diff --git a/libisoburn/isofs_wrap.c b/libisoburn/isofs_wrap.c
index d51cdc4e..d9c51fbd 100644
--- a/libisoburn/isofs_wrap.c
+++ b/libisoburn/isofs_wrap.c
@@ -9,6 +9,16 @@
   Copyright 2007 Vreixo Formoso Lopes <metalpain2002@yahoo.es>
 */
 
+#include <stdlib.h>
+#include <string.h>
+
+#include "../libisofs/libisofs.h"
+#include "../libburn/libburn.h"
+#include "isoburn.h"
+
+// TODO this are libisofs internals, should then be imported here?
+#include "../libisofs/util.h"
+#include "../libisofs/ecma119.h"
 
 /* Vreixo:
 
@@ -25,11 +35,21 @@
 
 /* API function. See libisoburn.h
 */
-int isoburn_update_iso_descriptors(struct burn_drive *drive)
+int isoburn_activate_session(struct burn_drive *drive)
 {
+ int ret;
+ struct isoburn *o;
 
- /* >>>  code <<< */
+ ret = isoburn_find_emulator(&o, drive, 0);
+ if (ret < 0)
+   return -1;
 
+ if (o->emulation_mode != 1)
+   return 1; /* don't need to activate session */
+ 
+ ret = burn_random_access_write(drive, 0, o->target_iso_head, 64*2048, 0);
+
+ return ret;
 }
 
 
@@ -40,9 +60,26 @@ int isoburn_update_iso_descriptors(struct burn_drive *drive)
 */
 int isoburn_new_rwopts(struct isoburn *o)
 {
+ struct ecma119_source_opts *wopts;
 
  /* >>>  code <<< */
+ /* create and initialize target_ropts read options */
+ o->target_ropts = calloc(1, sizeof(struct ecma119_read_opts));
+ if (!p->target_ropts)
+   return -1;
 
+ /* TODO mmm, maybe we don't need struct ecma119_read_opts in libisoburn */
+
+ /* create and initialize new_wopts write options for new image */
+ wopts = calloc(1, sizeof(struct ecma119_source_opts));
+ if (!wopts)
+   return -1;
+
+ wopts->overwrite = o->target_iso_head;
+
+ o->new_wopts = wopts;
+
+ return 1;
 }
 
 
@@ -53,9 +90,9 @@ int isoburn_new_rwopts(struct isoburn *o)
 */
 int isoburn_free_rwopts(struct isoburn *o)
 {
-
- /* >>>  code <<< */
-
+ free(o->target_ropts);
+ free(o->new_wopts);
+ return 1;
 }
 
 
@@ -67,12 +104,60 @@ int isoburn_free_rwopts(struct isoburn *o)
 */
 int isoburn_start_emulation(struct isoburn *o, int flag)
 {
+ int ret;
+ off_t *data_count;
+ struct burn_drive *drive;
+ struct ecma119_pri_vol_desc *pvm;
 
- /* >>> code <<< */
+ drive= o->drive;
 
+ /* we can assume 0 as start block for image */
+ // TODO what about ms? where we validate valid iso image in ms disc?
+ ret = burn_read_data(drive, (off_t) 0, o->target_iso_head, 
+                      sizeof(o->target_iso_head), &data_count, 0);
+ if (ret <= 0)
+   return -1;
+
+ pvm = (struct ecma119_pri_vol_desc *)(o->target_iso_head + 16 * 2048);
+
+ /* sanity check */
+ if (pvm->vol_desc_type[0] != 1 || pvm->vol_desc_version[0] != 1 
+     || pvm->file_structure_version[0] != 1 ) {
+   // TODO unsupported image type, maybe not image or damaged image
+   // should this be an error?
+   return -2;
+ }
+
+ if (!strncmp((char*)pvm->std_identifier, "CD001", 5)) {
+   off_t size;
+
+   /* ok, PVM found, set size */
+   size = (off_t) iso_read_lsb(pvm->vol_space_size, 4);
+   size *= (off_t) 2048; /* block size in bytes */
+
+   // TODO where I get the struct burn_write_opts * from?
+   // why that function doesn't receive a struct isoburn
+   isoburn_write_opts_set_start_byte(XXXXXX, size);
+ } else if (!strncmp((char*)pvm->std_identifier, "CDXX1", 5)) {
+
+   /* empty image */
+   // TODO where I get the struct burn_write_opts * from?
+   // why that function doesn't receive a struct isoburn
+   isoburn_write_opts_set_start_byte(XXXXXX, (off_t) 0);
+ } else {
+   // TODO not valid iso image
+   // should this be an error?
+   return -2;
+ }
+ 
+ return 1;
 }
 
-
+// TODO why read is needed? can't I assume 64k are already cached?
+// TODO can I assume isoburn_start_emulation was already called and
+// disc contains a valid image?
+// TODO why "The result shall especially keep libisofs from accepting the 
+//           media image as ISO filesystem"?
 /** Reads, alters and writes the first 64 kB of a "media" to invalidate
     an ISO image. (It shall stay restorable by skilled humans, though).
     The result shall especially keep libisofs from accepting the media
@@ -83,9 +168,11 @@ int isoburn_start_emulation(struct isoburn *o, int flag)
 */
 int isoburn_invalidate_iso(struct isoburn *o, int flag)
 {
-
- /* >>>  code <<< */
-
+ /* 
+  * replace CD001 with CDXX1 in PVM.
+  * I think this is enought for invalidating an iso image
+  */
+ strncpy(o->target_iso_head + 16 * 2048 + 1, "CDXX1", 5);
+ return isoburn_activate_session(o->drive);
 }
 
-