Added lib/ansible/inventory/expand_hosts.py

lib/ansible/inventory/expand_hosts.py

+# (c) 2012, Zettar Inc.
+# Written by Chin Fang <fangchin@zettar.com>
+#
+# This file is part of Ansible
+#
+# This module is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This software is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this software.  If not, see <http://www.gnu.org/licenses/>.
+#
+'''
+This module is for enhancing ansible's inventory parsing capability such
+that it can deal with hostnames specified using a simple pattern in the
+form of [beg:end], example: [1:5] where if beg is not specified, it
+defaults to 0.
+
+If beg is given and is left-zero-padded, e.g. '001', it is taken as a
+formatting hint when the range is expanded. e.g. [001:010] is to be
+expanded into 001, 002 ...009, 010.
+
+Note that when beg is specified with left zero padding, then the length of
+end must be the same as that of beg, else a exception is raised.
+'''
+
+def detect_range(line = None):
+    '''
+    A helper function that checks a given host line to see if it contains
+    a range pattern descibed in the docstring above.
+
+    Returnes True if the given line contains a pattern, else False.
+    '''
+    if (not line.startswith("[") and 
+        line.find("[") != -1 and 
+        line.find(":") != -1 and
+        line.find("]") != -1 and
+        line.index("[") < line.index(":") < line.index("]")):   
+        return True
+    else:
+        return False
+        
+def expand_hostname_range(line = None):
+    '''
+    A helper function that expands a given line that contains a pattern
+    specified in top docstring, and returns a list that consists of the
+    expanded version.
+
+    The '[' and ']' characters are used to maintain the pseudo-code
+    appearance. They are replaced in this function with '|' to ease
+    string splitting.
+
+    References: http://ansible.github.com/patterns.html#hosts-and-groups
+    '''
+    all_hosts = []
+    if line:
+        # A hostname such as db[1:6]-node is considered to consists
+        # three parts: 
+        # head: 'db'
+        # nrange: [1:6]; range() is a built-in. Can't use the name
+        # tail: '-node'
+        
+        (head, nrange, tail) = line.replace('[','|').replace(']','|').split('|')
+        bounds = nrange.split(":")
+        if len(bounds) != 2:
+            raise ValueError("host range incorrectly specified!")
+        beg = bounds[0]
+        end = bounds[1]
+        if not beg:
+            beg = "0"
+        if not end:
+            raise ValueError("host range end value missing!")
+        if beg[0] == '0' and len(beg) > 1:
+            rlen = len(beg) # range length formatting hint
+        else:
+            rlen = None
+        if rlen > 1 and rlen != len(end):
+            raise ValueError("host range format incorrectly specified!")
+                
+        for _ in range(int(beg), int(end)):
+            if rlen:
+                rseq = str(_).zfill(rlen) # range sequence
+            else:
+                rseq = str(_)
+            hname = ''.join((head, rseq, tail))
+            all_hosts.append(hname)
+                   
+        return all_hosts