/* vmlwrap.c - the C side of the machine code helpers. build-ml.ps1 appends
 * this to the generated byte array to make vml.c; edit it here.
 *
 * Parameters go through a block at $c400 (not $cf00: the C stack lives just below $d000), then sys() jumps to the entry.
 * On the c64 sys() takes no bank argument: sys(addr, &a, &x, &y).
 */

extern char *bfr;
extern unsigned blen;
extern unsigned lptr[];
extern int nlines, top, leftcol;

/* move the code to $c000 and keep power c's heap and stack below it.
   must run before malloc() */
mlinit()
{
    char *d;
    int i;

    highmem(0xc000);
    d = (char *) 0xc000;
    for (i = 0; i < MLSIZE; i++) d[i] = mlcode[i];
    return 0;
}

/* call an entry, return what it left in A */
mlgo(addr)
unsigned addr;
{
    char a, x, y;

    a = 0;
    x = 0;
    y = 0;
    sys(addr, &a, &x, &y);
    return a & 255;
}

/* The wrappers fill the parameter block through one pointer instead of
   calling a helper per field: every power c function call costs a lot, and
   mlscr runs on every key. Words are stored low byte first. */

/* paint one row at screen address dst: len bytes from src, cursor at column
   cur (255 = none), rev = 128 for an all reverse row */
mlrow(src, len, dst, cur, rev)
unsigned src, dst;
int len, cur, rev;
{
    char *p;

    p = (char *) 0xc400;
    p[0] = src;
    p[1] = src >> 8;
    p[2] = len;
    p[3] = dst;
    p[4] = dst >> 8;
    p[5] = cur;
    p[6] = rev;
    mlgo(MLROW);
    return 0;
}

/* paint screen rows r0..r1 from the buffer; the cursor sits at screen row
   crow (255 = none), column ccol */
mlscr(r0, r1, crow, ccol)
int r0, r1, crow, ccol;
{
    char *p;
    unsigned v;

    p = (char *) 0xc400;
    v = (unsigned) bfr;
    p[0] = v;
    p[1] = v >> 8;
    v = (unsigned) lptr;
    p[2] = v;
    p[3] = v >> 8;
    p[4] = nlines;
    p[5] = nlines >> 8;
    p[6] = top;
    p[7] = top >> 8;
    p[8] = blen;
    p[9] = blen >> 8;
    p[10] = leftcol;
    p[11] = leftcol >> 8;
    p[12] = crow;
    p[13] = ccol;
    p[14] = r0;
    p[15] = r1;
    mlgo(MLSCRN);
    return 0;
}

/* memmove: n bytes from 'from' to 'to', overlap safe */
mlmove(from, to, n)
unsigned from, to, n;
{
    char *p;

    if (n == 0) return 0;
    p = (char *) 0xc400;
    p[0] = from;
    p[1] = from >> 8;
    p[2] = to;
    p[3] = to >> 8;
    p[4] = n;
    p[5] = n >> 8;
    mlgo(MLBMOVE);
    return 0;
}

/* add d to n words starting at address a (line index fix-ups) */
mladj(a, n, d)
unsigned a, n, d;
{
    char *p;

    if (n == 0) return 0;
    p = (char *) 0xc400;
    p[0] = a;
    p[1] = a >> 8;
    p[2] = n;
    p[3] = n >> 8;
    p[4] = d;
    p[5] = d >> 8;
    mlgo(MLLADJ);
    return 0;
}

/* next key from the kernal buffer, or 0 */
mlkey()
{
    return mlgo(MLKPOP);
}