Java Virtual Machine API

Installation

The file metaffi.api.jar is deployed in the MetaFFI installation directory.

MetaFFIRuntime Class

MetaFFIRuntime is a class that provides a simple and easy FFI framework to connect JVM-based languages with other languages. Pass to the constructor the runtime plugin you wish to load into the process (e.g. go, python3), and call loadRuntimePlugin to load the runtime.

Once the runtime is loaded, use loadModule to load the module and receive and instance of MetaFFIModule.

Methods

MetaFFIRuntime(String runtimePlugin)

Constructor specifies the requested runtime plugin to use

Parameters:

• runtimePlugin: The name of the runtime plugin to use

void loadRuntimePlugin()

Loads the runtime of the plugin.

void releaseRuntimePlugin()

Releases the loaded runtime. After calling this function, and loaded entity must not be used.

MetaFFIModule loadModule(String modulePath)

Loads a foreign module from a given. It returns a MetaFFIModule object that represents the foreign module.

The modulePath might contain multiple modules (for cases like dependencies). A runtime plugin specifies in its documentation what it expects.

Parameters:

• modulePath - Path to the module(s) to load

Return:

• Instance of MetaFFIModule representing the foreign module

static Caller makeMetaffiCallable(Method m)

The method wraps the given method m, and returns a cross-language Call. The returned Caller instance can be passed to other languages.

Parameter:

• f: a Python3 callable

Return:

• Caller instance wrapping the given method

MetaFFIModule Class

The MetaFFIModule class provides the load method, which loads a foreign entity and returns it as a Caller object.

The class usually should not be created directly, but using the MetaFFIRuntime.loadModule function.

Methods

MetaFFIModule(MetaFFIRuntime runtime, String modulePath)

The constructor method for the MetaFFIModule class. It initializes the instance with the given attributes.

Parameters:

• runtime: A MetaFFIRuntime object that specifies the runtime plugin for the module.
• modulePath: A string that contains the path to the module file.

Caller load(String entityPath, MetaFFITypeWithAlias[] parametersTypes, MetaFFITypeWithAlias[] retvalsTypes)

Caller load(String entityPath, MetaFFIType[] parametersTypes, MetaFFIType[] retvalsTypes)

The load method for the MetaFFIModule class loads a foreign entity from the module and returns a Caller that can be used to invoke the foreign entity from another language. If the Caller calls a Method or a Field of an object, the $1^{st}$ parameter is an instance of the object.

The load method receives a entity path telling the runtime plugin the location of the entity inside the module.

The method should also pass a list of MetaFFI Types, specifying the type of the parameters and return values.

In case there are no parameters or return values, pass null or empty arrays.

Parameters:

• entityPath: A string that contains the path to the function within the module.
• parametersTypes: MetaFFITypeWithAlias[] array that specify the parameter types for the function.
• retvalsTypes: MetaFFITypeWithAlias[] array that specify the return value types for the function.

Returns:

• A Caller object, with the Object[] call(Object... parameters) method which accepts the number of parameters defiend in parametersTypes and their expected corresponding types. The method returns the number of expected return values and their corresponding types.

  In case of an error during the call, or an error in the foreign entity, the call method throws MetaFFIException containing the error message.

MetaFFI Types In JVM

MetaFFI Type	JVM
metaffi_float64_type	double
metaffi_float32_type	float
metaffi_int8_type	byte
metaffi_int16_type	short
metaffi_int32_type	int
metaffi_int64_type	long
metaffi_uint8_type	byte
metaffi_uint16_type	short
metaffi_uint32_type	int
metaffi_uint64_type	long
metaffi_bool_type	boolean
metaffi_char8_type	byte
metaffi_char16_type	Character
metaffi_char32_type	int
metaffi_string8_type	String
metaffi_string16_type	String
metaffi_string32_type	String
metaffi_handle_type	MetaFFIHandle
metaffi_any_type	Object
metaffi_null_type	null
metaffi_callable_type	Method (returned by MakeCallable)
metaffi_float64_array_type	[]double
metaffi_float32_array_type	[]float
metaffi_int8_array_type	byte[]
metaffi_int16_array_type	short[]
metaffi_int32_array_type	int[]
metaffi_int64_array_type	long[]
metaffi_uint8_array_type	byte[]
metaffi_uint16_array_type	short[]
metaffi_uint32_array_type	int[]
metaffi_uint64_array_type	long[]
metaffi_bool_array_type	boolean[]
metaffi_char8_array_type	byte[]
metaffi_string8_array_type	String[]
metaffi_string16_array_type	String[]
metaffi_string32_array_type	String[]
metaffi_any_array_type	Object[]
metaffi_handle_array_type	MetaFFIHandle[]