otherlibs/unix/write.c

   1 /***********************************************************************/
   2 /*                                                                     */
   3 /*                           Objective Caml                            */
   4 /*                                                                     */
   5 /*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         */
   6 /*                                                                     */
   7 /*  Copyright 1996 Institut National de Recherche en Informatique et   */
   8 /*  en Automatique.  All rights reserved.  This file is distributed    */
   9 /*  under the terms of the GNU Library General Public License, with    */
  10 /*  the special exception on linking described in file ../../LICENSE.  */
  11 /*                                                                     */
  12 /***********************************************************************/
  13
  14 /* $Id$ */
  15
  16 #include <errno.h>
  17 #include <string.h>
  18 #include <mlvalues.h>
  19 #include <memory.h>
  20 #include <signals.h>
  21 #include "unixsupport.h"
  22
  23 #ifndef EAGAIN
  24 #define EAGAIN (-1)
  25 #endif
  26 #ifndef EWOULDBLOCK
  27 #define EWOULDBLOCK (-1)
  28 #endif
  29
  30 CAMLprim value unix_write(value fd, value buf, value vofs, value vlen)
  31 {
  32   long ofs, len, written;
  33   int numbytes, ret;
  34   char iobuf[UNIX_BUFFER_SIZE];
  35
  36   Begin_root (buf);
  37     ofs = Long_val(vofs);
  38     len = Long_val(vlen);
  39     written = 0;
  40     while (len > 0) {
  41       numbytes = len > UNIX_BUFFER_SIZE ? UNIX_BUFFER_SIZE : len;
  42       memmove (iobuf, &Byte(buf, ofs), numbytes);
  43       enter_blocking_section();
  44       ret = write(Int_val(fd), iobuf, numbytes);
  45       leave_blocking_section();
  46       if (ret == -1) {
  47         if ((errno == EAGAIN || errno == EWOULDBLOCK) && written > 0) break;
  48         uerror("write", Nothing);
  49       }
  50       written += ret;
  51       ofs += ret;
  52       len -= ret;
  53     }
  54   End_roots();
  55   return Val_long(written);
  56 }
  57
  58 /* When an error occurs after the first loop, unix_write reports the
  59    error and discards the number of already written characters.
  60    In this case, it would be better to discard the error and return the
  61    number of bytes written, since most likely, unix_write will be call again,
  62    and the error will be reproduced and this time will be reported.
  63    This problem is avoided in unix_single_write, which is faithful to the
  64    Unix system call. */
  65
  66 CAMLprim value unix_single_write(value fd, value buf, value vofs, value vlen)
  67 {
  68   long ofs, len;
  69   int numbytes, ret;
  70   char iobuf[UNIX_BUFFER_SIZE];
  71
  72   Begin_root (buf);
  73     ofs = Long_val(vofs);
  74     len = Long_val(vlen);
  75     ret = 0;
  76     if (len > 0) {
  77       numbytes = len > UNIX_BUFFER_SIZE ? UNIX_BUFFER_SIZE : len;
  78       memmove (iobuf, &Byte(buf, ofs), numbytes);
  79       enter_blocking_section();
  80       ret = write(Int_val(fd), iobuf, numbytes);
  81       leave_blocking_section();
  82       if (ret == -1) uerror("single_write", Nothing);
  83     }
  84   End_roots();
  85   return Val_int(ret);
  86 }
  87