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

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <sched.h>

typedef void *InputStream; /* hack, but 5.6.1 is simply toooo old ;) */
typedef void *OutputStream; /* hack, but 5.6.1 is simply toooo old ;) */
typedef void *InOutStream; /* hack, but 5.6.1 is simply toooo old ;) */

#define STACKSIZE 1024 /* yeah */

enum { REQ_QUIT, REQ_OPEN, REQ_CLOSE, REQ_READ, REQ_WRITE, REQ_STAT, REQ_LSTAT, REQ_FSTAT};

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

typedef struct {
  int type;
  aio_thread *thread;

  int fd;
  off_t offset;
  size_t length;
  ssize_t result;
  mode_t mode; /* open */
  int errorno;
  SV *data, *callback;
  void *dataptr;
  STRLEN dataoffset;

  struct stat64 *statdata;
} aio_cb;

typedef aio_cb *aio_req;

static int started;
static int nreqs;
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;
  New (0, req, 1, aio_cb);
  req->type = REQ_QUIT;
  write (reqpipe[1], &req, sizeof (aio_req));
}

static void
send_req (aio_req req)
{
  nreqs++;
  write (reqpipe[1], &req, sizeof (aio_req));
}

static void
read_write (pTHX_ int dowrite, int fd, off_t offset, size_t length,
            SV *data, STRLEN dataoffset, SV*callback)
{
  aio_req req;
  STRLEN svlen;
  char *svptr = SvPV (data, svlen);

  SvUPGRADE (data, SVt_PV);
  SvPOK_on (data);

  if (dataoffset < 0)
    dataoffset += svlen;

  if (dataoffset < 0 || dataoffset > svlen)
    croak ("data offset outside of string");

  if (dowrite)
    {
      /* write: check length and adjust. */
      if (length < 0 || length + dataoffset > svlen)
        length = svlen - dataoffset;
    }
  else
    {
      /* read: grow scalar as necessary */
      svptr = SvGROW (data, length + dataoffset);
    }

  if (length < 0)
    croak ("length must not be negative");

  Newz (0, req, 1, aio_cb);

  if (!req)
    croak ("out of memory during aio_req allocation");

  req->type = dowrite ? REQ_WRITE : REQ_READ;
  req->fd = fd;
  req->offset = offset;
  req->length = length;
  req->data = SvREFCNT_inc (data);
  req->dataptr = (char *)svptr + dataoffset;
  req->callback = SvREFCNT_inc (callback);

  send_req (req);
}

static int
poll_cb (pTHX)
{
  dSP;
  int count = 0;
  aio_req req;

  while (read (respipe[0], (void *)&req, sizeof (req)) == sizeof (req))
    {
      if (req->type == REQ_QUIT)
        {
          Safefree (req->thread);
          started--;
        }
      else
        {
          int errorno = errno;
          errno = req->errorno;

          if (req->type == REQ_READ)
            SvCUR_set (req->data, req->dataoffset
                                  + req->result > 0 ? req->result : 0);

          if (req->data)
            SvREFCNT_dec (req->data);

          if (req->type == REQ_STAT || req->type == REQ_LSTAT || req->type == REQ_FSTAT)
            {
              PL_laststype            = req->type == REQ_LSTAT ? OP_LSTAT : OP_STAT;
              PL_laststatval          = req->result;
              PL_statcache.st_dev     = req->statdata->st_dev;
              PL_statcache.st_ino     = req->statdata->st_ino;
              PL_statcache.st_mode    = req->statdata->st_mode;
              PL_statcache.st_nlink   = req->statdata->st_nlink;
              PL_statcache.st_uid     = req->statdata->st_uid;
              PL_statcache.st_gid     = req->statdata->st_gid;
              PL_statcache.st_rdev    = req->statdata->st_rdev;
              PL_statcache.st_size    = req->statdata->st_size;
              PL_statcache.st_atime   = req->statdata->st_atime;
              PL_statcache.st_mtime   = req->statdata->st_mtime;
              PL_statcache.st_ctime   = req->statdata->st_ctime;
              PL_statcache.st_blksize = req->statdata->st_blksize;
              PL_statcache.st_blocks  = req->statdata->st_blocks;

              Safefree (req->statdata);
            }

          PUSHMARK (SP);
          XPUSHs (sv_2mortal (newSViv (req->result)));
          PUTBACK;
          call_sv (req->callback, G_VOID);
          SPAGAIN;
          
          if (req->callback)
            SvREFCNT_dec (req->callback);

          errno = errorno;
          nreqs--;
          count++;
        }

      Safefree (req);
    }

  return count;
}

static sigset_t fullsigset;

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

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

  /* this is very much x86 and kernel-specific :(:(:( */
  /* we rely on gcc's ability to create closures. */
  _syscall3(int,read,int,fd,char *,buf,size_t,count)
  _syscall3(int,write,int,fd,char *,buf,size_t,count)

  _syscall3(int,open,char *,pathname,int,flags,mode_t,mode)
  _syscall1(int,close,int,fd)

  _syscall5(int,pread,int,fd,char *,buf,size_t,count,unsigned int,offset_lo,unsigned int,offset_hi)
  _syscall5(int,pwrite,int,fd,char *,buf,size_t,count,unsigned int,offset_lo,unsigned int,offset_hi)

