samples/embed/test-invoke.c

   1 #include <mono/jit/jit.h>
   2 #include <mono/metadata/object.h>
   3 #include <mono/metadata/environment.h>
   4 #include <mono/metadata/assembly.h>
   5 #include <mono/metadata/debug-helpers.h>
   6 #include <string.h>
   7 #include <stdlib.h>
   8
   9 /*
  10  * Simple mono embedding example.
  11  * We show how to create objects and invoke methods and set fields in them.
  12  * Compile with:
  13  *      gcc -Wall -o test-invoke test-invoke.c `pkg-config --cflags --libs mono` -lm
  14  *      mcs invoke.cs
  15  * Run with:
  16  *      ./test-invoke invoke.exe
  17  */
  18
  19 static void
  20 access_valuetype_field (MonoObject *obj)
  21 {
  22         MonoClass *klass;
  23         MonoClassField *field;
  24         int val;
  25
  26         klass = mono_object_get_class (obj);
  27
  28         /* Now we'll change the value of the 'val' field (see invoke.cs) */
  29         field = mono_class_get_field_from_name (klass, "val");
  30
  31         /* This time we also add a bit of error checking... */
  32         if (!field) {
  33                 fprintf (stderr, "Can't find field val in MyType\n");
  34                 exit (1);
  35         }
  36         /* Check that val is an int (if you're paranoid or if you need to
  37          * show how this API is used)
  38          */
  39         if (mono_type_get_type (mono_field_get_type (field)) != MONO_TYPE_I4) {
  40                 fprintf (stderr, "Field val is not a 32 bit integer\n");
  41                 exit (1);
  42         }
  43
  44         /* Note we pass a pointer to the value */
  45         mono_field_get_value (obj, field, &val);
  46         printf ("Value of field is: %d\n", val);
  47         val = 10;
  48
  49         /* Note we pass a pointer to the value here as well */
  50         mono_field_set_value (obj, field, &val);
  51
  52 }
  53
  54 static void
  55 access_reference_field (MonoObject *obj)
  56 {
  57         MonoClass *klass;
  58         MonoDomain *domain;
  59         MonoClassField *str;
  60         MonoString *strval;
  61         char *p;
  62
  63         klass = mono_object_get_class (obj);
  64         domain = mono_object_get_domain (obj);
  65
  66         /* Now we'll see that a reference type is handled slightly differently.
  67          * First, get the MonoClassField representing it.
  68          */
  69         str = mono_class_get_field_from_name (klass, "str");
  70
  71         /* No change here, we always pass a pointer */
  72         mono_field_get_value (obj, str, &strval);
  73
  74         /* get the string in UTF-8 encoding to print it */
  75         p = mono_string_to_utf8 (strval);
  76         printf ("Value of str is: %s\n", p);
  77         /* we need to free the result from mono_string_to_utf8 () */
  78         g_free (p);
  79
  80         /* string are immutable, so we need to create a different string */
  81         strval = mono_string_new (domain, "hello from the embedding API");
  82
  83         /* Here is the slight difference: for reference types we pass
  84          * the pointer directly, instead of a pointer to the value.
  85          */
  86         mono_field_set_value (obj, str, strval);
  87
  88 }
  89
  90 /* Demostrate how to call methods */
  91 static void
  92 call_methods (MonoObject *obj)
  93 {
  94         MonoClass *klass;
  95         MonoDomain *domain;
  96         MonoMethod *method = NULL, *m = NULL, *ctor = NULL, *fail = NULL, *mvalues;
  97         MonoProperty *prop;
  98         MonoObject *result, *exception;
  99         MonoString *str;
 100         char *p;
 101         gpointer iter;
 102         gpointer args [2];
 103         int val;
 104
 105         klass = mono_object_get_class (obj);
 106         domain = mono_object_get_domain (obj);
 107
 108         /* retrieve all the methods we need */
 109         iter = NULL;
 110         while ((m = mono_class_get_methods (klass, &iter))) {
 111                 if (strcmp (mono_method_get_name (m), "method") == 0) {
 112                         method = m;
 113                 } else if (strcmp (mono_method_get_name (m), "Fail") == 0) {
 114                         fail = m;
 115                 } else if (strcmp (mono_method_get_name (m), "Values") == 0) {
 116                         mvalues = m;
 117                 } else if (strcmp (mono_method_get_name (m), ".ctor") == 0) {
 118                         /* Check it's the ctor that takes two args:
 119                          * as you see a contrsuctor is a method like any other.
