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diff --git a/src/service/messenger/gnunet-service-messenger_message_store.h b/src/service/messenger/gnunet-service-messenger_message_store.h
new file mode 100644
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--- /dev/null
+++ b/src/service/messenger/gnunet-service-messenger_message_store.h
@@ -0,0 +1,168 @@
+/*
+   This file is part of GNUnet.
+   Copyright (C) 2020--2021 GNUnet e.V.
+
+   GNUnet is free software: you can redistribute it and/or modify it
+   under the terms of the GNU Affero General Public License as published
+   by the Free Software Foundation, either version 3 of the License,
+   or (at your option) any later version.
+
+   GNUnet 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
+   Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+   SPDX-License-Identifier: AGPL3.0-or-later
+ */
+/**
+ * @author Tobias Frisch
+ * @file src/messenger/gnunet-service-messenger_message_store.h
+ * @brief GNUnet MESSENGER service
+ */
+
+#ifndef GNUNET_SERVICE_MESSENGER_MESSAGE_STORE_H
+#define GNUNET_SERVICE_MESSENGER_MESSAGE_STORE_H
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+
+struct GNUNET_MESSENGER_MessageEntry
+{
+  off_t offset;
+  uint16_t length;
+};
+
+struct GNUNET_MESSENGER_Message;
+
+struct GNUNET_MESSENGER_MessageLink
+{
+  uint8_t multiple;
+
+  struct GNUNET_HashCode first;
+  struct GNUNET_HashCode second;
+};
+
+struct GNUNET_MESSENGER_MessageStore
+{
+  struct GNUNET_DISK_FileHandle *storage_messages;
+
+  struct GNUNET_CONTAINER_MultiHashMap *entries;
+  struct GNUNET_CONTAINER_MultiHashMap *messages;
+  struct GNUNET_CONTAINER_MultiHashMap *links;
+
+  int rewrite_entries;
+  int write_links;
+};
+
+/**
+ * Initializes a message <i>store</i> as fully empty.
+ *
+ * @param[out] store Message store
+ */
+void
+init_message_store (struct GNUNET_MESSENGER_MessageStore *store);
+
+/**
+ * Clears a message <i>store</i>, wipes its content and deallocates its memory.
+ *
+ * @param[in,out] store Message store
+ */
+void
+clear_message_store (struct GNUNET_MESSENGER_MessageStore *store);
+
+/**
+ * Loads messages from a <i>directory</i> into a message <i>store</i>.
+ *
+ * @param[out] store Message store
+ * @param[in] directory Path to a directory
+ */
+void
+load_message_store (struct GNUNET_MESSENGER_MessageStore *store,
+                    const char *directory);
+
+/**
+ * Saves messages from a message <i>store</i> into a <i>directory</i>.
+ *
+ * @param[in] store Message store
+ * @param[in] directory Path to a directory
+ */
+void
+save_message_store (struct GNUNET_MESSENGER_MessageStore *store,
+                    const char *directory);
+
+/**
+ * Checks if a message matching a given <i>hash</i> is stored in a message <i>store</i>.
+ * The function returns #GNUNET_YES if a match is found, #GNUNET_NO otherwise.
+ *
+ * The message has not to be loaded from disk into memory for this check!
+ *
+ * @param[in] store Message store
+ * @param[in] hash Hash of message
+ * @return #GNUNET_YES on match, otherwise #GNUNET_NO
+ */
+int
+contains_store_message (const struct GNUNET_MESSENGER_MessageStore *store,
+                        const struct GNUNET_HashCode *hash);
+
+/**
+ * Returns the message from a message <i>store</i> matching a given <i>hash</i>. If no matching
+ * message is found, NULL gets returned.
+ *
+ * This function requires the message to be loaded into memory!
+ * @see contains_store_message()
+ *
+ * @param[in,out] store Message store
+ * @param[in] hash Hash of message
+ * @return Message or NULL
+ */
+const struct GNUNET_MESSENGER_Message*
+get_store_message (struct GNUNET_MESSENGER_MessageStore *store,
+                   const struct GNUNET_HashCode *hash);
+
+/**
+ * Returns the message link from a message <i>store</i> matching a given <i>hash</i>. If the
+ * flag is set to #GNUNET_YES, only links from deleted messages will be returned or NULL.
+ *
+ * Otherwise message links will also returned for messages found in the store under the given
+ * hash. The link which will be returned copies link information from the message for
+ * temporary usage.
+ *
+ * @param[in,out] store Message store
+ * @param[in] hash Hash of message
+ * @param[in] deleted_only Flag
+ * @return Message link or NULL
+ */
+const struct GNUNET_MESSENGER_MessageLink*
+get_store_message_link (struct GNUNET_MESSENGER_MessageStore *store,
+                        const struct GNUNET_HashCode *hash,
+                        int deleted_only);
+
+/**
+ * Stores a message into the message store. The result indicates if the operation was successful.
+ *
+ * @param[in,out] store Message store
+ * @param[in] hash Hash of message
+ * @param[in,out] message Message
+ * @return #GNUNET_OK on success, otherwise #GNUNET_NO
+ */
+int
+put_store_message (struct GNUNET_MESSENGER_MessageStore *store,
+                   const struct GNUNET_HashCode *hash,
+                   struct GNUNET_MESSENGER_Message *message);
+
+/**
+ * Deletes a message in the message store. It will be removed from disk space and memory. The result
+ * indicates if the operation was successful.
+ *
+ * @param[in,out] store Message store
+ * @param[in] hash Hash of message
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+ */
+int
+delete_store_message (struct GNUNET_MESSENGER_MessageStore *store,
+                      const struct GNUNET_HashCode *hash);
+
+#endif //GNUNET_SERVICE_MESSENGER_MESSAGE_STORE_H