Initial checking of Tcl sample extension

README

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+sha1 - manipulate sha1 message digests
+
+SHA1 is NIST's Secure Hashing Algorithm (also known as Secure Hashing
+Standard) with the minor modification that they proposed on 7/11/94.
+
+To make type:
+
+      ./configure
+      make 
+      make install
+
+The configure script will deduce $PREFIX from the tcl installation.
+The generated Makefile uses the file $PREFIX/lib/tclConfig.sh that was left by
+the make of tcl for most of its configuration parameters.
+
+The Makefile generates pkgIndex.tcl files that are compatible with
+tcl7.6.   If you are using tcl7.5 then you will need to edit 
+$PREFIX/lib/pkgIndex.tcl by hand.
+
+Usage:
+
+      sha1 ?-log2base log2base? -string string
+
+	or
+
+      sha1 ?-log2base log2base? ?-copychan chanID? -chan chanID
+
+	or
+
+      sha1 -init (returns descriptor)
+      sha1 -update descriptor ?-maxbytes n? ?-copychan chanID? -chan chanID
+      sha1 ?-log2base log2base? -final descriptor
+
+
+Switches can be in any order.
+
+Returns a sha1 digest in base 2 ** log2base ascii representation.
+log2base defaults to 4, i.e. hex representation.
+
+       log2base   length   chars 
+         1          160      01            (binary)
+         2           80      0..3
+         3           54      0...7         (octal)
+         4           40      0..9a..f      (hex)
+         5           32      0..9a..v      
+         6           27      0..9a..zA..Z_, 
+
+(The characters in the digest string have been chosen to be usable in 
+filenames so that the sha1 command can be used, for example, 
+to digest URLs into shorter strings for filenames in a cache.)
+
+In the -string version, returns sha1 digest of string.
+
+In the -chan version, returns list of 2 items: length of data
+in chanID followed by sha1 digest of all data in chanID.  ChanID is
+identifier returned from "open" for example.  If -copychan is supplied,
+will also copy all data from chanID to copychanID.
+
+In the third form, -init returns a descriptor, -update can be called
+any number of times with that descriptor and returns the number of
+bytes read, and -final returns the result in the same form as the
+standalone -chan.
+
+Written by:  John Ellson ([email protected])
+modified by: Dave Dykstra ([email protected])
+
+Use at your own risk.  No support.  No copyright.