Kernel: Make File::write() and File::read() return KResultOr<size_t>

Instead of returning a ssize_t where negative values mean error,
we now return KResultOr<size_t> and use the error state to report
errors exclusively.

1 files changed, 16 insertions, 12 deletions

diff --git a/Kernel/FileSystem/FileDescription.cpp b/Kernel/FileSystem/FileDescription.cpp
index c4c3f8f700..43750a074c 100644
--- a/Kernel/FileSystem/FileDescription.cpp
+++ b/Kernel/FileSystem/FileDescription.cpp
@@ -124,28 +124,32 @@ off_t FileDescription::seek(off_t offset, int whence)
     return m_current_offset;
 }
 
-ssize_t FileDescription::read(u8* buffer, ssize_t count)
+KResultOr<size_t> FileDescription::read(u8* buffer, size_t count)
 {
     LOCKER(m_lock);
-    if ((m_current_offset + count) < 0)
+    Checked<size_t> new_offset = m_current_offset;
+    new_offset += count;
+    if (new_offset.has_overflow())
         return -EOVERFLOW;
     SmapDisabler disabler;
-    int nread = m_file->read(*this, offset(), buffer, count);
-    if (nread > 0 && m_file->is_seekable())
-        m_current_offset += nread;
-    return nread;
+    auto nread_or_error = m_file->read(*this, offset(), buffer, count);
+    if (!nread_or_error.is_error() && m_file->is_seekable())
+        m_current_offset += nread_or_error.value();
+    return nread_or_error;
 }
 
-ssize_t FileDescription::write(const u8* data, ssize_t size)
+KResultOr<size_t> FileDescription::write(const u8* data, size_t size)
 {
     LOCKER(m_lock);
-    if ((m_current_offset + size) < 0)
+    Checked<size_t> new_offset = m_current_offset;
+    new_offset += size;
+    if (new_offset.has_overflow())
         return -EOVERFLOW;
     SmapDisabler disabler;
-    int nwritten = m_file->write(*this, offset(), data, size);
-    if (nwritten > 0 && m_file->is_seekable())
-        m_current_offset += nwritten;
-    return nwritten;
+    auto nwritten_or_error = m_file->write(*this, offset(), data, size);
+    if (!nwritten_or_error.is_error() && m_file->is_seekable())
+        m_current_offset += nwritten_or_error.value();
+    return nwritten_or_error;
 }
 
 bool FileDescription::can_write() const