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121 lines
2.2 KiB
Ruby
121 lines
2.2 KiB
Ruby
#!/usr/local/bin/ruby
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# How to use:
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#
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# db = PStore.new("/tmp/foo")
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# db.transaction do
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# p db.roots
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# ary = db["root"] = [1,2,3,4]
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# ary[0] = [1,1.5]
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# end
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# db.transaction do
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# p db["root"]
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# end
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require "marshal"
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class PStore
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Exception(:Error)
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def initialize(file)
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dir = File::dirname(file)
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unless File::directory? dir
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raise PStore::Error, format("directory %s does not exist", dir)
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end
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unless File::writable? dir
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raise PStore::Error, format("directory %s not writable", dir)
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end
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if File::exist? file and not File::readable? file
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raise PStore::Error, format("file %s not readable", file)
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end
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@transaction = false
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@filename = file
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@abort = false
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end
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def in_transaction
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raise PStore::Error, "not in transaction" unless @transaction
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end
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private :in_transaction
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def [](name)
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in_transaction
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value = @table[name]
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if value == nil
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raise PStore::Error, format("undefined root name `%s'", name)
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end
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value
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end
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def []=(name, value)
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in_transaction
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@table[name] = value
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end
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def roots
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in_transaction
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@table.keys
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end
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def root?(name)
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in_transaction
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@table.key? name
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end
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def path
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@filename
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end
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def commit
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@abort = false
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throw :pstore_abort_transaction
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end
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def abort
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@abort = true
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throw :pstore_abort_transaction
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end
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def transaction
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raise PStore::Error, "nested transaction" if @transaction
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begin
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@transaction = true
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value = file = nil
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begin
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File::open(@filename, "r") do |file|
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@table = Marshal.load(file)
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end
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rescue Errno::ENOENT
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@table = {}
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end
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begin
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catch(:pstore_abort_transaction) do
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value = yield(self)
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end
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ensure
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unless @abort
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File::rename @filename, @filename+"~"
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begin
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File::open(@filename, "w") do |file|
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Marshal::dump(@table, file)
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end
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rescue
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File::rename @filename+"~", @filename
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end
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end
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@abort = false
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end
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ensure
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@transaction = false
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end
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value
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end
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end
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db = PStore.new("/tmp/foo")
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db.transaction do
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p db.roots
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ary = db["root"] = [1,2,3,4]
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ary[0] = [1,1.5]
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end
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db.transaction do
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p db["root"]
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end
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