Imported Upstream version 0.79.2

rs02-recognize.c

@@ -0,0 +1,175 @@
+/*  dvdisaster: Additional error correction for optical media.
+ *  Copyright (C) 2004-2010 Carsten Gnoerlich.
+ *  Project home page: http://www.dvdisaster.com
+ *  Email: carsten@dvdisaster.com  -or-  cgnoerlich@fsfe.org
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA,
+ *  or direct your browser at http://www.gnu.org.
+ */
+
+#include "dvdisaster.h"
+
+#include "rs02-includes.h"
+
+/***
+ *** Recognize RS02 error correction data in the image
+ ***/
+
+/*
+ * Search for ecc headers in RS02 style image files.
+ * Note that udf.c has a similar function FindHeaderInMedium().
+ */
+
+static int read_fingerprint(LargeFile *file, unsigned char *fingerprint, gint64 sector)
+{  struct MD5Context md5ctxt;
+   unsigned char buf[2048];
+   int n;
+
+   if(!LargeSeek(file, 2048LL*sector))
+     return FALSE;
+
+   n = LargeRead(file, buf, 2048);
+
+   if(n != 2048) return FALSE;
+
+   if(CheckForMissingSector(buf, sector, NULL, 0) != SECTOR_PRESENT)
+     return FALSE;
+
+   MD5Init(&md5ctxt);
+   MD5Update(&md5ctxt, buf, 2048);
+   MD5Final(fingerprint, &md5ctxt);
+
+   return TRUE;
+}
+
+EccHeader* FindRS02HeaderInImage(LargeFile *file)
+{  EccHeader *eh = NULL;
+   unsigned char buf[4096];
+   gint64 sectors,pos;
+   gint64 header_modulo;
+   gint64 last_fp = -1;
+   unsigned char fingerprint[16];
+
+   header_modulo = (gint64)1<<62;
+   sectors = file->size / 2048;
+
+   /*** Search for the headers */
+
+   while(header_modulo >= 32)
+   {  pos = sectors & ~(header_modulo - 1);
+
+//printf("Trying modulo %lld\n", header_modulo);
+
+      while(pos > 0)
+      {  if(LargeSeek(file, 2048*pos))
+	 {  int n;
+
+//printf(" trying sector %lld\n", pos);
+	    n = LargeRead(file, buf, sizeof(EccHeader));
+
+	    if(n != sizeof(EccHeader))
+	      goto check_next_header;
+
+	    eh = (EccHeader*)buf;
+
+	    /* Medium read error in ecc header? */
+
+	    if(   (CheckForMissingSector(buf, pos, NULL, 0) != SECTOR_PRESENT)
+	       || (CheckForMissingSector(buf+2048, pos+1, NULL, 0) != SECTOR_PRESENT))
+	    {  
+//printf(" header at %lld: read error\n", (long long int)pos);
+	       goto check_next_header;
+	    }
+
+	    /* See if the magic cookie is there */
+
+	    if(   !strncmp((char*)eh->cookie, "*dvdisaster*", 12)
+	       && !strncmp((char*)eh->method, "RS02", 4))
+	    {  guint32 recorded_crc = eh->selfCRC;
+	       guint32 real_crc;
+
+//printf(" header at %lld: magic cookie found\n", (long long int)pos);
+
+#ifdef HAVE_BIG_ENDIAN
+	       eh->selfCRC = 0x47504c00;
+#else
+	       eh->selfCRC = 0x4c5047;
+#endif
+	       real_crc = Crc32((unsigned char*)eh, sizeof(EccHeader));
+
+	       if(real_crc == recorded_crc)
+	       {  eh = g_malloc(sizeof(EccHeader));
+		  memcpy(eh, buf, sizeof(EccHeader));
+#ifdef HAVE_BIG_ENDIAN
+		  SwapEccHeaderBytes(eh);
+#endif
+		  eh->selfCRC = recorded_crc;
+//printf(" --> CRC okay, using it\n");
+
+		  if(last_fp != eh->fpSector)
+		  {  int status;
+
+		     status = read_fingerprint(file, fingerprint, eh->fpSector);
+		     last_fp = eh->fpSector;
+
+		     if(!status)  /* be optimistic if fingerprint sector is unreadable */
+		     {  return eh;
+		     }
+		  }
+
+		  if(!memcmp(fingerprint, eh->mediumFP, 16))  /* good fingerprint */
+		  {  return eh;
+		  }
+
+		  /* might be a header from a larger previous session.
+		     discard it and continue */
+
+		  g_free(eh);
+	       }
+//printf(" CRC failed, skipping it\n");
+	       goto check_next_header;
+	    }
+	    else
+	    {
+//printf(" no cookie, skipping current modulo\n");
+	      goto check_next_modulo;
+	    }
+	 }
+
+      check_next_header:
+	pos -= header_modulo;
+      }
+
+   check_next_modulo:
+      header_modulo >>= 1;
+   }
+
+   return NULL;
+}
+
+
+
+int RS02Recognize(Method *self, LargeFile *ecc_file)
+{  EccHeader *eh;
+
+   eh = FindRS02HeaderInImage(ecc_file); 
+  
+   if(!eh) return FALSE;
+
+   if(self->lastEh) g_free(self->lastEh);
+   self->lastEh = eh;
+
+   return TRUE;
+}