# Mono Internals

This section documents some of the internal APIs used inside Mono that developers extending or altering Mono might want to use.

## Strings

### Other Encodings

These routines are used when coping with strings that come from Mono's environment, and might be encoded in one or more of the external encodings.

For example, some file systems might historically contain a mix of file names with both old and new encodings, typically UTF8 for new files, and the old files would be encoded in an 8 bit character set (ISO-8859-1 for example).

These routines try a number of encodings, those specified in the `MONO_ENCODINGS` environment variable and return unicode strings that can be used internally.

See the mono(1) man page for more details.

#### mono_unicode_from_external

#### mono_unicode_to_external

#### mono_utf8_from_external

## Marshalling functions

#### mono_marshal_alloc

#### mono_marshal_asany

#### mono_marshal_free_array

#### mono_marshal_free_asany

#### mono_marshal_free

#### mono_marshal_get_castclass

#### mono_marshal_get_delegate_begin_invoke

#### mono_marshal_get_delegate_end_invoke

#### mono_marshal_get_delegate_invoke

#### mono_marshal_get_icall_wrapper

#### mono_marshal_get_isinst

#### mono_marshal_get_ldfld_remote_wrapper

#### mono_marshal_get_ldfld_wrapper

#### mono_marshal_get_managed_wrapper

#### mono_marshal_get_native_wrapper

#### mono_marshal_get_proxy_cancast

#### mono_marshal_get_ptr_to_struct

#### mono_marshal_get_remoting_invoke_for_target

#### mono_marshal_get_remoting_invoke

#### mono_marshal_get_remoting_invoke_with_check

#### mono_marshal_get_runtime_invoke

#### mono_marshal_get_stelemref

#### mono_marshal_get_stfld_remote_wrapper

#### mono_marshal_get_stfld_wrapper

#### mono_marshal_get_struct_to_ptr

#### mono_marshal_get_synchronized_wrapper

#### mono_marshal_get_unbox_wrapper

#### mono_marshal_get_xappdomain_invoke

#### mono_marshal_load_type_info

#### mono_marshal_method_from_wrapper

#### mono_marshal_realloc

#### mono_marshal_set_last_error

#### mono_marshal_type_size

## Metadata Loading Errors

The routines in this section are used to cope with errors during metadata loading. Errors in metadata handling can happen for many reason, and these include (this is not an exhaustive list).

- An assembly referenced is missing.
- Fields referenced are missing.
- Methods referenced are missing.

The `mono_loader_set_*` routines are invoked during metadata loading to flag that an error has happened. The class loading errros are flagged in a per-thread basis.

In various spots in the runtime the `mono_loader_get_last_error` routine is called to check if there was a problem, and then errors are propagated upwards on the stack until we reach a point where an exception can be raised and no runtime locks are held.

The `mono_loader_error_prepare_exception` takes a `MonoLoaderError` structure (the value returned from `mono_loader_get_last_error`), turns that into an exception and clears the error condition from the current thread.

#### mono_loader_set_error_field_load

#### mono_loader_set_error_method_load

#### mono_loader_set_error_type_load

#### mono_loader_get_last_error

#### mono_loader_clear_error

#### mono_loader_error_prepare_exception

## Metadata Loader Locking: Internals

The locking functions here are used by code in class.c and metadata.c to lock access to the shared hashtables inside the MonoImage.

#### mono_loader_lock

#### mono_loader_unlock

## Garbage Collector Internal Interface

The internal interface of the Mono GC is the interface used between the runtime engine and the garbage collector.

#### mono_gc_disable

#### mono_gc_enable

#### mono_gc_start_world

#### mono_gc_stop_world

#### mono_gc_alloc_fixed

#### mono_gc_free_fixed

#### mono_gc_make_descr_from_bitmap

#### mono_gc_base_init

#### mono_gc_invoke_finalizers

#### mono_gc_is_gc_thread

#### mono_gc_pending_finalizers

#### mono_gc_register_thread

#### mono_gc_finalize_notify