com.ibm.security12.sun.security.util
Class DerInputStream

java.lang.Object
  |
  +--com.ibm.security12.sun.security.util.DerInputStream

public class DerInputStream
extends Object

A DER input stream, used for parsing ASN.1 DER-encoded data such as that found in X.509 certificates. DER is a subset of BER/1, which has the advantage that it allows only a single encoding of primitive data. (High level data such as dates still support many encodings.) That is, it uses the "Definite" Encoding Rules (DER) not the "Basic" ones (BER).

Note that, like BER/1, DER streams are streams of explicitly tagged data values. Accordingly, this programming interface does not expose any variant of the java.io.InputStream interface, since that kind of input stream holds untagged data values and using that I/O model could prevent correct parsing of the DER data.

At this time, this class supports only a subset of the types of DER data encodings which are defined. That subset is sufficient for parsing most X.509 certificates.

Version:
1.41
Author:
David Brownell, Amit Kapoor, Hemma Prafullchandra

Constructor Summary
DerInputStream(byte[] data)
          Create a DER input stream from a data buffer.
DerInputStream(byte[] data, int offset, int len)
          Create a DER input stream from part of a data buffer.
 
Method Summary
 int available()
          Returns the number of bytes available for reading.
 byte[] getBitString()
          Get a bit string from the input stream.
 void getBytes(byte[] val)
          Returns the asked number of bytes from the input stream.
 DerValue getDerValue()
          Get a single DER-encoded value from the input stream.
 BigInt getEnumerated()
          Get an enumerated from the input stream.
 Date getGeneralizedTime()
          Get a Generalized encoded time value from the input stream.
 BigInt getInteger()
          Get an (unsigned) integer from the input stream.
 void getNull()
          Reads an encoded null value from the input stream.
 byte[] getOctetString()
          Returns an ASN.1 OCTET STRING from the input stream.
 ObjectIdentifier getOID()
          Reads an X.200 style Object Identifier from the stream.
 DerValue[] getSequence(int startLen)
          Return a sequence of encoded entities.
 DerValue[] getSet(int startLen)
          Return a set of encoded entities.
 DerValue[] getSet(int startLen, boolean implicit)
          Return a set of encoded entities.
 BitArray getUnalignedBitString()
          Get a bit string from the input stream.
 Date getUTCTime()
          Get a UTC encoded time value from the input stream.
 void mark(int value)
          Mark the current position in the buffer, so that a later call to reset will return here.
 int peekByte()
           
protected  DerValue[] readVector(int startLen)
           
 void reset()
          Return to the position of the last mark call.
 DerInputStream subStream(int len, boolean do_skip)
          Creates a new DER input stream from part of this input stream.
 byte[] toByteArray()
          Return what has been written to this DerInputStream as a byte array.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DerInputStream

public DerInputStream(byte[] data)
Create a DER input stream from a data buffer. The buffer is not copied, it is shared. Accordingly, the buffer should be treated as read-only.
Parameters:
data - the buffer from which to create the string (CONSUMED)

DerInputStream

public DerInputStream(byte[] data,
                      int offset,
                      int len)
Create a DER input stream from part of a data buffer. The buffer is not copied, it is shared. Accordingly, the buffer should be treated as read-only.
Parameters:
data - the buffer from which to create the string (CONSUMED)
offset - the first index of data which will be read as DER input in the new stream
len - how long a chunk of the buffer to use, starting at "offset"
Method Detail

subStream

public DerInputStream subStream(int len,
                                boolean do_skip)
                         throws IOException
Creates a new DER input stream from part of this input stream.
Parameters:
len - how long a chunk of the current input stream to use, starting at the current position.
do_skip - true if the existing data in the input stream should be skipped. If this value is false, the next data read on this stream and the newly created stream will be the same.

toByteArray

public byte[] toByteArray()
Return what has been written to this DerInputStream as a byte array. Useful for debugging.

getInteger

public BigInt getInteger()
                  throws IOException
Get an (unsigned) integer from the input stream.

getEnumerated

public BigInt getEnumerated()
                     throws IOException
Get an enumerated from the input stream.

getBitString

public byte[] getBitString()
                    throws IOException
Get a bit string from the input stream. Only octet-aligned bitstrings (multiples of eight bits in length) are handled by this method.

getUnalignedBitString

public BitArray getUnalignedBitString()
                               throws IOException
Get a bit string from the input stream. The bit string need not be byte-aligned.

getOctetString

public byte[] getOctetString()
                      throws IOException
Returns an ASN.1 OCTET STRING from the input stream.

getBytes

public void getBytes(byte[] val)
              throws IOException
Returns the asked number of bytes from the input stream.

getNull

public void getNull()
             throws IOException
Reads an encoded null value from the input stream.

getOID

public ObjectIdentifier getOID()
                        throws IOException
Reads an X.200 style Object Identifier from the stream.

getSequence

public DerValue[] getSequence(int startLen)
                       throws IOException
Return a sequence of encoded entities. ASN.1 sequences are ordered, and they are often used, like a "struct" in C or C++, to group data values. They may have optional or context specific values.
Parameters:
startLen - guess about how long the sequence will be (used to initialize an auto-growing data structure)
Returns:
array of the values in the sequence

getSet

public DerValue[] getSet(int startLen)
                  throws IOException
Return a set of encoded entities. ASN.1 sets are unordered, though DER may specify an order for some kinds of sets (such as the attributes in an X.500 relative distinguished name) to facilitate binary comparisons of encoded values.
Parameters:
startLen - guess about how large the set will be (used to initialize an auto-growing data structure)
Returns:
array of the values in the sequence

getSet

public DerValue[] getSet(int startLen,
                         boolean implicit)
                  throws IOException
Return a set of encoded entities. ASN.1 sets are unordered, though DER may specify an order for some kinds of sets (such as the attributes in an X.500 relative distinguished name) to facilitate binary comparisons of encoded values.
Parameters:
startLen - guess about how large the set will be (used to initialize an auto-growing data structure)
implicit - if true tag is assumed implicit.
Returns:
array of the values in the sequence

readVector

protected DerValue[] readVector(int startLen)
                         throws IOException

getDerValue

public DerValue getDerValue()
                     throws IOException
Get a single DER-encoded value from the input stream. It can often be useful to pull a value from the stream and defer parsing it. For example, you can pull a nested sequence out with one call, and only examine its elements later when you really need to.

getUTCTime

public Date getUTCTime()
                throws IOException
Get a UTC encoded time value from the input stream.

getGeneralizedTime

public Date getGeneralizedTime()
                        throws IOException
Get a Generalized encoded time value from the input stream.

peekByte

public int peekByte()
             throws IOException

mark

public void mark(int value)
Mark the current position in the buffer, so that a later call to reset will return here.

reset

public void reset()
Return to the position of the last mark call. A mark is implicitly set at the beginning of the stream when it is created.

available

public int available()
Returns the number of bytes available for reading. This is most useful for testing whether the stream is empty.