ucar.nc2.iosp

Interface IOServiceProvider

All Known Subinterfaces:

IOServiceProviderWriter

All Known Implementing Classes:

AbstractIOServiceProvider

public interface IOServiceProvider

This is the service provider interface for the low-level I/O access classes (read only). This is only used by service implementors. An implementation must have a no-argument constructor. The NetcdfFile class manages all registered IOServiceProvider classes. When NetcdfFile.open() is called:

1. the file is opened as a ucar.unidata.io.RandomAccessFile;
2. the file is handed to the isValidFile() method of each registered IOServiceProvider class (until one returns true, which means it can read the file).
3. the open() method on the resulting IOServiceProvider class is handed the file.

Method Summary

Modifier and Type	Method and Description
void	build(RandomAccessFile raf, Group.Builder rootGroup, CancelTask cancelTask) Open existing file, and populate it.
void	buildFinish(NetcdfFile ncfile) Sometimes the builder needs access to the finished objects.
void	close() Close the file.
String	getDetailInfo() Show debug / underlying implementation details
String	getFileTypeDescription() Get a human-readable description for this file type.
String	getFileTypeId() Get a unique id for this file type.
String	getFileTypeVersion() Get the version of this file type.
StructureDataIterator	getStructureIterator(Structure s, int bufferSize) Get the structure iterator.
boolean	isBuilder() If this iosp implements build().
boolean	isValidFile(RandomAccessFile raf) Check if this is a valid file for this IOServiceProvider.
void	open(RandomAccessFile raf, NetcdfFile ncfile, CancelTask cancelTask) Deprecated. Use build(RandomAccessFile raf, Group.Builder rootGroup, CancelTask cancelTask)
void	reacquire() Reacquire any resources like file handles Used when reactivating in cache.
Array	readData(Variable v2, Section section) Read data from a top level Variable and return a memory resident Array.
Array	readSection(ParsedSectionSpec cer) Allows reading sections of nested variables
long	readToByteChannel(Variable v2, Section section, WritableByteChannel channel) Deprecated. do not use
long	readToOutputStream(Variable v2, Section section, OutputStream out) Read data from a top level Variable and send data to a OutputStream.
void	release() Release any system resources like file handles.
Object	sendIospMessage(Object message) A way to communicate arbitrary information to an iosp.
long	streamToByteChannel(Variable v2, Section section, WritableByteChannel channel) Deprecated. do not use
boolean	syncExtend() Deprecated. Do not use.
String	toStringDebug(Object o) Debug info for this object.

Method Detail

isValidFile

boolean isValidFile(RandomAccessFile raf)
             throws IOException

Check if this is a valid file for this IOServiceProvider. You must make this method thread safe, ie dont keep any state.

Parameters:

raf - RandomAccessFile

Returns:

true if valid.

Throws:

IOException - if read error

open

@Deprecated
void open(RandomAccessFile raf,
                      NetcdfFile ncfile,
                      CancelTask cancelTask)
               throws IOException

Deprecated. Use build(RandomAccessFile raf, Group.Builder rootGroup, CancelTask cancelTask)

Open existing file, and populate ncfile with it. This method is only called by the NetcdfFile constructor on itself. The provided NetcdfFile object will be empty except for the location String and the IOServiceProvider associated with this NetcdfFile object.

Parameters:

raf - the file to work on, it has already passed the isValidFile() test.

ncfile - add objects to this empty NetcdfFile

cancelTask - used to monitor user cancellation; may be null.

Throws:

IOException - if read error

isBuilder

boolean isBuilder()

If this iosp implements build().

build

void build(RandomAccessFile raf,
           Group.Builder rootGroup,
           CancelTask cancelTask)
    throws IOException

Open existing file, and populate it. Note that you cannot reference the NetcdfFile within this routine. This is the bridge to immutable objects that will be used exclusively in version 6.

Parameters:

raf - the file to work on, it has already passed the isValidFile() test.

rootGroup - add objects to the root group.

cancelTask - used to monitor user cancellation; may be null.

Throws:

IOException - if read error

buildFinish

void buildFinish(NetcdfFile ncfile)

Sometimes the builder needs access to the finished objects. This is called after ncfile.build()

readData

Array readData(Variable v2,
               Section section)
        throws IOException,
               InvalidRangeException

Read data from a top level Variable and return a memory resident Array. This Array has the same element type as the Variable, and the requested shape.

