1 files changed, 106 insertions, 0 deletions
diff --git a/ruby/lib/ftsearch/document_map_reader.rb b/ruby/lib/ftsearch/document_map_reader.rb
new file mode 100644
index 0000000..5d842c0
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+++ b/ruby/lib/ftsearch/document_map_reader.rb
@@ -0,0 +1,106 @@
+# Copyright (C) 2006  Mauricio Fernandez <mfp@acm.org>
+#
+
+module FTSearch
+
+class DocumentMapReader
+  DEFAULT_OPTIONS = {
+    :path => nil,
+    :io   => nil,
+  }
+  def initialize(options = {})
+    options = DEFAULT_OPTIONS.merge(options)
+    unless options[:path] || options[:io]
+      raise ArgumentError, "Need either the path to the suffix array file or an IO."
+    end
+    if options[:path]
+      io = File.open(options[:path], "rb")
+    else
+      io = options[:io]
+    end
+    @uri_tbl, @field_arr = Marshal.load(io)
+  end
+
+  def document_id(suffix_idx, offset)
+    idx = binary_search(@field_arr, offset, 0, @field_arr.size)
+    @field_arr[idx][1]
+  end
+
+  def field_id(suffix_idx, offset)
+    idx = binary_search(@field_arr, offset, 0, @field_arr.size)
+    @field_arr[idx][2]
+  end
+
+  def field_size(suffix_idx, offset)
+    idx = binary_search(@field_arr, offset, 0, @field_arr.size)
+    @field_arr[idx][3]
+  end
+
+  def field_info(suffix_idx, offset)
+    idx = binary_search(@field_arr, offset, 0, @field_arr.size)
+    @field_arr[idx]
+  end
+
+  def document_uri(suffix_idx, offset)
+    doc_id = document_id(suffix_idx, offset)
+    @uri_tbl[doc_id]
+  end
+
+  def document_id_to_uri(doc_id)
+    @uri_tbl[doc_id]
+  end
+
+  def offsets_to_field_infos(offsets)
+    offsets.map{|off| @field_arr[binary_search(@field_arr, off, 0, @field_arr.size)]}
+  end
+
+  def rank_offsets(offsets, weights)
+    h = Hash.new{|h,k| h[k] = 0.0}
+    offsets_to_field_infos(offsets).each do |offset, doc_id, field_id, field_size|
+      h[doc_id] += weights[field_id] / field_size
+    end
+    sort_score_hash(h)
+  end
+
+  def rank_offsets_probabilistic(offsets, weights, iterations)
+    h     = Hash.new{|h,k| h[k] = 0.0}
+    infos = offsets_to_field_infos(offsets)
+    max   = infos.size
+    while iterations > 0
+      offset, doc_id, field_id, field_size = infos[rand(max)]
+      h[doc_id] += weights[field_id] / field_size
+      iterations -= 1
+    end
+    sort_score_hash(h)
+  end
+
+  def dump_data
+    [@uri_tbl, @field_arr]
+  end
+
+  def num_documents
+    @uri_tbl.size
+  end
+
+  private
+  def sort_score_hash(h)
+    h.sort_by{|_,score| -score}
+  end
+
+  def binary_search(arr, offset, from, to)
+    middle = 0
+    while to - from > 1
+      middle = (from + to) / 2
+      pivot,  = arr[middle]
+      if offset < pivot
+        to = middle
+      else
+        from = middle
+      end
+    end
+
+    from
+  end
+
+end
+end  # FTSearch