, size_t minor, size_t block_size);
     virtual ~block_device() = default;
 
     virtual auto read_block(size_t block_index, void * buffer) const -> void = 0;
     virtual auto write_block(size_t block_index, void const * buffer) -> void = 0;
+
+  protected:
+    struct transfer_info
+    {
+      size_t offset;
+      size_t to_transfer;
+      size_t remainder;
+    };
+
+    virtual auto size() const -> size_t = 0;
+    auto calculate_transfer(size_t block_index) const -> transfer_info;
+
+    size_t m_block_size;
   };
 }  // namespace devices
 
diff --git a/kernel/devices/include/devices/storage/RAMDisk/RAMDiskDevice.hpp b/kernel/devices/include/devices/storage/RAMDisk/RAMDiskDevice.hpp
index b3838e4..5971970 100644
--- a/kernel/devices/include/devices/storage/RAMDisk/RAMDiskDevice.hpp
+++ b/kernel/devices/include/devices/storage/RAMDisk/RAMDiskDevice.hpp
@@ -11,8 +11,6 @@ namespace devices::storage::ram_disk
 {
   struct ram_disk_device : block_device
   {
-    constexpr size_t static block_size = 512uz;  // TODO BA-FS26 really correct / good??
-
     ram_disk_device();  // TODO BA-FS26 remove when kstd::vector is available
     ram_disk_device(kapi::boot_modules::boot_module const & module, size_t major, size_t minor);
 
@@ -20,6 +18,8 @@ namespace devices::storage::ram_disk
     auto write_block(size_t block_index, void const * buffer) -> void override;
 
   private:
+    auto size() const -> size_t override;
+
     kapi::boot_modules::boot_module m_boot_module{};
   };
 }  // namespace devices::storage::ram_disk
diff --git a/kernel/devices/src/BlockDevice.cpp b/kernel/devices/src/BlockDevice.cpp
index 6d43073..edc0109 100644
--- a/kernel/devices/src/BlockDevice.cpp
+++ b/kernel/devices/src/BlockDevice.cpp
@@ -6,7 +6,19 @@
 
 namespace devices
 {
-  block_device::block_device(size_t major, size_t minor)
+  block_device::block_device(size_t major, size_t minor, size_t block_size)
       : device(major, minor)
+      , m_block_size(block_size)
   {}
+
+  auto block_device::calculate_transfer(size_t block_index) const -> transfer_info
+  {
+    size_t const offset = block_index * m_block_size;
+    size_t const limit = size();
+
+    size_t const available = (offset < limit) ? (limit - offset) : 0;
+    size_t const to_transfer = (available < m_block_size) ? available : m_block_size;
+
+    return {offset, to_transfer, m_block_size - to_transfer};
+  }
 }  // namespace devices
\ No newline at end of file
diff --git a/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp b/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
index 627641c..f3b8799 100644
--- a/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
+++ b/kernel/devices/src/storage/RAMDisk/RAMDiskDevice.cpp
@@ -11,12 +11,17 @@
 
 namespace devices::storage::ram_disk
 {
+  namespace
+  {
+    constexpr size_t RAM_DISK_BLOCK_SIZE = 512uz;  // TODO BA-FS26 really correct / good??
+  }  // namespace
+
   ram_disk_device::ram_disk_device()  // TODO BA-FS26 remove when kstd::vector is available
-      : block_device(0, 0)
+      : block_device(0, 0, RAM_DISK_BLOCK_SIZE)
   {}
 
   ram_disk_device::ram_disk_device(kapi::boot_modules::boot_module const & module, size_t major, size_t minor)
-      : block_device(major, minor)
+      : block_device(major, minor, RAM_DISK_BLOCK_SIZE)
       , m_boot_module(module)
   {}
 
@@ -27,21 +32,17 @@ namespace devices::storage::ram_disk
       kapi::system::panic("[RAM DISK DEVICE] read_block called with null buffer.");
     }
 
-    size_t const offset = block_index * block_size;
-    size_t const limit = m_boot_module.size;
+    auto const info = calculate_transfer(block_index);
 
-    size_t const available = (offset < limit) ? (limit - offset) : 0;
-    size_t const to_copy = (available < block_size) ? available : block_size;
-
-    if (to_copy > 0)
+    if (info.to_transfer > 0)
     {
-      auto const source = static_cast<std::byte const *>(m_boot_module.start_address) + offset;
-      kstd::libc::memcpy(buffer, source, to_copy);
+      auto const src = static_cast<std::byte const *>(m_boot_module.start_address) + info.offset;
+      kstd::libc::memcpy(buffer, src, info.to_transfer);
     }
 
-    if (to_copy < block_size)
+    if (info.remainder > 0)
     {
-      kstd::libc::memset(static_cast<std::byte *>(buffer) + to_copy, std::byte{0}, block_size - to_copy);
+      kstd::libc::memset(static_cast<std::byte *>(buffer) + info.to_transfer, 0, info.remainder);
     }
   }
 
@@ -52,16 +53,17 @@ namespace devices::storage::ram_disk
       kapi::system::panic("[RAM DISK DEVICE] write_block called with null buffer.");
     }
 
-    size_t const offset = block_index * block_size;
-    size_t const limit = m_boot_module.size;
-
-    if (offset >= limit)
-      return;
+    auto const info = calculate_transfer(block_index);
 
-    size_t const available = limit - offset;
-    size_t const to_write = (available < block_size) ? available : block_size;
+    if (info.to_transfer > 0)
+    {
+      auto const dest = static_cast<std::byte *>(m_boot_module.start_address) + info.offset;
+      kstd::libc::memcpy(dest, buffer, info.to_transfer);
+    }
+  }
 
-    auto const destination = static_cast<std::byte *>(m_boot_module.start_address) + offset;
-    kstd::libc::memcpy(destination, buffer, to_write);
+  auto ram_disk_device::size() const -> size_t
+  {
+    return m_boot_module.size;
   }
 }  // namespace devices::storage::ram_disk
\ No newline at end of file