[PATCH 2/6] Add a few helper util functions

[Cole Robinson <crobinso@xxxxxxxxxx>]

This patch adds a few functions to virtinst.util:

1. is_storage_capable: receives an active connection
   and attempts to determine if it supports storage
   management. This is used in a few places to maintain
   existing behavior and error paths for connections
   to older libvirt versions.

2. is_remote: receives a uri and determines if it
   specifies a remote connection. Used for various
   validation checks.

3. get_xml_path: Receives an xml blob and an
   xPath, and returns that path from the xml. This
   is largely a convenience function since we have
   this code duplicated in about 10 places throughout
   virtinst and virt-manager.

Thanks,
Cole

# HG changeset patch
# User "Cole Robinson <crobinso@xxxxxxxxxx>"
# Date 1217990239 14400
# Node ID 3fd6f72be4ee2a841ecf7ef8428284c5c365a6ea
# Parent  4fc92b37ef96adb71f3890343e7e3ca77c7bdce8
Add is_remote, is_storage_capable, and get_xml_path helpers to util.

diff -r 4fc92b37ef96 -r 3fd6f72be4ee virtinst/util.py
--- a/virtinst/util.py	Tue Aug 05 21:17:37 2008 -0400
+++ b/virtinst/util.py	Tue Aug 05 22:37:19 2008 -0400
@@ -23,6 +23,7 @@
 import random
 import os.path
 import re
+import libxml2
 import logging
 from sys import stderr
 
@@ -297,3 +298,80 @@
     if platform.system() == "SunOS":
         return "/usr/lib/xen/bin/pygrub"
     return "/usr/bin/pygrub"
+
+def is_remote(uri):
+    def uri_split(uri):
+        username = netloc = query = fragment = ''
+        i = uri.find(":")
+        if i > 0:
+            scheme, uri = uri[:i].lower(), uri[i+1:]
+            if uri[:2] == '//':
+                netloc, uri = splitnetloc(uri, 2)
+                offset = netloc.find("@")
+                if offset > 0:
+                    username = netloc[0:offset]
+                    netloc = netloc[offset+1:]
+            if '#' in uri:
+                uri, fragment = uri.split('#', 1)
+            if '?' in uri:
+                uri, query = uri.split('?', 1)
+        else:
+            scheme = uri.lower()
+
+        return scheme, username, netloc, uri, query, fragment
+
+    def splitnetloc(url, start=0):
+        for c in '/?#': # the order is important!
+            delim = url.find(c, start)
+            if delim >= 0:
+                break
+        else:
+            delim = len(url)
+        return url[start:delim], url[delim:]
+
+    try:
+        (scheme, username, netloc, path, query, fragment) = uri_split(uri)
+        if netloc == "":
+            return False
+        return True
+    except Exception, e:
+        logging.exception("Error parsing URI in is_remote: %s" % e)
+        return True
+
+def is_storage_capable(conn):
+    """check if virConnectPtr passed has storage API support"""
+    if not isinstance(conn, libvirt.virConnect):
+        raise ValueError(_("'conn' must be a virConnect instance."))
+    try:
+        if not dir(conn).count("listStoragePools"):
+            return False
+        n = conn.listStoragePools()
+    except libvirt.libvirtError, e:
+        if e.get_error_code() == libvirt.VIR_ERR_RPC:
+            return False
+    return True
+
+def get_xml_path(xml, path):
+    """return the xpath from the passed xml"""
+    doc = None
+    ctx = None
+    result = None
+    try:
+        doc = libxml2.parseDoc(xml)
+        ctx = doc.xpathNewContext()
+        ret = ctx.xpathEval(path)
+        str = None
+        if ret != None:
+            if type(ret) == list:
+                if len(ret) == 1:
+                    str = ret[0].content
+            else:
+                str = ret
+        result = str
+    finally:
+        if doc:
+            doc.freeDoc()
+        if ctx:
+            ctx.xpathFreeContext()
+    return result
+

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