#include "xil_printf.h"
#include "xparameters.h"

#include "../hardware/interface_access.h"
#include "../hardware/interface_fds.h"

// newlib offers a (weak) write implementation which
// is reentrant by calling _read_r which in turn
// relies on _read which we implement here.
// This way, we get a global, reentrant read implementation
// NOTE: This might be architecture dependent, so check your
// newlib implementation!
int _read(int fd, char *ptr, int len) {
  if (ptr == NULL) {
    return 0;
  }
  
  // 0 is stdin, TODO: do we support it?
  if (fd < 1) {
    return -1;
  }
  
  // stdout and stderr
  if (fd < 3) {
    return -1;
  }

  if (fd < INTERFACE_FDS_NEXT) {
    return hw_interface_read(fd, ptr, len);
  }

  // we do not have dynamic fds, so fd is invalid
  return -1;
}