1 files changed, 48 insertions, 0 deletions
diff --git a/bda.h b/bda.h
new file mode 100644
index 0000000..29b842a
--- /dev/null
+++ b/bda.h
@@ -0,0 +1,48 @@
+#ifndef BDA_H
+#define BDA_H
+
+#include "utils.h"
+
+#define BIOS_DATA_AREA_SEGMENT 0x40
+
+static inline uint32_t bda_get_dword(unsigned int offset) {
+	uint32_t __far *p = MK_FP(BIOS_DATA_AREA_SEGMENT, offset);
+	return *p;
+}
+
+static inline uint16_t bda_get_word(unsigned int offset) {
+	uint16_t __far *p = MK_FP(BIOS_DATA_AREA_SEGMENT, offset);
+	return *p;
+}
+
+static inline uint8_t bda_get_byte(unsigned int offset) {
+	uint8_t __far *p = MK_FP(BIOS_DATA_AREA_SEGMENT, offset);
+	return *p;
+}
+
+#define bda_get_ebda_segment()    bda_get_word(0x0e)
+
+#define bda_get_video_mode()      bda_get_byte(0x49)
+#define bda_get_num_columns()     bda_get_word(0x4a)
+#define bda_get_video_page_size() bda_get_word(0x4c)
+#define bda_get_cur_video_page()  bda_get_word(0x62)
+#define bda_get_last_row()        bda_get_byte(0x84)
+#define bda_get_char_height()     bda_get_word(0x85)
+
+#define bda_get_tick_count()      bda_get_dword(0x6c)
+#define bda_get_tick_count_lo()   bda_get_word(0x6c)
+
+static inline void bda_wait_tick() {
+	uint16_t cur_ticks = bda_get_tick_count_lo();
+	do {
+		pause();
+	} while (cur_ticks == bda_get_tick_count_lo());
+}
+
+static inline void bda_wait_ticks(unsigned int ticks) {
+	for (; ticks > 0; ticks--) {
+		bda_wait_tick();
+	}
+}
+
+#endif // BDA_H