tar_manifest.py

import base64
import json

files = {'c/o': {'name': 'tox.ini', 'size': 3935},
         'c/o2': {'name': 'setup.cfg', 'size': 4396}}

def tar_padding(sz):
    return '\x00' * (512 - (sz - 1) % 512 - 1)

def tar_header(v):
    buf = []
    buf.append(v['name'][:100])
    buf.append('\x00' * (100 - len(v['name'][:100])))
    buf.append('0000640\x00')  # mode
    buf.append(2 * '0000000\x00')  # owner/group
    buf.append('%011o\x00' % v['size'])
    buf.append('%011o\x00' % 0)  # last-modified
    buf.append(' ' * 8)  # checksum placeholder
    buf.append('0')
    buf = ''.join(buf)
    chksum = sum(ord(c) for c in buf)
    buf = buf[:148] + ('%06o\x00 ' % chksum) + buf[156:]
    buf += tar_padding(len(buf))
    assert len(buf) == 512, len(buf)
    return buf

print json.dumps([
    {'path': k,
     'preamble': base64.b64encode(tar_header(v)),
     'postamble': base64.b64encode(tar_padding(v['size']))}
    for k, v in files.items()] + [{'path': 'c/__end_tar'}])