fastjar/shift.c

   1 /* shift.c -- utilities to move regions of data in a file.
   2    Copyright (C) 2004  Free Software Foundation, Inc.
   3
   4 This program is free software; you can redistribute it and/or modify
   5 it under the terms of the GNU General Public License as published by
   6 the Free Software Foundation; either version 2 of the License, or (at
   7 your option) any later version.
   8
   9 This program is distributed in the hope that it will be useful, but
  10 WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program; if not, write to the Free Software
  16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  17 USA.  */
  18
  19
  20 #include <sys/types.h>
  21 #include <unistd.h>
  22 #include <stdio.h>
  23 #include "jartool.h"
  24 #include "shift.h"
  25
  26 #define BUFFER_SIZE 1024
  27
  28 #define MIN(a, b) ((a) < (b) ? (a) : (b))
  29
  30 /*
  31  * Shift the contents of a file up by `amount' bytes, starting at `begin'.
  32  * The file is not truncated, data from `amount' to `begin - amount' is
  33  * overwritten. The current file pointer of `fd' is preserved. Note that
  34  * this might be past the new "end" of the file.
  35  *
  36  * If this function is passed a `struct zipentry', then all `offset'
  37  * fields from that entry down the list that are greater than or equal
  38  * to `begin' will be decreased by `amount'.
  39  *
  40  * fd     - The file descriptor.
  41  * begin  - The offset of the first byte that should be shifted.
  42  * amount - The number of bytes to shift by.
  43  * ze     - A pointer into a list of zip entries that should be updated
  44  *          to reflect the modified offset.
  45  */
  46 int
  47 shift_up (int fd, off_t begin, off_t amount, struct zipentry *ze)
  48 {
  49   extern off_t end_of_entries;
  50   int len, moved = 0;
  51   ub1 buffer[BUFFER_SIZE];
  52   off_t where, end, save;
  53
  54   if (amount <= 0)
  55     return 0;
  56
  57   if ((save = lseek (fd, 0, SEEK_CUR)) == -1)
  58     return 1;
  59   if ((end = lseek (fd, 0, SEEK_END)) == -1)
  60     return 1;
  61   if (end < begin)
  62     return 0;
  63
  64   where = begin;
  65
  66   do
  67     {
  68       if (lseek (fd, where, SEEK_SET) < 0)
  69         return 1;
  70       if ((len = read (fd, buffer, BUFFER_SIZE)) < 0)
  71         return 1;
  72       if (len == 0)
  73         break;
  74       if (lseek (fd, where - amount, SEEK_SET) < 0)
  75         return 1;
  76       if (write (fd, buffer, len) < 0)
  77         return 1;
  78       where += len;
  79     }
  80   while (where < end);
  81
  82   for (; ze; ze = ze->next_entry)
  83     {
  84       if (ze->offset >= begin)
  85         {
  86           ze->offset -= amount;
  87           moved = 1;
  88         }
  89     }
  90   if (moved)
  91     end_of_entries -= amount;
  92
  93   if (lseek (fd, save, SEEK_SET) == -1)
  94     return 1;
  95   return 0;
  96 }
  97
  98 /*
  99  * Shift the contents of this file down by `amount' bytes, extending the
 100  * end of file, starting at `begin'. This function will preserve the
 101  * current file pointer of `fd'. Naturally, this function will fail if
 102  * `fd' is not seekable.
 103  *
 104  * If this function is passed a `struct zipentry', then all `offset'
 105  * fields from that entry down the list that are greater than or equal
 106  * to `begin' will be increased by `amount'.
 107  *
 108  * fd     - The file descriptor.
 109  * begin  - The offset of the first byte that should be shifted.
 110  * amount - The number of bytes to shift by.
 111  * ze     - A pointer into a list of zip entries that should be updated
 112  *          to reflect the modified offset.
 113  */
 114 int
 115 shift_down (int fd, off_t begin, off_t amount, struct zipentry *ze)
 116 {
 117   extern off_t end_of_entries;
 118   int off, len, moved = 0;
 119   ub1 buffer[BUFFER_SIZE];
 120   off_t where, save;
 121
 122   if (amount <= 0)
 123     return 0;
 124
 125   if ((save = lseek (fd, 0, SEEK_CUR)) == -1)
 126     return 1;
 127   if ((where = lseek (fd, 0, SEEK_END)) == -1)
 128     return 1;
 129   if (where < begin)
 130     return 0;
 131   off = (where - begin) % BUFFER_SIZE;
 132   if (off == 0)
 133     where -= BUFFER_SIZE;
 134   else
 135     where -= off;
 136
 137   do
 138     {
 139       if (lseek (fd, where, SEEK_SET) < 0)
 140         return 1;
 141       if ((len = read (fd, buffer, BUFFER_SIZE)) < 0)
 142         return 1;
 143       if (lseek (fd, where + amount, SEEK_SET) < 0)
 144         return 1;
 145       if (write (fd, buffer, len) < 0)
 146         return 1;
 147       where -= BUFFER_SIZE;
 148     }
 149   while (where >= begin);
 150
 151   for (; ze; ze = ze->next_entry)
 152     {
 153       if (ze->offset >= begin)
 154         {
 155           ze->offset += amount;
 156           moved = 1;
 157         }
 158     }
 159   if (moved)
 160     end_of_entries += amount;
 161
 162   if (lseek (fd, save, SEEK_SET) == -1)
 163     return 1;
 164
 165   return 0;
 166 }