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
27 access_valuetype_field (MonoObject *obj)
30 MonoClassField *field;
33 klass = mono_object_get_class (obj);
35 /* Now we'll change the value of the 'val' field (see invoke.cs) */
36 field = mono_class_get_field_from_name (klass, "val");
38 /* This time we also add a bit of error checking... */
40 fprintf (stderr, "Can't find field val in MyType\n");
43 /* Check that val is an int (if you're paranoid or if you need to
44 * show how this API is used)
46 if (mono_type_get_type (mono_field_get_type (field)) != MONO_TYPE_I4) {
47 fprintf (stderr, "Field val is not a 32 bit integer\n");
51 /* Note we pass a pointer to the value */
52 mono_field_get_value (obj, field, &val);
53 printf ("Value of field is: %d\n", val);
56 /* Note we pass a pointer to the value here as well */
57 mono_field_set_value (obj, field, &val);
62 access_reference_field (MonoObject *obj)
70 klass = mono_object_get_class (obj);
71 domain = mono_object_get_domain (obj);
73 /* Now we'll see that a reference type is handled slightly differently.
74 * First, get the MonoClassField representing it.
76 str = mono_class_get_field_from_name (klass, "str");
78 /* No change here, we always pass a pointer */
79 mono_field_get_value (obj, str, &strval);
81 /* get the string in UTF-8 encoding to print it */
82 p = mono_string_to_utf8 (strval);
83 printf ("Value of str is: %s\n", p);
84 /* we need to free the result from mono_string_to_utf8 () */
87 /* string are immutable, so we need to create a different string */
88 strval = mono_string_new (domain, "hello from the embedding API");
90 /* Here is the slight difference: for reference types we pass
91 * the pointer directly, instead of a pointer to the value.
93 mono_field_set_value (obj, str, strval);
97 /* Demostrate how to call methods */
99 call_methods (MonoObject *obj)
103 MonoMethod *method = NULL, *m = NULL, *ctor = NULL, *fail = NULL, *mvalues;
105 MonoObject *result, *exception;
112 klass = mono_object_get_class (obj);
113 domain = mono_object_get_domain (obj);
115 /* retrieve all the methods we need */
117 while ((m = mono_class_get_methods (klass, &iter))) {
118 if (strcmp (mono_method_get_name (m), "method") == 0) {
120 } else if (strcmp (mono_method_get_name (m), "Fail") == 0) {
122 } else if (strcmp (mono_method_get_name (m), "Values") == 0) {
124 } else if (strcmp (mono_method_get_name (m), ".ctor") == 0) {
125 /* Check it's the ctor that takes two args:
126 * as you see a contrsuctor is a method like any other.
128 MonoMethodSignature * sig = mono_method_signature (m);
129 if (mono_signature_get_param_count (sig) == 2) {
134 /* Now we'll call method () on obj: since it takes no arguments
135 * we can pass NULL as the third argument to mono_runtime_invoke ().
136 * The method will print the updated value.
138 mono_runtime_invoke (method, obj, NULL, NULL);
140 /* mono_object_new () doesn't call any constructor: this means that
141 * we'll have to invoke the constructor if needed ourselves. Note:
142 * invoking a constructor is no different than calling any other method,
143 * so we'll still call mono_runtime_invoke (). This also means that we
144 * can invoke a constructor at any time, like now.
145 * First, setup the array of arguments and their values.
148 /* As usual, we use the address of the data for valuetype arguments */
151 /* and the pointer for reference types: mono_array_new () returns a MonoArray* */
152 args [1] = mono_array_new (domain, mono_get_byte_class (), 256);
153 mono_runtime_invoke (ctor, obj, args, NULL);
155 /* A property exists only as a metadata entity, so getting or setting the value
156 * is nothing more than calling mono_runtime_invoke () on the getter or setter method.
158 prop = mono_class_get_property_from_name (klass, "Value");
159 method = mono_property_get_get_method (prop);
160 result = mono_runtime_invoke (method, obj, NULL, NULL);
161 /* mono_runtime_invoke () always boxes the return value if it's a valuetype */
162 val = *(int*)mono_object_unbox (result);
164 printf ("Value of val from property is: %d\n", val);
166 /* we also have an helper method: note that reference types are returned as is */
167 prop = mono_class_get_property_from_name (klass, "Message");
168 str = (MonoString*)mono_property_get_value (prop, obj, NULL, NULL);
169 /* get the string in UTF-8 encoding to print it */
170 p = mono_string_to_utf8 (str);
171 printf ("Value of str from property is: %s\n", p);
172 /* we need to free the result from mono_string_to_utf8 () */
175 /* Now we'll show two things:
176 * 1) static methods are invoked with mono_runtime_invoke () as well,
177 * we just pass NULL as the second argument.
178 * 2) we can catch exceptions thrown by the called method.
179 * Note: fail is declared as static void Fail () in invoke.cs.
180 * We first set result to NULL: if after the invocation it will have
181 * a different value, it will be the exception that was thrown from
182 * the Fail () method. Note that if an exception was thrown, the return
183 * value (if any) is undefined and can't be used in any way (yes, the above
184 * invocations don't have this type of error checking to make things simpler).
