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 #include <glib.h>
   9
  10 /*
  11  * Simple mono embedding example.
  12  * We show how to create objects and invoke methods and set fields in them.
  13  * Compile with:
  14  *      gcc -Wall -o test-invoke test-invoke.c `pkg-config --cflags --libs mono-2` -lm
  15  *      mcs invoke.cs
  16  * Run with:
  17  *      ./test-invoke invoke.exe
  18  */
  19
  20 static void
  21 access_valuetype_field (MonoObject *obj)
  22 {
  23         MonoClass *klass;
  24         MonoClassField *field;
  25         int val;
  26
  27         klass = mono_object_get_class (obj);
  28
  29         /* Now we'll change the value of the 'val' field (see invoke.cs) */
  30         field = mono_class_get_field_from_name (klass, "val");
  31
  32         /* This time we also add a bit of error checking... */
  33         if (!field) {
  34                 fprintf (stderr, "Can't find field val in MyType\n");
  35                 exit (1);
  36         }
  37         /* Check that val is an int (if you're paranoid or if you need to
  38          * show how this API is used)
  39          */
  40         if (mono_type_get_type (mono_field_get_type (field)) != MONO_TYPE_I4) {
  41                 fprintf (stderr, "Field val is not a 32 bit integer\n");
  42                 exit (1);
  43         }
  44
  45         /* Note we pass a pointer to the value */
  46         mono_field_get_value (obj, field, &val);
  47         printf ("Value of field is: %d\n", val);
  48         val = 10;
  49
  50         /* Note we pass a pointer to the value here as well */
  51         mono_field_set_value (obj, field, &val);
  52
  53 }
  54
  55 static void
  56 access_reference_field (MonoObject *obj)
  57 {
  58         MonoClass *klass;
  59         MonoDomain *domain;
  60         MonoClassField *str;
  61         MonoString *strval;
  62         char *p;
  63
  64         klass = mono_object_get_class (obj);
  65         domain = mono_object_get_domain (obj);
  66
  67         /* Now we'll see that a reference type is handled slightly differently.
  68          * First, get the MonoClassField representing it.
  69          */
  70         str = mono_class_get_field_from_name (klass, "str");
  71
  72         /* No change here, we always pass a pointer */
  73         mono_field_get_value (obj, str, &strval);
  74
  75         /* get the string in UTF-8 encoding to print it */
  76         p = mono_string_to_utf8 (strval);
  77         printf ("Value of str is: %s\n", p);
  78         /* we need to free the result from mono_string_to_utf8 () */
  79         g_free (p);
  80
  81         /* string are immutable, so we need to create a different string */
  82         strval = mono_string_new (domain, "hello from the embedding API");
  83
  84         /* Here is the slight difference: for reference types we pass
  85          * the pointer directly, instead of a pointer to the value.
  86          */
  87         mono_field_set_value (obj, str, strval);
  88
  89 }
  90
  91 /* Demostrate how to call methods */
  92 static void
  93 call_methods (MonoObject *obj)
  94 {
  95         MonoClass *klass;
  96         MonoDomain *domain;
  97         MonoMethod *method = NULL, *m = NULL, *ctor = NULL, *fail = NULL, *mvalues;
  98         MonoProperty *prop;
  99         MonoObject *result, *exception;
 100         MonoString *str;
 101         char *p;
 102         gpointer iter;
 103         gpointer args [2];
 104         int val;
 105
 106         klass = mono_object_get_class (obj);
 107         domain = mono_object_get_domain (obj);
 108
 109         /* retrieve all the methods we need */
 110         iter = NULL;
 111         while ((m = mono_class_get_methods (klass, &iter))) {
 112                 if (strcmp (mono_method_get_name (m), "method") == 0) {
 113                         method = m;
 114                 } else if (strcmp (mono_method_get_name (m), "Fail") == 0) {
 115                         fail = m;
 116                 } else if (strcmp (mono_method_get_name (m), "Values") == 0) {
 117                         mvalues = m;
 118                 } else if (strcmp (mono_method_get_name (m), ".ctor") == 0) {
 119                         /* Check it's the ctor that takes two args:
 120                          * as you see a contrsuctor is a method like any other.
 121                          */
 122                         MonoMethodSignature * sig = mono_method_signature (m);
 123                         if (mono_signature_get_param_count (sig) == 2) {
 124                                 ctor = m;
 125                         }
 126                 }
 127         }
 128         /* Now we'll call method () on obj: since it takes no arguments
 129          * we can pass NULL as the third argument to mono_runtime_invoke ().
