Class: Flt::DPDFormat

Inherits:

DecimalFormatBase

• Object
• FormatBase
• DecimalFormatBase
• Flt::DPDFormat

Defined in:

lib/float-formats/classes.rb

Overview

DPD (Densely-Packed-Decimal) formats

Constant Summary

Constants included from Flt

APPLE, IEEE_128, IEEE_128_BE, IEEE_DEC128, IEEE_DEC32, IEEE_DEC64, IEEE_DOUBLE, IEEE_D_BE, IEEE_EXTENDED, IEEE_HALF, IEEE_H_BE, IEEE_QUAD, IEEE_Q_BE, IEEE_SINGLE, IEEE_S_BE, IEEE_X_BE, IEEE_binaryx, RPL, RPL_X

Instance Attribute Summary

Attributes inherited from FormatBase

#exponent, #sign, #significand

Class Method Summary

• .define(params) ⇒ Object

  The field that need to be defined (with lenghts given in decimal digits) are * :sign * :combination * :exponent_continuation * :significand_continuation.

• .pack(s, m, e) ⇒ Object
• .pack_fields(*fields) ⇒ Object
• .total_bits ⇒ Object

  :stopdoc:.

• .total_bytes ⇒ Object
• .unpack(v) ⇒ Object
• .unpack_fields(v) ⇒ Object

Methods inherited from DecimalFormatBase

decimal_digits_necessary, decimal_digits_stored, decimal_max_exp, decimal_min_exp, radix, radix_log, radix_log10, radix_power

Methods inherited from FormatBase

#<=>, arithmetic, arithmetic_type, bias, canonicalized, context, #convert_to, decimal_digits_necessary, decimal_digits_stored, decimal_max_exp, decimal_min_exp, endianness, epsilon, #form_class, #fp_format, from, from_bits, from_bits_text, from_bytes, from_hex, from_number, from_text, gradual_underflow?, half_epsilon, #infinite?, infinity, #initialize, join, max_value, maximum_integral_significand, min_normalized_value, min_value, minimum_normalized_integral_significand, #minus, minus_sign_value, nan, #nan?, #next_minus, #next_plus, nio_read_neutral, #nio_write_neutral, #normal?, num, num_class, pack_fields_hash, radix_log, radix_log10, radix_max_exp, radix_min_exp, radix_power, rounding_mode, sign_from_unit, sign_to_unit, #split, strict_epsilon, #subnormal?, switch_sign_value, #to, #to_a, #to_bits, #to_bits_text, #to_bytes, #to_hex, #to_num, #to_text, #ulp, unpack_fields_hash, zero, #zero?

Methods included from Flt

#*, #+, #-, #-@, #/, bcd2dpd, bitnot, convert_bytes, dbl_from_float, dbl_from_text, dbl_to_float, dpd2bcd, dpd_to_hexbcd, float_bin, float_dec, float_from_integral_sign_significand_exponent, float_from_integral_significand_exponent, float_shortest_dec, float_significant_dec, float_to_integral_sign_significand_exponent, float_to_integral_significand_exponent, hex_from_float, hex_to_float, hexbcd_to_dpd, sgl_from_float, sgl_from_text, sgl_to_float

Constructor Details

This class inherits a constructor from Flt::FormatBase

Class Method Details

.define(params) ⇒ Object

The field that need to be defined (with lenghts given in decimal digits) are

• :sign

• :combination

• :exponent_continuation

• :significand_continuation

# File 'lib/float-formats/classes.rb', line 1246

def self.define(params)

  @splitted_fields_supported = false
  define_fields params[:fields]
  @internal_field_lengths = @field_lengths
  @internal_field_meaning = @field_meaning
  @internal_fields = @fields
  raise "Unsupported DPD format" unless @internal_fields[:combination]==5 && @internal_fields[:sign]==1 && [0,4,7].include?(@internal_fields[:significand_continuation]%10)


  @exponent_bits = 2 + @internal_fields[:exponent_continuation]

  extra_bits = (@internal_fields[:significand_continuation] % 10)
  extra_digits = (extra_bits==0) ? 0 : ((extra_bits==4) ? 1 : 2)
  @significand_digits = 1 + 3*(@internal_fields[:significand_continuation]/10) + extra_digits

  define_fields [:type,1,:sign,1,:exponent,@exponent_bits,:significand,@significand_digits]

  if params[:bias].nil?

