From 00b4f875b0ef4fc0e1c685f1839a45545164ce03 Mon Sep 17 00:00:00 2001
From: Matthias Ringwald <matthias@ringwald.ch>
Date: Fri, 14 Mar 2025 12:37:01 +0100
Subject: [PATCH] att_db: add gatt_server_get_database_hash

---
 src/ble/att_db.c | 23 +++++++++++++++++++++++
 src/ble/att_db.h |  8 ++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/ble/att_db.c b/src/ble/att_db.c
index ae85bbc3f..6c34814f8 100644
--- a/src/ble/att_db.c
+++ b/src/ble/att_db.c
@@ -42,6 +42,7 @@
 #include "ble/att_db.h"
 #include "ble/core.h"
 #include "bluetooth.h"
+#include "bluetooth_gatt.h"
 #include "btstack_debug.h"
 #include "btstack_util.h"
 
@@ -1644,6 +1645,28 @@ bool gatt_server_get_included_service_with_uuid16(uint16_t start_handle, uint16_
     return false;
 }
 
+bool gatt_server_get_database_hash(uint8_t * hash) {
+    att_iterator_t it;
+    att_iterator_init(&it);
+    uint16_t value_handle = 0xffff;
+    while (att_iterator_has_next(&it)){
+        att_iterator_fetch_next(&it);
+        // Find Characteristic declaration for Database Hash
+        if ((it.value_len == 5u) && (att_iterator_match_uuid16(&it, GATT_CHARACTERISTICS_UUID))){
+            uint16_t characteristic_uuid = little_endian_read_16(it.value, 3);
+            if (characteristic_uuid == ORG_BLUETOOTH_CHARACTERISTIC_DATABASE_HASH){
+                value_handle = little_endian_read_16(it.value, 1);
+            }
+        }
+        // Find Characteristic Value for Database Hash and get value
+        if ((it.handle == value_handle) && (it.value_len == 16u)){
+            att_copy_value(&it, 0, hash, 16, HCI_CON_HANDLE_INVALID);
+            return true;
+        }
+    }
+    return false;
+}
+
 // 1-item cache to optimize query during write_callback
 static void att_persistent_ccc_cache(att_iterator_t * it){
     att_persistent_ccc_handle = it->handle;
diff --git a/src/ble/att_db.h b/src/ble/att_db.h
index fa6d1545d..a96ab0241 100644
--- a/src/ble/att_db.h
+++ b/src/ble/att_db.h
@@ -420,6 +420,14 @@ uint16_t gatt_server_get_value_handle_for_characteristic_with_uuid128(uint16_t s
  */
 uint16_t gatt_server_get_client_configuration_handle_for_characteristic_with_uuid128(uint16_t start_handle, uint16_t end_handle, const uint8_t * uuid128);
 
+/**
+ * @brief Get Database Hash provided via GATT Database Hash characteristic
+ * @note Used by att_server to discard stored CCCD values for bonded devices if hash has changed
+ * @param hash
+ * @return true if hash is available
+ */
+bool gatt_server_get_database_hash(uint8_t * hash);
+
 /* API_END */
 
 // non-user functionality for att_server