* The PerfDataBufferProlog class supports parsing of the following * C structure: *
* typedef struct {
* jint magic; // magic number - 0xcafec0c0
* jbyte byte_order; // byte order of the buffer
* jbyte major_version; // major and minor version numbers
* jbyte minor_version;
* jbyte reserved_byte1; // reserved - see concrete implementations for
* // possible definition.
* ... // remainder is handled by the subclasses.
* } PerfDataPrologue
*
*
* @author Brian Doherty
* @since 1.5
*/
public abstract class AbstractPerfDataBufferPrologue {
protected ByteBuffer byteBuffer;
/*
* the following constants must match the field offsets and sizes
* in the PerfDataPrologue structure in perfMemory.hpp
*/
final static int PERFDATA_PROLOG_OFFSET=0;
final static int PERFDATA_PROLOG_MAGIC_OFFSET=0;
final static int PERFDATA_PROLOG_BYTEORDER_OFFSET=4;
final static int PERFDATA_PROLOG_BYTEORDER_SIZE=1; // sizeof(byte)
final static int PERFDATA_PROLOG_MAJOR_OFFSET=5;
final static int PERFDATA_PROLOG_MAJOR_SIZE=1; // sizeof(byte)
final static int PERFDATA_PROLOG_MINOR_OFFSET=6;
final static int PERFDATA_PROLOG_MINOR_SIZE=1; // sizeof(byte)
final static int PERFDATA_PROLOG_RESERVEDB1_OFFSET=7;
final static int PERFDATA_PROLOG_RESERVEDB1_SIZE=1; // sizeof(byte)
final static int PERFDATA_PROLOG_SIZE=8; // sizeof(struct PerfDataProlog)
// these constants should match their #define counterparts in perfMemory.hpp
final static byte PERFDATA_BIG_ENDIAN=0;
final static byte PERFDATA_LITTLE_ENDIAN=1;
final static int PERFDATA_MAGIC = 0xcafec0c0;
// names for counters that expose the prolog fields
public final static String PERFDATA_MAJOR_NAME =
"sun.perfdata.majorVersion";
public final static String PERFDATA_MINOR_NAME =
"sun.perfdata.minorVersion";
/**
* Construct a PerfDataBufferPrologue instance.
*
* @param byteBuffer buffer containing the instrumentation data
*/
public AbstractPerfDataBufferPrologue(ByteBuffer byteBuffer)
throws MonitorException {
this.byteBuffer = byteBuffer.duplicate();
// the magic number is always stored in big-endian format
if (getMagic() != PERFDATA_MAGIC) {
throw new MonitorVersionException(
"Bad Magic: " + Integer.toHexString(getMagic()));
}
// set the byte order
this.byteBuffer.order(getByteOrder());
}
/**
* Get the magic number.
*
* @return int - the magic number
*/
public int getMagic() {
// the magic number is always stored in big-endian format
ByteOrder order = byteBuffer.order();
byteBuffer.order(ByteOrder.BIG_ENDIAN);
// get the magic number
byteBuffer.position(PERFDATA_PROLOG_MAGIC_OFFSET);
int magic = byteBuffer.getInt();
// restore the byte order
byteBuffer.order(order);
return magic;
}
/**
* Get the byte order.
*
* @return int - the byte order of the instrumentation buffer
*/
public ByteOrder getByteOrder() {
// byte order field is byte order independent
byteBuffer.position(PERFDATA_PROLOG_BYTEORDER_OFFSET);
byte byte_order = byteBuffer.get();
if (byte_order == PERFDATA_BIG_ENDIAN) {
return ByteOrder.BIG_ENDIAN;
} else {
return ByteOrder.LITTLE_ENDIAN;
}
}
/**
* Get the major version.
*
* @return int - the major version
*/
public int getMajorVersion() {
// major version field is byte order independent
byteBuffer.position(PERFDATA_PROLOG_MAJOR_OFFSET);
return (int)byteBuffer.get();
}
/**
* Get the minor version.
*
* @return int - the minor version
*/
public int getMinorVersion() {
// minor version field is byte order independent
byteBuffer.position(PERFDATA_PROLOG_MINOR_OFFSET);
return (int)byteBuffer.get();
}
/**
* Get the accessible flag. If supported, it indicates that the shared
* memory region is sufficiently initialized for client acccess.
*
* @return boolean - the initialized status
* @see #supportsAccessible()
*/
public abstract boolean isAccessible();
/**
* Test if the accessible flag is supported by this version of
* the PerfDataBufferPrologue. Although not an abstract method, this
* method should be overridden by version specific subclasses.
*
* @return boolean - the initialized flag support status.
* @see #isAccessible()
*/
public abstract boolean supportsAccessible();
/**
* Get the size of the header portion of the instrumentation buffer.
*
* @return int - the size of the header
*/
public int getSize() {
return PERFDATA_PROLOG_SIZE; // sizeof(struct PerfDataProlog)
}
/**
* Return an IntBuffer that accesses the major version number.
* This is used to create a Monitor object for this value.
*
* @return IntBuffer - a ByteBuffer that accesses the major version number
* in the instrumentation buffer header.
*/
public IntBuffer majorVersionBuffer() {
int[] holder = new int[1];
holder[0] = getMajorVersion();
IntBuffer ib = IntBuffer.wrap(holder);
ib.limit(1);
return ib;
}
/**
* Return an IntBuffer that accesses the minor version number.
* This is used to create a Monitor object for this value.
*
* @return IntBuffer - a ByteBuffer that accesses the minor version number
* in the instrumentation buffer header.
*/
public IntBuffer minorVersionBuffer() {
int[] holder = new int[1];
holder[0] = getMinorVersion();
IntBuffer ib = IntBuffer.wrap(holder);
ib.limit(1);
return ib;
}
/**
* Get the magic number from the given byteBuffer.
*
* @return int - the magic number
*/
public static int getMagic(ByteBuffer bb) {
// save buffer state
int position = bb.position();
ByteOrder order = bb.order();
// the magic number is always stored in big-endian format
bb.order(ByteOrder.BIG_ENDIAN);
bb.position(PERFDATA_PROLOG_MAGIC_OFFSET);
int magic = bb.getInt();
// restore buffer state.
bb.order(order);
bb.position(position);
return magic;
}
/**
* Get the major version number from the given ByteBuffer.
*
* @return int - the major version
*/
public static int getMajorVersion(ByteBuffer bb) {
// save buffer state
int position = bb.position();
bb.position(PERFDATA_PROLOG_MAJOR_OFFSET);
int major = (int) bb.get();
// restore buffer state.
bb.position(position);
return major;
}
/**
* Get the minor version number from the given ByteBuffer.
*
* @return int - the minor version
*/
public static int getMinorVersion(ByteBuffer bb) {
// save buffer state
int position = bb.position();
bb.position(PERFDATA_PROLOG_MINOR_OFFSET);
int minor = (int)bb.get();
// restore buffer state.
bb.position(position);
return minor;
}
/**
* Get the byte order for the given ByteBuffer.
*
* @return int - the byte order of the instrumentation buffer
*/
public static ByteOrder getByteOrder(ByteBuffer bb) {
// save buffer state
int position = bb.position();
bb.position(PERFDATA_PROLOG_BYTEORDER_OFFSET);
ByteOrder order = (bb.get() == PERFDATA_BIG_ENDIAN)
? ByteOrder.BIG_ENDIAN
: ByteOrder.LITTLE_ENDIAN;
// restore buffer state.
bb.position(position);
return order;
}
}