util.h

/*
 * util.h - BIOS interface and other basic helpers
 *
 * author: luke8086
 * license: GPL-2
 */

/*
 * Note: this library only covers a tiny subset of available functionality
 * of BIOS. To learn more, see http://stanislavs.org/helppc/idx_interrupt.html
 * and http://www.ctyme.com/rbrown.htm
 */

#ifndef _UTIL_H_
#define _UTIL_H_

#include <stdint.h>

/* ------------------------------------------------------------------------- *
 * Misc declarations and basic helper functions
 * ------------------------------------------------------------------------- */

typedef __SIZE_TYPE__ size_t;

/* Function attribute moving it to the .start section */
#define ENTRY_POINT __attribute__((section(".start")))

/* Breakpoint trigger for Bochs */
#define BOCHS_BREAKPOINT  __asm__ volatile ("xchg %bx, %bx")

/* Set values of the FS / GS registers */
void set_fs(uint16_t);
void set_gs(uint16_t);

/* Standard library functions (may be called implicitly by the compiler) */
void *memcpy(void *, const void *, size_t);
size_t strlen(const char *s);

/* Return a pseudo-random number between 0 - 65534 */
uint16_t rand(void);


/* ------------------------------------------------------------------------- *
 * Code for triggering software interrupts, in particular to call BIOS services
 * ------------------------------------------------------------------------- */

/*
 * Container for values of the CPU registers
 *
 * Note: initializing fields of different structs at once,
 * e.g. struct regs r = { .ah = 1, .bx = 2 }), doesn't seem to work
 */
struct regs {
    union {
        struct {
            int32_t eax, ebx, ecx, edx;
            uint32_t ebp, edi, esi;
        };

        struct {
            int16_t ax, _eax_fill;
            int16_t bx, _ebx_fill;
            int16_t cx, _ecx_fill;
            int16_t dx, _edx_fill;
            uint16_t bp, _ebp_fill;
            uint16_t di, _edi_fill;
            uint16_t si, _esi_fill;
        };

        struct {
            int8_t al, ah; int16_t _eax_fill_;
            int8_t bl, bh; int16_t _ebx_fill_;
            int8_t cl, ch; int16_t _ecx_fill_;
            int8_t dl, dh; int16_t _edx_fill_;
        };
    };

    uint32_t eflags;
};

/* Trigger software interrupt */
void intr(int int_no, struct regs *);


/* ------------------------------------------------------------------------- *
 * Video services
 * ------------------------------------------------------------------------- */

/* Text attributes */
enum {
    CL_BLACK,     CL_BLUE,          CL_GREEN,       CL_CYAN,
    CL_RED,       CL_MAGENTA,       CL_BROWN,       CL_LIGHT_GRAY,

    /* Bright colors require additional setup to be used for bg */
    CL_DARK_GRAY, CL_LIGHT_BLUE,    CL_LIGHT_GREEN, CL_LIGHT_CYAN,
    CL_LIGHT_RED, CL_LIGHT_MAGENTA, CL_YELLOW,      CL_WHITE
};

/* Toggle visibility of the cursor */
void toggle_cursor(int visible);

/* Get cursor position (high byte = row, low byte = column) */
uint16_t get_cursor(void);

/* Move text cursor to the given position */
void move_cursor(uint16_t pos);

/* Write a single character at the cursor position */
void put_char(char);

/* Write a null-terminated string with attribute at the cursor position */
void put_string(char *, uint8_t);

/*
 * Direct access to the text-mode video memory.
 * Requires calling set_fs(TEXT_MEM_SEG);
 */

/* Default text-mode dimensions */
#define TEXT_WIDTH  80
#define TEXT_HEIGHT 25

/* Attributed character, a single item of the text-mode memory */
struct attr_char {
    uint8_t ascii;
    uint8_t attr;
};

/* Text-mode memory */
#define TEXT_MEM_SEG    0xb800
#define TEXT_MEM        ((struct attr_char __seg_fs volatile *) 0x00)

/* Access a single character, assuming default screen dimensions */
#define CHAR_AT(x, y)   (TEXT_MEM[(y) * TEXT_WIDTH + (x)])


/* ------------------------------------------------------------------------- *
 * Keyboard services
 * ------------------------------------------------------------------------- */

/* Single keystroke in the keyboard buffer */
struct keystroke {
    char scancode;
    char ascii;
};

/* Keyboard scan codes */
enum {
    SC_ESC   = 0x01,
    SC_UP    = 0x48,
    SC_DOWN  = 0x50,
    SC_LEFT  = 0x4b,
    SC_RIGHT = 0x4d,
    SC_PGUP  = 0x49,
    SC_PGDN  = 0x51,
};

/* Check if a keystroke is ready in the keyboard buffer */
int check_keystroke(void);

/* Wait for, and return the next keystroke from the keyboard buffer */
struct keystroke get_keystroke(void);


/* ------------------------------------------------------------------------- *
 * Clock services
 * ------------------------------------------------------------------------- */

/* Get system time in 18.2Hz ticks since midnight */
uint32_t get_time(void);

#endif /* _UTIL_H_ */