This patch moves the remaining code from subprocess.{h,c} to more
appropriate places in the process.c and process_win32.c module.
We also delete the now empty subprocess module files.
See: https://bugs.torproject.org/28179
This patch adds a new Process subsystem for running external programs in
the background of Tor. The design is focused around a new type named
`process_t` which have an API that allows the developer to easily write
code that interacts with the given child process. These interactions
includes:
- Easy API for writing output to the child process's standard input
handle.
- Receive callbacks whenever the child has output on either its standard
output or standard error handles.
- Receive callback when the child process terminates.
We also support two different "protocols" for handling output from the
child process. The default protocol is the "line" protocol where the
process output callbacks will be invoked only when there is complete
lines (either "\r\n" or "\n" terminated). We also support the "raw"
protocol where the read callbacks will get whatever the operating system
delivered to us in a single read operation.
This patch does not include any operating system backends, but the Unix
and Windows backends will be included in separate commits.
See: https://bugs.torproject.org/28179
Rather than initializing the "Dormant" status to "off" and the "last
activity" count to "now", initialize them based on our state file:
stay dormant if we were dormant, or remember the amount of time
we've spent inactive.
The DormantClientTimeout option controls how long Tor will wait before
going dormant. It also provides a way to disable the feature by setting
DormantClientTimeout to e.g. "50 years".
The DormantTimeoutDisabledByIdleStreams option controls whether open but
inactive streams count as "client activity". To implement it, I had to
make it so that reading or writing on a client stream *always* counts as
activity.
Closes ticket 28429.
Our tests showed that this function is responsible for a huge number
of our malloc/free() calls. It's a prime candidate for being
memoized.
Closes ticket 27225.
