Update on CODA (evio) format

[Elliott Wolin <wolin@jlab.org>]

To all interested in binary formats for Hall D,

The more I look at coda format (aka evio) the more I like it.  Previously I
proposed a binary format using 4-byte headers;  evio includes this, as well as a
number of other packing options (8-byte, 4-byte, 2-byte).

The evio package was written years ago, but few new ideas in the "binary format"
field have appeared since then.   The JLab DAQ group is willing to update the
evio package to meet Hall D needs.

evio seems well suited for serializing data described via xml.  It encodes a
recursively self-similar tree structure.  The existing package is thread-safe,
handles byte-swapping, has a command-line and Motif browser, and includes a
blocking scheme that allows you to recover data in case of file corruption.

Currently only a c-based api is available.  A java version would be nice, but I
don't know if the DAQ group plans to provide this.  We could easily encapsulate
the c api in a C++ class, if needed (I'm not sure this is needed).

The existing browser programs use a "data dictionary" using a special evio
format...I've written a simple perl script that converts an xml data description
to evio format (/group/halld/utilities/xml2evio).

Details of evio can be found in http://coda.jlab.org under the docs for coda
version 1.4. Please have a look at this.  If we decide to use evio we could
start using it immediately.

				Sincerely,
					Elliott
 

================================================================================

   Help feed the hungry, one click at a time:  http://www.thehungersite.com

    "Science plays a major role in satisfying the minor needs of mankind"

================================================================================
begin:vcard 
n:Wolin;Elliott 
tel;fax:757-269-5800
tel;home:757-229-2724
tel;work:757-269-7365
x-mozilla-html:FALSE
org:Jefferson Lab;Physics Department
version:2.1
email;internet:wolin@jlab.org
title:Physicist
note:A218 CEBAF Center
adr;quoted-printable:;;12000 Jefferson Ave MS12H=0D=0A;Newport News;VA;23606;US
x-mozilla-cpt:;21408
fn:Elliott Wolin
end:vcard