Module: Wordmap::FileAccess

Defined in:
lib/wordmap/file_access.rb

Class Method Summary collapse

Class Method Details

.each_cell(file, start = 0, meta:, count: Float::INFINITY, batch_size: meta[:batch_size], trace: nil) ⇒ Object 



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# File 'lib/wordmap/file_access.rb', line 5

def each_cell file, start = 0,
  meta:,
  count: Float::INFINITY,
  batch_size: meta[:batch_size],
  trace: nil

  unless block_given?
    return enum_for(__method__, file, start,
      meta: meta,
      count: count,
      batch_size: batch_size,
      trace: trace
    )
  end

  seen = 0

  loop do
    batch_size = count if (count < batch_size)
    cells = read_cells(file, start + seen, batch_size, meta, trace)
    cells.each do |cell|
      yield(cell)
    end

    seen += cells.size
    count -= cells.size
    break if count < 1
    break if cells.size < batch_size
  end
end

.read_at(file, pos, bytes) ⇒ Object 



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# File 'lib/wordmap/file_access.rb', line 68

def read_at(file, pos, bytes)
  # puts "Seeking in #{file.path.split('.wmap', 2)[1][1..-1]} to #{pos}, "    #      "and reading #{bytes} bytes"
  file.pread(bytes, pos)
end

.read_cells(file, i, count, meta, trace) ⇒ Object 



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# File 'lib/wordmap/file_access.rb', line 36

def read_cells(file, i, count, meta, trace)
  meta_offset, cell_size, cell_count =
    meta.values_at(:offset, :cell_size, :cell_count)

  return [] if i + 1 > meta[:cell_count]

  if i + count + 1 > meta[:cell_count]
    count = (meta[:cell_count] - i)
  end

  pos   = meta[:offset] + (i * meta[:cell_size])
  bytes = meta[:cell_size] * count

  if trace
    parts = file.path.split('.wmap', 2)
    subpath = (File.basename(parts[0]) + '.wmap') + parts[1]
    trace << [:read_cells, subpath, i, count, pos, bytes]
  end
  read_at(file, pos, bytes).unpack("a#{meta[:cell_size]}" * count)
end

.read_meta(file, spacer) ⇒ Object 



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# File 'lib/wordmap/file_access.rb', line 57

def read_meta(file, spacer)
  meta_string = read_at(file, 0, 30).split(spacer, 2)[0]
  cell_size, cell_count = meta_string.split(',').map(&:to_i)
  {
    offset:     meta_string.bytesize + 1,
    cell_size:  cell_size,
    cell_count: cell_count,
    batch_size: [[10_000 / cell_size, 1].max, cell_count].min
  }
end