Initial revision

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@8 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/pstore.rb

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