packfile.h

   1 /*
   2     Copyright (C) 2005-2007 Tom Beaumont
   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
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12     GNU 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  17 */
  18
  19 #include <stdint.h>
  20 #include <SDL/SDL_endian.h>
  21
  22 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
  23 #define SWAP16(X)    (X)
  24 #define SWAP32(X)    (X)
  25 #else
  26 #define SWAP16(X)    SDL_Swap16(X)
  27 #define SWAP32(X)    SDL_Swap32(X)
  28 #endif
  29
  30 struct PackFile1
  31 {
  32   /* Is it *NOT* save to interpret a byte stream as list of Entries!
  33    * The alignment could increase the Entry size on some systems without attribute.
  34    *
  35    * It works on: i386, amd64, mips o32 ABI, powerPC
  36    * Maybe it's also compiler dependent ...
  37    *
  38    * See also http://c-faq.com/struct/padding.html,
  39    * http://c-faq.com/strangeprob/ptralign.html and Debian bug #442854
  40    * (Need to refer to a C FAQ in a (so called) C++ program, argh ...)
  41    * */
  42         class Entry {
  43                 int32_t len;
  44         public:
  45                 // an array of size 1 (no char* pointer!) is saved after len,
  46                 // accessing name[0] should (but doesn't always) fit the first byte after len
  47                 // See e.g. http://c-faq.com/aryptr/index.html
  48                 char name[1];
  49
  50                 Entry* GetNext()
  51                 {
  52                         return (Entry*)((char*)name + len);
  53                 }
  54
  55                 void* Data()
  56                 {
  57                         char* pos = name;
  58                         while (*pos!=0)
  59                                 pos++;
  60                         return pos+1;
  61                 }
  62
  63                 int DataLen()
  64                 {
  65                         return len - strlen(name) - 1;
  66                 }
  67         }
  68 #ifdef __GNUC__
  69    __attribute__ ((__packed__));
  70          int static_assert1[sizeof(Entry)==5 ? 0 : -1];
  71 #else
  72   int static_assert1[sizeof(Entry)<=8 ? 0 : -1];
  73 #endif
  74
  75         int numfiles;
  76         Entry** e;
  77         void* data;
  78
  79         PackFile1() : numfiles(0), e(0), data(0)
  80         {}
  81
  82         Entry* Find(const char* name)
  83         {
  84                 if (numfiles==0) return 0;
  85                 int a=0, b=numfiles;
  86                 while (b>a)
  87                 {
  88                         const int mid = (a+b)>>1;
  89                         int diff = strcmp(name, e[mid]->name);
  90                         if (diff==0)
  91                                 return e[mid];
  92                         else if (diff < 0)
  93                                 b=mid;
  94                         else
  95                                 a=mid+1;
  96                 }
  97                 return 0;
  98         }
  99
 100         void Read(FILE* f)
 101         {
 102                 if (numfiles || e || data)
 103                         FATAL("Calling Packfile1::Read when already initialised.");
 104
 105                 int32_t size;
 106                 fseek(f, -(int)sizeof(size), SEEK_END);
 107                 int end_offset = ftell(f);
 108                 fread(&size, sizeof(size), 1, f);
 109                 size = SWAP32(size);
 110                 fseek(f, end_offset - size, SEEK_SET);
 111
 112                 data = malloc(size);
 113                 char* data_end = (char*)data + size;
 114                 fread(data, 1, size, f);
 115
 116                 numfiles=0;
 117                 Entry* i = (Entry*)data;
 118                 while ((void*)i < data_end)
 119                 {
 120                         numfiles++;
 121                         int32_t *data_length = (int32_t*)i;
 122                         *data_length = SWAP32(*data_length);
 123                         i = i->GetNext();
 124                 }
 125
 126                 e = new Entry* [numfiles]; // CHECKME: where to delete?
 127
 128                 i = (Entry*)data;
 129                 for (int j=0; j<numfiles; j++, i = i->GetNext())
 130                         e[j] = i;
 131         }
 132
 133         ~PackFile1()
 134         {
 135                 free(data);
 136         }
 137
 138 };