/**
* method to extract the next monitor entry from the instrumentation memory. assumes that
* nextEntry is the offset into the byte array at which to start the search for the next entry.
* method leaves next entry pointing to the next entry or to the end of data.
*/
protected Monitor getNextMonitorEntry() throws MonitorException {
Monitor monitor = null;
// entries are always 4 byte aligned.
if ((nextEntry % 4) != 0) {
throw new MonitorStructureException("Entry index not properly aligned: " + nextEntry);
}
// protect against a corrupted shared memory region.
if ((nextEntry < 0) || (nextEntry > buffer.limit())) {
throw new MonitorStructureException(
"Entry index out of bounds: nextEntry = " + nextEntry + ", limit = " + buffer.limit());
}
// check for the end of the buffer
if (nextEntry == buffer.limit()) {
lognl("getNextMonitorEntry():" + " nextEntry == buffer.limit(): returning");
return null;
}
buffer.position(nextEntry);
int entryStart = buffer.position();
int entryLength = buffer.getInt();
// check for valid entry length
if ((entryLength < 0) || (entryLength > buffer.limit())) {
throw new MonitorStructureException("Invalid entry length: entryLength = " + entryLength);
}
// check if last entry occurs before the eof.
if ((entryStart + entryLength) > buffer.limit()) {
throw new MonitorStructureException(
"Entry extends beyond end of buffer: "
+ " entryStart = "
+ entryStart
+ " entryLength = "
+ entryLength
+ " buffer limit = "
+ buffer.limit());
}
if (entryLength == 0) {
// end of data
return null;
}
int nameLength = buffer.getInt();
int vectorLength = buffer.getInt();
byte dataType = buffer.get();
byte flags = buffer.get();
Units u = Units.toUnits(buffer.get());
Variability v = Variability.toVariability(buffer.get());
boolean supported = (flags & 0x01) != 0;
// defend against corrupt entries
if ((nameLength <= 0) || (nameLength > entryLength)) {
throw new MonitorStructureException("Invalid Monitor name length: " + nameLength);
}
if ((vectorLength < 0) || (vectorLength > entryLength)) {
throw new MonitorStructureException("Invalid Monitor vector length: " + vectorLength);
}
// read in the perfData item name, casting bytes to chars. skip the
// null terminator
//
byte[] nameBytes = new byte[nameLength - 1];
for (int i = 0; i < nameLength - 1; i++) {
nameBytes[i] = buffer.get();
}
// convert name into a String
String name = new String(nameBytes, 0, nameLength - 1);
if (v == Variability.INVALID) {
throw new MonitorDataException(
"Invalid variability attribute:" + " entry index = " + perfDataItem + " name = " + name);
}
if (u == Units.INVALID) {
throw new MonitorDataException(
"Invalid units attribute: " + " entry index = " + perfDataItem + " name = " + name);
}
int offset;
if (vectorLength == 0) {
// scalar Types
if (dataType == BasicType.LONG.intValue()) {
offset = entryStart + entryLength - 8; /* 8 = sizeof(long) */
buffer.position(offset);
LongBuffer lb = buffer.asLongBuffer();
lb.limit(1);
monitor = new PerfLongMonitor(name, u, v, supported, lb);
perfDataItem++;
} else {
// bad data types.
throw new MonitorTypeException(
"Invalid Monitor type:"
+ " entry index = "
+ perfDataItem
+ " name = "
+ name
+ " type = "
+ dataType);
}
} else {
// vector types
if (dataType == BasicType.BYTE.intValue()) {
if (u != Units.STRING) {
// only byte arrays of type STRING are currently supported
throw new MonitorTypeException(
"Invalid Monitor type:"
+ " entry index = "
+ perfDataItem
+ " name = "
+ name
+ " type = "
+ dataType);
}
offset = entryStart + PERFDATA_NAME_OFFSET + nameLength;
buffer.position(offset);
ByteBuffer bb = buffer.slice();
bb.limit(vectorLength);
bb.position(0);
if (v == Variability.CONSTANT) {
monitor = new PerfStringConstantMonitor(name, supported, bb);
} else if (v == Variability.VARIABLE) {
monitor = new PerfStringVariableMonitor(name, supported, bb, vectorLength - 1);
} else {
// Monotonically increasing byte arrays are not supported
throw new MonitorDataException(
"Invalid variability attribute:"
+ " entry index = "
+ perfDataItem
+ " name = "
+ name
+ " variability = "
+ v);
}
perfDataItem++;
} else {
// bad data types.
throw new MonitorTypeException(
"Invalid Monitor type:"
+ " entry index = "
+ perfDataItem
+ " name = "
+ name
+ " type = "
+ dataType);
}
}
// setup index to next entry for next iteration of the loop.
nextEntry = entryStart + entryLength;
return monitor;
}
