1 #include <mono/jit/jit.h>
2 #include <mono/metadata/environment.h>
3 #include <mono/metadata/assembly.h>
4 #include <mono/metadata/debug-helpers.h>
9 * Simple mono embedding example.
10 * We show how to create objects and invoke methods and set fields in them.
12 * gcc -Wall -o test-invoke test-invoke.c `pkg-config --cflags --libs mono` -lm
15 * ./test-invoke invoke.exe
19 access_valuetype_field (MonoObject *obj)
22 MonoClassField *field;
25 klass = mono_object_get_class (obj);
27 /* Now we'll change the value of the 'val' field (see invoke.cs) */
28 field = mono_class_get_field_from_name (klass, "val");
30 /* This time we also add a bit of error checking... */
32 fprintf (stderr, "Can't find field val in MyType\n");
35 /* Check that val is an int (if you're paranoid or if you need to
36 * show how this API is used)
38 if (mono_type_get_type (mono_field_get_type (field)) != MONO_TYPE_I4) {
39 fprintf (stderr, "Field val is not a 32 bit integer\n");
43 /* Note we pass a pointer to the value */
44 mono_field_get_value (obj, field, &val);
45 printf ("Value of field is: %d\n", val);
48 /* Note we pass a pointer to the value here as well */
49 mono_field_set_value (obj, field, &val);
54 access_reference_field (MonoObject *obj)
62 klass = mono_object_get_class (obj);
63 domain = mono_object_get_domain (obj);
65 /* Now we'll see that a reference type is handled slightly differently.
66 * First, get the MonoClassField representing it.
68 str = mono_class_get_field_from_name (klass, "str");
70 /* No change here, we always pass a pointer */
71 mono_field_get_value (obj, str, &strval);
73 /* get the string in UTF-8 encoding to print it */
74 p = mono_string_to_utf8 (strval);
75 printf ("Value of str is: %s\n", p);
76 /* we need to free the result from mono_string_to_utf8 () */
79 /* string are immutable, so we need to create a different string */
80 strval = mono_string_new (domain, "hello from the embedding API");
82 /* Here is the slight difference: for reference types we pass
83 * the pointer directly, instead of a pointer to the value.
85 mono_field_set_value (obj, str, strval);
89 /* Demostrate how to call methods */
91 call_methods (MonoObject *obj)
95 MonoMethod *method = NULL, *m = NULL, *ctor = NULL, *fail = NULL, *mvalues;
97 MonoObject *result, *exception;
104 klass = mono_object_get_class (obj);
105 domain = mono_object_get_domain (obj);
107 /* retrieve all the methods we need */
109 while ((m = mono_class_get_methods (klass, &iter))) {
110 if (strcmp (mono_method_get_name (m), "method") == 0) {
112 } else if (strcmp (mono_method_get_name (m), "Fail") == 0) {
114 } else if (strcmp (mono_method_get_name (m), "Values") == 0) {
116 } else if (strcmp (mono_method_get_name (m), ".ctor") == 0) {
117 /* Check it's the ctor that takes two args:
118 * as you see a contrsuctor is a method like any other.
120 MonoMethodSignature * sig = mono_method_signature (m);
121 if (mono_signature_get_param_count (sig) == 2) {
126 /* Now we'll call method () on obj: since it takes no arguments
127 * we can pass NULL as the third argument to mono_runtime_invoke ().
128 * The method will print the updated value.
130 mono_runtime_invoke (method, obj, NULL, NULL);
132 /* mono_object_new () doesn't call any constructor: this means that
133 * we'll have to invoke the constructor if needed ourselves. Note:
134 * invoking a constructor is no different than calling any other method,
135 * so we'll still call mono_runtime_invoke (). This also means that we
136 * can invoke a constructor at any time, like now.
137 * First, setup the array of arguments and their values.
140 /* As usual, we use the address of the data for valuetype arguments */
143 /* and the pointer for reference types: mono_array_new () returns a MonoArray* */
144 args [1] = mono_array_new (domain, mono_get_byte_class (), 256);
145 mono_runtime_invoke (ctor, obj, args, NULL);
147 /* A property exists only as a metadata entity, so getting or setting the value
148 * is nothing more than calling mono_runtime_invoke () on the getter or setter method.
150 prop = mono_class_get_property_from_name (klass, "Value");
151 method = mono_property_get_get_method (prop);
152 result = mono_runtime_invoke (method, obj, NULL, NULL);
153 /* mono_runtime_invoke () always boxes the return value if it's a valuetype */
154 val = *(int*)mono_object_unbox (result);
156 printf ("Value of val from property is: %d\n", val);
158 /* we also have an helper method: note that reference types are returned as is */
159 prop = mono_class_get_property_from_name (klass, "Message");
160 str = (MonoString*)mono_property_get_value (prop, obj, NULL, NULL);
161 /* get the string in UTF-8 encoding to print it */
162 p = mono_string_to_utf8 (str);
163 printf ("Value of str from property is: %s\n", p);
164 /* we need to free the result from mono_string_to_utf8 () */
167 /* Now we'll show two things:
168 * 1) static methods are invoked with mono_runtime_invoke () as well,
169 * we just pass NULL as the second argument.
170 * 2) we can catch exceptions thrown by the called method.
