DataAccess

java.lang.Object
- org.basex.io.random.DataAccess

```
public final class DataAccess
extends java.lang.Object
```
This class allows positional read and write access to a database file.

Author:

BaseX Team 2005-12, BSD License, Christian Gruen

Constructor Summary

Constructors
Constructor and Description

DataAccess(IOFile f)
Constructor, initializing the file reader.

Constructors
Constructor and Description
`DataAccess(IOFile f)` Constructor, initializing the file reader.

Method Summary

Methods
Modifier and Type	Method and Description
`long`	`appendNums(int[] v)` Appends integers to the file in compressed form.
`void`	`close()` Closes the data access.
`long`	`cursor()` Returns the current file position.
`void`	`cursor(long p)` Sets the disk cursor.
`void`	`flush()` Flushes the buffered data.
`long`	`free(long pos, int size)` Returns the offset to a free slot for writing an entry with the specified length.
`long`	`length()` Returns the file length.
`boolean`	`more()` Checks if more bytes can be read.
`byte`	`read1()` Reads a byte value.
`byte`	`read1(long p)` Reads a byte value from the specified position.
`int`	`read4()` Reads an integer value.
`int`	`read4(long p)` Reads an integer value from the specified position.
`long`	`read5()` Reads a 5-byte value.
`long`	`read5(long p)` Reads a 5-byte value from the specified file offset.
`byte[]`	`readBytes(int n)` Reads a number of bytes.
`byte[]`	`readBytes(long p, int l)` Reads a number of bytes from the specified offset.
`int`	`readNum()` Reads the next compressed number and returns it as integer.
`int`	`readNum(long p)` Reads a `Num` value from disk.
`byte[]`	`readToken()` Reads the next token from disk.
`byte[]`	`readToken(long p)` Reads a token from disk.
`void`	`write4(int v)` Writes an integer value to the current position.
`void`	`write4(long p, int v)` Writes an integer value to the specified position.
`void`	`write5(long p, long v)` Writes a 5-byte value to the specified position.
`void`	`writeNum(long p, int v)` Write a value to the file.
`void`	`writeNums(long p, int[] v)` Writes integers to the file in compressed form.
`void`	`writeToken(byte[] buf, int offset, int length)` Write a token to the file.
`void`	`writeToken(long p, byte[] v)` Appends a value to the file and return it's offset.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DataAccess
```
public DataAccess(IOFile f)
           throws java.io.IOException
```
    Constructor, initializing the file reader.
    
    Parameters:
    f - the file to be read
    
    Throws:
    
    java.io.IOException - I/O Exception
- Method Detail
  - flush
```
public void flush()
           throws java.io.IOException
```
    Flushes the buffered data.
    
    Throws:
    
    java.io.IOException - I/O exception
  - close
```
public void close()
           throws java.io.IOException
```
    Closes the data access.
    
    Throws:
    
    java.io.IOException - I/O exception
  - cursor
```
public long cursor()
```
    Returns the current file position.
    
    Returns:
    position in the file
  - length
```
public long length()
```
    Returns the file length.
    
    Returns:
    file length
  - more
```
public boolean more()
```
    Checks if more bytes can be read.
    
    Returns:
    result of check
  - read1
```
public byte read1(long p)
```
    Reads a byte value from the specified position.
    
    Parameters:
    p - position
    
    Returns:
    integer value
  - read1
```
public byte read1()
```
    Reads a byte value.
    
    Returns:
    integer value
  - read4
```
public int read4(long p)
```
    Reads an integer value from the specified position.
    
    Parameters:
    p - position
    
    Returns:
    integer value
  - read4
```
public int read4()
```
    Reads an integer value.
    
    Returns:
    integer value
  - read5
```
public long read5(long p)
```
    Reads a 5-byte value from the specified file offset.
    
    Parameters:
    p - position
    
    Returns:
    long value
  - read5
```
public long read5()
```
    Reads a 5-byte value.
    
    Returns:
    long value
  - readNum
```
public int readNum(long p)
```
    Reads a Num value from disk.
    
    Parameters:
    p - text position
    
    Returns:
    read num
  - readToken
```
public byte[] readToken(long p)
```
    Reads a token from disk.
    
    Parameters:
    p - text position
    
    Returns:
    text as byte array
  - readToken
```
public byte[] readToken()
```
    Reads the next token from disk.
    
    Returns:
    text as byte array
  - readBytes
```
public byte[] readBytes(long p,
               int l)
```
    Reads a number of bytes from the specified offset.
    
    Parameters:
    p - position
    l - length
    
    Returns:
    byte array
  - readBytes
```
public byte[] readBytes(int n)
```
    Reads a number of bytes.
    
    Parameters:
    n - length
    
    Returns:
    byte array
  - cursor
```
public void cursor(long p)
```
    Sets the disk cursor.
    
    Parameters:
    p - read position
  - readNum
```
public int readNum()
```
    Reads the next compressed number and returns it as integer.
    
    Returns:
    next integer
  - write5
```
public void write5(long p,
          long v)
```
    Writes a 5-byte value to the specified position.
    
    Parameters:
    p - position in the file
    v - value to be written
  - write4
```
public void write4(long p,
          int v)
```
    Writes an integer value to the specified position.
    
    Parameters:
    p - write position
    v - byte array to be appended
  - write4
```
public void write4(int v)
```
    Writes an integer value to the current position.
    
    Parameters:
    v - value to be written
  - writeNum
```
public void writeNum(long p,
            int v)
```
    Write a value to the file.
    
    Parameters:
    p - write position
    v - value to be written
  - writeNums
```
public void writeNums(long p,
             int[] v)
```
    Writes integers to the file in compressed form.
    
    Parameters:
    p - write position
    v - integer values
  - appendNums
```
public long appendNums(int[] v)
```
    Appends integers to the file in compressed form.
    
    Parameters:
    v - integer values
    
    Returns:
    the position in the file where the values have been written
  - writeToken
```
public void writeToken(long p,
              byte[] v)
```
    Appends a value to the file and return it's offset.
    
    Parameters:
    p - write position
    v - byte array to be appended
  - writeToken
```
public void writeToken(byte[] buf,
              int offset,
              int length)
```
    Write a token to the file.
    
    Parameters:
    buf - buffer containing the token
    offset - offset in the buffer where the token starts
    length - token length
  - free
```
public long free(long pos,
        int size)
```
    Returns the offset to a free slot for writing an entry with the specified length. Fills the original space with 0xFF to facilitate future write operations.
    
    Parameters:
    pos - original offset
    size - size of new text entry
    
    Returns:
    new offset to store text

Class DataAccess

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DataAccess

Method Detail

flush

close

cursor

length

more

read1

read1

read4

read4

read5

read5

readNum

readToken

readToken

readBytes

readBytes

cursor

readNum

write5

write4

write4

writeNum

writeNums

appendNums

writeToken

writeToken

free