ej.event

Interface EventDataReader

public interface EventDataReader

An EventDataReader contains the methods to read the data of an extended event.

EventDataReaders are created by the system and passed to extended events listeners when calling EventQueueListener.handleExtendedEvent(int, EventDataReader) method.

There are two ways to read the data of an extended event:

• Read the data with read(byte[], int, int) or readFully(byte[]) methods.
  • You will get the data in a byte array and can process it on your own in EventQueueListener.handleExtendedEvent(int, EventDataReader).
• Read the data with the methods related to the primitive types such as readBoolean() or readByte().
  • This is useful when the extended data you send through the Event Queue is a C structure with multiple fields.
  • To use the methods, your fields must follow this alignment:
    • A boolean (1 byte) will be 1-byte aligned.
    • A byte (1 byte) will be 1-byte aligned.
    • A char (2 bytes) will be 2-byte aligned.
    • A double (8 bytes) will be 8-byte aligned.
    • A float (4 bytes) will be 4-byte aligned.
    • An int (4 bytes) will be 4-byte aligned.
    • A long (8 bytes) will be 8-byte aligned.
    • A short (2 bytes) will be 2-byte aligned.
    • An unsigned byte (1 byte) will be 1-byte aligned.
    • A unsigned short (2 bytes) will be 2-byte aligned.

Method Summary

Modifier and Type	Method and Description
int	available() Returns the number of bytes that can be read (or skipped over).
int	read(byte[] b, int off, int len) Reads len bytes of data and store them into the buffer b.
boolean	readBoolean() Reads the next boolean of data.
byte	readByte() Reads the next byte of data.
char	readChar() Reads the next char of data.
double	readDouble() Reads the next double of data.
float	readFloat() Reads the next float of data.
int	readFully(byte[] b) Reads all the bytes of data and store them into the buffer b.
int	readInt() Reads the next integer of data.
long	readLong() Reads the next long of data.
short	readShort() Reads the next short of data.
int	readUnsignedByte() Reads the next unsigned byte of data.
int	readUnsignedShort() Reads the next unsigned short of data.
int	skipBytes(int n) Skips over and discard n bytes of data.

Method Detail

available

int available()

Returns the number of bytes that can be read (or skipped over).

Returns:

the number of available data bytes.

read

int read(byte[] b,
         int off,
         int len)
  throws IOException

Reads len bytes of data and store them into the buffer b.

Parameters:

b - the buffer into which the data is read.

off - the start offset in the buffer b at which the data is written.

len - the number of bytes to read.

Returns:

the total number of bytes read into the buffer.

Throws:

IOException - if there are not enough bytes remaining in the data of the extended event or if the buffer is too small to store the event data.

readBoolean

boolean readBoolean()
             throws IOException

Reads the next boolean of data.

Returns:

the next boolean of data.

Throws:

IOException - if there is no boolean remaining in the data of the extended event.

readByte

byte readByte()
       throws IOException

Reads the next byte of data.

Returns:

the next byte of data.

Throws:

IOException - if there is no byte remaining in the data of the extended event.

readChar

char readChar()
       throws IOException

Reads the next char of data.

Returns:

the next char of data.

Throws:

IOException - if there is no char remaining in the data of the extended event.

readDouble

double readDouble()
           throws IOException

Reads the next double of data.

Returns:

the next double of data.

Throws:

IOException - if there is no double remaining in the data of the extended event.

readFloat

float readFloat()
         throws IOException

Reads the next float of data.

Returns:

the next float of data.

Throws:

IOException - if there is no float remaining in the data of the extended event.

readFully

int readFully(byte[] b)
       throws IOException

Reads all the bytes of data and store them into the buffer b.

Parameters:

b - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer.

Throws:

IOException - if there is no byte remaining in the data of the extended event or if the buffer is too small to store the event data.

readInt

int readInt()
     throws IOException

Reads the next integer of data.

Returns:

the next integer of data.

Throws:

IOException - if there is no integer remaining in the data of the extended event.

readLong

long readLong()
       throws IOException

Reads the next long of data.

Returns:

the next long of data.

Throws:

IOException - if there is no long remaining in the data of the extended event.

readShort

short readShort()
         throws IOException

Reads the next short of data.

Returns:

the next short of data.

Throws:

IOException - if there is no short remaining in the data of the extended event.

readUnsignedByte

int readUnsignedByte()
              throws IOException

Reads the next unsigned byte of data.

Returns:

the next unsigned byte of data.

Throws:

IOException - if there is no unsigned byte remaining in the data of the extended event.

readUnsignedShort

int readUnsignedShort()
               throws IOException

Reads the next unsigned short of data.

Returns:

the next unsigned short of data.

Throws:

IOException - if there is no unsigned short remaining in the data of the extended event.

skipBytes

int skipBytes(int n)

Skips over and discard n bytes of data.

Parameters:

n - the number of bytes to skip.

Returns:

0 if OK and -1 if an error occurs.