Project creation.

1 files changed, 45 insertions, 0 deletions

diff --git a/permission.py b/permission.py
new file mode 100644
index 0000000..310cef2
--- /dev/null
+++ b/permission.py
@@ -0,0 +1,45 @@
+# -*- coding: utf-8 -*-
+#TODO : move the globals to a config file (use the config file parser module)
+PERM_LIST=['READ','MODIFY','APPEND'] #just add a string here to define a new permission
+PERMS = len(PERM_LIST)
+MAX = (1<<PERMS)-1
+
+class PermissionError(Exception) :
+    def __init__(self,error_string) :
+        self.error = error_string
+        
+    def __str__(self) :
+        str(self.error)
+
+class Permission :
+    
+    def __init__(self,init) : 
+        if isinstance(init,int) :
+            if (init > MAX) or (init < 0) :
+                raise PermissionError('Permission int not in correct range')
+            result = []
+            for shift in range(PERMS-1,-1,-1) :
+                if init>>shift :
+                    result.append(PERM_LIST[shift])
+                    init = init-(1<<shift)
+            self.perm_list = result
+        elif isinstance(init,list) :
+            if (set(init) <= set(PERM_LIST)) :
+                self.perm_list = init
+            else :
+                raise PermissionError('Undefined permission')
+            
+    def __str__(self) :
+        return str(self.perm_list)
+        
+    def toInt(self) :
+        result = 0
+        for i,perm in enumerate(PERM_LIST) :
+            if perm in self.perm_list :
+                result += 1<<i
+        return result
+        
+if __name__== '__main__' :
+    for i in range(MAX+1) :
+        print i, Permission(i), Permission(i).toInt()
+    
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