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1 | 1 | # appendfile.py - special classes to make repo updates atomic |
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2 | 2 | # |
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3 | 3 | # Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com> |
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4 | 4 | # |
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5 | 5 | # This software may be used and distributed according to the terms |
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6 | 6 | # of the GNU General Public License, incorporated herein by reference. |
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7 | 7 | |
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8 | 8 | from demandload import * |
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9 | 9 | demandload(globals(), "cStringIO changelog errno manifest os tempfile") |
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10 | 10 | |
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11 | 11 | # writes to metadata files are ordered. reads: changelog, manifest, |
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12 | 12 | # normal files. writes: normal files, manifest, changelog. |
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13 | 13 | |
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14 | 14 | # manifest contains pointers to offsets in normal files. changelog |
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15 | 15 | # contains pointers to offsets in manifest. if reader reads old |
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16 | 16 | # changelog while manifest or normal files are written, it has no |
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17 | 17 | # pointers into new parts of those files that are maybe not consistent |
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18 | 18 | # yet, so will not read them. |
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19 | 19 | |
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20 | 20 | # localrepo.addchangegroup thinks it writes changelog first, then |
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21 | 21 | # manifest, then normal files (this is order they are available, and |
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22 | 22 | # needed for computing linkrev fields), but uses appendfile to hide |
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23 | 23 | # updates from readers. data not written to manifest or changelog |
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24 | 24 | # until all normal files updated. write manifest first, then |
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25 | 25 | # changelog. |
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26 | 26 | |
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27 | 27 | # with this write ordering, readers cannot see inconsistent view of |
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28 | 28 | # repo during update. |
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29 | 29 | |
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30 | 30 | class appendfile(object): |
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31 | 31 | '''implement enough of file protocol to append to revlog file. |
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32 | 32 | appended data is written to temp file. reads and seeks span real |
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33 | 33 | file and temp file. readers cannot see appended data until |
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34 | 34 | writedata called.''' |
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35 | 35 | |
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36 | 36 | def __init__(self, fp, tmpname): |
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37 | 37 | if tmpname: |
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38 | 38 | self.tmpname = tmpname |
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39 | 39 | self.tmpfp = open(self.tmpname, 'ab+') |
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40 | 40 | else: |
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41 | 41 | fd, self.tmpname = tempfile.mkstemp() |
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42 | 42 | self.tmpfp = os.fdopen(fd, 'ab+') |
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43 | 43 | self.realfp = fp |
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44 | 44 | self.offset = fp.tell() |
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45 | 45 | # real file is not written by anyone else. cache its size so |
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46 | 46 | # seek and read can be fast. |
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47 | 47 | self.realsize = os.fstat(fp.fileno()).st_size |
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48 | 48 | |
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49 | 49 | def end(self): |
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50 | 50 | self.tmpfp.flush() # make sure the stat is correct |
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51 | 51 | return self.realsize + os.fstat(self.tmpfp.fileno()).st_size |
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52 | 52 | |
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53 | 53 | def tell(self): |
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54 | 54 | return self.offset |
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55 | 55 | |
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56 | 56 | def flush(self): |
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57 | 57 | self.tmpfp.flush() |
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58 | 58 | |
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59 | 59 | def close(self): |
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60 | 60 | self.realfp.close() |
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61 | 61 | self.tmpfp.close() |
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62 | 62 | |
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63 | 63 | def seek(self, offset, whence=0): |
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64 | 64 | '''virtual file offset spans real file and temp file.''' |
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65 | 65 | if whence == 0: |
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66 | 66 | self.offset = offset |
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67 | 67 | elif whence == 1: |
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68 | 68 | self.offset += offset |
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69 | 69 | elif whence == 2: |
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70 | 70 | self.offset = self.end() + offset |
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71 | 71 | |
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72 | 72 | if self.offset < self.realsize: |
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73 | 73 | self.realfp.seek(self.offset) |
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74 | 74 | else: |
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75 | 75 | self.tmpfp.seek(self.offset - self.realsize) |
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76 | 76 | |
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77 | 77 | def read(self, count=-1): |
