attachment_help.py

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#! /usr/bin/env python
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##\author Scott Hassan, Kevin Watts

"""
Utilities for loading attachment into WG Inventory System. Used in 
wg_invent_client package only. No external code API
"""

import urllib2
import mimetypes
import mimetools

## -------------------------------------------------------------

def _encode_multipart_formdata(fields, files, BOUNDARY = '-----'+mimetools.choose_boundary()+'-----'):
    """ 
    Encodes fields and files for uploading.
    fields is a sequence of (name, value) elements for regular form fields - or a dictionary.
    files is a sequence of (name, filename, value) elements for data to be uploaded as files.
    Return (content_type, body) ready for urllib2.Request instance
    You can optionally pass in a boundary string to use or we'll let mimetools provide one.
    """    

    CRLF = '\r\n'

    L = []

    if isinstance(fields, dict):
        fields = fields.items()

    for (key, value) in fields:
        L.append('--' + BOUNDARY)
        L.append('Content-Disposition: form-data; name="%s"' % key)
        L.append('')
        L.append(value)

    for (key, filename, value) in files:
        #encoded = value.encode('base64')
        encoded = value
        filetype = mimetypes.guess_type(filename)[0] or 'application/octet-stream'
        L.append('--' + BOUNDARY)
        L.append('Content-Disposition: form-data; name="%s"; filename="%s"' % (key, filename))
        L.append('Content-Length: %s' % len(encoded))
        L.append('Content-Type: %s' % filetype)
        L.append('Content-Transfer-Encoding: binary')
        L.append('')
        L.append(encoded)

    L.append('--' + BOUNDARY + '--')
    L.append('')
    body = CRLF.join([str(l) for l in L])

    content_type = 'multipart/form-data; boundary=%s' % BOUNDARY        # XXX what if no files are encoded

    return content_type, body

def build_request(theurl, fields, files, txheaders=None):
  content_type, body = _encode_multipart_formdata(fields, files)
  if not txheaders: txheaders = {}
  txheaders['Content-type'] = content_type
  txheaders['Content-length'] = str(len(body))
  return urllib2.Request(theurl, body, txheaders)