python,scons: Move readCommand and compareVersions into site_scons.

These functions are only used by scons, so it makes sense to move them
to site_scons/gem5_scons/util.py.

Change-Id: If2b3995f208cb71adf3c59aac4eabe378c47f94f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41599
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

site_scons/gem5_scons/util.py

@@ -38,6 +38,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import itertools
+import re
 import sys
 
 import SCons.Script
@@ -50,3 +52,60 @@ def ignore_style():
 
 def get_termcap():
     return m5.util.terminal.get_termcap(SCons.Script.GetOption('use_colors'))
+
+def readCommand(cmd, **kwargs):
+    """
+    run the command cmd, read the results and return them
+    this is sorta like `cmd` in shell
+
+    :param cmd: command to run with Popen
+    :type cmd: string, list
+    :returns: command stdout
+    :rtype: string
+    """
+    from subprocess import Popen, PIPE, STDOUT
+
+    if isinstance(cmd, str):
+        cmd = cmd.split()
+
+    no_exception = 'exception' in kwargs
+    exception = kwargs.pop('exception', None)
+
+    kwargs.setdefault('shell', False)
+    kwargs.setdefault('stdout', PIPE)
+    kwargs.setdefault('stderr', STDOUT)
+    kwargs.setdefault('close_fds', True)
+    try:
+        subp = Popen(cmd, **kwargs)
+    except Exception as e:
+        if no_exception:
+            return -1, exception
+        raise
+
+    output = subp.communicate()[0].decode('utf-8')
+    return output
+
+def compareVersions(v1, v2):
+    """helper function: compare arrays or strings of version numbers.
+    E.g., compare_version((1,3,25), (1,4,1)')
+    returns -1, 0, 1 if v1 is <, ==, > v2
+    """
+    def make_version_list(v):
+        if isinstance(v, (list,tuple)):
+            return v
+        elif isinstance(v, str):
+            return list(map(lambda x: int(re.match('\d+', x).group()),
+                            v.split('.')))
+        else:
+            raise TypeError()
+
+    v1 = make_version_list(v1)
+    v2 = make_version_list(v2)
+
+    # Compare corresponding elements of lists
+    # The shorter list is filled with 0 till the lists have the same length
+    for n1,n2 in itertools.zip_longest(v1, v2, fillvalue=0):
+        if n1 < n2: return -1
+        if n1 > n2: return  1
+
+    return 0

site_scons/site_tools/git.py

@@ -42,7 +42,6 @@ import os
 import sys
 
 import gem5_scons.util
-from m5.util import readCommand
 
 git_style_message = """
 You're missing the gem5 style or commit message hook. These hooks help
@@ -52,7 +51,7 @@ Press enter to continue, or ctrl-c to abort: """
 
 def install_style_hooks(env):
     try:
-        gitdir = env.Dir(readCommand(
+        gitdir = env.Dir(gem5_scons.util.readCommand(
             ["git", "rev-parse", "--git-dir"]).strip("\n"))
     except Exception as e:
         print("Warning: Failed to find git repo directory: %s" % e)