Implement a simplified xargs in python

pre_commit/xargs.py

@@ -0,0 +1,59 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from pre_commit.util import cmd_output
+
+
+# Limit used previously to avoid "xargs ... Bad file number" on windows
+# This is slightly less than the posix mandated minimum
+MAX_LENGTH = 4000
+
+
+class ArgumentTooLongError(RuntimeError):
+    pass
+
+
+def partition(cmd, varargs, _max_length=MAX_LENGTH):
+    cmd = tuple(cmd)
+    ret = []
+
+    ret_cmd = []
+    total_len = len(' '.join(cmd))
+    # Reversed so arguments are in order
+    varargs = list(reversed(varargs))
+
+    while varargs:
+        arg = varargs.pop()
+
+        if total_len + 1 + len(arg) <= _max_length:
+            ret_cmd.append(arg)
+            total_len += len(arg)
+        elif not ret_cmd:
+            raise ArgumentTooLongError(arg)
+        else:
+            # We've exceeded the length, yield a command
+            ret.append(cmd + tuple(ret_cmd))
+            ret_cmd = []
+            total_len = len(' '.join(cmd))
+            varargs.append(arg)
+
+    ret.append(cmd + tuple(ret_cmd))
+
+    return tuple(ret)
+
+
+def xargs(cmd, varargs):
+    """A simplified implementation of xargs."""
+    retcode = 0
+    stdout = b''
+    stderr = b''
+
+    for run_cmd in partition(cmd, varargs):
+        proc_retcode, proc_out, proc_err = cmd_output(
+            *run_cmd, encoding=None, retcode=None
+        )
+        retcode |= proc_retcode
+        stdout += proc_out
+        stderr += proc_err
+
+    return retcode, stdout, stderr