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,
  31                            unsigned long long chunksize)
  32 {
  33         size_t nread, nwritten, size;
  34         char buffer[BUFSIZ];
  35
  36         while (chunksize != 0) {
  37                 if (chunksize > BUFSIZ)
  38                         size = BUFSIZ;
  39                 else
  40                         size = chunksize;
  41
  42                 nread = fread(buffer, 1, size, src_file);
  43
  44                 if (nread != size && ferror(src_file)) {
  45                         perror_msg("read");
  46                         return -1;
  47                 } else if (nread == 0) {
  48                         if (chunksize != -1) {
  49                                 error_msg("Unable to read all data");
  50                                 return -1;
  51                         }
  52
  53                         return 0;
  54                 }
  55
  56                 nwritten = fwrite(buffer, 1, nread, dst_file);
  57
  58                 if (nwritten != nread) {
  59                         if (ferror(dst_file))
  60                                 perror_msg("write");
  61                         else
  62                                 error_msg("Unable to write all data");
  63                         return -1;
  64                 }
  65
  66                 if (chunksize != -1)
  67                         chunksize -= nwritten;
  68         }
  69
  70         return 0;
  71 }