proper array index validation (dash, unsigned int)

According to the spec
http://tools.ietf.org/html/draft-ietf-appsawg-json-pointer-06

   o  If the currently referenced value is a JSON array, the reference
      token MUST contain either:

      *  characters that represent an unsigned base-10 integer value
         (possibly with leading zeros), making the new referenced value
         the array element with the zero-based index identified by the
         token, or

      *  exactly the single character "-", making the new referenced
         value the (non-existant) member after the last array element.

1 files changed, 8 insertions, 3 deletions

diff --git a/jsonpointer.py b/jsonpointer.py
index 041fa4a..5b118a1 100644
--- a/jsonpointer.py
+++ b/jsonpointer.py
@@ -49,6 +49,11 @@ except ImportError: # Python 3
     izip = zip
 
 from itertools import tee
+import re
+
+
+# array indices must not contain signs, spaces, decimal parts, etc
+RE_ARRAY_INDEX=re.compile('^[0-9]+$')
 
 
 class JsonPointerException(Exception):
@@ -227,11 +232,11 @@ class JsonPointer(object):
             if part == '-':
                 return part
 
-            try:
-                return int(part)
-            except ValueError:
+            if not RE_ARRAY_INDEX.match(part):
                 raise JsonPointerException("'%s' is not a valid list index" % (part, ))
 
+            return int(part)
+
         else:
             raise JsonPointerException("Unknown document type '%s'" % (doc.__class__,))