 120                          */
 121                         MonoMethodSignature * sig = mono_method_signature (m);
 122                         if (mono_signature_get_param_count (sig) == 2) {
 123                                 ctor = m;
 124                         }
 125                 }
 126         }
 127         /* Now we'll call method () on obj: since it takes no arguments
 128          * we can pass NULL as the third argument to mono_runtime_invoke ().
 129          * The method will print the updated value.
 130          */
 131         mono_runtime_invoke (method, obj, NULL, NULL);
 132
 133         /* mono_object_new () doesn't call any constructor: this means that
 134          * we'll have to invoke the constructor if needed ourselves. Note:
 135          * invoking a constructor is no different than calling any other method,
 136          * so we'll still call mono_runtime_invoke (). This also means that we
 137          * can invoke a constructor at any time, like now.
 138          * First, setup the array of arguments and their values.
 139          */
 140
 141         /* As usual, we use the address of the data for valuetype arguments */
 142         val = 7;
 143         args [0] = &val;
 144         /* and the pointer for reference types: mono_array_new () returns a MonoArray* */
 145         args [1] = mono_array_new (domain, mono_get_byte_class (), 256);
 146         mono_runtime_invoke (ctor, obj, args, NULL);
 147
 148         /* A property exists only as a metadata entity, so getting or setting the value
 149          * is nothing more than calling mono_runtime_invoke () on the getter or setter method.
 150          */
 151         prop = mono_class_get_property_from_name (klass, "Value");
 152         method = mono_property_get_get_method (prop);
 153         result = mono_runtime_invoke (method, obj, NULL, NULL);
 154         /* mono_runtime_invoke () always boxes the return value if it's a valuetype */
 155         val = *(int*)mono_object_unbox (result);
 156
 157         printf ("Value of val from property is: %d\n", val);
 158
 159         /* we also have an helper method: note that reference types are returned as is */
 160         prop = mono_class_get_property_from_name (klass, "Message");
 161         str = (MonoString*)mono_property_get_value (prop, obj, NULL, NULL);
 162         /* get the string in UTF-8 encoding to print it */
 163         p = mono_string_to_utf8 (str);
 164         printf ("Value of str from property is: %s\n", p);
 165         /* we need to free the result from mono_string_to_utf8 () */
 166         g_free (p);
 167
 168         /* Now we'll show two things:
 169          * 1) static methods are invoked with mono_runtime_invoke () as well,
 170          * we just pass NULL as the second argument.
 171          * 2) we can catch exceptions thrown by the called method.
 172          * Note: fail is declared as static void Fail () in invoke.cs.
 173          * We first set result to NULL: if after the invocation it will have
 174          * a different value, it will be the exception that was thrown from
 175          * the Fail () method. Note that if an exception was thrown, the return
 176          * value (if any) is undefined and can't be used in any way (yes, the above
 177          * invocations don't have this type of error checking to make things simpler).
 178          */
 179         exception = NULL;
 180         mono_runtime_invoke (fail, NULL, NULL, &exception);
 181         if (exception) {
 182                 printf ("An exception was thrown in Fail ()\n");
 183         }
 184
 185         /* Now let's see how to handle methods that take by ref arguments:
 186          * Valuetypes continue to be passed as pointers to the data.
 187          * Reference arguments passed by ref (ref or out is the same)
 188          * are handled the same way: a pointer to the pointer is used
 189          * (so that the result can be read back).
 190          * Small note: in this case (a System.Int32 valuetype) we can just
 191          * use &val where val is a C 32 bit integer. In the general case
 192          * unmanaged code doesn't know the size of a valuetype, since the
 193          * runtime may decide to lay it out in what it thinks is a better way
 194          * (unless ExplicitLayout is set). To avoid issues, the best thing is to
 195          * create an object of the valuetype's class and retrieve the pointer
 196          * to the data with the mono_object_unbox () function.
 197          */
 198         val = 100;
 199         str = mono_string_new (domain, "another string");
 200         args [0] = &val;
 201         args [1] = &str;
 202         mono_runtime_invoke (mvalues, obj, args, NULL);
 203         /* get the string in UTF-8 encoding to print it */
 204         p = mono_string_to_utf8 (str);
 205         printf ("Values of str/val from Values () are: %s/%d\n", p, val);
 206         /* we need to free the result from mono_string_to_utf8 () */
 207         g_free (p);
 208 }
 209
 210 static void
 211 more_methods (MonoDomain *domain)
 212 {
 213         MonoClass *klass;
 214         MonoMethodDesc* mdesc;
 215         MonoMethod *method, *vtmethod;
 216         MonoString *str;
 217         MonoObject *obj;
 218         char *p;
 219         int val;
 220
 221         /* Now let's call an instance method on a valuetype. There are two
 222          * different case:
 223          * 1) calling a virtual method defined in a base class, like ToString ():
 224          * we need to pass the value boxed in an object
 225          * 2) calling a normal instance method: in this case
 226          * we pass the address to the valuetype as the second argument
 227          * instead of an object.
