tahoe-lafs/docs/codemap.txt

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CODE OVERVIEW
A brief map to where the code lives in this distribution:
src/zfec: the erasure-coding library, turns data into shares and back again.
When installed, this provides the 'zfec' package.
src/allmydata: the bulk of the code for this project. When installed, this
provides the 'allmydata' package. This includes a few pieces
copied from the PyCrypto package, in allmydata/Crypto/* .
Within src/allmydata/ :
interfaces.py: declaration of zope.interface-style Interfaces for most
components, also defines Foolscap RemoteInterfaces for
all remotely-accessible components
node.py: the base Node, which handles connection establishment and
application startup
client.py, introducer_and_vdrive.py:
these are two specialized subclasses of Node, for users and the central
introducer/vdrive handler, respectively. Each works by assembling a
collection of services underneath a top-level Node instance.
introducer.py: node introduction handlers, client is used by client.py,
server is used by introducer_and_vdrive.py
storageserver.py: provides storage services to other nodes
codec.py: low-level erasure coding, wraps zfec
encode.py: handles turning data into shares and blocks, computes hash trees
upload.py: upload-side peer selection, reading data from upload sources
download.py: download-side peer selection, share retrieval, decoding
dirnode.py: implements the directory nodes. One part runs on the
global vdrive server, the other runs inside a client
(starting with vdrive.py)
vdrive.py: provides a client-side service that accesses the global
shared virtual drive and the per-user private drive.
webish.py, web/*.xhtml: provides the web frontend, using a Nevow server
uri.py: URI packing/parsing routines
hashtree.py: Merkle hash tree classes
debugshell.py, manhole.py: SSH-connected python shell, for debug purposes
util/*.py: misc utility classes
test/*.py: unit tests
Both the client and the central introducer-and-vdrive node runs as a tree of
(twisted.application.service) Service instances. The Foolscap "Tub" is one of
these. Client nodes have an Uploader service and a Downloader service that
turn data into URIs and back again. They also have a VirtualDrive service
which provides access to the single global shared filesystem.
The Uploader is given an "upload source" (which could be an open filehandle,
a filename on local disk, or even a string), and returns a Deferred that
fires with the URI once the upload is complete. The Downloader is given a URI
and a "download target" (an open filehandle, filename, or instructions to
provide a string), and fires a Deferred with a target-specific value when the
download is complete. The source/target API is intended to make it easy to
stream the incoming data to a media player or HTTP connection without having
to consume a lot of memory for buffering.