Feature/add who am i and you are services (#1024)

* Added Who-Am-I-Request encoding, decoding, unit tests, and command line application bacwhoami.

* Added You-Are-Request encoding, decoding, unit tests, and command line application bacyouare.

* Added Who-Am-I with Who-Is and You-Are handling into the example server application when run as device 4194303.

src/bacnet/whoami.c

@@ -0,0 +1,153 @@
+/**
+ * @file
+ * @brief Encode/Decode Who-Am-I requests
+ * @author Steve Karg <skarg@users.sourceforge.net>
+ * @date June 2025
+ * @copyright SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0
+ */
+#include <stdint.h>
+/* BACnet Stack defines - first */
+#include "bacnet/bacdef.h"
+/* BACnet Stack API */
+#include "bacnet/bacdcode.h"
+#include "bacnet/whoami.h"
+
+/**
+ * @brief Encode a Who-Am-I-Request APDU
+ *
+ *  Who-Am-I-Request ::= SEQUENCE {
+ *      vendor-id Unsigned16,
+ *      model-name CharacterString,
+ *      serial-number CharacterString
+ *  }
+ *
+ * @param apdu [out] Buffer in which the APDU contents are built, or NULL for
+ *  length determination
+ * @param vendor_id the identity of the vendor of the device initiating
+ *  the Who-Am-I service request.
+ * @param model_name the model name of the device initiating the Who-Am-I
+ *  service request.
+ * @param serial_number the serial identifier of the device initiating
+ *  the Who-Am-I service request.
+ * @return The length of the apdu encoded
+ */
+int who_am_i_request_encode(
+    uint8_t *apdu,
+    uint16_t vendor_id,
+    const BACNET_CHARACTER_STRING *model_name,
+    const BACNET_CHARACTER_STRING *serial_number)
+{
+    int len = 0;
+    int apdu_len = 0;
+
+    len = encode_application_unsigned(apdu, vendor_id);
+    apdu_len += len;
+    if (apdu) {
+        apdu += len;
+    }
+    len = encode_application_character_string(apdu, model_name);
+    apdu_len += len;
+    if (apdu) {
+        apdu += len;
+    }
+    len = encode_application_character_string(apdu, serial_number);
+    apdu_len += len;
+
+    return apdu_len;
+}
+
+/**
+ * @brief Encode a Who-Am-I-Request unconfirmed service APDU
+ * @param apdu [out] Buffer in which the APDU contents are built, or NULL for
+ *  length determination
+ * @param vendor_id the identity of the vendor of the device initiating
+ *  the Who-Am-I service request.
+ * @param model_name the model name of the device initiating the Who-Am-I
+ *  service request.
+ * @param serial_number the serial identifier of the device initiating
+ *  the Who-Am-I service request.
+ * @return The length of the apdu encoded
+ */
+int who_am_i_request_service_encode(
+    uint8_t *apdu,
+    uint16_t vendor_id,
+    const BACNET_CHARACTER_STRING *model_name,
+    const BACNET_CHARACTER_STRING *serial_number)
+{
+    int len = 0; /* length of each encoding */
+    int apdu_len = 0; /* total length of the apdu, return value */
+
+    if (apdu) {
+        apdu[0] = PDU_TYPE_UNCONFIRMED_SERVICE_REQUEST;
+        apdu[1] = SERVICE_UNCONFIRMED_WHO_AM_I; /* service choice */
+    }
+    len = 2;
+    apdu_len += len;
+    if (apdu) {
+        apdu += len;
+    }
+    len = who_am_i_request_encode(apdu, vendor_id, model_name, serial_number);
+    apdu_len += len;
+
+    return apdu_len;
+}
+
+/**
+ * @brief Decode a Who-Is-Request APDU
+ * @param apdu [in] Buffer containing the APDU
+ * @param apdu_size [in] The length of the APDU
+ * @param vendor_id the identity of the vendor of the device initiating
+ *  the Who-Am-I service request.
+ * @param model_name the model name of the device initiating the Who-Am-I
+ *  service request.
+ * @param serial_number the serial identifier of the device initiating
+ *  the Who-Am-I service request.
+ * @return The number of bytes decoded , or #BACNET_STATUS_ERROR on error
+ */
+int who_am_i_request_decode(
+    const uint8_t *apdu,
+    size_t apdu_size,
+    uint16_t *vendor_id,
+    BACNET_CHARACTER_STRING *model_name,
+    BACNET_CHARACTER_STRING *serial_number)
+{
+    int len = 0, apdu_len = 0;
+    BACNET_UNSIGNED_INTEGER unsigned_value = 0;
+
+    if (!apdu) {
+        return BACNET_STATUS_ERROR;
+    }
+    if (apdu_size == 0) {
+        return BACNET_STATUS_ERROR;
+    }
+    len = bacnet_unsigned_application_decode(
+        &apdu[apdu_len], apdu_size - apdu_len, &unsigned_value);
+    if (len > 0) {
+        if (unsigned_value <= UINT16_MAX) {
+            if (vendor_id) {
+                *vendor_id = (uint16_t)unsigned_value;
+            }
+        } else {
+            return BACNET_STATUS_ERROR;
+        }
+    } else {
+        return BACNET_STATUS_ERROR;
+    }
+    apdu_len += len;
+    len = bacnet_character_string_application_decode(
+        &apdu[apdu_len], apdu_size - apdu_len, model_name);
+    if (len > 0) {
+        apdu_len += len;
+    } else {
+        return BACNET_STATUS_ERROR;
+    }
+    len = bacnet_character_string_application_decode(
+        &apdu[apdu_len], apdu_size - apdu_len, serial_number);
+    if (len > 0) {
+        apdu_len += len;
+    } else {
+        return BACNET_STATUS_ERROR;
+    }
+
+    return apdu_len;
+}