org.jikesrvm.jni

Class JNIGenericHelpers

java.lang.Object

org.jikesrvm.jni.JNIGenericHelpers

Direct Known Subclasses:

JNIHelpers

public abstract class JNIGenericHelpers
extends Object

Platform independent utility functions called from JNIFunctions (cannot be placed in JNIFunctions because methods there are specially compiled to be called from native).

See Also:

JNIFunctions

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	ALLOW_READS_OF_UNDEFINED_MEMORY Whether to allow reads of undefined memory when computing strlen(..).

Constructor Summary

Constructors

Constructor and Description
JNIGenericHelpers()

Method Summary

Modifier and Type	Method and Description
protected static Object	callMethod(Object obj, MethodReference mr, Object[] args, TypeReference expectedReturnType, boolean nonVirtual) Dispatch method call
protected static Object	callMethodJValuePtr(JNIEnvironment env, int objJREF, int methodID, Address argAddress, TypeReference expectedReturnType, boolean nonVirtual) Dispatch method call, arguments in jvalue*
static byte[]	createByteArrayFromC(Address stringAddress) Given an address in C that points to a null-terminated string, create a new Java byte[] with a copy of the string.
private static String	createString(CharsetDecoder csd, ByteBuffer bbuf)
static String	createStringFromC(Address stringAddress) Given an address in C that points to a null-terminated string, create a new Java String with a copy of the string.
static void	createUTFForCFromString(String str, Address copyBuffer, int len) Converts a String into a a malloced regions.
static String	createUTFStringFromC(Address stringAddress) Given an address in C that points to a null-terminated string, create a new UTF encoded Java String with a copy of the string.
static boolean	implementedInJava(int functionTableIndex)
protected static Object[]	packageParametersFromJValuePtr(MethodReference targetMethod, Address argAddress) Repackage the arguments passed as an array of jvalue into an array of Object, used by the JNI functions CallStatic<type>MethodA
(package private) static void	setBoolStar(Address boolPtr, boolean val) A JNI helper function, to set the value pointed to by a C pointer of type (jboolean *).
static int	strlen(Address ptr) Computes the length of the given null-terminated string.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ALLOW_READS_OF_UNDEFINED_MEMORY

private static final boolean ALLOW_READS_OF_UNDEFINED_MEMORY

Whether to allow reads of undefined memory when computing strlen(..). This is enabled by default to improve performance. It will never cause undefined behaviour but it may turn up as a false positive when using tools such as Valgrind.

See Also:

Constant Field Values

Constructor Detail

JNIGenericHelpers

public JNIGenericHelpers()

Method Detail

strlen

public static int strlen(Address ptr)

Computes the length of the given null-terminated string.

NOTE: This method may read undefined memory if ALLOW_READS_OF_UNDEFINED_MEMORY is true. However, the behaviour of this method is always well-defined.

Parameters:

ptr - address of string in memory

Returns:

the length of the string in bytes

createByteArrayFromC

public static byte[] createByteArrayFromC(Address stringAddress)

Given an address in C that points to a null-terminated string, create a new Java byte[] with a copy of the string.

Parameters:

stringAddress - an address in C space for a string

Returns:

a new Java byte[]

createString

private static String createString(CharsetDecoder csd,
                                   ByteBuffer bbuf)
                            throws CharacterCodingException

Throws:

CharacterCodingException

createStringFromC

public static String createStringFromC(Address stringAddress)

Given an address in C that points to a null-terminated string, create a new Java String with a copy of the string.

Parameters:

stringAddress - an address in C space for a string

Returns:

a new Java String

createUTFStringFromC

public static String createUTFStringFromC(Address stringAddress)

Given an address in C that points to a null-terminated string, create a new UTF encoded Java String with a copy of the string.

Parameters:

stringAddress - an address in C space for a string

Returns:

a new Java String

createUTFForCFromString

public static void createUTFForCFromString(String str,
                                           Address copyBuffer,
                                           int len)

Converts a String into a a malloced regions.

Parameters:

str - the string to convert

copyBuffer - start address for a newly allocated buffer

len - length of the buffer

setBoolStar

static void setBoolStar(Address boolPtr,
                        boolean val)

A JNI helper function, to set the value pointed to by a C pointer of type (jboolean *).

Parameters:

boolPtr - Native pointer to a jboolean variable to be set. May be the NULL pointer, in which case we do nothing.

val - Value to set it to (usually TRUE)

callMethod

protected static Object callMethod(Object obj,
                                   MethodReference mr,
                                   Object[] args,
                                   TypeReference expectedReturnType,
                                   boolean nonVirtual)
                            throws InvocationTargetException

Dispatch method call

Parameters:

obj - this pointer for method to be invoked, or null if method is static

mr - reference to method to be invoked

args - argument array

expectedReturnType - a type reference for the expected return type

nonVirtual - should invocation be of the given method or should we use virtual dispatch on the object?

Returns:

return value of the method (boxed if primitive)

Throws:

InvocationTargetException - when the reflective method call fails

callMethodJValuePtr

protected static Object callMethodJValuePtr(JNIEnvironment env,
                                            int objJREF,
                                            int methodID,
                                            Address argAddress,
                                            TypeReference expectedReturnType,
                                            boolean nonVirtual)
                                     throws InvocationTargetException

Dispatch method call, arguments in jvalue*

Parameters:

env - the JNI environemnt for the thread

objJREF - a JREF index for the object

methodID - id of a MethodReference

argAddress - address of an array of jvalues (jvalue*)

expectedReturnType - a type reference for the expected return type

nonVirtual - should invocation be of the given method or should we use virtual dispatch on the object?

Returns:

return value of the method (boxed if primitive)

Throws:

InvocationTargetException - when reflective invocation fails

packageParametersFromJValuePtr

protected static Object[] packageParametersFromJValuePtr(MethodReference targetMethod,
                                                         Address argAddress)

Repackage the arguments passed as an array of jvalue into an array of Object, used by the JNI functions CallStatic<type>MethodA

Parameters:

targetMethod - the target MethodReference

argAddress - an address into the C space for the array of jvalue unions

Returns:

an Object array holding the arguments wrapped at Objects

implementedInJava

public static boolean implementedInJava(int functionTableIndex)

Parameters:

functionTableIndex - slot in the JNI function table

Returns:

true if the function is implemented in Java (i.e. its code is in org.jikesrvm.jni.JNIFunctions) and false if the function is implemented in C (i.e. its code is in the bootloader)