 130          * The method will print the updated value.
 131          */
 132         mono_runtime_invoke (method, obj, NULL, NULL);
 133
 134         /* mono_object_new () doesn't call any constructor: this means that
 135          * we'll have to invoke the constructor if needed ourselves. Note:
 136          * invoking a constructor is no different than calling any other method,
 137          * so we'll still call mono_runtime_invoke (). This also means that we
 138          * can invoke a constructor at any time, like now.
 139          * First, setup the array of arguments and their values.
 140          */
 141
 142         /* As usual, we use the address of the data for valuetype arguments */
 143         val = 7;
 144         args [0] = &val;
 145         /* and the pointer for reference types: mono_array_new () returns a MonoArray* */
 146         args [1] = mono_array_new (domain, mono_get_byte_class (), 256);
 147         mono_runtime_invoke (ctor, obj, args, NULL);
 148
 149         /* A property exists only as a metadata entity, so getting or setting the value
 150          * is nothing more than calling mono_runtime_invoke () on the getter or setter method.
 151          */
 152         prop = mono_class_get_property_from_name (klass, "Value");
 153         method = mono_property_get_get_method (prop);
 154         result = mono_runtime_invoke (method, obj, NULL, NULL);
 155         /* mono_runtime_invoke () always boxes the return value if it's a valuetype */
 156         val = *(int*)mono_object_unbox (result);
 157
 158         printf ("Value of val from property is: %d\n", val);
 159
 160         /* we also have an helper method: note that reference types are returned as is */
 161         prop = mono_class_get_property_from_name (klass, "Message");
 162         str = (MonoString*)mono_property_get_value (prop, obj, NULL, NULL);
 163         /* get the string in UTF-8 encoding to print it */
 164         p = mono_string_to_utf8 (str);
 165         printf ("Value of str from property is: %s\n", p);
 166         /* we need to free the result from mono_string_to_utf8 () */
 167         g_free (p);
 168
 169         /* Now we'll show two things:
 170          * 1) static methods are invoked with mono_runtime_invoke () as well,
 171          * we just pass NULL as the second argument.
 172          * 2) we can catch exceptions thrown by the called method.
 173          * Note: fail is declared as static void Fail () in invoke.cs.
 174          * We first set result to NULL: if after the invocation it will have
 175          * a different value, it will be the exception that was thrown from
 176          * the Fail () method. Note that if an exception was thrown, the return
 177          * value (if any) is undefined and can't be used in any way (yes, the above
 178          * invocations don't have this type of error checking to make things simpler).
 179          */
 180         exception = NULL;
 181         mono_runtime_invoke (fail, NULL, NULL, &exception);
 182         if (exception) {
 183                 printf ("An exception was thrown in Fail ()\n");
 184         }
 185
 186         /* Now let's see how to handle methods that take by ref arguments:
 187          * Valuetypes continue to be passed as pointers to the data.
 188          * Reference arguments passed by ref (ref or out is the same)
 189          * are handled the same way: a pointer to the pointer is used
 190          * (so that the result can be read back).
 191          * Small note: in this case (a System.Int32 valuetype) we can just
 192          * use &val where val is a C 32 bit integer. In the general case
 193          * unmanaged code doesn't know the size of a valuetype, since the
 194          * runtime may decide to lay it out in what it thinks is a better way
 195          * (unless ExplicitLayout is set). To avoid issues, the best thing is to
 196          * create an object of the valuetype's class and retrieve the pointer
 197          * to the data with the mono_object_unbox () function.
 198          */
 199         val = 100;
 200         str = mono_string_new (domain, "another string");
 201         args [0] = &val;
 202         args [1] = &str;
 203         mono_runtime_invoke (mvalues, obj, args, NULL);
 204         /* get the string in UTF-8 encoding to print it */
 205         p = mono_string_to_utf8 (str);
 206         printf ("Values of str/val from Values () are: %s/%d\n", p, val);
 207         /* we need to free the result from mono_string_to_utf8 () */
 208         g_free (p);
 209 }
 210
 211 static void
 212 more_methods (MonoDomain *domain)
 213 {
 214         MonoClass *klass;
 215         MonoMethodDesc* mdesc;
 216         MonoMethod *method, *vtmethod;
 217         MonoString *str;
 218         MonoObject *obj;
 219         char *p;
 220         int val;
 221
 222         /* Now let's call an instance method on a valuetype. There are two
 223          * different case:
 224          * 1) calling a virtual method defined in a base class, like ToString ():
 225          * we need to pass the value boxed in an object
 226          * 2) calling a normal instance method: in this case
 227          * we pass the address to the valuetype as the second argument
 228          * instead of an object.
