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# frozen_string_literal: true
# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
require "google/cloud/env/lazy_value"
module Google
module Cloud
class Env
##
# Access to file system contents.
#
# This is a simple class that reads the contents of objects in the file
# system, caching data so that subsequent accesses do not need to reread
# the file system.
#
# You can also "mock" the file system by providing a hash of overrides.
# If overrides are present, actual file system access is disabled; that
# is, overrides are "all or nothing".
#
# This class does not provide any controls for data size. If you read a
# large file, its contents will stay in memory for the lifetime of the
# Ruby process.
#
class FileSystem
##
# Create a file system access object with no overrides.
#
def initialize
@overrides = nil
@cache = LazyDict.new do |path, binary|
if binary
File.binread path
else
File.read path
end
rescue IOError, SystemCallError
nil
end
# This mutex protects the overrides variable. Its setting (i.e.
# whether nil or an overrides hash) will not change within a
# synchronize block.
@mutex = Thread::Mutex.new
end
##
# Read the given file from the file system and return its contents.
#
# @param path [String] The path to the file.
# @param binary [boolean] Whether to read in binary mode. Defaults to
# false. This must be consistent across multiple requests for the
# same path; if it is not, an error will be raised.
# @return [String] if the file exists.
# @return [nil] if the file does not exist.
#
def read path, binary: false
result = false
@mutex.synchronize do
result = @overrides[path] if @overrides
end
result = @cache.get(path, binary) if result == false
if result && binary != (result.encoding == Encoding::ASCII_8BIT)
raise IOError, "binary encoding flag mismatch"
end
result
end
##
# The overrides hash, or nil if overrides are not present.
# The hash maps paths to contents of the file at that path.
#
# @return [Hash{String => String},nil]
#
attr_reader :overrides
##
# Set the overrides hash. You can either provide a hash of file paths
# to content, or nil to disable overrides. If overrides are present,
# actual filesystem access is disabled; overrides are "all or nothing".
#
# @param new_overrides [Hash{String => String},nil]
#
def overrides= new_overrides
@mutex.synchronize do
@overrides = new_overrides
end
end
##
# Run the given block with the overrides replaced with the given hash
# (or nil to disable overrides in the block). The original overrides
# setting is restored at the end of the block. This is used for
# debugging/testing/mocking.
#
# @param temp_overrides [nil,Hash{String => String}]
#
def with_overrides temp_overrides
old_overrides = @overrides
begin
@mutex.synchronize do
@overrides = temp_overrides
end
yield
ensure
@mutex.synchronize do
@overrides = old_overrides
end
end
end
end
end
end
end
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