#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include <sys/types.h>
#include <unistd.h>
#include <sched.h>

#define STACKSIZE 128 /* yeah */

#define REQ_QUIT  0
#define REQ_READ  1
#define REQ_WRITE 2

typedef struct {
  char stack[STACKSIZE];
} aio_thread;

typedef struct {
  int type;
  aio_thread *thread;

/* read/write */
  int fd;
  off_t offset;
  size_t length;
  ssize_t result;
  int errorno;

  SV *data;
  void *dataptr;
  STRLEN dataoffset;
} aio_cb;

typedef aio_cb *aio_req;

static int started;
static int reqpipe[2], respipe[2];

static int aio_proc(void *arg);

static void
start_thread(void)
{
  aio_thread *thr;

  New (0, thr, 1, aio_thread);

  if (clone (aio_proc,
             &(thr->stack[STACKSIZE]),
             CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND,
             thr) >= 0)
    started++;
  else
    Safefree (thr);
}

static void
end_thread(void)
{
  aio_req req = 0;
  write (reqpipe[1], &req, sizeof (aio_req));
  started--;
}

static void
set_errno(int errorno)
{
  errno = errorno;
}

#undef errno
#include <asm/unistd.h>

static int
aio_proc(void *thr_arg)
{
  aio_thread *thr = thr_arg;
  int sig;
  int errno;
  aio_req req;

  /* we rely on gcc's ability to create closures. */
  _syscall3(int,lseek,int,fd,off_t,offset,int,whence);
  _syscall3(int,read,int,fd,char *,buf,off_t,count);
  _syscall3(int,write,int,fd,char *,buf,off_t,count);

  /* first get rid of any signals */
  for (sig = 1; sig < _NSIG; sig++)
    signal (sig, SIG_IGN);

  signal (SIGTERM, SIG_DFL);
 
  /* then loop */
  while (read (reqpipe[0], (void *)&req, sizeof (req)) == sizeof (req))
    {
      req->thread = thr;

      if (req->type == REQ_READ || req->type == REQ_WRITE)
        {
          errno = 0;

          if (lseek (req->fd, req->offset, SEEK_SET) == req->offset)
            {
              if (req->type == REQ_READ)
                req->result = read (req->fd, req->dataptr, req->length);
              else
                req->result = write(req->fd, req->dataptr, req->length);
            }

          req->errorno = errno;
        }
      else
        {
          write (respipe[1], (void *)&req, sizeof (req));
          break;
        }

      write (respipe[1], (void *)&req, sizeof (req));
    }

  return 0;
}

MODULE = Linux::AIO                PACKAGE = Linux::AIO

BOOT:
{
        if (pipe (reqpipe) || pipe (respipe))
          croak ("unable to initialize request or result pipe");
}

void
min_parallel(nthreads)
	int	nthreads
        CODE:
        while (nthreads > started)
          start_thread ();

void
max_parallel(nthreads)
	int	nthreads
        CODE:
        while (started > nthreads)
          end_thread ();

void
read(fh,offset,length,data,dataoffset,callback)
	ALIAS:
          write = 1
	CODE: