## Dynamic Code Generation

The dynamic code generation interface inside the Mono runtime is similar to the API exposed by System.Reflection.Emit.

This interface is used by Mono internally to generate code on the flight in a cross-platform fashion. For example, P/Invoke marshalling in Mono is implemented in terms of this interface, but it is also used in various other parts of the runtime.

Unlike Reflection.Emit, the dynamic code generation interface does not start with an assembly builder. The code generation interface starts directly at the method level, which is represented by a pointer to the MonoMethodBuilder structure.

To JIT this method, the process is this:

- Create a `MonoMethodBuilder` object using the `mono_mb_new` method. The method's class is specified as the first argument.
- Create the method signature, using `mono_metadata_signature_alloc`. The call takes the number of arguments that the method takes. Then you must initialize the types for each one of the parameters.
- Emit the CIL code, using one of the `mono_mb_emit_*` functions. There are some helper routines that you can use.
- Create the `MonoMethod` from the `MethodBuilder` using `mono_mb_create_method`.
- Release the `MonoMethodBuilder` resources using mono_mb_free.

The result of this process is a `MonoMethod` which can be called using `mono_create_jit_trampoline` routine or can be passed to any other functions that require the MonoMethod.

Example:

    MonoMethod *adder ()
    {
        MonoMethodBuilder *mb;
        MonoMethodSignature *sig;
        MonoMethod *method;

        mb = mono_mb_new (mono_defaults.object_class, "adder", MONO_WRAPPER_NONE);

        /* Setup method signature */
        sig = mono_metadata_signature_alloc (2);
        sig->ret = &mono_get_int32_class ()->byval_arg;
        sig->params [0] = &mono_get_int32_class ()->byval_arg;
        sig->params [1] = &mono_defaults.int32_class->byval_arg;

        /* Emit CIL code */
        mono_mb_emit_ldarg (mb, 0);
        mono_mb_emit_ldarg (mb, 1);
        mono_mb_emit_byte (mb, CEE_ADD);
        mono_mb_emit_byte (mb, CEE_RET);

        /* Get the method */
        method = mono_mb_create_method (mb, sig, max_stack);

        /* Cleanup */
        mono_mb-free (mb);
        return method;
    }

#### mono_mb_new

The possible values for the type argument are:

            MONO_WRAPPER_NONE
            MONO_WRAPPER_DELEGATE_INVOKE
            MONO_WRAPPER_DELEGATE_BEGIN_INVOKE
            MONO_WRAPPER_DELEGATE_END_INVOKE
            MONO_WRAPPER_RUNTIME_INVOKE
            MONO_WRAPPER_NATIVE_TO_MANAGED
            MONO_WRAPPER_MANAGED_TO_NATIVE
            MONO_WRAPPER_REMOTING_INVOKE
            MONO_WRAPPER_REMOTING_INVOKE_WITH_CHECK
            MONO_WRAPPER_XDOMAIN_INVOKE
            MONO_WRAPPER_XDOMAIN_DISPATCH
            MONO_WRAPPER_LDFLD
            MONO_WRAPPER_STFLD
            MONO_WRAPPER_LDFLD_REMOTE
            MONO_WRAPPER_STFLD_REMOTE
            MONO_WRAPPER_SYNCHRONIZED
            MONO_WRAPPER_DYNAMIC_METHOD
            MONO_WRAPPER_ISINST
            MONO_WRAPPER_CASTCLASS
            MONO_WRAPPER_PROXY_ISINST
            MONO_WRAPPER_STELEMREF
            MONO_WRAPPER_UNBOX
            MONO_WRAPPER_LDFLDA
            MONO_WRAPPER_UNKNOWN

### Emitting IL

Functions that can be used to generate IL on the flight, similar in spirit to System.Reflection.Emit.ILGenerator.

#### mono_mb_emit_add_to_local

#### mono_mb_emit_branch

#### mono_mb_emit_byte

#### mono_mb_emit_exception

#### mono_mb_emit_i2

#### mono_mb_emit_i4

#### mono_mb_emit_icon

#### mono_mb_emit_ldarg_addr

#### mono_mb_emit_ldarg

#### mono_mb_emit_ldflda

#### mono_mb_emit_ldloc_addr

#### mono_mb_emit_ldloc

#### mono_mb_emit_ldstr

#### mono_mb_emit_managed_call

#### mono_mb_emit_native_call

#### mono_mb_emit_stloc

### Local variables and Methods

#### mono_mb_create_method

#### mono_mb_add_data

#### mono_mb_add_local

#### mono_mb_free

### Patching Addresses

#### mono_mb_patch_addr

#### mono_mb_patch_addr_s

### Method Signatures

#### mono_metadata_signature_alloc

#### mono_metadata_signature_dup

#### mono_metadata_signature_equal