hashfile.py

#!/usr/bin/python
# -*- encoding: utf-8 -*-

import os
import hashlib
import logging

_hashes = {}

def get_absolute_path(root, path):
  """Returns the absolute path
  """
  abspath = os.path.abspath(os.path.join(root, path))
  return abspath

def get_content(abspath, start=None, end=None):
  """Retunrs the content of given absolute path
  """
  with open(abspath, "rb") as file:
    if start is not None:
      file.seek(start)
    if end is not None:
      remaining = end - ( start or 0)
    else:
      remaining = None
    while True:
      chunk_size = 64 * 1024
      if remaining is not None and remaining < chunk_size:
        chunk_size = remaining
      chunk = file.read(chunk_size)
      if chunk:
        if remaining is not None:
          remaining -= len(chunk)
        yield chunk
      else:
        if remaining is not None:
          assert remaining == 0
        return

def get_content_version(abspath):
  """Returns a version string for the resource at the given path
  """
  data = get_content(abspath)
  hasher = hashlib.md5()
  if isinstance(data, bytes):
    hasher.update(data)
  else:
    for chunk in data:
      hasher.update(chunk)
  return hasher.hexdigest()

def get_version(abs_path):
  """Generate the version string to be used in static URLs
  """
  hashes = _hashes
  if abs_path not in hashes:
    try:
      hashes[abs_path] = get_content_version(abs_path)
    except Exception:
      logging.error("Could not open file %r", abs_path)
      hashes[abs_path] = None
  hsh = hashes.get(abs_path)
  if hsh:
    return hsh
  return None


def init():
  root = os.path.dirname(__file__)
  path = 'example/underscore.js'
  abs_path = get_absolute_path(root, path)
  print(get_version(abs_path))


if __name__ == '__main__':
  init()