electrum-obelisk

Electrum server using libbitcoin as its backend
git clone https://git.parazyd.org/electrum-obelisk
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helpers.py (2401B)

      1 #!/usr/bin/env python3
      2 # electrum-obelisk
      3 # Copyright (C) 2020-2021 Ivan J. <parazyd@dyne.org>
      4 # Copyright (c) 2018-2020 Chris Belcher (MIT License)
      5 #
      6 # This program is free software: you can redistribute it and/or modify
      7 # it under the terms of the GNU Affero General Public License as published by
      8 # the Free Software Foundation, either version 3 of the License, or
      9 # (at your option) any later version.
     10 #
     11 # This program is distributed in the hope that it will be useful,
     12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
     13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14 # GNU Affero General Public License for more details.
     15 #
     16 # You should have received a copy of the GNU Affero General Public License
     17 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
     18 """ Useful helper functions """
     19 from binascii import hexlify
     20 
     21 code_strings = {
     22     2: '01',
     23     10: '0123456789',
     24     16: '0123456789abcdef',
     25     32: 'abcdefghijklmnopqrstuvwxyz234567',
     26     58: '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz',
     27     256: ''.join([chr(x) for x in range(256)]),
     28 }
     29 
     30 
     31 def get_code_string(base):
     32     """ Get valid characters for base """
     33     if base in code_strings:
     34         return code_strings[base]
     35     raise ValueError('Invalid base!')
     36 
     37 
     38 def encode(val, base, minlen=0):
     39     """ Encoding for serialization """
     40     base, minlen = int(base), int(minlen)
     41     code_string = get_code_string(base)
     42     result_bytes = bytes()
     43     while val > 0:
     44         curcode = code_string[val % base]
     45         result_bytes = bytes([ord(curcode)]) + result_bytes
     46         val //= base
     47 
     48     pad_size = minlen - len(result_bytes)
     49 
     50     padding_element = b'\x00' if base == 256 else b'1' \
     51         if base == 58 else b'0'
     52     if pad_size > 0:
     53         result_bytes = padding_element * pad_size + result_bytes
     54 
     55     result_string = ''.join([chr(y) for y in result_bytes])
     56     result = result_bytes if base == 256 else result_string
     57     return result
     58 
     59 
     60 def safe_hexlify(_str):
     61     """ hexlify and return a string """
     62     return str(hexlify(_str), 'utf-8')
     63 
     64 
     65 def num_to_var_int(num):
     66     """ number to bytes """
     67     num = int(num)
     68     if num < 253:
     69         return bytes([num])
     70     if num < 65536:
     71         return bytes([253]) + encode(num, 256, 2)[::-1]
     72     if num < 4294967296:
     73         return bytes([254]) + encode(num, 256, 4)[::-1]
     74     return bytes([255]) + encode(num, 256, 8)[::-1]