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@@ -1,79 +1,80 b'' | |||
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1 | 1 | # base85.py: pure python base85 codec |
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2 | 2 | # |
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3 | 3 | # Copyright (C) 2009 Brendan Cully <brendan@kublai.com> |
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4 | 4 | # |
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5 | 5 | # This software may be used and distributed according to the terms of the |
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6 | 6 | # GNU General Public License version 2 or any later version. |
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7 | 7 | |
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8 | 8 | from __future__ import absolute_import |
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9 | 9 | |
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10 | 10 | import struct |
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11 | 11 | |
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12 | 12 | from .. import pycompat |
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13 | 13 | |
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14 | 14 | _b85chars = pycompat.bytestr("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef" |
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15 | 15 | "ghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~") |
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16 | 16 | _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars] |
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17 | 17 | _b85dec = {} |
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18 | 18 | |
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19 | 19 | def _mkb85dec(): |
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20 | 20 | for i, c in enumerate(_b85chars): |
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21 | 21 | _b85dec[c] = i |
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22 | 22 | |
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23 | 23 | def b85encode(text, pad=False): |
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24 | 24 | """encode text in base85 format""" |
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25 | 25 | l = len(text) |
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26 | 26 | r = l % 4 |
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27 | 27 | if r: |
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28 | 28 | text += '\0' * (4 - r) |
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29 | 29 | longs = len(text) >> 2 |
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30 | 30 | words = struct.unpack('>%dL' % (longs), text) |
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31 | 31 | |
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32 | 32 | out = ''.join(_b85chars[(word // 52200625) % 85] + |
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33 | 33 | _b85chars2[(word // 7225) % 7225] + |
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34 | 34 | _b85chars2[word % 7225] |
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35 | 35 | for word in words) |
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36 | 36 | |
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37 | 37 | if pad: |
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38 | 38 | return out |
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39 | 39 | |
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40 | 40 | # Trim padding |
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41 | 41 | olen = l % 4 |
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42 | 42 | if olen: |
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43 | 43 | olen += 1 |
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44 | 44 | olen += l // 4 * 5 |
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45 | 45 | return out[:olen] |
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46 | 46 | |
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47 | 47 | def b85decode(text): |
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48 | 48 | """decode base85-encoded text""" |
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49 | 49 | if not _b85dec: |
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50 | 50 | _mkb85dec() |
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51 | 51 | |
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52 | 52 | l = len(text) |
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53 | 53 | out = [] |
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54 | 54 | for i in range(0, len(text), 5): |
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55 | 55 | chunk = text[i:i + 5] |
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56 | chunk = pycompat.bytestr(chunk) | |
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56 | 57 | acc = 0 |
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57 | 58 | for j, c in enumerate(chunk): |
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58 | 59 | try: |
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59 | 60 | acc = acc * 85 + _b85dec[c] |
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60 | 61 | except KeyError: |
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61 | 62 | raise ValueError('bad base85 character at position %d' |
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62 | 63 | % (i + j)) |
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63 | 64 | if acc > 4294967295: |
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64 | 65 | raise ValueError('Base85 overflow in hunk starting at byte %d' % i) |
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65 | 66 | out.append(acc) |
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66 | 67 | |
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67 | 68 | # Pad final chunk if necessary |
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68 | 69 | cl = l % 5 |
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69 | 70 | if cl: |
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70 | 71 | acc *= 85 ** (5 - cl) |
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71 | 72 | if cl > 1: |
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72 | 73 | acc += 0xffffff >> (cl - 2) * 8 |
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73 | 74 | out[-1] = acc |
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74 | 75 | |
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75 | 76 | out = struct.pack('>%dL' % (len(out)), *out) |
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76 | 77 | if cl: |
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77 | 78 | out = out[:-(5 - cl)] |
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78 | 79 | |
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79 | 80 | return out |
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