#include "substdio.h"

#include "byte.h"

#include "error.h"

static int oneread(op,fd,buf,len)

register int (*op)();

register int fd;

register char *buf;

register int len;

{

  register int r;

  for (;;) {

    r = op(fd,buf,len);

    if (r == -1) if (errno == error_intr) continue;

    return r;

  }

}

static int getthis(s,buf,len)

register substdio *s;

register char *buf;

register int len;

{

  register int r;

  register int q;

  r = s->p;

  q = r - len;

  if (q > 0) { r = len; s->p = q; } else s->p = 0;

  byte_copy(buf,r,s->x + s->n);

  s->n += r;

  return r;

}

int substdio_feed(s)

register substdio *s;

{

  register int r;

  register int q;

  if (s->p) return s->p;

  q = s->n;

  r = oneread(s->op,s->fd,s->x,q);

  if (r <= 0) return r;

  s->p = r;

  q -= r;

  s->n = q;

  if (q > 0) /* damn, gotta shift */ byte_copyr(s->x + q,r,s->x);

  return r;

}

int substdio_bget(s,buf,len)

register substdio *s;

register char *buf;

register int len;

{

  register int r;

  if (s->p > 0) return getthis(s,buf,len);

  r = s->n; if (r <= len) return oneread(s->op,s->fd,buf,r);

  r = substdio_feed(s); if (r <= 0) return r;

  return getthis(s,buf,len);

}

int substdio_get(s,buf,len)

register substdio *s;

register char *buf;

register int len;

{

  register int r;

  if (s->p > 0) return getthis(s,buf,len);

  if (s->n <= len) return oneread(s->op,s->fd,buf,len);

  r = substdio_feed(s); if (r <= 0) return r;

  return getthis(s,buf,len);

}

char *substdio_peek(s)

register substdio *s;

{

  return s->x + s->n;

}

void substdio_seek(s,len)

register substdio *s;

register int len;

{

  s->n += len;

  s->p -= len;

}