gpg: Improve the keyblock cache's transparency.

* kbx/keybox-search.c (keybox_seek): New function.
* g10/keydb.c (keydb_search): When reading from the cache, seek to
just after the cached record.

--
Signed-off-by: Neal H. Walfield <neal@g10code.com>

g10/keydb.c

@@ -1717,6 +1717,12 @@ keydb_search (KEYDB_HANDLE hd, KEYDB_SEARCH_DESC *desc,
       /* (DESCINDEX is already set).  */
       if (DBG_CLOCK)
         log_clock ("keydb_search leave (cached)");
+
+      hd->current = hd->keyblock_cache.resource;
+      /* HD->KEYBLOCK_CACHE.OFFSET is the last byte in the record.
+         Seek just beyond that.  */
+      keybox_seek (hd->active[hd->current].u.kb,
+                   hd->keyblock_cache.offset + 1);
       return 0;
     }
 

kbx/keybox-search.c

@@ -1196,3 +1196,32 @@ keybox_offset (KEYBOX_HANDLE hd)
     return 0;
   return ftello (hd->fp);
 }
+
+gpg_error_t
+keybox_seek (KEYBOX_HANDLE hd, off_t offset)
+{
+  int err;
+
+  if (hd->error)
+    return hd->error; /* still in error state */
+
+  if (! hd->fp)
+    {
+      if (offset == 0)
+        /* No need to open the file.  An unopened file is effectively at
+           offset 0.  */
+        return 0;
+
+      hd->fp = fopen (hd->kb->fname, "rb");
+      if (!hd->fp)
+        {
+          hd->error = gpg_error_from_syserror ();
+          return hd->error;
+        }
+    }
+
+  err = fseeko (hd->fp, offset, SEEK_SET);
+  hd->error = gpg_error_from_errno (err);
+
+  return hd->error;
+}

kbx/keybox.h

@@ -77,8 +77,6 @@ int keybox_set_ephemeral (KEYBOX_HANDLE hd, int yes);
 
 int keybox_lock (KEYBOX_HANDLE hd, int yes);
 
-off_t keybox_offset (KEYBOX_HANDLE hd);
-
 /*-- keybox-file.c --*/
 /* Fixme: This function does not belong here: Provide a better
    interface to create a new keybox file.  */
@@ -97,6 +95,8 @@ int keybox_search (KEYBOX_HANDLE hd, KEYBOX_SEARCH_DESC *desc, size_t ndesc,
                    keybox_blobtype_t want_blobtype,
                    size_t *r_descindex, unsigned long *r_skipped);
 
+off_t keybox_offset (KEYBOX_HANDLE hd);
+gpg_error_t keybox_seek (KEYBOX_HANDLE hd, off_t offset);
 
 /*-- keybox-update.c --*/
 gpg_error_t keybox_insert_keyblock (KEYBOX_HANDLE hd,