utils.py

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#!/usr/bin/python
# -*- coding: utf-8 -*- 
 
import random
import importlib
import base64
 
# =====================================================================
def MakeRID():
  """Returns a random 32-bit int ID.
  """
  return random.randint(-2147483648, 2147483647)
 
# =====================================================================
def MakeRBID():
  """Returns a random 64-bit int ID.
  """  
  return random.randint(-9223372036854775808, 9223372036854775807)
 
# =====================================================================
def Bound(val, min, max):
  """Returns a value that is no smaller than min or larger than max.
  """
  if val < min:
    val = min
    
  if val > max:
    val = max
    
  return val
 
# =====================================================================
def ToShortCode(
  val, 
  chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_'
):
  """Turns a 32-bit value into a six character alphanumeric code. Useful
  for shortening JSON data or use in URLs.
  
  Thanks to http://programanddesign.com/php/base62-encode/
  """
  val  = int(val) + 2147483648
  
  base = len(chars)
  code  = ''
  
  while True:
    mod = int(val % base)
    code = chars[mod] + code
    val = (val - mod) / base
    
    if val <= 0:
      break
    
  while len(code) < 6:
    code  = '0' + code
  
  return code
 
# =====================================================================
def FromShortCode(
  code, 
  chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_'
):
  """Turns a six character alphanumeric code into a 32-bit value. It's 
  the reverse of ToShortCode()
  """
  base  = len(chars)
  
  l     = len(code)
  val   = 0;
 
  chars = [c for c in chars]
  arr   = {}
 
  for i in range(0, base):
    arr[chars[i]] = i
 
  for i in range(0, l):
    val = val + (arr[code[i]] * (base ** (l - i - 1)))
 
  val  = val - 2147483648
 
  return val
 
# =====================================================================
def CodeDir(code):
  """Separates a filename into three character segments with the 
  directory separator '/' in between. Useful for avoiding having
  millions of small files inside of the same directory, which is known
  to severely degrade performance on some filesystems.
  """
  ls  = []
  i   = 0
  l   = len(code)
  
  while i < l:
    ls.append(code[i:i + 3])
    i += 3
 
  return '/'.join(ls)
 
# =====================================================================
def BestTranslation(translations, languages, defaultlang = 'en'):
  """Returns the best translation found in a dict of different
  translations. 
  
  languages should be a list of of ISO 639-1 language codes.
  
  defaultlang is set to 'en', so be sure to set it to your native
  language if used on other systems.
  """
  if not translations:
    return '--'
  
  if not isinstance(languages, list):
    languages = [languages]
  
  for l in languages:
    if l in translations and translations[l]:
      return translations[l]
    
  if defaultlang in translations:
    return translations[defaultlang]
  
  return translations[list(translations.keys())[0]]
 
# =====================================================================
def LoadTranslation(g, app, translation, languages):
  """Load the translation into the global language dict in g.T
  
  languages should be a list of of ISO 639-1 language codes.
  
  'en' will always be the last language code on the list.
  """
  T = g.T
  
  if not isinstance(languages, list):
    languages = [languages]
    
  languages.append('en')
  
  for lang in languages:
    try:
      with open('static/' + app + '/translations/' + lang + '/' + translation + '.js', 'r') as f:
        exec(f.read())        
        
      return lang
    except Exception as e:
      pass
    
  raise Exception(f"Translation {app}/{translation} was not found for {languages}")
 
# =====================================================================
def GetModel(model):
  """Returns the model object from the correct module.
  """
  if not model:
    raise Exception('GetModel: Missing model name')
  
  parts = model.split('_')
  
  if len(parts) != 2:
    raise Exception(f"GetModel: {model} doesn't look like a valid model name.")
  
  module  = importlib.import_module('apps.' + parts[0])
  
  if model not in dir(module):
    raise Exception(f"GetModel: Model {model} not found in module apps.{parts[0]}")
  
  return getattr(module, model)
 
# =====================================================================
def b64decodepad(s):
  """Helper function to ensure that a b64 string is correctly padded to 
  four spaces.
  """
  
  #if not isinstance(s, bytes):
  #  s = s.encode('utf-8')
  
  missing_padding = len(s) % 4
  
  if missing_padding:
    s += '=' * (4 - missing_padding)
  
  return base64.b64decode(s)
 
# =====================================================================
def EscapeSQL(s):
  """Escapes special characters to be used in a SQL query string. 
  
  Taken from mysql-connector's version.
  """
  ls  = [];
  
  for c in s:
    if c == '\\n':      
      ls.append('\\\\n')
    elif c == '\\r':
      ls.append('\\\\r')
    elif c == '\\':
      ls.append('\\\\')
    elif c == "'":
      ls.append("\\'")
    elif c == '"': 
      ls.append('\\"')
    elif c == '\u00a5' or c == '\u20a9':
      #escape characters interpreted as backslash by mysql
      #fall through
      pass
    else:
      ls.append(c)
  
  return ''.join(ls)
 
# =====================================================================
def KeyFromValue(ls, value):
  """Does a reverse lookup to find the key of a value in a dict.
  """
  return ls.keys()[ls.values().index(value)]