The Apache ASN.1 runtime is a high performance non-blocking replacement for the Snacc4J runtime and eventually its Java stub compiler for ASN.1. It is designed from the ground up to work with NIO constructs like Channels and ByteBuffers. There are currently three sub subprojects associated with the asn1 project. They are described below:
| Subproject | Description |
|---|---|
| ASN.1 Codecs | Extensions to commons-codec interfaces for non-blocking stateful encode and decode operations for chunking. |
| ASN.1 BER Runtime | Library used for ASN.1 data structures encoded onto and decoded off of the wire using Basic Encoding Rules (BER). By dealing only with BER TLV tuples this library remains independent of any ASN.1 based protocol. |
| ASN.1 DER Runtime | Library used for ASN.1 data structures encoded onto and decoded off of the wire using Distinguished Encoding Rules (DER). By dealing only with DER TLV tuples this library remains independent of any ASN.1 based protocol. |
| Java Stub Compiler | The Apache ASN.1 Java Stub Compiler generates interfaces and classes for complex ASN.1 data types. These classes are used with the BER codec runtime API to marshal and demarshal protocol data units (PDU). |
For the next dev cycle we're radically refactoring the structure of these modules. For more information you can take a look here.
Non-blocking IO in stateful protocol servers imposes stricter performance requirements on codecs. In the Eve Directory Server, the BER codec must be fast, efficient, and take a very small relatively fixed size memory footprint while actively encoding or decoding variable sized messages.
ASN.1 BER codecs for Java are few and far between. No BSD license compatible open source API is currently available for Java. Initially the Snacc4J runtime from IBM was used however it has mysteriously disappeared and is no longer available. Furthermore Snacc4J is completely incompatible with any licence we know of: it's practically not even Open Source. Even with license issues Snacc4J is terribly inefficient and imposes security threats especially where decodes are concerned. Snacc4J decoders block until an entire message is read and decoded. They hence require approximately twice the transfer footprint of a message to decode it and there is no limit to the accepted transfer footprint size. DoS attacks could easily be mounted using a single large request to bring the server to its knees making it totally unresponsive.
The ASN.1 BER runtime is a high performance codec optimized for use with selectable channels and non blocking IO: it's processes the substrate in small chunks rather than in a single massive peice. The runtime is destined to replace stateless BER codecs like Snacc4J, and keep ASN.1 based high performance protocol server implementors satisfied. A user definable parameter will be used to set the fixed in memory footprint of the decoder while actively decoding ASN.1 data structures encoded using Basic Encoding Rules. Furthermore, when large indivisible parts of messages like byte[] fields are encountered, they are streamed to disk and referred to using a URL rather than allocating primary memory to store such an object. Note: this experimental feature is being added as we speak. Access to the object is provided to the application via a URL. The handling of the large streamable data is left to the discretion of the application.