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78 | 78 | '''only trick here is reads that span real file and temp file.''' |
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79 | 79 | fp = cStringIO.StringIO() |
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80 | 80 | old_offset = self.offset |
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81 | 81 | if self.offset < self.realsize: |
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82 | 82 | s = self.realfp.read(count) |
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83 | 83 | fp.write(s) |
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84 | 84 | self.offset += len(s) |
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85 | 85 | if count > 0: |
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86 | 86 | count -= len(s) |
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87 | 87 | if count != 0: |
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88 | 88 | if old_offset != self.offset: |
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89 | 89 | self.tmpfp.seek(self.offset - self.realsize) |
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90 | 90 | s = self.tmpfp.read(count) |
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91 | 91 | fp.write(s) |
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92 | 92 | self.offset += len(s) |
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93 | 93 | return fp.getvalue() |
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94 | 94 | |
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95 | 95 | def write(self, s): |
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96 | 96 | '''append to temp file.''' |
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97 | 97 | self.tmpfp.seek(0, 2) |
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98 | 98 | self.tmpfp.write(s) |
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99 | 99 | # all writes are appends, so offset must go to end of file. |
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100 | 100 | self.offset = self.realsize + self.tmpfp.tell() |
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101 | 101 | |
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102 | 102 | class appendopener(object): |
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103 | 103 | '''special opener for files that only read or append.''' |
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104 | 104 | |
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105 | 105 | def __init__(self, opener): |
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106 | 106 | self.realopener = opener |
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107 | 107 | # key: file name, value: appendfile name |
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108 | 108 | self.tmpnames = {} |
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109 | 109 | |
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110 | 110 | def __call__(self, name, mode='r'): |
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111 | 111 | '''open file.''' |
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112 | 112 | |
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113 | 113 | assert mode in 'ra+' |
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114 | 114 | try: |
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115 | 115 | realfp = self.realopener(name, 'r') |
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116 | 116 | except IOError, err: |
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117 | 117 | if err.errno != errno.ENOENT: raise |
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118 | 118 | realfp = self.realopener(name, 'w+') |
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119 | 119 | tmpname = self.tmpnames.get(name) |
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120 | 120 | fp = appendfile(realfp, tmpname) |
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121 | 121 | if tmpname is None: |
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122 | 122 | self.tmpnames[name] = fp.tmpname |
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123 | 123 | return fp |
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124 | 124 | |
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125 | 125 | def writedata(self): |
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126 | 126 | '''copy data from temp files to real files.''' |
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127 | 127 | # write .d file before .i file. |
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128 | 128 | tmpnames = self.tmpnames.items() |
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129 | 129 | tmpnames.sort() |
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130 | 130 | for name, tmpname in tmpnames: |
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131 | 131 | fp = open(tmpname, 'rb') |
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132 | 132 | s = fp.read() |
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133 | 133 | fp.close() |
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134 | os.unlink(tmpname) | |
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134 | 135 | fp = self.realopener(name, 'a') |
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135 | 136 | fp.write(s) |
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136 | 137 | fp.close() |
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137 | 138 | |
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138 | def __del__(self): | |
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139 | for tmpname in self.tmpnames.itervalues(): | |
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140 | os.unlink(tmpname) | |
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141 | ||
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142 | 139 | # files for changelog and manifest are in different appendopeners, so |
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143 | 140 | # not mixed up together. |
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144 | 141 | |
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145 | 142 | class appendchangelog(changelog.changelog, appendopener): |
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146 | 143 | def __init__(self, opener, version): |
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147 | 144 | appendopener.__init__(self, opener) |
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148 | 145 | changelog.changelog.__init__(self, self, version) |
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149 | 146 | def checkinlinesize(self, fp, tr): |
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150 | 147 | return |
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151 | 148 | |
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152 | 149 | class appendmanifest(manifest.manifest, appendopener): |
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153 | 150 | def __init__(self, opener, version): |
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154 | 151 | appendopener.__init__(self, opener) |
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155 | 152 | manifest.manifest.__init__(self, self, version) |
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156 | 153 | def checkinlinesize(self, fp, tr): |
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157 | 154 | return |
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