Mercurial > hgrepos > Python > apps > py-cutils

annotate cutils/util/digest.py @ 122:1e5127028254

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Move the real computation of digests from files and streams into dedicated submodule cutils.util.digest
author Franz Glasner <fzglas.hg@dom66.de>
date Wed, 01 Jan 2025 18:57:25 +0100
parents
children a813094ae4f5
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122
1e5127028254 Move the real computation of digests from files and streams into dedicated submodule cutils.util.digest
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1 # -*- coding: utf-8 -*-
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2 # :-
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3 # :Copyright: (c) 2020-2025 Franz Glasner
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4 # :License: BSD-3-Clause
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5 # :-
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6 r"""Utility sub-module to implement a file and stream digest computations.
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7
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8 """
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9
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10 __all__ = ["compute_digest_file", "compute_digest_stream"]
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11
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12
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13 import errno
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14 import io
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15 import os
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16 try:
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17 import mmap
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18 except ImportError:
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19 mmap = None
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20 import stat
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21
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22 from . import constants
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23
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24
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25 def compute_digest_file(hashobj, path, use_mmap=None):
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26 """Compute the digest for a file with a filename of an open fd.
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27
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28 :param hashobj: a :mod:`hashlib` compatible hash algorithm type or factory
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29 :param path: filename within the filesystem or a file descriptor opened in
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30 binary mode (also a socket or pipe)
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31 :param use_mmap: Use the :mod:`mmap` module if available.
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32 If `None` determine automatically.
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33 :type use_mmap: bool or None
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34 :return: the digest in binary form
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35 :rtype: bytes
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36
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37 If a file descriptor is given is must support :func:`os.read`.
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38
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39 """
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40 h = hashobj()
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41 if isinstance(path, constants.PATH_TYPES):
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42 flags = os.O_RDONLY | getattr(os, "O_BINARY", 0) \
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43 | getattr(os, "O_SEQUENTIAL", 0) | getattr(os, "O_NOCTTY", 0)
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44 fd = os.open(path, flags)
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45 own_fd = True
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46 else:
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47 fd = path
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48 own_fd = False
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49 try:
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50 try:
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51 st = os.fstat(fd)
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52 except TypeError:
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53 #
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54 # "fd" is most probably a Python socket object.
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55 # (a pipe typically supports fstat)
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56 #
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57 use_mmap = False
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58 else:
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59 if stat.S_ISREG(st[stat.ST_MODE]):
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60 filesize = st[stat.ST_SIZE]
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61 if (use_mmap is None) \
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62 and (filesize > constants.MAX_AUTO_MAP_SIZE):
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63 #
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64 # This is borrowed from FreeBSD's cp(1) implementation:
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65 # Mmap and process if less than 8M (the limit is
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66 # so we don't totally trash memory on big files.
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67 # This is really a minor hack, but it wins some
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68 # CPU back. Some filesystems, such as smbnetfs,
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69 # don't support mmap, so this is a best-effort
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70 # attempt.
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71 #
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72 use_mmap = False
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73 else:
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74 use_mmap = False
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75 if use_mmap is None:
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76 use_mmap = True
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77 if mmap is None or not use_mmap:
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78 # No mmap available or wanted -> use traditional low-level file IO
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79 fadvise = getattr(os, "posix_fadvise", None)
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80 if fadvise:
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81 fadvise(fd, 0, 0, os.POSIX_FADV_SEQUENTIAL)
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82 if not constants.PY2:
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83 fileobj = io.FileIO(fd, mode="r", closefd=False)
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84 buf = bytearray(constants.READ_CHUNK_SIZE)
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85 with memoryview(buf) as full_view:
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86 while True:
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87 try:
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88 n = fileobj.readinto(buf)
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89 except OSError as e:
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90 if e.errno not in (errno.EAGAIN,
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91 errno.EWOULDBLOCK,
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92 errno.EINTR):
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93 raise
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94 else:
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95 if n == 0:
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96 break
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97 if n == constants.READ_CHUNK_SIZE:
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98 h.update(buf)
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99 else:
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100 with full_view[:n] as partial_view:
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101 h.update(partial_view)
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102 else:
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103 while True:
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104 try:
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105 buf = os.read(fd, constants.READ_CHUNK_SIZE)
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106 except OSError as e:
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107 if e.errno not in (errno.EAGAIN,
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108 errno.EWOULDBLOCK,
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109 errno.EINTR):
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110 raise
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111 else:
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112 if len(buf) == 0:
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113 break
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114 h.update(buf)
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115 else:
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116 #
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117 # Use mmap
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118 #
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119 # NOTE: On Windows mmapped files with length 0 are not supported.
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120 # So ensure to not call mmap.mmap() if the file size is 0.
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121 #
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122 madvise = getattr(mmap.mmap, "madvise", None)
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123 if filesize <= constants.MAP_WINDOW_SIZE:
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124 mapsize = filesize
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125 else:
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126 mapsize = constants.MAP_WINDOW_SIZE
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127 mapoffset = 0
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128 rest = filesize
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129 while rest > 0:
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130 m = mmap.mmap(fd,
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131 mapsize,
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132 access=mmap.ACCESS_READ,
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133 offset=mapoffset)
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134 if madvise:
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135 madvise(m, mmap.MADV_SEQUENTIAL)
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136 try:
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137 h.update(m)
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138 finally:
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139 m.close()
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140 rest -= mapsize
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141 mapoffset += mapsize
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142 if rest < mapsize:
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143 mapsize = rest
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144 finally:
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145 if own_fd:
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146 os.close(fd)
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147 return h.digest()
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148
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149
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150 def compute_digest_stream(hashobj, instream):
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151 """Compute the digest for a given byte string `instream`.
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152
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153 :param hashobj: a :mod:`hashlib` compatible hash algorithm type or factory
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154 :param instream: a bytes input stream to read the data to be hashed from
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155 :return: the digest in binary form
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156 :rtype: bytes
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157
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158 """
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159 h = hashobj()
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160 while True:
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161 try:
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162 buf = instream.read(constants.READ_CHUNK_SIZE)
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163 except OSError as e:
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164 if e.errno not in (errno.EAGAIN, errno.EWOULDBLOCK, errno.EINTR):
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165 raise
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166 else:
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167 if buf is not None:
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168 if len(buf) == 0:
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169 break
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170 h.update(buf)
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171 return h.digest()