Peter M. Groen / redox

* Use lock_guard instead of unique_lock when possible
* Make a few types non-atomic since they are already guarded by a mutex
* Create setVariable helpers that lock and notify

…ill make debugging easier if the error condition does occur.

Very similar to the fixes for Command and Subscriber, adds locking
around booleans used as flags for condition variables.

Similar to the fixes for subscriber, without holding the waiter_lock_,
updating the waiting_done_ flag may cause deadlock. In the deadlock
example below, Thread1 is waiting for the response, thread 2 is
processing the response and updating the waiter_lock_ variable:

----------------------------------------------------
|        Thread 1          |       Thread 2        |
----------------------------------------------------
| locks 'waiter_lock_'     |                       |
| check 'waiting_done_'    |                       |
|                          | Update 'waiting done' |
|                          | Send notification     |
| begin waiting for signal |                       |
| *deadlocked*             |                       |
----------------------------------------------------

The lock used with the condition variable should always be the same one
guarding changes to the condition itself, in these cases, the lock
guarding changes to the subscribe and psubscibe data structures.

This commit also limits the number of locks held by the subscribeBase
function at any one time.

In case of a connection failure (i.e. specify incorrect port number),
the main thread would be blocked. This is fixed by setting the condition
variables correctly in case of a connection error. The test
TestConnectionFailure will hang without this fix.

Add EVRUN_ONCE evloop call at the start of the event loop thread,
instead of just an EVRUN_NOWAIT call. We want to block until the
connection happens, or else we hang on the condition variable wait.

User can now enable no-wait mode, which chooses whether we use the
EVRUN_NOWAIT flag in ev_run. The default is off, so that we don't
use 100% CPU. Note added in tutorial to enable when performance
is critical. Added to the speed test examples.

Bump to 0.2.1. Remove patch number from HISTORY entry - that's what the
git log is for. Make note on minor release.

Instructions in README, some minor changes to comments.

This enables full support for binary data, with no tokenization needed
and all the assumptions that come with that. All of the core methods are
changed to accept vector<string>& instead of string&. Ported all
examples and tutorial as well.

Call Redox::disconnectCallback from processReply

This makes more sense logically, and lets the Redox object get default
constructed with nothing but the optional logger parameters.

Separate include directory so that examples can reference the same thing
whether installed in the system or from the local folder.

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.