/**************************************************************************/
/*                                                                        */
/*                                 OCaml                                  */
/*                                                                        */
/*             Xavier Leroy, projet Cristal, INRIA Rocquencourt           */
/*                                                                        */
/*   Copyright 1996 Institut National de Recherche en Informatique et     */
/*     en Automatique.                                                    */
/*                                                                        */
/*   All rights reserved.  This file is distributed under the terms of    */
/*   the GNU Lesser General Public License version 2.1, with the          */
/*   special exception on linking described in the file LICENSE.          */
/*                                                                        */
/**************************************************************************/

#include <string.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/signals.h>
#include "unixsupport.h"

CAMLprim value unix_read(value fd, value buf, value ofs, value vlen)
{
  intnat len;
  DWORD numbytes, numread;
  char iobuf[UNIX_BUFFER_SIZE];
  DWORD err = 0;

  Begin_root (buf);
    len = Long_val(vlen);
    numbytes = len > UNIX_BUFFER_SIZE ? UNIX_BUFFER_SIZE : len;
    if (Descr_kind_val(fd) == KIND_SOCKET) {
      int ret;
      SOCKET s = Socket_val(fd);
      caml_enter_blocking_section();
      ret = recv(s, iobuf, numbytes, 0);
      if (ret == SOCKET_ERROR) err = WSAGetLastError();
      caml_leave_blocking_section();
      numread = ret;
    } else {
      HANDLE h = Handle_val(fd);
      caml_enter_blocking_section();
      if (! ReadFile(h, iobuf, numbytes, &numread, NULL))
        err = GetLastError();
      caml_leave_blocking_section();
    }
    if (err) {
      if (err == ERROR_BROKEN_PIPE) {
        // The write handle for an anonymous pipe has been closed. We match the
        // Unix behavior, and treat this as a zero-read instead of a Unix_error.
        err = 0;
        numread = 0;
      } else {
        win32_maperr(err);
        uerror("read", Nothing);
      }
    }
    memmove (&Byte(buf, Long_val(ofs)), iobuf, numread);
  End_roots();
  return Val_int(numread);
}