Class: Ephem::Excerpt::DAFWriter

Inherits:
Object
  • Object
show all
Defined in:
lib/ephem/excerpt.rb

Overview

Helper class for writing DAF files This class handles the low-level details of DAF file format

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(file, debug = false) ⇒ DAFWriter

Returns a new instance of DAFWriter.



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# File 'lib/ephem/excerpt.rb', line 247

def initialize(file, debug = false)
  @file = file
  @debug = debug
  @mutex = Mutex.new
end

Instance Attribute Details

#bward ⇒ Object

Returns the value of attribute bward.



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# File 'lib/ephem/excerpt.rb', line 233

def bward
  @bward
end

#double_format ⇒ Object

Returns the value of attribute double_format.



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# File 'lib/ephem/excerpt.rb', line 233

def double_format
  @double_format
end

#endianness ⇒ Object

Returns the value of attribute endianness.



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# File 'lib/ephem/excerpt.rb', line 233

def endianness
  @endianness
end

#file ⇒ Object (readonly)

Returns the value of attribute file.



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# File 'lib/ephem/excerpt.rb', line 232

def file
  @file
end

#free ⇒ Object

Returns the value of attribute free.



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# File 'lib/ephem/excerpt.rb', line 233

def free
  @free
end

#fward ⇒ Object

Returns the value of attribute fward.



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# File 'lib/ephem/excerpt.rb', line 233

def fward
  @fward
end

#int_format ⇒ Object

Returns the value of attribute int_format.



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# File 'lib/ephem/excerpt.rb', line 233

def int_format
  @int_format
end

#nd ⇒ Object

Returns the value of attribute nd.



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# File 'lib/ephem/excerpt.rb', line 233

def nd
  @nd
end

#ni ⇒ Object

Returns the value of attribute ni.



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# File 'lib/ephem/excerpt.rb', line 233

def ni
  @ni
end

#summaries_per_record ⇒ Object

Returns the value of attribute summaries_per_record.



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# File 'lib/ephem/excerpt.rb', line 233

def summaries_per_record
  @summaries_per_record
end

#summary_control_format ⇒ Object

Returns the value of attribute summary_control_format.



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# File 'lib/ephem/excerpt.rb', line 233

def summary_control_format
  @summary_control_format
end

#summary_format ⇒ Object

Returns the value of attribute summary_format.



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# File 'lib/ephem/excerpt.rb', line 233

def summary_format
  @summary_format
end

#summary_length ⇒ Object

Returns the value of attribute summary_length.



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# File 'lib/ephem/excerpt.rb', line 233

def summary_length
  @summary_length
end

#summary_step ⇒ Object

Returns the value of attribute summary_step.



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# File 'lib/ephem/excerpt.rb', line 233

def summary_step
  @summary_step
end

Instance Method Details

#add_array(name, values, array) ⇒ Object 



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# File 'lib/ephem/excerpt.rb', line 322

def add_array(name, values, array)
  record_number = @bward
  data = read_record(record_number).dup

  control_data = data[0, 24].unpack(@summary_control_format)
  next_record = control_data[0].to_i
  previous_record = control_data[1].to_i
  n_summaries = control_data[2].to_i

  if n_summaries < @summaries_per_record
    # Add to the existing record
    summary_record = record_number
    data[0, 24] = [next_record, previous_record, n_summaries + 1]
      .pack(@summary_control_format)
    write_record(summary_record, data)
  else
    # Create a new record
    summary_record = ((@free - 1) * 8 + 1023) / 1024 + 1
    name_record = summary_record + 1
    free_record = summary_record + 2

    data[0, 24] = [summary_record, previous_record, n_summaries]
      .pack(@summary_control_format)
    write_record(record_number, data)

    n_summaries = 0
    summaries = [0, record_number, 1]
      .pack(@summary_control_format)
      .ljust(RECORD_SIZE, "\0")
    names = " ".ljust(RECORD_SIZE, "\0")
    write_record(summary_record, summaries)
    write_record(name_record, names)

    @bward = summary_record
    @free = (free_record - 1) * RECORD_SIZE / 8 + 1
  end

  # Convert array to binary data
  array_data = array.pack("#{@double_format}*")

  start_word = @free
  @file.seek((start_word - 1) * 8)
  @file.write(array_data)
  end_word = @file.tell / 8

  @free = end_word + 1
  write_file_record

  # Using values up to nd+ni-2, then adding start_word and end_word
  new_values = values[0, @nd + @ni - 2] + [start_word, end_word]

  base = RECORD_SIZE * (summary_record - 1)
  offset = n_summaries * @summary_step
  @file.seek(base + 24 + offset)  # 24 is summary_control_struct size
  @file.write(new_values.pack(@summary_format))
  @file.seek(base + RECORD_SIZE + offset)
  @file.write(name[0, @summary_length].ljust(@summary_step, " "))
end

#read_record(n) ⇒ Object 



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# File 'lib/ephem/excerpt.rb', line 308

def read_record(n)
  @mutex.synchronize do
    @file.seek(n * RECORD_SIZE - RECORD_SIZE)
    @file.read(RECORD_SIZE)
  end
end

#setup_formats(nd, ni) ⇒ Object 



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# File 'lib/ephem/excerpt.rb', line 253

def setup_formats(nd, ni)
  @nd = nd
  @ni = ni

  # Double is always 8 bytes, int is always 4 bytes
  double_size = 8
  int_size = 4

  # Set formats based on endianness
  if @endianness == :little
    @double_format = "E"  # Little-endian double
    @int_format = "l"     # Little-endian signed long (32-bit)
  else
    @double_format = "G"  # Big-endian double
    @int_format = "l>"    # Big-endian signed long (32-bit)
  end

  # Create formats for summary structures
  @summary_control_format =
    "#{@double_format}#{@double_format}#{@double_format}"
  @summary_format = @double_format.to_s * @nd + @int_format.to_s * @ni

  # Calculate segment summary sizes
  @summary_length = double_size * @nd + int_size * @ni

  # Pad to 8 bytes
  @summary_step = @summary_length + (-@summary_length % 8)

  @summaries_per_record = (RECORD_SIZE - 8 * 3) / @summary_step
end

#write_file_record ⇒ Object 



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# File 'lib/ephem/excerpt.rb', line 284

def write_file_record
  @file.seek(0)
  data = @file.read(RECORD_SIZE)

  # Update pointers directly in the data buffer
  fward_pos = 76
  bward_pos = 80
  free_pos = 84

  if @endianness == :little
    data[fward_pos, 4] = [@fward].pack("l")
    data[bward_pos, 4] = [@bward].pack("l")
    data[free_pos, 4] = [@free].pack("l")
  else
    data[fward_pos, 4] = [@fward].pack("N")
    data[bward_pos, 4] = [@bward].pack("N")
    data[free_pos, 4] = [@free].pack("N")
  end

  # Write the updated record back to the file
  @file.seek(0)
  @file.write(data)
end

#write_record(n, data) ⇒ Object 



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# File 'lib/ephem/excerpt.rb', line 315

def write_record(n, data)
  @mutex.synchronize do
    @file.seek(n * RECORD_SIZE - RECORD_SIZE)
    @file.write(data)
  end
end