com.sun.jna
Class Pointer

java.lang.Object
  com.sun.jna.Pointer

Direct Known Subclasses:

Function, Memory

public class Pointer
extends Object

An abstraction for a native pointer data type. A Pointer instance represents, on the Java side, a native pointer. The native pointer could be any type of native pointer. Methods such as write, read, getXXX, and setXXX, provide means to access memory underlying the native pointer.

The constructors are intentionally package-private, since it's not generally a good idea to be creating C pointers de novo.

Author:

Sheng Liang, originator, Todd Fast, suitability modifications, Timothy Wall, robust library loading

See Also:

Function

SIZE

public static final int SIZE

Size of a native pointer, in bytes.

NULL

public static final Pointer NULL

Convenience constant, same as null.

peer

protected long peer

Pointer value of the real native pointer. Use long to be 64-bit safe.

Pointer

Pointer()

Derived class must assign peer pointer value.

Pointer

public Pointer(long peer)

Create from native pointer. Don't use this unless you know what you're doing.

createConstant

public static final Pointer createConstant(long peer)

Convenience constant, equivalent to (void*)CONSTANT.

createConstant

public static final Pointer createConstant(int peer)

Convenience constant, equivalent to (void*)CONSTANT. This version will avoid setting any of the high bits on 64-bit systems.

share

public Pointer share(long offset)

share

public Pointer share(long offset,
                     long sz)

Provide a view of this pointer with a different peer base.

clear

public void clear(long size)

Zero memory for the given number of bytes.

equals

public boolean equals(Object o)

Compares this Pointer to the specified object.

Overrides:

equals in class Object

Parameters:

o - A Pointer instance

Returns:

True if the other object is a Pointer, and the C pointers being pointed to by these objects are also equal. Returns false otherwise.

hashCode

public int hashCode()

Returns a hashcode for the native pointer represented by this Pointer object

Overrides:

hashCode in class Object

Returns:

A hash code value for the represented native pointer

indexOf

public long indexOf(long offset,
                    byte value)

Returns the offset of the given value in memory from the given offset, or -1 if the value is not found.

read

public void read(long offset,
                 byte[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - byte array into which data is copied

index - array index from which to start copying

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 short[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - short array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 char[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - char array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 int[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - int array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 long[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - long array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 float[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - float array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 double[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - double array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

read

public void read(long offset,
                 Pointer[] buf,
                 int index,
                 int length)

Indirect the native pointer, copying from memory pointed to by native pointer, into the specified array.

Parameters:

offset - byte offset from pointer from which data is copied

buf - Pointer array into which data is copied

index - array index to which data is copied

length - number of elements from native pointer that must be copied

write

public void write(long offset,
                  byte[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - byte array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  short[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - short array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  char[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - char array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  int[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - int array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  long[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - long array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  float[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - float array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long offset,
                  double[] buf,
                  int index,
                  int length)

Indirect the native pointer, copying into memory pointed to by native pointer, from the specified array.

Parameters:

offset - byte offset from pointer into which data is copied

buf - double array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

write

public void write(long bOff,
                  Pointer[] buf,
                  int index,
                  int length)

Write the given array of Pointer to native memory.

Parameters:

bOff - byte offset from pointer into which data is copied

buf - Pointer array from which to copy

index - array index from which to start copying

length - number of elements from buf that must be copied

getValue

Object getValue(long offset,
                Class type,
                Object currentValue)

getByte

public byte getByte(long offset)

Indirect the native pointer as a pointer to byte. This is equivalent to the expression *((jbyte *)((char *)Pointer + offset)).

Parameters:

offset - offset from pointer to perform the indirection

Returns:

the byte value being pointed to

getChar

public char getChar(long offset)

Indirect the native pointer as a pointer to wchar_t. This is equivalent to the expression *((wchar_t*)((char *)Pointer + offset)).

Parameters:

offset - offset from pointer to perform the indirection

Returns:

the wchar_t value being pointed to

getShort

public short getShort(long offset)

Indirect the native pointer as a pointer to short. This is equivalent to the expression *((jshort *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the short value being pointed to

getInt

public int getInt(long offset)

Indirect the native pointer as a pointer to int. This is equivalent to the expression *((jint *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the int value being pointed to

getLong

public long getLong(long offset)

Indirect the native pointer as a pointer to long. This is equivalent to the expression *((jlong *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the long value being pointed to

getNativeLong

public NativeLong getNativeLong(long offset)

Indirect the native pointer as a pointer to long. This is equivalent to the expression *((long *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the long value being pointed to

getFloat

public float getFloat(long offset)

Indirect the native pointer as a pointer to float. This is equivalent to the expression *((jfloat *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the float value being pointed to

getDouble

public double getDouble(long offset)

Indirect the native pointer as a pointer to double. This is equivalent to the expression *((jdouble *)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

the double value being pointed to

getPointer

public Pointer getPointer(long offset)

Indirect the native pointer as a pointer to pointer. This is equivalent to the expression *((void **)((char *)Pointer + offset)).

Parameters:

offset - byte offset from pointer to perform the indirection

Returns:

a Pointer equivalent of the pointer value being pointed to, or null if the pointer value is NULL;

getByteBuffer

public ByteBuffer getByteBuffer(long offset,
                                long length)

Get a ByteBuffer mapped to the memory pointed to by the pointer, ensuring the buffer uses native byte order.