171 * Note: fail is declared as static void Fail () in invoke.cs.
172 * We first set result to NULL: if after the invocation it will have
173 * a different value, it will be the exception that was thrown from
174 * the Fail () method. Note that if an exception was thrown, the return
175 * value (if any) is undefined and can't be used in any way (yes, the above
176 * invocations don't have this type of error checking to make things simpler).
179 mono_runtime_invoke (fail, NULL, NULL, &exception);
181 printf ("An exception was thrown in Fail ()\n");
184 /* Now let's see how to handle methods that take by ref arguments:
185 * Valuetypes continue to be passed as pointers to the data.
186 * Reference arguments passed by ref (ref or out is the same)
187 * are handled the same way: a pointer to the pointer is used
188 * (so that the result can be read back).
189 * Small note: in this case (a System.Int32 valuetype) we can just
190 * use &val where val is a C 32 bit integer. In the general case
191 * unmanaged code doesn't know the size of a valuetype, since the
192 * runtime may decide to lay it out in what it thinks is a better way
193 * (unless ExplicitLayout is set). To avoid issues, the best thing is to
194 * create an object of the valuetype's class and retrieve the pointer
195 * to the data with the mono_object_unbox () function.
198 str = mono_string_new (domain, "another string");
201 mono_runtime_invoke (mvalues, obj, args, NULL);
202 /* get the string in UTF-8 encoding to print it */
203 p = mono_string_to_utf8 (str);
204 printf ("Values of str/val from Values () are: %s/%d\n", p, val);
205 /* we need to free the result from mono_string_to_utf8 () */
210 more_methods (MonoDomain *domain)
213 MonoMethodDesc* mdesc;
214 MonoMethod *method, *vtmethod;
220 /* Now let's call an instance method on a valuetype. There are two
222 * 1) calling a virtual method defined in a base class, like ToString ():
223 * we need to pass the value boxed in an object
224 * 2) calling a normal instance method: in this case
225 * we pass the address to the valuetype as the second argument
226 * instead of an object.
227 * First some initialization.
230 klass = mono_get_int32_class ();
231 obj = mono_value_box (domain, klass, &val);
233 /* A different way to search for a method */
234 mdesc = mono_method_desc_new (":ToString()", FALSE);
235 vtmethod = mono_method_desc_search_in_class (mdesc, klass);
237 str = (MonoString*)mono_runtime_invoke (vtmethod, &val, NULL, NULL);
238 /* get the string in UTF-8 encoding to print it */
239 p = mono_string_to_utf8 (str);
240 printf ("25.ToString (): %s\n", p);
241 /* we need to free the result from mono_string_to_utf8 () */
244 /* Now: see how the result is different if we search for the ToString ()
245 * method in System.Object: mono_runtime_invoke () doesn't do any sort of
246 * virtual method invocation: it calls the exact method that it was given
247 * to execute. If a virtual call is needed, mono_object_get_virtual_method ()
250 method = mono_method_desc_search_in_class (mdesc, mono_get_object_class ());
251 str = (MonoString*)mono_runtime_invoke (method, obj, NULL, NULL);
252 /* get the string in UTF-8 encoding to print it */
253 p = mono_string_to_utf8 (str);
254 printf ("25.ToString (), from System.Object: %s\n", p);
255 /* we need to free the result from mono_string_to_utf8 () */
258 /* Now get the method that overrides ToString () in obj */
259 vtmethod = mono_object_get_virtual_method (obj, method);
260 if (mono_class_is_valuetype (mono_method_get_class (vtmethod))) {
261 printf ("Need to unbox this for call to virtual ToString () for %s\n", mono_class_get_name (klass));
264 mono_method_desc_free (mdesc);
268 create_object (MonoDomain *domain, MonoImage *image)
273 klass = mono_class_from_name (image, "Embed", "MyType");
275 fprintf (stderr, "Can't find MyType in assembly %s\n", mono_image_get_filename (image));
279 obj = mono_object_new (domain, klass);
280 /* mono_object_new () only allocates the storage:
281 * it doesn't run any constructor. Tell the runtime to run
282 * the default argumentless constructor.
284 mono_runtime_object_init (obj);
286 access_valuetype_field (obj);
287 access_reference_field (obj);
290 more_methods (domain);
293 static void main_function (MonoDomain *domain, const char *file, int argc, char **argv)
295 MonoAssembly *assembly;
297 /* Loading an assembly makes the runtime setup everything
298 * needed to execute it. If we're just interested in the metadata
299 * we'd use mono_image_load (), instead and we'd get a MonoImage*.
301 assembly = mono_domain_assembly_open (domain, file);
305 * mono_jit_exec() will run the Main() method in the assembly.
306 * The return value needs to be looked up from
307 * System.Environment.ExitCode.
309 mono_jit_exec (domain, assembly, argc, argv);
311 create_object (domain, mono_assembly_get_image (assembly));
315 main (int argc, char* argv[]) {
321 fprintf (stderr, "Please provide an assembly to load\n");
326 * mono_jit_init() creates a domain: each assembly is
327 * loaded and run in a MonoDomain.
329 domain = mono_jit_init (file);
331 main_function (domain, file, argc - 1, argv + 1);
333 retval = mono_environment_exitcode_get ();
335 mono_jit_cleanup (domain);