Peter M. Groen / redox

Made redox into a more formal package with CMake. It now by default
builds a dynamic library in release mode. Tests and examples can be
enabled with options. Added semantic versioning. Documented the install
from source procedure which is very easy, just make and make install.

Users now have to just link one library (redox) and include one header
(redox.hpp), and the rest is linked from those.

Used CPack to add capability to create a debian package. Useful for
getting it into the apt repos.

Also redid the readme introduction.

More intuitive if disconnect() blocks like connect(). Most clients will
want to use these two methods. For more fine grained control,
disconnect() is just a combo of stop() and wait().

Configure CMake to generate libredox.so and libredox_static.a, and have
all examples use the dynamic library. This is how Redox should be used
in practice, and greatly reduces the compilation time of the examples.

Also renamed redox.[ch]pp to client.[ch]pp and created one master header
redox.hpp for users to include. This header right now just includes
client.hpp, command.hpp, and subscriber.hpp.

Make .free() on commands send a message over an async watcher to the
event loop, just like adding commands. This gets rid of some very tough
to find memory bugs. Combined .cancel() with .free(), so there is only
one method to call, whether for synchronous commands or for looped
commands.

Also debug some horrible segfaults related to Subscriber. Something is
odd with hiredis and subscriptions, need to ask them. It seems when we
flood with commands it doesn't disconnect cleanly. Look for a way to
wait until all commands are processed.

Conform (mostly) to Google C++ guidelines.

Apache license notice and link above each core file.

Refactor state management code to use three methods .connect(),
.disconnect(), and .wait(). Start conforming to uniform coding style
already applied to Command class.

Split off subscribe functionality into its own class Subscriber. This is
good because it was introducing unnecessary state and complexity into
the main client. Now, Redox handles publishing like any other command
and the Subscriber receives messages.

Using free_guard_ as the same mutex in .reply() causes deadlock when a
callback accesses .reply(). Make a separate mutex.

Also make cmd.reply() copy the value and use a mutex to make it thread
safe. No noticable speed hits, probably thanks to RVO.

Split up command into command, command_blocking, and command_looping.
The original command no longer returns anything, which clarifies how it
should be used in most cases. command_looping and command_blocking both
return a command object.

Also added a waiting CV to the Command object, though it is not used in
command_blocking yet.

Now, there is only one callback for command(), and it returns a const
reference to the Command object. The user is responsible for error
checking using c.ok(), c.status(), and getting the reply with c.reply().
This significantly cleans up the library code and the user code.

Greatly refactored the data type specialization code in command.cpp.

* Member variables with trailing underscore
* Methods camelCase
* Explicit template instantiation, move definitions to .cpp
* Reorder methods to make more sense
* Limit public API, comment well

subscribe/psubscribe/unsubscribe/punsubscribe methods that keep track of
subscribed topics to make sure we don't ask hiredis for bad things. It
appears all crashes are eliminated, though no stress testing has been
done.

subscribe/unsubscribe/publish with proper and working callbacks. Guard
added that throws an exception if a non-pubsub command is issued after a
subscribe.

Also removed all std:: prefixes from redox.cpp. Just made the decision
for "using namespace std" there for readability. Not a header, of
course.

Also added another async watcher for breaking the loop, since ev_break
doesn't actually do anything when called outside of an ev_run callback.

utils/logger.[ch]pp gives a logger implementation based on ostringstream
that is pretty nice. I took this from Stack Overflow and added some
things to make syntax nicer. Changed all cout and cerr statements in
Redox to be of the form logger.{debug/info/warning/error/fatal}() <<
stuff. Arguments for non-printed statements are still evaluated. Gives a
performance hit if we actually add statements on every callback and run
speed tests. For most use cases, doesn't matter. For now, not including
such low level output anyway. Would be nice to have a macro to leave
out/include the low-level logs at compile-time.

Implemented limited but useful binary data support without breaking the
API. If the last character of the command is a ", look for the first ",
and everything in between the quotes treat as binary data. Takes care of
setting a key with a binary value. Not useful if there need to be
multiple binary entries in one command, or for binary keys. Also need to
be careful if the last character of the value actually needs to be a
quote, in which case we need to quote the value.

Useful based on what kind of data you need.

Added GTest under test/. Great for unit testing commands. Added some
nice helper functions to make writing tests easy.

Added options to CMakeLists to build the library, tests, and examples
separately, configurable through ccmake. Also default the build type
to RelWithDebInfo, but don't override user settings.

Consolidated user callbacks into one, improved some logic.

Created an atomic_int connect_state that keeps track of not yet
connected, connected, disconnected, and errors. Used to implement good
error behavior when the server is down and you start() a Redox instance,
or when the server goes down in the middle of running commands. Now,
nothing should hang, but should return errors (or throw exceptions) when
the server goes down.

Also added hooks for a user connect/disconnect callback in the
constructor, which is helpful for client programs.

Added an example with three Redox clients in one thread.

Finally getting rid of the busy loop in the event thread. Now, we use
an ev_async watcher that processes commands in the queue, which we
can signal in a thread-safe manner using ev_async_send.

Instead of busy looping event thread, use a condition variable that
is notified every time a command is sent or received, or every 100
milliseconds anyway.

Better than using a laptop, because it can be reproduced by others
much more easily

submit_command_callback

Also plan to add in set<string> and unordered_set<string>. Maybe
queue<string>. Looking at likely removing char* as an option, if it
shows to be about the same speed as string.

Thoroughly cleaned up redox.hpp to expose a minimal public API, and
commented those well. Generally cleaned up a bunch of stuff.

Added wrapper function DEL, which could be useful.

Easy few lines for get and set commands that are easy to use.

Implemented a condition variable that blocks run() until the event
loop is running and Redis is connected. Also added a check to
command() that will throw an exception if you try to add a command
before calling run().

Fixed a couple of bugs found with a test case of 100 parallel
asynchronous clients. As of now, there are no known memory
leaks, segfaults, or deadlocks in Redox.

Ran into a nasty segfault when using 100 parallel asynchronous command
loops, where a command's address would match up with a previous
command's
address. To circumvent the whole issue, Redox keeps a counter of how
many Commands it has created and assigns each Command a unique id in
the order they are created.

Changed all data structures and methods to pass around Command IDs, so
nothing uses void* anymore. I consider this a very good thing, but it
did seem to slow down performance 20-30% because of the extra lookups.
Will see if there's a solution later.

Take that, hours of debugging memory leaks! Did lots of structural
tweaks to more smartly keep track of commands and make sure everything
is evenutally freed from the heap.

Created a pointer Command.rdx (Redox*) to allow commands
to increment Redox.cmd_count, and simplify a couple of
other things.

Did a little bit of moving and renaming context objects,
so the context is always .ctx and commands can always
be called c.

Added Command<nullptr_t> which successfully returns NIL
replies from Redis, with REDOX_OK. Also renamed constants
from REDISX_ -> REDOX_.

Moved a bunch of code from redox.cpp into command.cpp, where
it logically makes more sense.

Move as much as possible into the .cpp file, and clean things up.