    params[:bias_mode] = :scientific_significand

    @exp_limit = 3*(2**@internal_fields[:exponent_continuation])-1

    params[:max_exp] = @exp_limit/2
    params[:min_exp] = -params[:max_exp]
    params[:max_exp] += 1 if (@exp_limit%2)==1
    params[:bias]= -params[:min_exp]

  end

  super  params

end

.pack(s, m, e) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1392

def self.pack(s,m,e)
  msb = radix_power(@significand_digits-1)
  t = nil
  if e==:zero
    e = @zero_encoded_exp
    m = 0
  elsif e==:infinity
    e = @infinite_encoded_exp || radix_power(@fields[:exponent])-1
    m = 0
    t = :infinity
  elsif e==:nan
    t = :nan
    e = 0
    s = 0
    m = 0
  elsif e==:denormal
    e = @denormal_encoded_exp || @zero_encoded_exp
  else
    # TODO: try to adjust m to keep e in range if out of valid range
    # TODO: reduce m and adjust e if m too big

    min_exp = radix_min_exp(:integral_significand)
    if m>0 && false
      while m<msb && e>min_exp
        e -= 1
        m *= radix
      end
    end
    if m<msb && @denormal_encoded_exp && false
      e = @denormal_encoded_exp
    elsif m==0 # => && @denormal_encoded_exp.nil?
      e = 0
    else
      e = encode_exponent(e, :integral_significand)
    end
  end
  s = sign_from_unit(s)
  m,e = neg_significand_exponent(0,m,e) if s%2==1
  pack_fields_hash :sign=>s, :significand=>m, :exponent=>e, :type=>t
end

.pack_fields(*fields) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1332

def self.pack_fields(*fields)
  fields = fields[0] if fields.size==1 and fields[0].kind_of?(Array)
  handle_fields fields
  type,sign,exponent,significand = fields

  sig_hex = "%0#{@significand_digits-1}d"%significand
  sig_cont_bits = 4*(@significand_digits-1)
  sig_msd = sig_hex[0,1].to_i
  i_significand_continuation,bits = hexbcd_to_dpd(sig_hex[1..-1])



  exp_msb = exponent>>(@exponent_bits-2)
  i_exponent_continuation = exponent&((1<<(@exponent_bits-2))-1)

  i_sign = ((sign==0) ? 0 : 1)


  case type
  when :infinity
    i_combination = 0x1E
  when :nan
    i_combination = 0x1F
  else
    if sig_msd&0x8==0
      i_combination = sig_msd|(exp_msb<<3)
    else
      i_combination = sig_msd|(1<<4)|(exp_msb<<1)
    end
  end
  h = {:sign=>i_sign, :combination=>i_combination, :exponent_continuation=>i_exponent_continuation, :significand_continuation=>i_significand_continuation}
  fields =  @internal_field_meaning.collect{|f| h[f]}
  Bytes.from_bitfields(@internal_field_lengths,fields,@endianness)
end

.total_bits ⇒ Object

:stopdoc:

# File 'lib/float-formats/classes.rb', line 1282

def self.total_bits
  @internal_field_lengths.inject{|x,y| x+y}
end

.total_bytes ⇒ Object

# File 'lib/float-formats/classes.rb', line 1285

def self.total_bytes
  (total_bits+7)/8
end

.unpack(v) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1368

def self.unpack(v)
  f = unpack_fields_hash(v)
  m = f[:significand]
  e = f[:exponent]
  s = f[:sign]
  t = f[:type]
  m,e = neg_significand_exponent(s,m,e) if s%2==1
  if m==0
    # +-zero
    e = :zero
  elsif t==:infinity
    # +-inifinity
    e = :infinity
  elsif t==:nan
    # NaN
    e = :nan
  else
    # normalized number
     e = decode_exponent(e, :integral_significand)
  end
  s = sign_to_unit(s)
  [s,m,e]
end

.unpack_fields(v) ⇒ Object

# File 'lib/float-formats/classes.rb', line 1290

def self.unpack_fields(v)
  # convert internal binary fields to bcd decoded fields
  a = input_bytes(v).to_bitfields(@internal_field_lengths,@endianness)
  h = {}
  (0...a.size).each do |i|
    h[@internal_field_meaning[i]] = a[i]
  end

  i_sign = h[:sign]
  i_combination = h[:combination]
  i_exponent_continuation = h[:exponent_continuation]
  i_significand_continuation = h[:significand_continuation]


  type = nil
  sign = i_sign==0 ? 0 : 9

  a,b,c,d,e = ("%05B"%i_combination).split('').collect{|bit| bit.to_i}

  exp_msb = 0
  sig_msd = 0

  if a==0 || b==0
    exp_msb = (a<<1)|b
    sig_msd = (c<<2)|(d<<1)|e
  elsif c==0 || d==0
    exp_msb = (c<<1)|d
    sig_msd = (1<<3)|e
  elsif e==0
    type = :infinity
  else
    type = :nan
  end


  hex_sig = sig_msd.to_s
  hex_sig << dpd_to_hexbcd(i_significand_continuation,@internal_fields[:significand_continuation])
  significand = hex_sig.to_i

  exponent = i_exponent_continuation | (exp_msb << (@exponent_bits-2))
  [type,sign,exponent,significand]
end