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# -*- coding => binary -*-
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require 'json'
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require 'fileutils'
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#
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# This class provides a thread-friendly hash file store in JSON format
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#
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module Rex
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class JSONHashFile
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  attr_accessor :path
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  def initialize(path)
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    self.path = path
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    @lock = Mutex.new
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    @hash = {}
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    @last = 0
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  end
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  def [](k)
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    synced_update
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    @hash[k]
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  end
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  def []=(k,v)
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    synced_update do
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      @hash[k] = v
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    end
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  end
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  def keys
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    synced_update
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    @hash.keys
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  end
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  def delete(k)
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    synced_update do
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      @hash.delete(k)
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    end
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  end
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  def clear
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    synced_update do
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      @hash.clear
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    end
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  end
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private
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  # Save the file, but prevent thread & process contention
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  def synced_update(&block)
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    @lock.synchronize do
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      ::FileUtils.mkdir_p(::File.dirname(path))
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      ::File.open(path, ::File::RDWR|::File::CREAT) do |fd|
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        fd.flock(::File::LOCK_EX)
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        # Reload and merge if the file has changed recently
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        if fd.stat.mtime.to_f > @last
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          parse_data(fd.read).merge(@hash).each_pair do |k,v|
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            @hash[k] = v
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          end
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        end
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        res = nil
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        # Update the file on disk if new data is written
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        if block_given?
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          res = block.call
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          fd.rewind
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          fd.write(JSON.pretty_generate(@hash))
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          fd.sync
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          fd.truncate(fd.pos)
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        end
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        @last = fd.stat.mtime.to_f
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        res
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      end
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    end
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  end
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  def parse_data(data)
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    return {} if data.to_s.strip.length == 0
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    begin
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      JSON.parse(data)
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    rescue JSON::ParserError => e
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      elog("JSONHashFile at #{path} was corrupt", error: e)
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      {}
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    end
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  end
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end
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end
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