Class: Cabriolet::Binary::ENCINTReader

Inherits:
Object
  • Object
show all
Defined in:
lib/cabriolet/binary/chm_structures.rb

Overview

Helper class for reading ENCINT (variable-length integers)

Class Method Summary collapse

Class Method Details

.read(io) ⇒ Object

Read an ENCINT from an IO stream Returns the integer value



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# File 'lib/cabriolet/binary/chm_structures.rb', line 116

def self.read(io)
  result = 0
  byte = 0x80
  bytes_read = 0
  max_bytes = 9 # 63 bits max

  while byte.anybits?(0x80) && bytes_read < max_bytes
    byte_data = io.read(1)
    if byte_data.nil?
      raise Cabriolet::FormatError,
            "Unexpected end of ENCINT"
    end

    byte = byte_data.unpack1("C")
    result = (result << 7) | (byte & 0x7F)
    bytes_read += 1
  end

  if bytes_read == max_bytes && byte.anybits?(0x80)
    raise Cabriolet::FormatError,
          "ENCINT too large"
  end

  result
end

.read_from_string(str, pos) ⇒ Object

Read an ENCINT from a string at a given position Returns [value, new_position]



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# File 'lib/cabriolet/binary/chm_structures.rb', line 144

def self.read_from_string(str, pos)
  result = 0
  byte = 0x80
  bytes_read = 0
  max_bytes = 9

  while byte.anybits?(0x80) && bytes_read < max_bytes
    if pos >= str.length
      raise Cabriolet::FormatError,
            "ENCINT beyond string"
    end

    byte = str.getbyte(pos)
    pos += 1
    result = (result << 7) | (byte & 0x7F)
    bytes_read += 1
  end

  if bytes_read == max_bytes && byte.anybits?(0x80)
    raise Cabriolet::FormatError,
          "ENCINT too large"
  end

  [result, pos]
end