 229          * First some initialization.
 230          */
 231         val = 25;
 232         klass = mono_get_int32_class ();
 233         obj = mono_value_box (domain, klass, &val);
 234
 235         /* A different way to search for a method */
 236         mdesc = mono_method_desc_new (":ToString()", FALSE);
 237         vtmethod = mono_method_desc_search_in_class (mdesc, klass);
 238
 239         str = (MonoString*)mono_runtime_invoke (vtmethod, &val, NULL, NULL);
 240         /* get the string in UTF-8 encoding to print it */
 241         p = mono_string_to_utf8 (str);
 242         printf ("25.ToString (): %s\n", p);
 243         /* we need to free the result from mono_string_to_utf8 () */
 244         g_free (p);
 245
 246         /* Now: see how the result is different if we search for the ToString ()
 247          * method in System.Object: mono_runtime_invoke () doesn't do any sort of
 248          * virtual method invocation: it calls the exact method that it was given
 249          * to execute. If a virtual call is needed, mono_object_get_virtual_method ()
 250          * can be called.
 251          */
 252         method = mono_method_desc_search_in_class (mdesc, mono_get_object_class ());
 253         str = (MonoString*)mono_runtime_invoke (method, obj, NULL, NULL);
 254         /* get the string in UTF-8 encoding to print it */
 255         p = mono_string_to_utf8 (str);
 256         printf ("25.ToString (), from System.Object: %s\n", p);
 257         /* we need to free the result from mono_string_to_utf8 () */
 258         g_free (p);
 259
 260         /* Now get the method that overrides ToString () in obj */
 261         vtmethod = mono_object_get_virtual_method (obj, method);
 262         if (mono_class_is_valuetype (mono_method_get_class (vtmethod))) {
 263                 printf ("Need to unbox this for call to virtual ToString () for %s\n", mono_class_get_name (klass));
 264         }
 265
 266         mono_method_desc_free (mdesc);
 267 }
 268
 269 static void
 270 create_object (MonoDomain *domain, MonoImage *image)
 271 {
 272         MonoClass *klass;
 273         MonoObject *obj;
 274
 275         klass = mono_class_from_name (image, "Embed", "MyType");
 276         if (!klass) {
 277                 fprintf (stderr, "Can't find MyType in assembly %s\n", mono_image_get_filename (image));
 278                 exit (1);
 279         }
 280
 281         obj = mono_object_new (domain, klass);
 282         /* mono_object_new () only allocates the storage:
 283          * it doesn't run any constructor. Tell the runtime to run
 284          * the default argumentless constructor.
 285          */
 286         mono_runtime_object_init (obj);
 287
 288         access_valuetype_field (obj);
 289         access_reference_field (obj);
 290
 291         call_methods (obj);
 292         more_methods (domain);
 293 }
 294
 295 static void main_function (MonoDomain *domain, const char *file, int argc, char **argv)
 296 {
 297         MonoAssembly *assembly;
 298
 299         /* Loading an assembly makes the runtime setup everything
 300          * needed to execute it. If we're just interested in the metadata
 301          * we'd use mono_image_load (), instead and we'd get a MonoImage*.
 302          */
 303         assembly = mono_domain_assembly_open (domain, file);
 304         if (!assembly)
 305                 exit (2);
 306         /*
 307          * mono_jit_exec() will run the Main() method in the assembly.
 308          * The return value needs to be looked up from
 309          * System.Environment.ExitCode.
 310          */
 311         mono_jit_exec (domain, assembly, argc, argv);
 312
 313         create_object (domain, mono_assembly_get_image (assembly));
 314 }
 315
 316 int
 317 main (int argc, char* argv[]) {
 318         MonoDomain *domain;
 319         const char *file;
 320         int retval;
 321
 322         if (argc < 2){
 323                 fprintf (stderr, "Please provide an assembly to load\n");
 324                 return 1;
 325         }
 326         file = argv [1];
 327         /*
 328          * mono_jit_init() creates a domain: each assembly is
 329          * loaded and run in a MonoDomain.
 330          */
 331         domain = mono_jit_init (file);
 332
 333         main_function (domain, file, argc - 1, argv + 1);
 334
 335         retval = mono_environment_exitcode_get ();
 336
 337         mono_jit_cleanup (domain);
 338         return retval;
 339 }
 340