kernel+libluna: Add Buffer::dequeue_data()

kernel/src/fs/devices/ConsoleDevice.cpp

@@ -49,13 +49,7 @@ Result<usize> ConsoleDevice::read(u8* buf, usize, usize length) const
 {
     TRY(handle_background_process_group(false, SIGTTIN));
 
-    if (length > m_input_buffer.size()) length = m_input_buffer.size();
-
-    memcpy(buf, m_input_buffer.data(), length);
-
-    memmove(m_input_buffer.data(), m_input_buffer.data() + length, m_input_buffer.size() - length);
-
-    m_input_buffer.try_resize(m_input_buffer.size() - length).release_value();
+    length = m_input_buffer.dequeue_data(buf, length);
 
     if (!length && m_may_read_without_blocking) m_may_read_without_blocking = false;
 

libluna/include/luna/Buffer.h

@@ -21,6 +21,8 @@ class Buffer
 
     Result<void> append_data(const u8* data, usize size);
 
+    usize dequeue_data(u8* data, usize size);
+
     u8* data()
     {
         return m_data;

libluna/src/Buffer.cpp

@@ -53,6 +53,20 @@ Result<void> Buffer::append_data(const u8* data, usize size)
     return {};
 }
 
+usize Buffer::dequeue_data(u8* data, usize size)
+{
+    if (size > m_size) size = m_size;
+    if (!size) return 0;
+
+    memcpy(data, m_data, size);
+
+    memmove(m_data, m_data + size, m_size - size);
+
+    m_size -= size;
+
+    return size;
+}
+
 u8* Buffer::release_data()
 {
     u8* data = m_data;