zephyr: copy zmake to platform/ec

This copies zmake into platform/ec/zephyr/zmake, as explained in
go/zephyr-fewer-repos.

Follow-on CLs will be submitted to:
- Update the chromeos-base/zephyr-build-tools ebuild to reference this
  directory instead of the one in zephyr-chrome.
- Remove the copy of zmake in zephyr-chrome.

Those interested in the git history of this code prior to it being
moved to platform/ec can find it here:
  https://chromium.googlesource.com/chromiumos/platform/zephyr-chrome/+log/bacea2e3e62c41000e5bdb4ed6433f24386d14bf/util

BUG=b:177003034
BRANCH=none
TEST=emerge with new path (requires follow-on CL)

Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Change-Id: Ia957b3e35ce3b732968ebf8df603ef13298cc6b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2618501
Reviewed-by: Yuval Peress <peress@chromium.org>

1 files changed, 142 insertions, 0 deletions

diff --git a/zephyr/zmake/zmake/jobserver.py b/zephyr/zmake/zmake/jobserver.py
new file mode 100644
index 0000000000..d9788c6ac6
--- /dev/null
+++ b/zephyr/zmake/zmake/jobserver.py
@@ -0,0 +1,142 @@
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Module for job counters, limiting the amount of concurrent executions."""
+
+import multiprocessing
+import os
+import re
+import select
+import subprocess
+
+
+class JobHandle:
+    """Small object to handle claim of a job."""
+    def __init__(self, release_func, *args, **kwargs):
+        self.release_func = release_func
+        self.args = args
+        self.kwargs = kwargs
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.release_func(*self.args, **self.kwargs)
+
+
+class JobClient:
+    """Abstract base class for all job clients."""
+    def get_job(self):
+        """Claim a job."""
+        raise NotImplementedError('Abstract method not implemented')
+
+    def env(self):
+        """Get the environment variables necessary to share the job server."""
+        return {}
+
+    def popen(self, *args, claim_job=True, **kwargs):
+        """Start a process using subprocess.Popen, optionally claiming a job.
+
+        Args:
+            claim_job: True if a job should be claimed.
+
+        All other arguments are passed to subprocess.Popen.
+
+        Returns:
+            A Popen object.
+        """
+        if claim_job:
+            with self.get_job():
+                return self.popen(*args, claim_job=False, **kwargs)
+
+        kwargs.setdefault('env', os.environ)
+        kwargs['env'].update(self.env())
+
+        return subprocess.Popen(*args, **kwargs)
+
+    def run(self, *args, claim_job=True, **kwargs):
+        """Run a process using subprocess.run, optionally claiming a job.
+
+        Args:
+            claim_job: True if a job should be claimed.
+
+        All other arguments are passed to subprocess.run.
+
+        Returns:
+            A CompletedProcess object.
+        """
+        if claim_job:
+            with self.get_job():
+                return self.run(*args, claim_job=False, **kwargs)
+
+        kwargs.setdefault('env', os.environ)
+        kwargs['env'].update(self.env())
+
+        return subprocess.run(*args, **kwargs)
+
+
+class JobServer(JobClient):
+    """Abstract Job Server."""
+    def __init__(self, jobs=0):
+        raise NotImplementedError('Abstract method not implemented')
+
+
+class GNUMakeJobClient(JobClient):
+    def __init__(self, read_fd, write_fd):
+        self._pipe = [read_fd, write_fd]
+
+    @classmethod
+    def from_environ(cls, env=None):
+        """Create a job client from an environment with the MAKEFLAGS variable.
+
+        If we are started under a GNU Make Job Server, we can search
+        the environment for a string "--jobserver-auth=R,W", where R
+        and W will be the read and write file descriptors to the pipe
+        respectively.  If we don't find this environment variable (or
+        the string inside of it), this will raise an OSError.
+
+        Args:
+            env: Optionally, the environment to search.
+
+        Returns:
+            A GNUMakeJobClient configured appropriately.
+        """
+        if env is None:
+            env = os.environ
+        makeflags = env.get('MAKEFLAGS')
+        if not makeflags:
+            raise OSError('MAKEFLAGS is not set in the environment')
+        match = re.search(r'--jobserver-auth=(\d+),(\d+)', makeflags)
+        if not match:
+            raise OSError('MAKEFLAGS did not contain jobserver flags')
+        read_fd, write_fd = map(int, match.groups())
+        return cls(read_fd, write_fd)
+
+    def get_job(self):
+        """Claim a job.
+
+        Returns:
+            A JobHandle object.
+        """
+        byte = os.read(self._pipe[0], 1)
+        return JobHandle(lambda: os.write(self._pipe[1], byte))
+
+    def env(self):
+        """Get the environment variables necessary to share the job server."""
+        return {'MAKEFLAGS': '--jobserver-auth={},{}'.format(*self._pipe)}
+
+
+class GNUMakeJobServer(JobServer, GNUMakeJobClient):
+    """Implements a GNU Make POSIX Job Server.
+
+    See https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html
+    for specification.
+    """
+    def __init__(self, jobs=0):
+        if not jobs:
+            jobs = multiprocessing.cpu_count()
+        elif jobs > select.PIPE_BUF:
+            jobs = select.PIPE_BUF
+
+        self._pipe = os.pipe()
+        os.write(self._pipe[1], b'+' * jobs)