lib: Create API to read a GATT characteristic

2 files changed, 90 insertions, 1 deletions

diff --git a/lib/ble.c b/lib/ble.c
index a9e50ad..0a4530d 100644
--- a/lib/ble.c
+++ b/lib/ble.c
@@ -528,6 +528,62 @@ int ble_gatt_discover_descriptors(int conn_id, int char_id) {
     return 0;
 }
 
+/* Called when a GATT read characteristic operation returns */
+void read_characteristic_cb(int conn_id, int status,
+                            btgatt_read_params_t *p_data) {
+    ble_device_t *dev;
+    int id = -1;
+
+    dev = find_device_by_conn_id(conn_id);
+    if (dev)
+        id = find_characteristic(dev, &p_data->srvc_id, &p_data->char_id);
+
+    if (data.cbs.char_read_cb)
+        data.cbs.char_read_cb(conn_id, id, p_data->value.value,
+                              p_data->value.len, p_data->value_type, status);
+}
+
+static int ble_gatt_op(int operation, int conn_id, int id, int auth) {
+    ble_device_t *dev;
+    bt_status_t s = BT_STATUS_UNSUPPORTED;
+
+    if (id < 0)
+        return -1;
+
+    if (conn_id <= 0)
+        return -1;
+
+    if (!data.gattiface)
+        return -1;
+
+    dev = find_device_by_conn_id(conn_id);
+    if (!dev)
+        return -1;
+
+    switch (operation) {
+        case 0: /* Read characteristic */
+            if (dev->char_count <= 0)
+                return -1;
+            if (id >= dev->char_count)
+                return -1;
+
+            s = data.gattiface->client->read_characteristic(conn_id,
+	                                                    &dev->chars[id].s,
+	                                                    &dev->chars[id].c,
+                                                            auth);
+            break;
+    }
+
+    if (s != BT_STATUS_SUCCESS)
+        return -s;
+
+    return 0;
+}
+
+int ble_gatt_read_char(int conn_id, int char_id, int auth) {
+    return ble_gatt_op(0, conn_id, char_id, auth);
+}
+
 /* Called when the client registration is finished */
 static void register_client_cb(int status, int client_if, bt_uuid_t *app_uuid) {
     if (status == BT_STATUS_SUCCESS) {
@@ -551,7 +607,7 @@ static const btgatt_client_callbacks_t gattccbs = {
     NULL, /* get_included_service_cb */
     NULL, /* register_for_notification_cb */
     NULL, /* notify_cb */
-    NULL, /* read_characteristic_cb */
+    read_characteristic_cb,
     NULL, /* write_characteristic_cb */
     NULL, /* read_descriptor_cb */
     NULL, /* write_descriptor_cb */
diff --git a/lib/ble.h b/lib/ble.h
index 5c5c3a9..d963630 100644
--- a/lib/ble.h
+++ b/lib/ble.h
@@ -130,6 +130,23 @@ typedef void (*ble_gatt_found_cb_t)(int conn_id, int id, const uint8_t *uuid,
 typedef void (*ble_gatt_finished_cb_t)(int conn_id, int status);
 
 /**
+ * Type that represents a callback function to forward a GATT operation
+ * response.
+ *
+ * @param conn_id The identifier of the connected remote device.
+ * @param id ID of the GATT element that the operation was executed uppon.
+ * @param value The value in the operation response.
+ * @param value_len The length of the data pointed by the value parameter.
+ * @param value_type The type of the data pointed by the value parameter.
+ * @param status The status in which the operation has finished.
+ *
+ * TODO: Document the semantics of value_type
+ */
+typedef void (*ble_gatt_response_cb_t)(int conn_id, int id,
+                                       const uint8_t *value, uint16_t value_len,
+                                       uint16_t value_type, int status);
+
+/**
  * List of callbacks for BLE operations.
  */
 typedef struct ble_cbs {
@@ -145,6 +162,7 @@ typedef struct ble_cbs {
     ble_gatt_finished_cb_t char_finished_cb;
     ble_gatt_found_cb_t desc_found_cb;
     ble_gatt_finished_cb_t desc_finished_cb;
+    ble_gatt_response_cb_t char_read_cb;
 } ble_cbs_t;
 
 /**
@@ -291,4 +309,19 @@ int ble_gatt_discover_characteristics(int conn_id, int service_id);
  * @return -1 if failed to request descriptor discovery.
  */
 int ble_gatt_discover_descriptors(int conn_id, int char_id);
+
+/**
+ * Read the value of a characteristic.
+ *
+ * There should be an active connection with the device.
+ *
+ * @param conn_id The identifier of the connected remote device.
+ * @param char_id The identifier of the characteristic to be read.
+ * @param auth Whether or not link authentication should be requested before
+ *             trying to read the characteristic: 1 request, 0 do not request.
+ *
+ * @return 0 if characteristic read has been successfully requested.
+ * @return -1 if failed to request characteristic read.
+ */
+int ble_gatt_read_char(int conn_id, int char_id, int auth);
 #endif