Move to a more canonicalized output from qemu-img info.

Move to a form that is all lower cased, dashes->underscores, underscores
instead of spaces which allows for better integration with python. Also
make the parser more robust to failures when encountering new fields such
as snapshot lists. Provide a new qemu img info object that can be used
to do the parsing and access the underlying attributes.

Change-Id: Ie098dbd9f06dd4ef966768e2caa128f1d09b019c

1 files changed, 38 insertions, 0 deletions

diff --git a/nova/utils.py b/nova/utils.py
index 01df19b27..fe81ffd93 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -63,6 +63,16 @@ FLAGS.register_opt(
     cfg.BoolOpt('disable_process_locking', default=False,
                 help='Whether to disable inter-process locks'))
 
+# Used for looking up extensions of text
+# to their 'multiplied' byte amount
+BYTE_MULTIPLIERS = {
+    '': 1,
+    't': 1024 ** 4,
+    'g': 1024 ** 3,
+    'm': 1024 ** 2,
+    'k': 1024,
+}
+
 
 def vpn_ping(address, port, timeout=0.05, session_id=None):
     """Sends a vpn negotiation packet and returns the server session.
@@ -574,6 +584,34 @@ def utf8(value):
     return value
 
 
+def to_bytes(text, default=0):
+    """Try to turn a string into a number of bytes. Looks at the last
+    characters of the text to determine what conversion is needed to
+    turn the input text into a byte number.
+
+    Supports: B/b, K/k, M/m, G/g, T/t (or the same with b/B on the end)
+
+    """
+    # Take off everything not number 'like' (which should leave
+    # only the byte 'identifier' left)
+    mult_key_org = text.lstrip('-1234567890')
+    mult_key = mult_key_org.lower()
+    mult_key_len = len(mult_key)
+    if mult_key.endswith("b"):
+        mult_key = mult_key[0:-1]
+    try:
+        multiplier = BYTE_MULTIPLIERS[mult_key]
+        if mult_key_len:
+            # Empty cases shouldn't cause text[0:-0]
+            text = text[0:-mult_key_len]
+        return int(text) * multiplier
+    except KeyError:
+        msg = _('Unknown byte multiplier: %s') % mult_key_org
+        raise TypeError(msg)
+    except ValueError:
+        return default
+
+
 def delete_if_exists(pathname):
     """delete a file, but ignore file not found error"""