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| 1 | +# Encoding: utf-8 |
| 2 | +# Cloud Foundry Java Buildpack |
| 3 | +# Copyright (c) 2013 the original author or authors. |
| 4 | +# |
| 5 | +# Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | +# you may not use this file except in compliance with the License. |
| 7 | +# You may obtain a copy of the License at |
| 8 | +# |
| 9 | +# http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | +# |
| 11 | +# Unless required by applicable law or agreed to in writing, software |
| 12 | +# distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | +# See the License for the specific language governing permissions and |
| 15 | +# limitations under the License. |
| 16 | + |
| 17 | +require 'java_buildpack/util' |
| 18 | +require 'pathname' |
| 19 | +require 'set' |
| 20 | + |
| 21 | +module JavaBuildpack::Util |
| 22 | + |
| 23 | + # This class conforms to the interface of +Pathname+, but filters the set of files that can be accessed and does not |
| 24 | + # support +Pathname+'s class methods. |
| 25 | + # |
| 26 | + # If a +Pathname+ method which mutates the file system is called, it will throw an exception unless the instance is |
| 27 | + # mutable. |
| 28 | + # |
| 29 | + # If the underlying filesystem is modified once an instance of this path has been created, the view provided |
| 30 | + # by the instance will not change unless a file or directory allowed by the instance's filter is created, modified, or |
| 31 | + # deleted. |
| 32 | + class FilteringPathname |
| 33 | + |
| 34 | + # Create a +FilteringPathname+ which behaves like the given pathname, but which applies the given filter to all files. |
| 35 | + # |
| 36 | + # The filesystem underpinning the given pathname must not contain a file or directory whose name is the name of the |
| 37 | + # given pathname with '.nil' appended to it. This must be true for the lifetime of the +FilteringPathname+. |
| 38 | + # |
| 39 | + # The filter is applied to files which are accessed via the given pathname. |
| 40 | + # If the filter returns +true+ for a particular pathname, the pathname behaves normally for this instance. |
| 41 | + # If the filter returns +false+ for a particular pathname, the pathname behaves as if it does not exist. |
| 42 | + # |
| 43 | + # The +FilteringPathname+ may be immutable in which case calling a mutator method causes an exception to be thrown. |
| 44 | + # Alternatively, the +FilteringPathname+ may be mutable in which case calling a mutator method may mutate the |
| 45 | + # file system. The results of mutating the file system will be subject to filtering by the given filter. |
| 46 | + # |
| 47 | + # @param [Pathname] pathname the +Pathname+ which is to be filtered |
| 48 | + # @param [Proc] filter a lambda which takes a +Pathname+ and returns either +true+ (to 'keep' the pathname) or |
| 49 | + # +false+ (to filter out the pathname) |
| 50 | + # @param [Boolean] mutable +true+ if and only if the +FilteringPathname+ may be used to mutate the file system |
| 51 | + def initialize(pathname, filter, mutable = false) |
| 52 | + @pathname = pathname |
| 53 | + @filter = filter |
| 54 | + @non_existent = Pathname.new "#{pathname}.nil" |
| 55 | + FilteringPathname.check_file_does_not_exist @non_existent |
| 56 | + @delegated_pathname = @filter.call(@pathname) ? @pathname : @non_existent |
| 57 | + @mutable = mutable |
| 58 | + end |
| 59 | + |
| 60 | + # Dispatch superclass methods via method_missing. |
| 61 | + undef_method :<=> |
| 62 | + undef_method :== |
| 63 | + undef_method :=== |
| 64 | + undef_method :taint |
| 65 | + undef_method :untaint |
