linux-packaging-mono/docs/sources/mono-api-dynamic-codegen.html

<h2>Internal: Dynamic Code Generation</h2>

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

	<p>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.

	<p>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.

	<p>To JIT this method, the process is this:

	<ul>
		<li>Create a <tt>MonoMethodBuilder</tt> object using
		the <tt>mono_mb_new</tt> method.  The method's class
		is specified as the first argument.

		<li>Create the method signature, using
		<tt>mono_metadata_signature_alloc</tt>.  The call
		takes the number of arguments that the method takes.
		Then you must initialize the types for each one of the
		parameters.

		<li>Emit the CIL code, using one of the
		<tt>mono_mb_emit_*</tt> functions.   There are some
		helper routines that you can use.

		<li>Create the <tt>MonoMethod</tt> from the
		<tt>MethodBuilder</tt> using
		<tt>mono_mb_create_method</tt>.

		<li>Release the <tt>MonoMethodBuilder</tt> resources
		using mono_mb_free. 
	</ul>

	<p>The result of this process is a <tt>MonoMethod</tt> which
	can be called using <tt><a
	href="api:mono_create_jit_trampoline">mono_create_jit_trampoline</a></tt>
	routine or can be passed to any other functions that require
	the MonoMethod.

	<p>Example:

	<pre>
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 = &amp;mono_get_int32_class ()->byval_arg;
    sig->params [0] = &amp;mono_get_int32_class ()->byval_arg;
    sig->params [1] = &amp;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;
}
	</pre>
	
<h4><a name="api:mono_mb_new">mono_mb_new</a></h4>

	<p>The possible values for the <i>type</i> argument are:

<pre>
        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
</pre>

<h3>Emitting IL</h3>

	<p>Functions that can be used to generate IL on the flight,
	similar in spirit to System.Reflection.Emit.ILGenerator.
	
<h4><a name="api:mono_mb_emit_add_to_local">mono_mb_emit_add_to_local</a></h4>
<h4><a name="api:mono_mb_emit_branch">mono_mb_emit_branch</a></h4>
<h4><a name="api:mono_mb_emit_byte">mono_mb_emit_byte</a></h4>
<h4><a name="api:mono_mb_emit_exception">mono_mb_emit_exception</a></h4>
<h4><a name="api:mono_mb_emit_i2">mono_mb_emit_i2</a></h4>
<h4><a name="api:mono_mb_emit_i4">mono_mb_emit_i4</a></h4>
<h4><a name="api:mono_mb_emit_icon">mono_mb_emit_icon</a></h4>
<h4><a name="api:mono_mb_emit_ldarg_addr">mono_mb_emit_ldarg_addr</a></h4>
<h4><a name="api:mono_mb_emit_ldarg">mono_mb_emit_ldarg</a></h4>
<h4><a name="api:mono_mb_emit_ldflda">mono_mb_emit_ldflda</a></h4>
<h4><a name="api:mono_mb_emit_ldloc_addr">mono_mb_emit_ldloc_addr</a></h4>
<h4><a name="api:mono_mb_emit_ldloc">mono_mb_emit_ldloc</a></h4>
<h4><a name="api:mono_mb_emit_ldstr">mono_mb_emit_ldstr</a></h4>
<h4><a name="api:mono_mb_emit_managed_call">mono_mb_emit_managed_call</a></h4>
<h4><a name="api:mono_mb_emit_native_call">mono_mb_emit_native_call</a></h4>
<h4><a name="api:mono_mb_emit_stloc">mono_mb_emit_stloc</a></h4>

<h3>Local variables and Methods</h3>
<h4><a name="api:mono_mb_create_method">mono_mb_create_method</a></h4>
<h4><a name="api:mono_mb_add_data">mono_mb_add_data</a></h4>
<h4><a name="api:mono_mb_add_local">mono_mb_add_local</a></h4>
<h4><a name="api:mono_mb_free">mono_mb_free</a></h4>

<h3>Patching Addresses</h3>
<h4><a name="api:mono_mb_patch_addr">mono_mb_patch_addr</a></h4>
<h4><a name="api:mono_mb_patch_addr_s">mono_mb_patch_addr_s</a></h4>

<h3>Method Signatures</h3>
<h4><a name="api:mono_metadata_signature_alloc">mono_metadata_signature_alloc</a></h4>
<h4><a name="api:mono_metadata_signature_dup">mono_metadata_signature_dup</a></h4>
<h4><a name="api:mono_metadata_signature_equal">mono_metadata_signature_equal</a></h4>