uk.ac.bristol.star.cdf
Class CdfReader

java.lang.Object
  extended by uk.ac.bristol.star.cdf.CdfReader

public class CdfReader
extends java.lang.Object

Examines a CDF file and provides methods to access its records.

Constructing an instance of this class reads enough of a file to identify it as a CDF and work out how to access its records. Most of the actual contents are only read from the data buffer as required. Although only the magic numbers and CDR are read during construction, in the case of a file-compressed CDF the whole thing is uncompressed, so it could still be an expensive operation.

For low-level access to the CDF internal records, use the getCdr() method to get the CdfDescriptorRecord and use that in conjunction with knowledge of the internal format of CDF files as a starting point to chase pointers around the file constructing other records. When you have a pointer to another record, you can use the record factory got from getRecordFactory() to turn it into a typed Record object.

Since:
19 Jun 2013

Constructor Summary
CdfReader(Buf buf)
          Constructs a CdfReader from a buffer containing its byte data.
CdfReader(java.io.File file)
          Constructs a CdfReader from a readable file containing its byte data.
 
Method Summary
 Buf getBuf()
          Returns the buffer containing the uncompressed record stream for this reader's CDF file.
 CdfDescriptorRecord getCdr()
          Returns the CDF Descriptor Record object for this reader's CDF.
 RecordFactory getRecordFactory()
          Returns a RecordFactory that can be applied to this reader's Buf to construct CDF Record objects.
static boolean isMagic(byte[] intro)
          Examines a byte array to see if it looks like the start of a CDF file.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CdfReader

public CdfReader(Buf buf)
          throws java.io.IOException
Constructs a CdfReader from a buffer containing its byte data.

Parameters:
buf - buffer containing CDF file
Throws:
java.io.IOException

CdfReader

public CdfReader(java.io.File file)
          throws java.io.IOException
Constructs a CdfReader from a readable file containing its byte data.

Parameters:
file - CDF file
Throws:
java.io.IOException
Method Detail

getBuf

public Buf getBuf()
Returns the buffer containing the uncompressed record stream for this reader's CDF file. This will be the buffer originally submitted at construction time only if the CDF does not use whole-file compression.

Returns:
buffer containing CDF records

getRecordFactory

public RecordFactory getRecordFactory()
Returns a RecordFactory that can be applied to this reader's Buf to construct CDF Record objects.

Returns:
record factory

getCdr

public CdfDescriptorRecord getCdr()
Returns the CDF Descriptor Record object for this reader's CDF.

Returns:
CDF Descriptor Record

isMagic

public static boolean isMagic(byte[] intro)
Examines a byte array to see if it looks like the start of a CDF file.

Parameters:
intro - byte array, at least 8 bytes if available
Returns:
true iff the first 8 bytes of intro are a CDF magic number