| 66 | + |
| 67 | + # @see Pathname. |
| 68 | + def each_entry(&block) |
| 69 | + delegate_and_yield_visible(:each_entry, &block) |
| 70 | + end |
| 71 | + |
| 72 | + # @see Pathname. |
| 73 | + def entries |
| 74 | + visible delegate.entries |
| 75 | + end |
| 76 | + |
| 77 | + # @see Pathname. |
| 78 | + def open(mode = nil, perm = nil, opt = nil, &block) |
| 79 | + check_mutable if mode =~ /[wa]/ |
| 80 | + delegate.open(mode, perm, opt, &block) |
| 81 | + end |
| 82 | + |
| 83 | + # @see Pathname. |
| 84 | + def to_s |
| 85 | + @filter.call(@pathname) ? delegate.to_s : '' |
| 86 | + end |
| 87 | + |
| 88 | + # @see Pathname. |
| 89 | + def children(with_directory = true) |
| 90 | + if with_directory |
| 91 | + super # delegate to method_missing |
| 92 | + else |
| 93 | + visible delegate.children(false) |
| 94 | + end |
| 95 | + end |
| 96 | + |
| 97 | + # @see Pathname. |
| 98 | + def each_child(with_directory = true, &block) |
| 99 | + if with_directory |
| 100 | + super # delegate to method_missing |
| 101 | + else |
| 102 | + delegate_and_yield_visible(:each_child, false, &block) |
| 103 | + end |
| 104 | + end |
| 105 | + |
| 106 | + private |
| 107 | + |
| 108 | + MUTATORS = [:chmod, :chown, :delete, :lchmod, :lchown, :make_link, :make_symlink, :mkdir, :mkpath, :rename, :rmdir, :rmtree, :taint, :unlink, :untaint].to_set.freeze |
| 109 | + |
| 110 | + def self.check_file_does_not_exist(file) |
| 111 | + fail "#{file} should not exist" if file.exist? |
| 112 | + end |
| 113 | + |
| 114 | + def check_mutable |
| 115 | + fail 'FilteringPathname is immutable' unless @mutable |
| 116 | + end |
| 117 | + |
| 118 | + def convert_if_necessary(r) |
| 119 | + if r.instance_of?(Pathname) |
| 120 | + @filter.call(r) ? filtered_pathname(r) : nil |
| 121 | + else |
| 122 | + r |
| 123 | + end |
| 124 | + end |
| 125 | + |
| 126 | + def convert_result_if_necessary(result) |
| 127 | + if result.instance_of? Array |
| 128 | + result.map { |r| convert_if_necessary(r) }.compact |
| 129 | + else |
| 130 | + result ? convert_if_necessary(result) || @non_existent : nil |
| 131 | + end |
| 132 | + end |
| 133 | + |
| 134 | + def delegate |
| 135 | + FilteringPathname.check_file_does_not_exist @non_existent |
| 136 | + @delegated_pathname |
| 137 | + end |
| 138 | + |
| 139 | + def delegate_and_yield_visible(method, *args) |
| 140 | + delegate.send(method, *args) do |y| |
| 141 | + yield y if visible y |
| 142 | + end |
| 143 | + end |
| 144 | + |
| 145 | + def filtered_pathname(pathname) |
| 146 | + FilteringPathname.new(pathname, @filter) |
| 147 | + end |
| 148 | + |
| 149 | + def method_missing(method, *args) |
| 150 | + check_mutable if MUTATORS.member? method |
| 151 | + if block_given? |
| 152 | + result = delegate.send(method, *args) do |*values| |
| 153 | + converted_values = values.map { |value| convert_if_necessary(value) }.compact |
| 154 | + yield *converted_values unless converted_values.empty? # rubocop:disable Syntax |
| 155 | + end |
| 156 | + else |
| 157 | + result = delegate.send(method, *args) |
| 158 | + end |
| 159 | + convert_result_if_necessary(result) |
| 160 | + end |
| 161 | + |
| 162 | + def respond_to_missing?(symbol, include_private = false) |
| 163 | + delegate.respond_to?(symbol, include_private) |
| 164 | + end |
| 165 | + |
| 166 | + def visible(entry) |
| 167 | + if entry.instance_of? Array |
| 168 | + entry.select { |child| visible(child) } |
| 169 | + else |
| 170 | + @filter.call(@pathname + entry) |
| 171 | + end |
| 172 | + end |
| 173 | + |
| 174 | + end |
| 175 | +end |
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