implement a scrollback buffer

c_os/lib/ScrollbackBuffer.h

@@ -0,0 +1,39 @@
+#ifndef __SCROLLBACKBUFFER_INCLUDE_H_
+#define __SCROLLBACKBUFFER_INCLUDE_H_
+
+#include "devices/CGA.h"
+#include "lib/MyStdLib.h"
+#include <stddef.h>
+
+// NOTE: I added this file
+
+// The buffer dimensions must match with the destination dimensions
+class ScrollbackBuffer {
+private:
+    CGA::cga_line_t* buffer;      // Circular buffer to store lines that left the screen
+    CGA::cga_page_t* pagebuffer;  // Contains the current page separately from the scrollback
+    unsigned int current_linenumber;
+
+    CGA::cga_line_t* get_current_line() const;  // Translate linenumber to memory location
+    void buffer_next_line();                    // Moves the current_line one line forward
+
+public:
+    const unsigned int pageheight,  // Number of lines per page
+      pages,                        // Number of pages in buffer
+      lines;                        // Total number of lines in buffer
+
+    ScrollbackBuffer(unsigned char width, unsigned char height, unsigned char pages)
+      : current_linenumber(0), pageheight(height), pages(pages), lines(height * pages) {
+        this->buffer = new CGA::cga_line_t[lines];
+        this->pagebuffer = new CGA::cga_page_t;
+        this->clear();  // Null out the buffer so no crap gets displayed
+    }
+
+    void line_to_buffer(CGA::cga_line_t* line);
+    void copy_page_from_buffer(CGA::cga_line_t* destination, unsigned char page) const;
+    void copy_page_from_pagebuffer(CGA::cga_page_t* destination) const;
+    void copy_page_to_pagebuffer(CGA::cga_page_t* source);
+    void clear();
+};
+
+#endif