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#include "vga.h"
#include <stdbool.h>
#include "string.h"
static bool params_ok( vga_t *vga, const int x, const int y );
static int calculate_offset( vga_t *vga );
static uint8_t calculate_color_cell( vga_t *vga );
static void scroll_screen( vga_t *vga );
void vga_init( vga_t *vga )
{
memset( vga, 0, sizeof( vga_t ) );
vga->res_x = VGA_DEFAULT_RES_X;
vga->res_y = VGA_DEFAULT_RES_Y;
vga->color = VGA_COLOR_DARK_GREY;
vga->background_color = VGA_COLOR_BLACK;
// TODO: get current position from VGA hardware
//~ vga_set_cursor( vga, 0, 0 );
};
void vga_clear_screen( vga_t *vga )
{
volatile uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
for( int i = 0; i < 2 * ( vga->res_x * vga->res_y ); i += 2 ) {
*(VIDEO_MEMORY+i) = ' ';
*(VIDEO_MEMORY+i+1) = calculate_color_cell( vga );
}
vga_set_cursor( vga, 0, 0 );
}
void vga_set_cursor( vga_t *vga, const int x, const int y )
{
// TODO: PANIC? OUT OF BOUND ACCESS
if( !params_ok( vga, x, y ) ) return;
vga->cursor_x = x;
vga->cursor_y = y;
}
void vga_set_color( vga_t *vga, const vga_color_t color )
{
vga->color = color;
}
void vga_set_background_color( vga_t *vga, const vga_color_t color )
{
vga->background_color = color;
}
static int calculate_offset( vga_t *vga )
{
int offset = ( vga->res_x * vga->cursor_y + vga->cursor_x ) * 2;
return offset;
}
static void scroll_screen( vga_t *vga )
{
volatile uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
memmove( (void *)VIDEO_MEMORY, (const void *)VIDEO_MEMORY + 2 * vga->res_x, 2 * ( vga->res_y - 1 ) * vga->res_x );
for( int i = 2 * ( vga->res_x * ( vga->res_y - 1 ) ); i < 2 * ( vga->res_x * vga->res_y ); i += 2 ) {
*(VIDEO_MEMORY+i) = ' ';
*(VIDEO_MEMORY+i+1) = calculate_color_cell( vga );
}
vga->cursor_y = vga->res_y - 1;
}
static uint8_t calculate_color_cell( vga_t *vga )
{
uint8_t cell;
cell = ( vga->background_color << 4 ) | vga->color;
return cell;
}
static bool params_ok( vga_t *vga, const int x, const int y )
{
if( x > vga->res_x || y > vga->res_y ) return false;
return true;
}
void vga_put_char_at( vga_t *vga, const int x, const int y, const char c )
{
vga_set_cursor( vga, x, y );
vga_put_char( vga, c );
}
void vga_put_string_at( vga_t *vga, const int x, const int y, const char *s )
{
vga_set_cursor( vga, x, y );
vga_put_string( vga, s );
}
void vga_put_char( vga_t *vga, const char c )
{
int offset = calculate_offset( vga );
volatile uint8_t *VIDEO_MEMORY = (uint8_t *)0xb8000;
*(VIDEO_MEMORY+offset) = (uint8_t)c;
*(VIDEO_MEMORY+offset+1) = calculate_color_cell( vga );
vga->cursor_x++;
if( vga->cursor_x >= vga->res_x ) {
vga->cursor_x = 0;
vga->cursor_y++;
if( vga->cursor_y >= vga->res_y ) {
scroll_screen( vga );
}
}
}
void vga_put_string( vga_t *vga, const char *s )
{
for( size_t i = 0; i < strlen( s ); i++ ) {
vga_put_char( vga, s[i] );
}
}
void vga_put_newline( vga_t *vga )
{
vga->cursor_x = 0;
vga->cursor_y++;
if( vga->cursor_y >= vga->res_y ) {
scroll_screen( vga );
}
}
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