Einfaches mbed RPC Beispiel

Dependencies:   EthernetInterface HttpServer mbed-rtos mbed

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Remote Procedure Call (RPC - „Aufruf einer fernen Prozedur“) ist eine Technik zur Realisierung von Interprozesskommunikation. Sie ermöglicht den Aufruf von Funktionen in anderen Adressräumen. Im Normalfall werden die aufgerufenen Funktionen auf einem anderen Computer als das aufrufende Programm ausgeführt. Es existieren viele Implementierungen dieser Technik, in der Regel sind sie untereinander nicht kompatibel

Die mbed Plattform beinhaltet eine RPC Library, welche ausgesuchte mbed Objekte (DigitalPin, DigitalOut etc.) mittels Serieller Schnittstelle oder via HTTP Aufrufen, zur Verfügung stellt.

Die mbed RCP Klassen verwenden C++ Templates, siehe Zeilen mit <Argument> und den Namespace RPC, siehe Zeilen mit RPC::.

Client

Revision:
11:43e28c85fd75
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-rpc/rpc.cpp	Wed Apr 08 12:31:41 2015 +0000
@@ -0,0 +1,191 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "rpc.h"
+
+using namespace std;
+
+namespace mbed {
+
+RPC::RPC(const char *name) {
+    _from_construct = false;
+    if (name != NULL) {
+        _name = new char[strlen(name) + 1];
+        strcpy(_name, name);
+    } else {
+        _name = new char[12];
+        sprintf(_name, "obj%p", this);
+    }
+    // put this object at head of the list
+    _next = _head;
+    _head = this;
+}
+
+RPC::~RPC() {
+    // remove this object from the list
+    if (_head == this) { // first in the list, so just drop me
+        _head = _next;
+    } else {            // find the object before me, then drop me
+        RPC* p = _head;
+        while (p->_next != this) {
+            p = p->_next;
+        }
+        p->_next = _next;
+    }
+}
+
+const rpc_method *RPC::get_rpc_methods() {
+    static const rpc_method methods[] = {
+        {"delete", rpc_method_caller<RPC, &RPC::delete_self> },
+        RPC_METHOD_END
+    };
+    return methods;
+}
+
+RPC *RPC::lookup(const char *name) {
+    size_t len = strlen(name);
+    for (RPC *p = _head; p != NULL; p = p->_next) {
+        /* Check that p->_name matches name and is the correct length */
+        if (strncmp(p->_name, name, len) == 0 && (strlen(p->_name) == len)) {
+            return p;
+        }
+    }
+    return NULL;
+}
+
+void RPC::delete_self() {
+    delete[] _name;
+    if (_from_construct) {
+        delete this;
+    }
+}
+
+void RPC::list_objs(Arguments *args, Reply *result) {
+    for (RPC *ptr = RPC::_head; ptr != NULL; ptr = ptr->_next) {
+        if (ptr->_from_construct) {
+            result->putData<const char*>(ptr->_name);
+        }
+    }
+}
+
+void RPC::clear(Arguments*, Reply*) {
+    RPC *ptr = RPC::_head;
+    while (ptr != NULL) {
+        RPC *tmp = ptr;
+        ptr = ptr->_next;
+        delete[] tmp->_name;
+        if (tmp->_from_construct) {
+            delete tmp;
+        }
+    }
+}
+
+const rpc_function RPC::_RPC_funcs[] = {
+    {"clear", &RPC::clear },
+    { "objects", &RPC::list_objs },
+    RPC_METHOD_END
+};
+
+rpc_class RPC::_RPC_class = { "RPC", _RPC_funcs, NULL };
+
+RPC *RPC::_head = NULL;
+
+rpc_class *RPC::_classes = &_RPC_class;
+
+bool RPC::call(const char *request, char *reply) {
+    if (request == NULL) return false;
+
+    Arguments args(request);
+    Reply r(reply);
+
+    /* If there's no name print object and class names to result */
+    if (args.obj_name == NULL) {
+        for (RPC *p = RPC::_head; p != NULL; p = p->_next) {
+            r.putData<const char*>(p->_name);
+        }
+        for (rpc_class *c = RPC::_classes; c != NULL; c = c->next) {
+            r.putData<const char*>(c->name);
+        }
+        return true;
+    }
+
+    /* First try matching an instance */
+    RPC *p = lookup(args.obj_name);
+    if (p != NULL) {
+        /* Get the list of methods we support */
+        const rpc_method *cur_method = p->get_rpc_methods();
+
+        /* When there's no method print method names to result */
+        if (args.method_name == NULL) {
+            while (true) {
+                for (; cur_method->name != NULL; cur_method++) {
+                    r.putData<const char*>(cur_method->name);
+                }
+
+                /* write_name_arr's args are references, so result and cur_method will have changed */
+                if (cur_method->super != 0) {
+                    cur_method = cur_method->super(p);
+                } else {
+                    return true;
+                }
+            }
+        }
+
+        /* Look through the methods for the one whose name matches */
+        while (true) {
+            for (; cur_method->name != NULL; cur_method++) {
+                if (strcmp(cur_method->name, args.method_name) == 0) {
+                    (cur_method->method_caller)(p, &args, &r);
+                    return true;
+                }
+            }
+
+            if (cur_method->super != 0) {
+                cur_method = cur_method->super(p);
+            } else {
+                /* end of methods and no match */
+                return false;
+            }
+
+        }
+    }
+
+    /* Then try a class */
+    for (const rpc_class *q = _classes; q != NULL; q = q->next) {
+        if (strcmp(q->name, args.obj_name) == 0) {
+            /* Matched the class name, so get its functions */
+            const rpc_function *cur_func = q->static_functions;
+            if (args.method_name == NULL) {
+                for (; cur_func->name != NULL; cur_func++) {
+                    r.putData<const char*>(cur_func->name);
+                }
+                return true;
+            } else {
+                /* Otherwise call the appropriate function */
+                for (; cur_func->name != NULL; cur_func++) {
+                    if (strcmp(cur_func->name, args.method_name) == 0) {
+                        (cur_func->function_caller)(&args, &r);
+                        return true;
+                    }
+                }
+                return false;
+            }
+        }
+    }
+
+    return false;
+}
+
+} // namespace mbed