187 mono_runtime_invoke (fail, NULL, NULL, &exception);
189 printf ("An exception was thrown in Fail ()\n");
192 /* Now let's see how to handle methods that take by ref arguments:
193 * Valuetypes continue to be passed as pointers to the data.
194 * Reference arguments passed by ref (ref or out is the same)
195 * are handled the same way: a pointer to the pointer is used
196 * (so that the result can be read back).
197 * Small note: in this case (a System.Int32 valuetype) we can just
198 * use &val where val is a C 32 bit integer. In the general case
199 * unmanaged code doesn't know the size of a valuetype, since the
200 * runtime may decide to lay it out in what it thinks is a better way
201 * (unless ExplicitLayout is set). To avoid issues, the best thing is to
202 * create an object of the valuetype's class and retrieve the pointer
203 * to the data with the mono_object_unbox () function.
206 str = mono_string_new (domain, "another string");
209 mono_runtime_invoke (mvalues, obj, args, NULL);
210 /* get the string in UTF-8 encoding to print it */
211 p = mono_string_to_utf8 (str);
212 printf ("Values of str/val from Values () are: %s/%d\n", p, val);
213 /* we need to free the result from mono_string_to_utf8 () */
218 more_methods (MonoDomain *domain)
221 MonoMethodDesc* mdesc;
222 MonoMethod *method, *vtmethod;
228 /* Now let's call an instance method on a valuetype. There are two
230 * 1) calling a virtual method defined in a base class, like ToString ():
231 * we need to pass the value boxed in an object
232 * 2) calling a normal instance method: in this case
233 * we pass the address to the valuetype as the second argument
234 * instead of an object.
235 * First some initialization.
238 klass = mono_get_int32_class ();
239 obj = mono_value_box (domain, klass, &val);
241 /* A different way to search for a method */
242 mdesc = mono_method_desc_new (":ToString()", FALSE);
243 vtmethod = mono_method_desc_search_in_class (mdesc, klass);
245 str = (MonoString*)mono_runtime_invoke (vtmethod, &val, NULL, NULL);
246 /* get the string in UTF-8 encoding to print it */
247 p = mono_string_to_utf8 (str);
248 printf ("25.ToString (): %s\n", p);
249 /* we need to free the result from mono_string_to_utf8 () */
252 /* Now: see how the result is different if we search for the ToString ()
253 * method in System.Object: mono_runtime_invoke () doesn't do any sort of
254 * virtual method invocation: it calls the exact method that it was given
255 * to execute. If a virtual call is needed, mono_object_get_virtual_method ()
258 method = mono_method_desc_search_in_class (mdesc, mono_get_object_class ());
259 str = (MonoString*)mono_runtime_invoke (method, obj, NULL, NULL);
260 /* get the string in UTF-8 encoding to print it */
261 p = mono_string_to_utf8 (str);
262 printf ("25.ToString (), from System.Object: %s\n", p);
263 /* we need to free the result from mono_string_to_utf8 () */
266 /* Now get the method that overrides ToString () in obj */
267 vtmethod = mono_object_get_virtual_method (obj, method);
268 if (mono_class_is_valuetype (mono_method_get_class (vtmethod))) {
269 printf ("Need to unbox this for call to virtual ToString () for %s\n", mono_class_get_name (klass));
272 mono_method_desc_free (mdesc);
276 create_object (MonoDomain *domain, MonoImage *image)
281 klass = mono_class_from_name (image, "Embed", "MyType");
283 fprintf (stderr, "Can't find MyType in assembly %s\n", mono_image_get_filename (image));
287 obj = mono_object_new (domain, klass);
288 /* mono_object_new () only allocates the storage:
289 * it doesn't run any constructor. Tell the runtime to run
290 * the default argumentless constructor.
292 mono_runtime_object_init (obj);
294 access_valuetype_field (obj);
295 access_reference_field (obj);
298 more_methods (domain);
301 static void main_thread_handler (gpointer user_data)
303 MainThreadArgs *main_args=(MainThreadArgs *)user_data;
304 MonoAssembly *assembly;
306 /* Loading an assembly makes the runtime setup everything
307 * needed to execute it. If we're just interested in the metadata
308 * we'd use mono_image_load (), instead and we'd get a MonoImage*.
310 assembly = mono_domain_assembly_open (main_args->domain,
315 * mono_jit_exec() will run the Main() method in the assembly.
316 * The return value needs to be looked up from
317 * System.Environment.ExitCode.
319 mono_jit_exec (main_args->domain, assembly, main_args->argc,
322 create_object (main_args->domain, mono_assembly_get_image (assembly));
326 main (int argc, char* argv[]) {
330 MainThreadArgs main_args;
333 fprintf (stderr, "Please provide an assembly to load\n");
338 * mono_jit_init() creates a domain: each assembly is
339 * loaded and run in a MonoDomain.
341 domain = mono_jit_init (file);
343 main_args.domain=domain;
345 main_args.argc=argc-1;
346 main_args.argv=argv+1;
348 mono_runtime_exec_managed_code (domain, main_thread_handler,
351 retval=mono_environment_exitcode_get ();
353 mono_jit_cleanup (domain);