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key-value store for Rack
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$ git show HEAD:lib/metropolis/tc/hdb.rb	# shows this blob on the CLI

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# -*- encoding: binary -*-

# this module is NOT thread-safe, all performance is dependent on the
# local machine so there is never anything that needs yielding to threads.
module Metropolis::TC::HDB
  autoload :RO, 'metropolis/tc/hdb/ro'
  autoload :EX, 'metropolis/tc/hdb/ex'

  TCHDB = TokyoCabinet::HDB # :nodoc
  include Metropolis::Common

  def setup(opts)
    super
    @rd_flags = TCHDB::OREADER
    @wr_flags = TCHDB::OWRITER

    @optimize = nil
    if @query
      case @query['rdlock']
      when 'true', nil
      when 'false'
        @rd_flags |= TCHDB::ONOLCK
      else
        raise ArgumentError, "'rdlock' must be 'true' or 'false'"
      end

      case @query['wrlock']
      when 'true', nil
      when 'false'
        @wr_flags |= TCHDB::ONOLCK
      else
        raise ArgumentError, "'wrlock' must be 'true' or 'false'"
      end

      flags = 0
      @optimize = %w(bnum apow fpow).map do |x|
        v = @query[x]
        v ? v.to_i : nil
      end

      case large = @query['large']
      when 'false', nil
      when 'true'
        flags |= TCHDB::TLARGE
      else
        raise ArgumentError, "invalid 'large' value: #{large}"
      end

      case compress = @query['compress']
      when nil
      when 'deflate', 'bzip', 'tcbs'
        flags |= TCHDB.const_get("T#{compress.upcase}")
      else
        raise ArgumentError, "invalid 'compress' value: #{compress}"
      end
      @optimize << flags
    end
    @nr_slots = 1 unless @path_pattern
    @dbv = (0...@nr_slots).to_a.map do |slot|
      path = @path_pattern ? sprintf(@path_pattern, slot) : @uri.path
      hdb = TCHDB.new
      unless @readonly
        hdb.open(path, TCHDB::OWRITER | TCHDB::OCREAT) or ex!(:open, hdb)
        if @optimize
          hdb.optimize(*@optimize) or ex!(:optimize, hdb)
        end
        hdb.close or ex!(:close, hdb)
      end
      [ hdb, path ]
    end
    @multi_hash ||= :digest_sha1
    extend Metropolis::MultiHash
    extend(RO) if @readonly
    extend(EX) if @exclusive
  end

  def ex!(msg, hdb)
    raise "#{msg}: #{hdb.errmsg(hdb.ecode)}"
  end

  def writer(key, &block)
    hdb, path = @dbv[multi_hash(key) % @nr_slots]
    hdb.open(path, @wr_flags) or ex!(:open, hdb)
    yield hdb
    ensure
      hdb.close or ex!(:close, hdb)
  end

  def reader(key)
    hdb, path = @dbv[multi_hash(key) % @nr_slots]
    hdb.open(path, @rd_flags) or ex!(:open, hdb)
    yield hdb
    ensure
      hdb.close or ex!(:close, hdb)
  end

  def put(key, env)
    value = env[Rack_Input].read
    writer(key) do |hdb|
      case env[HTTP_X_TT_PDMODE]
      when "1"
        unless hdb.putkeep(key, value)
          TCHDB::EKEEP == hdb.ecode and return r(409)
          ex!(:putkeep, hdb)
        end
      when "2"
        hdb.putcat(key, value) or ex!(:putcat, hdb)
      else
        # ttserver does not care for other PDMODE values, so we don't, either
        hdb.put(key, value) or ex!(:put, hdb)
      end
    end
    r(201)
  end

  def delete(key)
    writer(key) do |hdb|
      unless hdb.delete(key)
        TCHDB::ENOREC == hdb.ecode and return r(404)
        ex!(:delete, hdb)
      end
    end
    r(200)
  end

  def get(key, env)
    value = nil
    reader(key) do |hdb|
      unless value = hdb.get(key)
        TCHDB::ENOREC == hdb.ecode and return r(404)
        ex!(:get, hdb)
      end
    end
    [ 200, { Content_Length => value.size.to_s }.merge!(@headers), [ value ] ]
  end

  def close!
    @dbv.each { |(hdb,_)| hdb.close }
  end
end

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