EmbeddedPkg: Extend NvVarStoreFormattedLib LIBRARY_CLASS

[mirror_edk2.git] / AppPkg / Applications / Python / Python-2.7.2 / Demo / pdist / README

Filesystem, RCS and CVS client and server classes\r
=================================================\r
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*** See the security warning at the end of this file! ***\r
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This directory contains various modules and classes that support\r
remote file system operations.\r
\r
CVS stuff\r
---------\r
\r
rcvs			Script to put in your bin directory\r
rcvs.py			Remote CVS client command line interface\r
\r
cvslib.py		CVS admin files classes (used by rrcs)\r
cvslock.py		CVS locking algorithms\r
\r
RCS stuff\r
---------\r
\r
rrcs			Script to put in your bin directory\r
rrcs.py			Remote RCS client command line interface\r
\r
rcsclient.py		Return an RCSProxyClient instance\r
			(has reasonable default server/port/directory)\r
\r
RCSProxy.py		RCS proxy and server classes (on top of rcslib.py)\r
\r
rcslib.py		Local-only RCS base class (affects stdout &\r
			local work files)\r
\r
FSProxy stuff\r
-------------\r
\r
sumtree.py		Old demo for FSProxy\r
cmptree.py		First FSProxy client (used to sync from the Mac)\r
FSProxy.py		Filesystem interface classes\r
\r
Generic client/server stuff\r
---------------------------\r
\r
client.py		Client class\r
server.py		Server class\r
\r
security.py		Security mix-in class (not very secure I think)\r
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Other generic stuff\r
-------------------\r
\r
cmdfw.py		CommandFrameWork class\r
			(used by rcvs, should be used by rrcs as well)\r
\r
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Client/Server operation\r
-----------------------\r
\r
The Client and Server classes implement a simple-minded RPC protocol,\r
using Python's pickle module to transfer arguments, return values and\r
exceptions with the most generality.  The Server class is instantiated\r
with a port number on which it should listen for requests; the Client\r
class is instantiated with a host name and a port number where it\r
should connect to.  Once a client is connected, a TCP connection is\r
maintained between client and server.\r
\r
The Server class currently handles only one connection at a time;\r
however it could be rewritten to allow various modes of operations,\r
using multiple threads or processes or the select() system call as\r
desired to serve multiple clients simultaneously (when using select(),\r
still handling one request at a time).  This would not require\r
rewriting of the Client class.  It may also be possible to adapt the\r
code to use UDP instead of TCP, but then both classes will have to be\r
rewritten (and unless extensive acknowlegements and request serial\r
numbers are used, the server should handle duplicate requests, so its\r
semantics should be idempotent -- shrudder).\r
\r
Even though the FSProxy and RCSProxy modules define client classes,\r
the client class is fully generic -- what methods it supports is\r
determined entirely by the server.  The server class, however, must be\r
derived from.  This is generally done as follows:\r
\r
	from server import Server\r
	from client import Client\r
\r
	# Define a class that performs the operations locally\r
	class MyClassLocal:\r
		def __init__(self): ...\r
		def _close(self): ...\r
\r
	# Derive a server class using multiple inheritance\r
	class MyClassServer(MyClassLocal, Server):\r
		def __init__(self, address):\r
			# Must initialize MyClassLocal as well as Server\r
			MyClassLocal.__init__(self)\r
			Server.__init__(self, address)\r
		def _close(self):\r
			Server._close()\r
			MyClassLocal._close()\r
\r
	# A dummy client class\r
	class MyClassClient(Client): pass\r
\r
Note that because MyClassLocal isn't used in the definition of\r
MyClassClient, it would actually be better to place it in a separate\r
module so the definition of MyClassLocal isn't executed when we only\r
instantiate a client.\r
\r
The modules client and server should probably be renamed to Client and\r
Server in order to match the class names.\r
\r
\r
*** Security warning: this version requires that you have a file\r
$HOME/.python_keyfile at the server and client side containing two\r
comma- separated numbers.  The security system at the moment makes no\r
guarantees of actuallng being secure -- however it requires that the\r
key file exists and contains the same numbers at both ends for this to\r
work.  (You can specify an alternative keyfile in $PYTHON_KEYFILE).\r
Have a look at the Security class in security.py for details;\r
basically, if the key file contains (x, y), then the security server\r
class chooses a random number z (the challenge) in the range\r
10..100000 and the client must be able to produce pow(z, x, y)\r
(i.e. z**x mod y).\r