Parameters:

offset - byte offset from pointer to start the buffer

length - Length of ByteBuffer

Returns:

a direct ByteBuffer that accesses the memory being pointed to,

getString

public String getString(long offset,
                        boolean wide)

Copy native memory to a Java String. If wide is true, access the memory as an array of wchar_t, otherwise as an array of char, using the default platform encoding.

Parameters:

offset - byte offset from pointer to obtain the native string v * @param wide whether to convert from a wide or standard C string

Returns:

the String value being pointed to

getString

public String getString(long offset)

Copy native memory to a Java String. If the system property jna.encoding is set, uses it as the native charset when decoding the value, otherwise falls back to the default platform encoding.

Parameters:

offset - byte offset from pointer to obtain the native string

Returns:

the String value being pointed to

getByteArray

public byte[] getByteArray(long offset,
                           int arraySize)

getCharArray

public char[] getCharArray(long offset,
                           int arraySize)

getShortArray

public short[] getShortArray(long offset,
                             int arraySize)

getIntArray

public int[] getIntArray(long offset,
                         int arraySize)

getLongArray

public long[] getLongArray(long offset,
                           int arraySize)

getFloatArray

public float[] getFloatArray(long offset,
                             int arraySize)

getDoubleArray

public double[] getDoubleArray(long offset,
                               int arraySize)

getPointerArray

public Pointer[] getPointerArray(long base)

Returns an array of Pointer. The array length is determined by a NULL-valued terminating element.

getPointerArray

public Pointer[] getPointerArray(long offset,
                                 int arraySize)

Returns an array of Pointer of the requested size.

getStringArray

public String[] getStringArray(long base)

Returns an array of String based on a native array of char *. The array length is determined by a NULL-valued terminating element.

getStringArray

public String[] getStringArray(long base,
                               int length)

Returns an array of String based on a native array of char *, using the given array length.

getStringArray

public String[] getStringArray(long base,
                               boolean wide)

Returns an array of String based on a native array of char* or wchar_t* based on the wide parameter. The array length is determined by a NULL-valued terminating element.

getStringArray

public String[] getStringArray(long base,
                               int length,
                               boolean wide)

Returns an array of String based on a native array of char* or wchar_t* based on the wide parameter, using the given array length.

setValue

void setValue(long offset,
              Object value,
              Class type)

setMemory

public void setMemory(long offset,
                      long length,
                      byte value)

Write value to the requested bank of memory.

Parameters:

offset - byte offset from pointer to start

length - number of bytes to write

value - value to be written

_setMemory

static void _setMemory(long addr,
                       long length,
                       byte value)

setByte

public void setByte(long offset,
                    byte value)

Set value at location being pointed to. This is equivalent to the expression *((jbyte *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - byte value to set

setShort

public void setShort(long offset,
                     short value)

Set value at location being pointed to. This is equivalent to the expression *((jshort *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - short value to set

setChar

public void setChar(long offset,
                    char value)

Set value at location being pointed to. This is equivalent to the expression *((wchar_t *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - char value to set

setInt

public void setInt(long offset,
                   int value)

Set value at location being pointed to. This is equivalent to the expression *((jint *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - int value to set

setLong

public void setLong(long offset,
                    long value)

Set value at location being pointed to. This is equivalent to the expression *((jlong *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - long value to set

setNativeLong

public void setNativeLong(long offset,
                          NativeLong value)

Set value at location being pointed to. This is equivalent to the expression *((long *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - long value to set

setFloat

public void setFloat(long offset,
                     float value)

Set value at location being pointed to. This is equivalent to the expression *((jfloat *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - float value to set

setDouble

public void setDouble(long offset,
                      double value)

Set value at location being pointed to. This is equivalent to the expression *((jdouble *)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - double value to set

setPointer

public void setPointer(long offset,
                       Pointer value)

Set value at location being pointed to. This is equivalent to the expression *((void **)((char *)Pointer + offset)) = value.

Parameters:

offset - byte offset from pointer at which value must be set

value - Pointer holding the actual pointer value to set, which may be null to indicate a NULL pointer.

setString

public void setString(long offset,
                      String value,
                      boolean wide)

Copy string value to the location being pointed to. Copy each element in value, converted to native encoding, at an offsetfrom the location pointed to by this pointer.

Parameters:

offset - byte offset from pointer at which characters in value must be set

value - java.lang.String value to set

wide - whether to write the native string as an array of wchar_t. If false, writes as a NUL-terminated array of char using the default platform encoding.

setString

public void setString(long offset,
                      String value)

Copy string value to the location being pointed to. Copy each element in value, converted to native encoding, at an offsetfrom the location pointed to by this pointer. Uses the value of the system property jna.encoding, if set, to determine the appropriate native charset in which to encode the value. If the property is not set, uses the default platform encoding.

Parameters:

offset - byte offset from pointer at which characters in value must be set

value - java.lang.String value to set

toString

public String toString()

Overrides:

toString in class Object

nativeValue

public static long nativeValue(Pointer p)

Read the native peer value. Use with caution.

nativeValue

public static void nativeValue(Pointer p,
                               long value)

Set the native peer value. Use with caution.