add GapBuffer::copy_to()

src/core/GapBuffer.h

@@ -99,6 +99,40 @@ public:
         move_gap(m_size);
     }
 
+    /**
+     * Copy a range of data from this GapBuffer to another.
+     *
+     * @param source_position
+     *   Position in the gap buffer containing the data to copy.
+     * @param length
+     *   Length of the data to copy.
+     * @param other
+     *   Destination GapBuffer to copy the data into.
+     * @param destination_position
+     *   Position in the destination GapBuffer to copy the data to.
+     */
+    void copy_to(size_t source_position, size_t length, GapBuffer & other, size_t destination_position)
+    {
+        if ((source_position < m_size) &&
+                (length > 0u) &&
+                ((source_position + length) <= m_size))
+        {
+            if ((m_gap_position <= source_position) ||
+                    (m_gap_position >= (source_position + length)))
+            {
+                /* The gap is before or after the range of data to copy. */
+                other.insert(destination_position, address(source_position), length);
+            }
+            else
+            {
+                /* The gap is in the middle of the range of data to copy. */
+                size_t pre_gap_size = m_gap_position - source_position;
+                other.insert(destination_position, address(source_position), pre_gap_size);
+                other.insert(destination_position + pre_gap_size, address(source_position + pre_gap_size), length - pre_gap_size);
+            }
+        }
+    }
+
 protected:
     /** Address of the allocated memory buffer. */
     uint8_t * m_buffer;