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1 | 1 | # mpatch.py - Python implementation of mpatch.c |
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2 | 2 | # |
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3 | 3 | # Copyright 2009 Matt Mackall <mpm@selenic.com> and others |
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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 cStringIO |
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11 | 11 | import struct |
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12 | 12 | |
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13 | 13 | StringIO = cStringIO.StringIO |
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14 | 14 | |
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15 | 15 | # This attempts to apply a series of patches in time proportional to |
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16 | 16 | # the total size of the patches, rather than patches * len(text). This |
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17 | 17 | # means rather than shuffling strings around, we shuffle around |
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18 | 18 | # pointers to fragments with fragment lists. |
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19 | 19 | # |
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20 | 20 | # When the fragment lists get too long, we collapse them. To do this |
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21 | 21 | # efficiently, we do all our operations inside a buffer created by |
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22 | 22 | # mmap and simply use memmove. This avoids creating a bunch of large |
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23 | 23 | # temporary string buffers. |
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24 | 24 | |
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25 | 25 | def _pull(dst, src, l): # pull l bytes from src |
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26 | 26 | while l: |
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27 | 27 | f = src.pop() |
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28 | 28 | if f[0] > l: # do we need to split? |
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29 | 29 | src.append((f[0] - l, f[1] + l)) |
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30 | 30 | dst.append((l, f[1])) |
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31 | 31 | return |
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32 | 32 | dst.append(f) |
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33 | 33 | l -= f[0] |
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34 | 34 | |
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35 | 35 | def _move(m, dest, src, count): |
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36 | 36 | """move count bytes from src to dest |
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37 | 37 | |
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38 | 38 | The file pointer is left at the end of dest. |
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39 | 39 | """ |
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40 | 40 | m.seek(src) |
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41 | 41 | buf = m.read(count) |
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42 | 42 | m.seek(dest) |
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43 | 43 | m.write(buf) |
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44 | 44 | |
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45 | def _collect(m, buf, list): | |
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46 | start = buf | |
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47 | for l, p in reversed(list): | |
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48 | _move(m, buf, p, l) | |
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49 | buf += l | |
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50 | return (buf - start, start) | |
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51 | ||
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45 | 52 | def patches(a, bins): |
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46 | 53 | if not bins: |
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47 | 54 | return a |
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48 | 55 | |
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49 | 56 | plens = [len(x) for x in bins] |
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50 | 57 | pl = sum(plens) |
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51 | 58 | bl = len(a) + pl |
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52 | 59 | tl = bl + bl + pl # enough for the patches and two working texts |
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53 | 60 | b1, b2 = 0, bl |
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54 | 61 | |
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55 | 62 | if not tl: |
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56 | 63 | return a |
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57 | 64 | |
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58 | 65 | m = StringIO() |
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59 | 66 | |
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60 | 67 | # load our original text |
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61 | 68 | m.write(a) |
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62 | 69 | frags = [(len(a), b1)] |
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63 | 70 | |
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64 | 71 | # copy all the patches into our segment so we can memmove from them |
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65 | 72 | pos = b2 + bl |
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66 | 73 | m.seek(pos) |
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67 | 74 | for p in bins: m.write(p) |
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68 | 75 | |
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69 | def collect(buf, list): | |
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70 | start = buf | |
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71 | for l, p in reversed(list): | |
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72 | _move(m, buf, p, l) | |
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73 | buf += l | |
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74 | return (buf - start, start) | |
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75 | ||
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76 | 76 | for plen in plens: |
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77 | 77 | # if our list gets too long, execute it |
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78 | 78 | if len(frags) > 128: |
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79 | 79 | b2, b1 = b1, b2 |
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80 | frags = [collect(b1, frags)] | |
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80 | frags = [_collect(m, b1, frags)] | |
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81 | 81 | |
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82 | 82 | new = [] |
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83 | 83 | end = pos + plen |
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84 | 84 | last = 0 |
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85 | 85 | while pos < end: |
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86 | 86 | m.seek(pos) |
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87 | 87 | p1, p2, l = struct.unpack(">lll", m.read(12)) |
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88 | 88 | _pull(new, frags, p1 - last) # what didn't change |
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89 | 89 | _pull([], frags, p2 - p1) # what got deleted |
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90 | 90 | new.append((l, pos + 12)) # what got added |
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91 | 91 | pos += l + 12 |
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92 | 92 | last = p2 |
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93 | 93 | frags.extend(reversed(new)) # what was left at the end |
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94 | 94 | |
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95 | t = collect(b2, frags) | |
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95 | t = _collect(m, b2, frags) | |
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96 | 96 | |
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97 | 97 | m.seek(t[1]) |
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98 | 98 | return m.read(t[0]) |
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99 | 99 | |
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100 | 100 | def patchedsize(orig, delta): |
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101 | 101 | outlen, last, bin = 0, 0, 0 |
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102 | 102 | binend = len(delta) |
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103 | 103 | data = 12 |
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104 | 104 | |
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105 | 105 | while data <= binend: |
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106 | 106 | decode = delta[bin:bin + 12] |
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107 | 107 | start, end, length = struct.unpack(">lll", decode) |
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108 | 108 | if start > end: |
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109 | 109 | break |
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110 | 110 | bin = data + length |
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111 | 111 | data = bin + 12 |
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112 | 112 | outlen += start - last |
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113 | 113 | last = end |
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114 | 114 | outlen += length |
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115 | 115 | |
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116 | 116 | if bin != binend: |
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117 | 117 | raise ValueError("patch cannot be decoded") |
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118 | 118 | |
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119 | 119 | outlen += orig - last |
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120 | 120 | return outlen |
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