 228          * First some initialization.
 229          */
 230         val = 25;
 231         klass = mono_get_int32_class ();
 232         obj = mono_value_box (domain, klass, &val);
 233
 234         /* A different way to search for a method */
 235         mdesc = mono_method_desc_new (":ToString()", FALSE);
 236         vtmethod = mono_method_desc_search_in_class (mdesc, klass);
 237
 238         str = (MonoString*)mono_runtime_invoke (vtmethod, &val, NULL, NULL);
 239         /* get the string in UTF-8 encoding to print it */
 240         p = mono_string_to_utf8 (str);
 241         printf ("25.ToString (): %s\n", p);
 242         /* we need to free the result from mono_string_to_utf8 () */
 243         g_free (p);
 244
 245         /* Now: see how the result is different if we search for the ToString ()
 246          * method in System.Object: mono_runtime_invoke () doesn't do any sort of
 247          * virtual method invocation: it calls the exact method that it was given
 248          * to execute. If a virtual call is needed, mono_object_get_virtual_method ()
 249          * can be called.
 250          */
 251         method = mono_method_desc_search_in_class (mdesc, mono_get_object_class ());
 252         str = (MonoString*)mono_runtime_invoke (method, obj, NULL, NULL);
 253         /* get the string in UTF-8 encoding to print it */
 254         p = mono_string_to_utf8 (str);
 255         printf ("25.ToString (), from System.Object: %s\n", p);
 256         /* we need to free the result from mono_string_to_utf8 () */
 257         g_free (p);
 258
 259         /* Now get the method that overrides ToString () in obj */
 260         vtmethod = mono_object_get_virtual_method (obj, method);
 261         if (mono_class_is_valuetype (mono_method_get_class (vtmethod))) {
 262                 printf ("Need to unbox this for call to virtual ToString () for %s\n", mono_class_get_name (klass));
 263         }
 264
 265         mono_method_desc_free (mdesc);
 266 }
 267
 268 static void
 269 create_object (MonoDomain *domain, MonoImage *image)
 270 {
 271         MonoClass *klass;
 272         MonoObject *obj;
 273
 274         klass = mono_class_from_name (image, "Embed", "MyType");
 275         if (!klass) {
 276                 fprintf (stderr, "Can't find MyType in assembly %s\n", mono_image_get_filename (image));
 277                 exit (1);
 278         }
 279
 280         obj = mono_object_new (domain, klass);
 281         /* mono_object_new () only allocates the storage:
 282          * it doesn't run any constructor. Tell the runtime to run
 283          * the default argumentless constructor.
 284          */
 285         mono_runtime_object_init (obj);
 286
 287         access_valuetype_field (obj);
 288         access_reference_field (obj);
 289
 290         call_methods (obj);
 291         more_methods (domain);
 292 }
 293
 294 static void main_function (MonoDomain *domain, const char *file, int argc, char **argv)
 295 {
 296         MonoAssembly *assembly;
 297
 298         /* Loading an assembly makes the runtime setup everything
 299          * needed to execute it. If we're just interested in the metadata
 300          * we'd use mono_image_load (), instead and we'd get a MonoImage*.
 301          */
 302         assembly = mono_domain_assembly_open (domain, file);
 303         if (!assembly)
 304                 exit (2);
 305         /*
 306          * mono_jit_exec() will run the Main() method in the assembly.
 307          * The return value needs to be looked up from
 308          * System.Environment.ExitCode.
 309          */
 310         mono_jit_exec (domain, assembly, argc, argv);
 311
 312         create_object (domain, mono_assembly_get_image (assembly));
 313 }
 314
 315 int
 316 main (int argc, char* argv[]) {
 317         MonoDomain *domain;
 318         const char *file;
 319         int retval;
 320
 321         if (argc < 2){
 322                 fprintf (stderr, "Please provide an assembly to load\n");
 323                 return 1;
 324         }
 325         file = argv [1];
 326         /*
 327          * mono_jit_init() creates a domain: each assembly is
 328          * loaded and run in a MonoDomain.
 329          */
 330         domain = mono_jit_init (file);
 331
 332         main_function (domain, file, argc - 1, argv + 1);
 333
 334         retval = mono_environment_exitcode_get ();
 335
 336         mono_jit_cleanup (domain);
 337         return retval;
 338 }
 339