python getopt: Add bytes option type

Add a new option type to the python command line options.
  Option("--size", type="bytes", metavar="SIZE")
To allow the input of file and memory sizes using unit suffixes i.e.
2Gb, 4KiB ...

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

python/samba/getopt.py

@@ -20,6 +20,7 @@
 __docformat__ = "restructuredText"
 
 import optparse
+from copy import copy
 import os
 from samba.credentials import (
     Credentials,
@@ -285,3 +286,47 @@ class CredentialsOptionsDouble(CredentialsOptions):
         if self.no_pass2:
             self.creds2.set_cmdline_callbacks()
         return self.creds2
+
+# Custom option type to allow the input of sizes using byte, kb, mb ...
+# units, e.g. 2Gb, 4KiB ...
+#    e.g. Option("--size", type="bytes", metavar="SIZE")
+#
+def check_bytes(option, opt, value):
+
+    multipliers = {
+            "B"  : 1,
+            "KB" : 1024,
+            "MB" : 1024 * 1024,
+            "GB" : 1024 * 1024 * 1024}
+
+    # strip out any spaces
+    v = value.replace(" ", "")
+
+    # extract the numeric prefix
+    digits = ""
+    while v and v[0:1].isdigit() or v[0:1] == '.':
+        digits += v[0]
+        v = v[1:]
+
+    try:
+        m = float(digits)
+    except ValueError:
+        msg = ("{0} option requires a numeric value, "
+               "with an optional unit suffix").format(opt)
+        raise optparse.OptionValueError(msg)
+
+
+    # strip out the 'i' and convert to upper case so
+    # kib Kib kb KB are all equivalent
+    suffix = v.upper().replace("I", "")
+    try:
+        return m * multipliers[suffix]
+    except KeyError as k:
+        msg = ("{0} invalid suffix '{1}', "
+               "should be B, Kb, Mb or Gb").format(opt, v)
+        raise optparse.OptionValueError(msg)
+
+class SambaOption(optparse.Option):
+    TYPES = optparse.Option.TYPES + ("bytes",)
+    TYPE_CHECKER = copy(optparse.Option.TYPE_CHECKER)
+    TYPE_CHECKER["bytes"] = check_bytes