Class: EncodeM::Encoder

Inherits:
Object
  • Object
show all
Defined in:
lib/encode_m/encoder.rb

Constant Summary collapse

KEY_DELIMITER =

Constants from the M language subscript encoding

0x00
STR_SUB_ESCAPE =

Terminator

0x01
SUBSCRIPT_ZERO =

Escape in strings

0x80
STR_SUB_PREFIX =

Zero value

0xFF
NEG_MNTSSA_END =

String marker

0xFF
NEG_EXPONENTS =

Negative exponent bytes (decreasing magnitude = increasing byte value)

{
  9 => 0x3B,  # -999,999,999 to -100,000,000
  8 => 0x3C,  # -99,999,999 to -10,000,000
  7 => 0x3D,  # -9,999,999 to -1,000,000
  6 => 0x3E,  # -999,999 to -100,000
  5 => 0x3F,  # -99,999 to -10,000
  4 => 0x40,  # -9,999 to -1,000
  3 => 0x41,  # -999 to -100
  2 => 0x42,  # -99 to -10
  1 => 0x43   # -9 to -1
}.freeze
POS_EXPONENTS =

Positive exponent bytes (increasing magnitude = increasing byte value)

{
  1 => 0xBC,  # 1 to 9
  2 => 0xBD,  # 10 to 99
  3 => 0xBE,  # 100 to 999
  4 => 0xBF,  # 1,000 to 9,999
  5 => 0xC0,  # 10,000 to 99,999
  6 => 0xC1,  # 100,000 to 999,999
  7 => 0xC2,  # 1,000,000 to 9,999,999
  8 => 0xC3,  # 10,000,000 to 99,999,999
  9 => 0xC4   # 100,000,000 to 999,999,999
}.freeze
POS_CODE =

Encoding tables for digit pairs (00-99)

[
  0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
  0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a,
  0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
  0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a,
  0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a,
  0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a,
  0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a,
  0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a,
  0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a,
  0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a
].freeze
NEG_CODE = 
[
  0xfe, 0xfd, 0xfc, 0xfb, 0xfa, 0xf9, 0xf8, 0xf7, 0xf6, 0xf5,
  0xee, 0xed, 0xec, 0xeb, 0xea, 0xe9, 0xe8, 0xe7, 0xe6, 0xe5,
  0xde, 0xdd, 0xdc, 0xdb, 0xda, 0xd9, 0xd8, 0xd7, 0xd6, 0xd5,
  0xce, 0xcd, 0xcc, 0xcb, 0xca, 0xc9, 0xc8, 0xc7, 0xc6, 0xc5,
  0xbe, 0xbd, 0xbc, 0xbb, 0xba, 0xb9, 0xb8, 0xb7, 0xb6, 0xb5,
  0xae, 0xad, 0xac, 0xab, 0xaa, 0xa9, 0xa8, 0xa7, 0xa6, 0xa5,
  0x9e, 0x9d, 0x9c, 0x9b, 0x9a, 0x99, 0x98, 0x97, 0x96, 0x95,
  0x8e, 0x8d, 0x8c, 0x8b, 0x8a, 0x89, 0x88, 0x87, 0x86, 0x85,
  0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78, 0x77, 0x76, 0x75,
  0x6e, 0x6d, 0x6c, 0x6b, 0x6a, 0x69, 0x68, 0x67, 0x66, 0x65
].freeze

Class Method Summary collapse

Class Method Details

.encode_decimal(value, result = []) ⇒ Object 



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# File 'lib/encode_m/encoder.rb', line 108

def self.encode_decimal(value, result = [])
  # For now, just convert to integer
  encode_integer(value.to_i)
end

.encode_integer(value) ⇒ Object 



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# File 'lib/encode_m/encoder.rb', line 65

def self.encode_integer(value)
  return [SUBSCRIPT_ZERO].pack('C') if value == 0

  is_negative = value < 0
  abs_value = is_negative ? -value : value

  # Count the number of digits
  digit_count = abs_value.to_s.length

  # Get the appropriate exponent byte
  if is_negative
    exp_byte = NEG_EXPONENTS[digit_count] || NEG_EXPONENTS[9]
  else
    exp_byte = POS_EXPONENTS[digit_count] || POS_EXPONENTS[9]
  end

  result = [exp_byte]

  # Encode the mantissa as digit pairs
  cvt_table = is_negative ? NEG_CODE : POS_CODE

  # Convert number to pairs of digits
  temp = abs_value
  pairs = []
  while temp > 0
    pairs.unshift(temp % 100)
    temp /= 100
  end

  # Handle single digit numbers specially
  if digit_count == 1
    pairs = [abs_value]
  end

  # Encode each pair
  pairs.each { |pair| result << cvt_table[pair] }

  # Add terminator for negative numbers
  result << NEG_MNTSSA_END if is_negative

  result.pack('C*')
end