libbb/copy_file_chunk.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) many different people.  If you wrote this, please
   6  * acknowledge your work.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21  * USA
  22  */
  23
  24 #include <stdio.h>
  25 #include <sys/stat.h>
  26 #include "libbb.h"
  27
  28 /* Copy CHUNKSIZE bytes (or until EOF if CHUNKSIZE equals -1) from SRC_FILE
  29  * to DST_FILE.  */
  30 extern int copy_file_chunk(FILE *src_file, FILE *dst_file, unsigned long long chunksize)
  31 {
  32         size_t nread, nwritten, size;
  33         char buffer[BUFSIZ];
  34
  35         while (chunksize != 0) {
  36                 if (chunksize > BUFSIZ)
  37                         size = BUFSIZ;
  38                 else
  39                         size = chunksize;
  40
  41                 nread = fread (buffer, 1, size, src_file);
  42
  43                 if (nread != size && ferror (src_file)) {
  44                         perror_msg ("read");
  45                         return -1;
  46                 } else if (nread == 0) {
  47                         if (chunksize != -1) {
  48                                 error_msg ("Unable to read all data");
  49                                 return -1;
  50                         }
  51
  52                         return 0;
  53                 }
  54
  55                 nwritten = fwrite (buffer, 1, nread, dst_file);
  56
  57                 if (nwritten != nread) {
  58                         if (ferror (dst_file))
  59                                 perror_msg ("write");
  60                         else
  61                                 error_msg ("Unable to write all data");
  62                         return -1;
  63                 }
  64
  65                 if (chunksize != -1)
  66                         chunksize -= nwritten;
  67         }
  68
  69         return 0;
  70 }