write vga strings and some cursor handling

7 files changed, 74 insertions, 24 deletions

diff --git a/src/Makefile b/src/Makefile
index 0d9cc1e..ec9e466 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -8,7 +8,7 @@ image.bin: boot.bin kernel.bin
 	cat boot.bin kernel.bin > image.bin
 	# truncate to correct number of sectors, we have
 	# 512 (boot, first stage) + N * 512 (N currenty is 3) + M * 512 (M is currently 3)
-	truncate -s 3584 image.bin
+	truncate -s 4096 image.bin
 	
 boot.bin: boot.asm gdt.asm stage1_functions.asm stage2_functions.asm switch_mode.asm
 	nasm boot.asm -f bin -o boot.bin
diff --git a/src/kernel.c b/src/kernel.c
index bdca5e7..1692259 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -9,26 +9,26 @@ void entry( void )
 
 	vga_set_color( &vga, VGA_COLOR_LIGHT_GREY );
 	vga_set_background_color( &vga, VGA_COLOR_BLACK );
+	// again volatile? const results in garbage on clang
+	volatile char msg[] = "ABAOS";
+	vga_put_string_at( &vga, 0, 0, (const char *)msg );
+	//~ vga_put_string_at( &vga, 0, 0, "ABAOS" );
 	
-	vga_put_char( &vga, 0, 0, 'A' );
-	vga_put_char( &vga, 1, 0, 'B' );
-	vga_put_char( &vga, 2, 0, 'A' );
-	vga_put_char( &vga, 3, 0, 'O' );
-	vga_put_char( &vga, 4, 0, 'S' );
-	
-	volatile uint8_t bar[] = "\\|/-";
+	// clang 4.0.0 needs volatile otherwise it takes a random value
+	// from the register in the second vga_put_char_at below??!
+	volatile char bar[] = "\\|/-";
 	int pos = 5;
 	int i = 0;
 	for( i = 0; i < 10000; i++ ) {
 		if( i % 1000 == 0 ) {
-			vga_put_char( &vga, pos, 0, '.' );
+			vga_put_char_at( &vga, pos, 0, '.' );
 			pos++;
 		}
-		vga_put_char( &vga, pos, 0, bar[i%4] );
-		for( int j = 0; j < 10000; j++ ) {
+		vga_put_char_at( &vga, pos, 0, bar[i%4] );
+		for( int j = 0; j < 3000; j++ ) {
 		}
 	}
-	vga_put_char( &vga, pos, 0, '.' );	
+	vga_put_char_at( &vga, pos, 0, '.' );	
 
 	vga_set_color( &vga, VGA_COLOR_WHITE );
 	vga_set_background_color( &vga, VGA_COLOR_RED );
diff --git a/src/stage1_functions.asm b/src/stage1_functions.asm
index 575a465..b32d23d 100644
--- a/src/stage1_functions.asm
+++ b/src/stage1_functions.asm
@@ -3,7 +3,7 @@
 ; 3 * 512 for bootloader stage2 and the kernel code 
 ; (note: the first sector gets loaded by the BIOS, so
 ; subtract 1 here!)
-NOF_LOAD_SECTORS equ 6
+NOF_LOAD_SECTORS equ 7
 
 ; IN bx: begin of memory area to dump
 ; IN ax: number of words to dump
diff --git a/src/string.c b/src/string.c
index 30ccba6..07042ce 100644
--- a/src/string.c
+++ b/src/string.c
@@ -3,9 +3,18 @@
 void *memset( void *s, int c, size_t n )
 {
 	for( size_t i = 0; i < n; i++ ) {
-		((uint8_t *)s)[i] = c;
+		((char *)s)[i] = c;
 	}
 	
 	return s;
 }
 
+size_t strlen( const char *s )
+{
+	size_t len;
+	const char *p = s;
+	
+	for( len = 0; *p; len++, p++ );
+	
+	return len;
+}
diff --git a/src/string.h b/src/string.h
index c380155..b82d1aa 100644
--- a/src/string.h
+++ b/src/string.h
@@ -4,5 +4,6 @@
 #include "sys/types.h"
 
 void *memset( void *s, int c, size_t n );
+size_t strlen( const char *s );
 
 #endif /* STRING_H */
diff --git a/src/vga.c b/src/vga.c
index 767d45f..0133ddf 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -1,7 +1,10 @@
 #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 );
 
@@ -32,6 +35,9 @@ void vga_clear_screen( vga_t *vga )
 
 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;
 }
@@ -62,16 +68,49 @@ static uint8_t calculate_color_cell( vga_t *vga )
 	return cell;
 }
 
-void vga_put_char( vga_t *vga, const int x, const int y, const uint8_t c )
+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 )
 {
-	// TODO: PANIC? OUT OF BOUND ACCESS
-	if( x > vga->res_x || y > vga->res_y ) return;
-	
 	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) = c;
-	*(VIDEO_MEMORY+offset+1) = calculate_color_cell( vga );
+	*(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 ) {
+			// TODO: implement scrolling
+			vga->res_y = 0;
+		}
+	}
+}
+
+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] );
+	}
 }
+
diff --git a/src/vga.h b/src/vga.h
index 8aef4e6..9664e2c 100644
--- a/src/vga.h
+++ b/src/vga.h
@@ -1,8 +1,6 @@
 #ifndef VGA_H
 #define VGA_H
 
-#include "sys/types.h"
-
 enum {
 	VGA_DEFAULT_RES_X = 80,
 	VGA_DEFAULT_RES_Y = 25
@@ -41,6 +39,9 @@ void vga_clear_screen( vga_t *vga );
 void vga_set_cursor( vga_t *vga, const int x, const int y );
 void vga_set_color( vga_t *vga, const vga_color_t color );
 void vga_set_background_color( vga_t *vga, const vga_color_t color );
-void vga_put_char( vga_t *vga, const int x, const int y, const uint8_t c );
+void vga_put_char_at( vga_t *vga, const int x, const int y, const char c );
+void vga_put_string_at( vga_t *vga, const int x, const int y, const char *s );
+void vga_put_char( vga_t *vga, const char c );
+void vga_put_string( vga_t *vga, const char *s );
  
 #endif /* VGA_H */