ev3dev.utils.io

Class NativeFile

java.lang.Object

ev3dev.utils.io.NativeFile

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

NativeDevice

public class NativeFile
extends java.lang.Object
implements java.io.Closeable, java.lang.AutoCloseable

This class provides access to Linux files using native I/O operations. It is implemented using the JNA package. The class is required because certain operations (like ioctl) that are required by the Lego kernel module interface are not support by standard Java methods. In addition standard Java memory mapped files do not seem to function correctly when used with Linux character devices.

Only JNA is used, the original interface used combination of Java and JNA.

Field Summary

Fields

Modifier and Type	Field and Description
private static int	DEFAULT_PRIVS
protected int	fd
private ILibc	libc

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	NativeFile() Basic constructor.
protected	NativeFile(ILibc libc) Basic constructor.
	NativeFile(java.lang.String fname, int flags) Create a NativeFile object and open the associated file/device for native access.
	NativeFile(java.lang.String fname, int flags, ILibc libc) Create a NativeFile object and open the associated file/device for native access.
	NativeFile(java.lang.String fname, int flags, int mode) Create a NativeFile object and open the associated file/device for native access.
	NativeFile(java.lang.String fname, int flags, int mode, ILibc libc) Create a NativeFile object and open the associated file/device for native access.

Method Summary

Modifier and Type	Method and Description
void	close() Close the associated file
int	ioctl(int req, IntByReference info) Perform a Linux style ioctl operation on the associated file.
int	ioctl(int req, Pointer buf) Perform a Linux style ioctl operation on the associated file.
boolean	isOpen() Check whether this file has been open()en.
Pointer	mmap(long len, int prot, int flags, long off) Map a portion of the associated file into memory and return a pointer that can be used to access that memory.
void	msync(Pointer addr, long len, int flags) Synchronize mapped memory region.
void	munmap(Pointer addr, long len) Unmap mapped memory region.
void	open(java.lang.String fname, int flags) Open the specified file/device for native access.
void	open(java.lang.String fname, int flags, int mode) Open the specified file/device for native access.
int	read(byte[] buf, int len) Attempt to read the requested number of bytes from the associated file.
int	read(byte[] buf, int offset, int len) Attempt to read the requested number of byte from the associated file.
int	write(byte[] buf, int len) Attempt to write the requested number of bytes to the associated file.
int	write(byte[] buf, int offset, int len) Attempt to write the requested number of bytes to the associated file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_PRIVS

private static int DEFAULT_PRIVS

fd

protected int fd

libc

private ILibc libc

Constructor Detail

NativeFile

protected NativeFile()

Basic constructor.

NativeFile

protected NativeFile(ILibc libc)

Basic constructor.

Parameters:

libc - standard C library interface to be used.

NativeFile

public NativeFile(java.lang.String fname,
                  int flags)
           throws LastErrorException

Create a NativeFile object and open the associated file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

Throws:

LastErrorException - when operations fails

NativeFile

public NativeFile(java.lang.String fname,
                  int flags,
                  int mode)
           throws LastErrorException

Create a NativeFile object and open the associated file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

mode - Linux style file access mode

Throws:

LastErrorException - when operations fails

NativeFile

public NativeFile(java.lang.String fname,
                  int flags,
                  ILibc libc)
           throws LastErrorException

Create a NativeFile object and open the associated file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

libc - standard C library interface to be used.

Throws:

LastErrorException - when operations fails

NativeFile

public NativeFile(java.lang.String fname,
                  int flags,
                  int mode,
                  ILibc libc)
           throws LastErrorException

Create a NativeFile object and open the associated file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

mode - Linux style file access mode

libc - standard C library interface to be used.

Throws:

LastErrorException - when operations fails

Method Detail

isOpen

public boolean isOpen()

Check whether this file has been open()en.

Returns:

True when the filedescriptor is valid.

open

public void open(java.lang.String fname,
                 int flags)
          throws LastErrorException

Open the specified file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

Throws:

LastErrorException - when operations fails

open

public void open(java.lang.String fname,
                 int flags,
                 int mode)
          throws LastErrorException

Open the specified file/device for native access.

Parameters:

fname - the name of the file to open

flags - Linux style file access flags

mode - Linux style file access mode

Throws:

LastErrorException - when operations fails

read

public int read(byte[] buf,
                int len)
         throws LastErrorException

Attempt to read the requested number of bytes from the associated file.

Parameters:

buf - location to store the read bytes

len - number of bytes to attempt to read

Returns:

number of bytes read

Throws:

LastErrorException - when operations fails

write

public int write(byte[] buf,
                 int offset,
                 int len)
          throws LastErrorException

Attempt to write the requested number of bytes to the associated file.

Parameters:

buf - location to store the read bytes

offset - the offset within buf to take data from for the write

len - number of bytes to attempt to read

Returns:

number of bytes read

Throws:

LastErrorException - when operations fails

read

public int read(byte[] buf,
                int offset,
                int len)
         throws LastErrorException

Attempt to read the requested number of byte from the associated file.

Parameters:

buf - location to store the read bytes

offset - offset with buf to start storing the read bytes

len - number of bytes to attempt to read

Returns:

number of bytes read

Throws:

LastErrorException - when operations fails

write

public int write(byte[] buf,
                 int len)
          throws LastErrorException

Attempt to write the requested number of bytes to the associated file.

Parameters:

buf - location to store the read bytes

len - number of bytes to attempt to read

Returns:

number of bytes read

Throws:

LastErrorException - when operations fails

ioctl

public int ioctl(int req,
                 IntByReference info)
          throws LastErrorException

Perform a Linux style ioctl operation on the associated file.

Parameters:

req - ioctl operation to be performed

info - output as integer

Returns:

Linux style ioctl return

Throws:

LastErrorException - when operations fails

ioctl

public int ioctl(int req,
                 Pointer buf)
          throws LastErrorException

Perform a Linux style ioctl operation on the associated file.

Parameters:

req - ioctl operation to be performed

buf - pointer to ioctl parameters

Returns:

Linux style ioctl return

Throws:

LastErrorException - when operations fails

close

public void close()
           throws LastErrorException

Close the associated file

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Throws:

LastErrorException - when operations fails

mmap

public Pointer mmap(long len,
                    int prot,
                    int flags,
                    long off)
             throws LastErrorException

Map a portion of the associated file into memory and return a pointer that can be used to access that memory.

Parameters:

len - size of the region to map

prot - protection for the memory region

flags - Linux mmap flags

off - offset within the file for the start of the region

Returns:

a pointer that can be used to access the mapped data

Throws:

LastErrorException - when operations fails

munmap

public void munmap(Pointer addr,
                   long len)
            throws LastErrorException

Unmap mapped memory region.

Parameters:

addr - Mapped address.

len - Region length.

Throws:

LastErrorException - when operations fails

msync

public void msync(Pointer addr,
                  long len,
                  int flags)
           throws LastErrorException

Synchronize mapped memory region.

Parameters:

addr - Mapped address.

len - Region length.

flags - Synchronization flags

Throws:

LastErrorException - when operations fails