/*     +-------------------------------------------------------------+
       | This code is my own work, it was written without consulting |
       |  a tutor or code written by other students - Nikhil Murthy  |
       +-------------------------------------------------------------+     */

#include "../../h/const.h"
#include "../../h/types.h"
#include "../../h/procq.e"
#include "../../h/asl.e"

/************************************************
  Global Variables
************************************************/
devreg_t *devregs = (devreg_t*)0x1400;

/***************************************************************************
 *                           FUNCTION PROTOTYPES                           *
 ***************************************************************************/
/* main functions */
void readfromterminal();
void writetoterminal();
void delay();
void gettimeofday();
void terminate();
/* utility functions*/
int vir2real_add(vad_t *vadd);

/* trap locations */
state_t *sys_old = (state_t *) 0x930;
state_t *sys_new = sys_old + 1;

/* Read_from_Terminal (SYS9) */
void
readfromterminal()
{
    char *data;
    int *cnt;
    int term;
    int done = 0;
    /* d3 = virtual address of buffer for data read */
    data = (char*)vir2real_add((vad_t*)sys_old->s_r[3]);
    /* d2 = return number of characters read */
    cnt = &(sys_old->s_r[2]);
    term = sys_old->s_tmp.tmp_sys.term_no;
    /* do the term i/o */
    devregs[term].d_stat = NULL;
    devregs[term].d_badd = data;
    devregs[term].d_op = IOREAD;
    while (!done)
        switch (devregs[term].d_stat) {
        case NULL:
            break;
        case NORMAL:
            *cnt = devregs[term].d_amnt;
            done = 1;
            break;
        case ENDOFINPUT:
            *cnt = -ENDOFINPUT;
            done = 1;
            break;
        default:
            *cnt = -devregs[term].d_stat;
            done = 1;
            break;
        }
    /* start the t-proc again */
    LDST(sys_old);
}

/* Write_to_Terminal (SYS10) */
void
writetoterminal()
{
    /* d3 = virtual address of data buffer to write */
    char *data = (char*)vir2real_add((vad_t*)sys_old->s_r[3]);
    /* d4 = count of number of characters to be written */
    int *cnt = &(sys_old->s_r[4]);
    int term = sys_old->s_tmp.tmp_sys.term_no;
    int done = 0;

    /* do the i/o */
    devregs[term].d_stat = NULL;
    devregs[term].d_badd = data;
    devregs[term].d_op = IOWRITE;
    while (!done)
        switch(devregs[term].d_stat) {
        case NULL:
            break;
        case NORMAL:
            *cnt = devregs[term].d_amnt;
            done = 1;
            break;
        default:
            *cnt = -devregs[term].d_stat;
            done = 1;
            break;
        }
    /* start up the t-proc again */
    LDST(sys_old);
}

/* Delay (SYS13) */
void
delay()
{
}

/* Get_Time_of_Day (SYS16) */
void
gettimeofday()
{
    /* d2 = time of day clock */
    STCK(&(sys_old->s_r[2]));
    /* start the process back up */
    LDST(sys_old);
}

/* Terminate (SYS17) */
void
terminate()
{
}

/************************************************
  Utility Functions
************************************************/

int
vir2real_add(vad_t *vadd)
{
    int segnum, pagenum, offset;
    sd_t seg;
    pd_t page;
    int ret;

    segnum = vadd.v_seg; pagenum = vadd.v_page; offset = vadd.v_offset;

    seg = sys_old->s_crp + segnum;
    page = seg.sd_pta + pagenum;
    if (page.pd_p == 1)
        /* page is present */
        ret = ((int)page.pd_frame)*512 + offset;
    else ret = -1;
    return ret;
}