7 files changed, 146 insertions, 12 deletions
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index b91b380c..19821797 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -26,6 +26,14 @@ target_include_directories(cru_base PUBLIC ${CRU_INCLUDE_DIR})
 target_compile_definitions(cru_base PUBLIC $<$<CONFIG:Debug>:CRU_DEBUG>)
 target_compile_definitions(cru_base PRIVATE CRU_BASE_EXPORT_API)
 
+if (UNIX)
+	target_sources(cru_base PRIVATE
+		io/UnixFileStream.cpp
+	PUBLIC
+		${CRU_BASE_INCLUDE_DIR}/io/UnixFileStream.hpp
+	)
+endif()
+
 if (WIN32)
 	target_compile_definitions(cru_base PUBLIC CRU_PLATFORM_WINDOWS)
 elseif(APPLE)
diff --git a/src/common/ErrnoException.cpp b/src/common/ErrnoException.cpp
new file mode 100644
index 00000000..df2349ac
--- /dev/null
+++ b/src/common/ErrnoException.cpp
@@ -0,0 +1,11 @@
+#include "cru/common/ErrnoException.hpp"
+
+#include <errno.h>
+
+namespace cru {
+ErrnoException::ErrnoException(const String& message)
+    : ErrnoException(message, errno) {}
+
+ErrnoException::ErrnoException(const String& message, int errno_code)
+    : Exception(message), errno_code_(errno_code) {}
+}  // namespace cru
diff --git a/src/common/io/Stream.cpp b/src/common/io/Stream.cpp
index 6addfdc0..1a39b653 100644
--- a/src/common/io/Stream.cpp
+++ b/src/common/io/Stream.cpp
@@ -18,4 +18,6 @@ Index Stream::Read(std::byte* buffer, Index size) {
 Index Stream::Write(const std::byte* buffer, Index size) {
   return Write(buffer, 0, size);
 }
+
+void Stream::Close() {}
 }  // namespace cru::io
diff --git a/src/common/io/UnixFileStream.cpp b/src/common/io/UnixFileStream.cpp
new file mode 100644
index 00000000..23c11dad
--- /dev/null
+++ b/src/common/io/UnixFileStream.cpp
@@ -0,0 +1,125 @@
+#include "cru/common/io/UnixFileStream.hpp"
+#include "cru/common/ErrnoException.hpp"
+#include "cru/common/io/OpenFileFlag.hpp"
+
+#include <fcntl.h>
+#include <unistd.h>
+
+namespace cru::io {
+
+namespace {
+int MapOpenFileFlag(OpenFileFlag flag) {
+  int result = 0;
+  if (flag & OpenFileFlags::Read) {
+    if (flag & OpenFileFlags::Write) {
+      result |= O_RDWR;
+    } else {
+      result |= O_RDONLY;
+    }
+  } else {
+    if (flag & OpenFileFlags::Write) {
+      result |= O_WRONLY;
+    } else {
+      throw Exception(u"Invalid open file flag.");
+    }
+  }
+
+  if (flag | OpenFileFlags::Append) {
+    result |= O_APPEND;
+  }
+
+  if (flag | OpenFileFlags::Create) {
+    result |= O_CREAT;
+  }
+
+  if (flag | OpenFileFlags::ThrowOnExist) {
+    result |= O_EXCL;
+  }
+
+  return result;
+}
+
+int MapSeekOrigin(Stream::SeekOrigin origin) {
+  switch (origin) {
+    case Stream::SeekOrigin::Begin:
+      return SEEK_SET;
+    case Stream::SeekOrigin::Current:
+      return SEEK_CUR;
+    case Stream::SeekOrigin::End:
+      return SEEK_END;
+    default:
+      throw Exception(u"Invalid seek origin.");
+  }
+}
+}  // namespace
+
+UnixFileStream::UnixFileStream(String path, OpenFileFlag flags) {
+  file_descriptor_ = ::open(path.ToUtf8().c_str(), MapOpenFileFlag(flags));
+  if (file_descriptor_ == -1) {
+    throw ErrnoException(u"Failed to open file.");
+  }
+}
+
+bool UnixFileStream::CanSeek() {
+  CheckClosed();
+  return true;
+}
+
+Index UnixFileStream::Tell() {
+  CheckClosed();
+  auto result = ::lseek(file_descriptor_, 0, SEEK_CUR);
+  if (result == -1) {
+    throw ErrnoException(u"Failed to get file position.");
+  }
+  return result;
+}
+
+void UnixFileStream::Seek(Index offset, SeekOrigin origin) {
+  CheckClosed();
+  int result = ::lseek(file_descriptor_, offset, MapSeekOrigin(origin));
+  if (result == -1) {
+    throw ErrnoException(u"Failed to seek file.");
+  }
+}
+
+bool UnixFileStream::CanRead() {
+  CheckClosed();
+  return flags & OpenFileFlags::Read;
+}
+
+Index UnixFileStream::Read(std::byte *buffer, Index offset, Index size) {
+  CheckClosed();
+  auto result = ::read(file_descriptor_, buffer + offset, size);
+  if (result == -1) {
+    throw ErrnoException(u"Failed to read file.");
+  }
+  return result;
+}
+
+bool UnixFileStream::CanWrite() {
+  CheckClosed();
+  return flags & OpenFileFlags::Write;
+}
+
+Index UnixFileStream::Write(const std::byte *buffer, Index offset, Index size) {
+  CheckClosed();
+  auto result = ::write(file_descriptor_, buffer + offset, size);
+  if (result == -1) {
+    throw ErrnoException(u"Failed to write file.");
+  }
+  return result;
+}
+
+void UnixFileStream::Close() {
+  if (closed_) return;
+  if (::close(file_descriptor_) == -1) {
+    throw ErrnoException(u"Failed to close file.");
+  }
+}
+
+void UnixFileStream::CheckClosed() {
+  if (closed_) {
+    throw Exception(u"File is closed.");
+  }
+}
+}  // namespace cru::io
diff --git a/src/platform/CMakeLists.txt b/src/platform/CMakeLists.txt
index 2d12ce86..e1ce69a3 100644
--- a/src/platform/CMakeLists.txt
+++ b/src/platform/CMakeLists.txt
@@ -15,15 +15,6 @@ target_sources(cru_platform_base PUBLIC
 target_link_libraries(cru_platform_base PUBLIC cru_base)
 target_compile_definitions(cru_platform_base PRIVATE CRU_PLATFORM_EXPORT_API)
 
-if (UNIX)
-target_sources(cru_platform_base PRIVATE
-	UnixFileStream.cpp
-PUBLIC
-	${CRU_PLATFORM_BASE_INCLUDE_DIR}/UnixFileStream.hpp
-)
-endif()
-
-add_subdirectory(filesystem)
 add_subdirectory(graphics)
 add_subdirectory(gui)
 
diff --git a/src/platform/UnixFileStream.cpp b/src/platform/UnixFileStream.cpp
deleted file mode 100644
index d4745980..00000000
--- a/src/platform/UnixFileStream.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-#include "cru/platform/UnixFileStream.hpp"
-
-
diff --git a/src/platform/filesystem/CMakeLists.txt b/src/platform/filesystem/CMakeLists.txt
deleted file mode 100644
index e69de29b..00000000
--- a/src/platform/filesystem/CMakeLists.txt
+++ /dev/null