Keep on hacking on g13. A simple --create and --mount does now work.

A hacked up encfs is required.

g13/utils.c

@@ -28,6 +28,17 @@
 #include "utils.h"
 
 
+/* Definition of the tuple descriptor object.  */
+struct tupledesc_s
+{
+  unsigned char *data; /* The tuple data.  */
+  size_t datalen;      /* The length of the data.  */
+  size_t pos;          /* The current position as used by next_tuple.  */
+  int refcount;        /* Number of references hold. */
+};
+
+
+
 /* Append the TAG and the VALUE to the MEMBUF.  There is no error
    checking here; this is instead done while getting the value back
    from the membuf. */
@@ -49,3 +60,121 @@ append_tuple (membuf_t *membuf, int tag, const void *value, size_t length)
     put_membuf (membuf, value, length);
 }
 
+
+/* Create a tuple object by moving the ownership of (DATA,DATALEN) to
+   a new object.  Returns 0 on success and stores the new object at
+   R_TUPLEHD.  The return object must be released using
+   destroy_tuples().  */
+gpg_error_t
+create_tupledesc (tupledesc_t *r_desc, void *data, size_t datalen)
+{
+  if (datalen < 5 || memcmp (data, "\x00\x00\x00\x01\x01", 5))
+    return gpg_error (GPG_ERR_NOT_SUPPORTED);
+
+  *r_desc = xtrymalloc (sizeof **r_desc);
+  if (!*r_desc)
+    return gpg_error_from_syserror ();
+  (*r_desc)->data = data;
+  (*r_desc)->datalen = datalen;
+  (*r_desc)->pos = 0;
+  (*r_desc)->refcount++;
+  return 0;
+}
+
+/* Unref a tuple descriptor and if the refcount is down to 0 release
+   its allocated storage.  */
+void
+destroy_tupledesc (tupledesc_t tupledesc)
+{
+  if (!tupledesc)
+    return;
+  
+  if (!--tupledesc->refcount)
+    {
+      xfree (tupledesc->data);
+      xfree (tupledesc);
+    }
+}
+
+
+tupledesc_t
+ref_tupledesc (tupledesc_t tupledesc)
+{
+  if (tupledesc)
+    tupledesc->refcount++;
+  return tupledesc;
+}
+
+
+/* Find the first tuple with tag TAG.  On success return a pointer to
+   its value and store the length of the value at R_LENGTH.  If no
+   tuple was return NULL.  For future use by next_tupe, the last
+   position is stored in the descriptor.  */
+const void *
+find_tuple (tupledesc_t tupledesc, unsigned int tag, size_t *r_length)
+{
+  const unsigned char *s;
+  const unsigned char *s_end; /* Points right behind the data. */
+  unsigned int t;
+  size_t n;
+
+  s = tupledesc->data;
+  if (!s)
+    return NULL;
+  s_end = s + tupledesc->datalen;
+  while (s < s_end)
+    {
+      if (s+3 >= s_end || s + 3 < s)
+        break;
+      t  = s[0] << 8;
+      t |= s[1];
+      n  = s[2] << 8;
+      n |= s[3];
+      s += 4;
+      if (s + n > s_end || s + n < s)
+        break;
+      if (t == tag)
+        {
+          tupledesc->pos = (s + n) - tupledesc->data;
+          *r_length = n;
+          return s;
+        }
+      s += n;
+    }
+  return NULL;
+}
+
+
+const void *
+next_tuple (tupledesc_t tupledesc, unsigned int *r_tag, size_t *r_length)
+{
+  const unsigned char *s;
+  const unsigned char *s_end; /* Points right behind the data.  */
+  unsigned int t;
+  size_t n;
+
+  s = tupledesc->data;
+  if (!s)
+    return NULL;
+  s_end = s + tupledesc->datalen;
+  s += tupledesc->pos;
+  if (s < s_end
+      && !(s+3 >= s_end || s + 3 < s))
+    {
+      t  = s[0] << 8;
+      t |= s[1];
+      n  = s[2] << 8;
+      n |= s[3];
+      s += 4;
+      if (!(s + n > s_end || s + n < s))
+        {
+          tupledesc->pos = (s + n) - tupledesc->data;
+          *r_tag = t;
+          *r_length = n;
+          return s;
+        }
+    }
+  
+  return NULL;
+}            
+