KeyReader (apache-cassandra API)

All Superinterfaces:

java.lang.AutoCloseable, java.io.Closeable

All Known Implementing Classes:

BigTableKeyReader
```
public interface KeyReader
extends java.io.Closeable
```
Reads keys from an SSTable.
It is specific to SSTable format how the keys are read but in general the assumption is that it will read all the keys in the order as they are placed in data file.
After creating it, it should be at the first key. Unless the SSTable is empty, key(), keyPositionForSecondaryIndex() and dataPosition() should return approriate values. If there is no data, isExhausted() returns true. In order to move to the next key, advance() should be called. It returns true if the reader moved to the next key; otherwise, there is no more data to read and the reader is exhausted. When the reader is exhausted, return values of key(), keyPositionForSecondaryIndex() and dataPosition() are undefined.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`boolean`	`advance()`	Moves the iterator forward.
`void`	`close()`	Closes the iterator quietly
`long`	`dataPosition()`	Position in the data file where the associated content resides
`boolean`	`isExhausted()`	Returns true if we reach EOF
`java.nio.ByteBuffer`	`key()`	Current key
`long`	`keyPositionForSecondaryIndex()`	Position in the component preferred for reading keys.
`void`	`reset()`	Resets the iterator to the initial position

- Method Detail
  - key
```
java.nio.ByteBuffer key()
```
    Current key
  - keyPositionForSecondaryIndex
```
long keyPositionForSecondaryIndex()
```
    Position in the component preferred for reading keys. This is specific to SSTable implementation
  - dataPosition
```
long dataPosition()
```
    Position in the data file where the associated content resides
  - advance
```
boolean advance()
         throws java.io.IOException
```
    Moves the iterator forward. Returns false if we reach EOF and there nothing more to read
    
    Throws:
    
    java.io.IOException
  - isExhausted
```
boolean isExhausted()
```
    Returns true if we reach EOF
  - reset
```
void reset()
    throws java.io.IOException
```
    Resets the iterator to the initial position
    
    Throws:
    
    java.io.IOException
  - close
```
void close()
```
    Closes the iterator quietly
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.Closeable