  _syscall2(int,stat64, const char *, filename, struct stat64 *, buf)
  _syscall2(int,lstat64, const char *, filename, struct stat64 *, buf)
  _syscall2(int,fstat64, int, fd, struct stat64 *, buf)

  sigprocmask (SIG_SETMASK, &fullsigset, 0);

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

      if (req->type == REQ_READ)
        req->result = pread (req->fd, req->dataptr, req->length, req->offset & 0xffffffff, req->offset >> 32);
      else if (req->type == REQ_WRITE)
        req->result = pwrite(req->fd, req->dataptr, req->length, req->offset & 0xffffffff, req->offset >> 32);
      else if (req->type == REQ_OPEN)
        req->result = open (req->dataptr, req->fd, req->mode);
      else if (req->type == REQ_CLOSE)
        req->result = close (req->fd);
      else if (req->type == REQ_STAT)
        req->result = stat64 (req->dataptr, req->statdata);
      else if (req->type == REQ_LSTAT)
        req->result = lstat64 (req->dataptr, req->statdata);
      else if (req->type == REQ_FSTAT)
        req->result = fstat64 (req->fd, req->statdata);
      else
        {
          write (respipe[1], (void *)&req, sizeof (req));
          break;
        }

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

  return 0;
}

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

BOOT:
{
        sigfillset (&fullsigset);
        sigdelset (&fullsigset, SIGTERM);
        sigdelset (&fullsigset, SIGQUIT);
        sigdelset (&fullsigset, SIGABRT);
        sigdelset (&fullsigset, SIGINT);

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

        if (fcntl (respipe[0], F_SETFL, O_NONBLOCK))
          croak ("cannot set result pipe to nonblocking mode");
}

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

void
max_parallel(nthreads)
	int	nthreads
	PROTOTYPE: $
        CODE:
        int cur = started;
        while (cur > nthreads)
          {          
            end_thread ();
            cur--;
          }

        while (started > nthreads)
          {
            fd_set rfd;
            FD_ZERO(&rfd);
            FD_SET(respipe[0], &rfd);

            select (respipe[0] + 1, &rfd, 0, 0, 0);
            poll_cb ();
          }

void
aio_open(pathname,flags,mode,callback)
	SV *	pathname
        int	flags
        int	mode
        SV *	callback
	PROTOTYPE: $$$$
	CODE:
        aio_req req;

        Newz (0, req, 1, aio_cb);

        if (!req)
          croak ("out of memory during aio_req allocation");

        req->type = REQ_OPEN;
        req->data = newSVsv (pathname);
        req->dataptr = SvPV_nolen (req->data);
        req->fd = flags;
        req->mode = mode;
        req->callback = SvREFCNT_inc (callback);

        send_req (req);

void
aio_close(fh,callback)
        InputStream	fh
        SV *		callback
	PROTOTYPE: $$
	CODE:
        aio_req req;

        Newz (0, req, 1, aio_cb);

        if (!req)
          croak ("out of memory during aio_req allocation");

        req->type = REQ_CLOSE;
        req->fd = PerlIO_fileno (fh);
        req->callback = SvREFCNT_inc (callback);

        send_req (req);

void
aio_read(fh,offset,length,data,dataoffset,callback)
        InputStream	fh
        UV		offset
        IV		length
        SV *		data
        IV		dataoffset
        SV *		callback
	PROTOTYPE: $$$$$$
        CODE:
        read_write (aTHX_ 0, PerlIO_fileno (fh), offset, length, data, dataoffset, callback);

void
aio_write(fh,offset,length,data,dataoffset,callback)
        OutputStream	fh
        UV		offset
        IV		length
        SV *		data
        IV		dataoffset
        SV *		callback
	PROTOTYPE: $$$$$$
        CODE:
        read_write (aTHX_ 1, PerlIO_fileno (fh), offset, length, data, dataoffset, callback);

void
aio_stat(fh_or_path,callback)
        SV *		fh_or_path
        SV *		callback
	PROTOTYPE: $$
        ALIAS:
           aio_lstat = 1
	CODE:
        aio_req req;

        Newz (0, req, 1, aio_cb);

        if (!req)
          croak ("out of memory during aio_req allocation");

        New (0, req->statdata, 1, struct stat64);

        if (!req->statdata)
          croak ("out of memory during aio_req->statdata allocation");

        if (SvPOK (fh_or_path))
          {
            req->type = ix ? REQ_LSTAT : REQ_STAT;
            req->data = newSVsv (fh_or_path);
            req->dataptr = SvPV_nolen (req->data);
          }
        else
          {
            req->type = REQ_FSTAT;
            req->fd = PerlIO_fileno (IoIFP (sv_2io (fh_or_path)));
          }

        req->callback = SvREFCNT_inc (callback);

        send_req (req);

int
poll_fileno()
	PROTOTYPE:
	CODE:
        RETVAL = respipe[0];
	OUTPUT:
	RETVAL

int
poll_cb(...)
	PROTOTYPE:
	CODE:
        RETVAL = poll_cb (aTHX);
	OUTPUT:
	RETVAL

int
nreqs()
	PROTOTYPE:
	CODE:
        RETVAL = nreqs;
	OUTPUT:
	RETVAL