Parameters:

v2 - a top-level Variable

section - the section of data to read. There must be a Range for each Dimension in the variable, in order. Note: no nulls allowed. IOSP may not modify.

Returns:

the requested data in a memory-resident Array

Throws:

IOException - if read error

InvalidRangeException - if invalid section

See Also:

Range

readToByteChannel

@Deprecated
long readToByteChannel(Variable v2,
                                   Section section,
                                   WritableByteChannel channel)
                            throws IOException,
                                   InvalidRangeException

Deprecated. do not use

Read data from a top level Variable and send data to a WritableByteChannel. Must be in big-endian order.

Parameters:

v2 - a top-level Variable

section - the section of data to read. There must be a Range for each Dimension in the variable, in order. Note: no nulls allowed. IOSP may not modify.

channel - write data to this WritableByteChannel

Returns:

the number of bytes written to the channel

Throws:

IOException - if read error

InvalidRangeException - if invalid section

streamToByteChannel

@Deprecated
long streamToByteChannel(Variable v2,
                                     Section section,
                                     WritableByteChannel channel)
                              throws IOException,
                                     InvalidRangeException

Deprecated. do not use

Throws:

IOException

InvalidRangeException

readToOutputStream

long readToOutputStream(Variable v2,
                        Section section,
                        OutputStream out)
                 throws IOException,
                        InvalidRangeException

Read data from a top level Variable and send data to a OutputStream. Must be in big-endian order, following ncstream conventions. Default implementation just reads to memory and writes to stream. Allow override for possible performance improvements.

Parameters:

v2 - a top-level Variable

section - the section of data to read. There must be a Range for each Dimension in the variable, in order. Note: no nulls allowed. IOSP may not modify.

out - write data to this OutputStream

Returns:

the number of bytes written to the channel

Throws:

IOException - if read error

InvalidRangeException - if invalid section

readSection

Array readSection(ParsedSectionSpec cer)
           throws IOException,
                  InvalidRangeException

Allows reading sections of nested variables

Parameters:

cer - section specification : what data is wanted

Returns:

requested data array

Throws:

IOException - on read error

InvalidRangeException - if section spec is invalid

getStructureIterator

StructureDataIterator getStructureIterator(Structure s,
                                           int bufferSize)
                                    throws IOException

Get the structure iterator. iosps with top level sequences must override. Not threadsafe; do not use multiple StructureDataIterator for the same iosp.

Parameters:

s - the Structure

bufferSize - the buffersize

Returns:

the data iterator

Throws:

IOException - if problem reading data

close

void close()
    throws IOException

Close the file. It is the IOServiceProvider's job to close the file (even though it didnt open it), and to free any other resources it has used.

Throws:

IOException - if read error

syncExtend

@Deprecated
boolean syncExtend()
                        throws IOException

Deprecated. Do not use.

Extend the NetcdfFile if the underlying dataset has changed in a way that is compatible with the current metadata. For example, if the unlimited dimension has grown.

Returns:

true if the NetcdfFile was extended.

Throws:

IOException - if a read error occured when accessing the underlying dataset.

release

void release()
      throws IOException

Release any system resources like file handles. Optional, implement only if you are able to reacquire. Used when object is made inactive in cache.

Throws:

IOException

reacquire

void reacquire()
        throws IOException

Reacquire any resources like file handles Used when reactivating in cache.

Throws:

IOException

sendIospMessage

Object sendIospMessage(Object message)

A way to communicate arbitrary information to an iosp.

Parameters:

message - opaque message sent to the IOSP object when its opened (not when isValidFile() is called)

Returns:

opaque return, may be null.

toStringDebug

String toStringDebug(Object o)

Debug info for this object.

Parameters:

o - which object

Returns:

debug info for this object

getDetailInfo

String getDetailInfo()

Show debug / underlying implementation details

Returns:

debug info

getFileTypeId

String getFileTypeId()

Get a unique id for this file type.

Returns:

registered id of the file type

See Also:

"https://www.unidata.ucar.edu/software/netcdf-java/formats/FileTypes.html"

getFileTypeVersion

String getFileTypeVersion()

Get the version of this file type.

Returns:

version of the file type

See Also:

"https://www.unidata.ucar.edu/software/netcdf-java/formats/FileTypes.html"

getFileTypeDescription

String getFileTypeDescription()

Get a human-readable description for this file type.

Returns:

description of the file type

See Also:

"https://www.unidata.ucar.edu/software/netcdf-java/formats/FileTypes.html"