alloc/linear: add capacity/size/remain implementations

alloc/linear.cpp

@@ -61,3 +61,27 @@ linear::reset (void)
 {
     m_cursor = m_begin;
 }
+
+
+///////////////////////////////////////////////////////////////////////////////
+size_t
+linear::capacity (void) const
+{
+    return m_end - m_begin;
+}
+
+
+//-----------------------------------------------------------------------------
+size_t
+linear::size (void) const
+{
+    return m_cursor - m_begin;
+}
+
+
+//-----------------------------------------------------------------------------
+size_t
+linear::remain (void) const
+{
+    return capacity () - size ();
+}

alloc/linear.hpp

@@ -39,6 +39,7 @@ namespace util { namespace alloc {
 
         size_t capacity (void) const;
         size_t size     (void) const;
+        size_t remain   (void) const;
 
     protected:
         char *m_begin, *m_end, *m_cursor;