Module: BinData::Integer

Defined in:
lib/bindata/int.rb

Overview

Provides a number of classes that contain an integer. The integer is defined by endian, signedness and number of bytes.

Class Method Summary collapse

Class Method Details

.create_int_methods(klass, nbits, endian) ⇒ Object

:nodoc: all



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# File 'lib/bindata/int.rb', line 8

def self.create_int_methods(klass, nbits, endian)
  max = (1 << (nbits - 1)) - 1
  min = -(max + 1)
  clamp = "val = (val < #{min}) ? #{min} : (val > #{max}) ? #{max} : val"

  int2uint = "val = val & #{(1 << nbits) - 1}"
  uint2int = "val = ((val & #{1 << (nbits - 1)}).zero?) ? " +
             "val & #{max} : -(((~val) & #{max}) + 1)"

  read = create_read_code(nbits, endian)
  to_s = create_to_s_code(nbits, endian)

  define_methods(klass, nbits / 8, clamp, read, to_s, int2uint, uint2int)
end

.create_read_code(nbits, endian) ⇒ Object 



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# File 'lib/bindata/int.rb', line 34

def self.create_read_code(nbits, endian)
  c16 = (endian == :little) ? 'v' : 'n'
  c32 = (endian == :little) ? 'V' : 'N'
  b1  = (endian == :little) ? 0 : 1
  b2  = (endian == :little) ? 1 : 0

  case nbits
  when  8; "readbytes(io,1)[0]"
  when 16; "readbytes(io,2).unpack('#{c16}').at(0)"
  when 32; "readbytes(io,4).unpack('#{c32}').at(0)"
  when 64; "(a = readbytes(io,8).unpack('#{c32 * 2}'); " +
                 "(a.at(#{b2}) << 32) + a.at(#{b1}))"
  else
    raise "unknown nbits '#{nbits}'"
  end
end

.create_to_s_code(nbits, endian) ⇒ Object 



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# File 'lib/bindata/int.rb', line 51

def self.create_to_s_code(nbits, endian)
  c16 = (endian == :little) ? 'v' : 'n'
  c32 = (endian == :little) ? 'V' : 'N'
  v1  = (endian == :little) ? 'val' : '(val >> 32)'
  v2  = (endian == :little) ? '(val >> 32)' : 'val'

  case nbits
  when  8; "val.chr"
  when 16; "[val].pack('#{c16}')"
  when 32; "[val].pack('#{c32}')"
  when 64; "[#{v1} & 0xffffffff, #{v2} & 0xffffffff].pack('#{c32 * 2}')"
  else
    raise "unknown nbits '#{nbits}'"
  end
end

.create_uint_methods(klass, nbits, endian) ⇒ Object 



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# File 'lib/bindata/int.rb', line 23

def self.create_uint_methods(klass, nbits, endian)
  min = 0
  max = (1 << nbits) - 1
  clamp = "val = (val < #{min}) ? #{min} : (val > #{max}) ? #{max} : val"

  read = create_read_code(nbits, endian)
  to_s = create_to_s_code(nbits, endian)

  define_methods(klass, nbits / 8, clamp, read, to_s)
end

.define_methods(klass, nbytes, clamp, read, to_s, int2uint = nil, uint2int = nil) ⇒ Object 



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# File 'lib/bindata/int.rb', line 67

def self.define_methods(klass, nbytes, clamp, read, to_s,
                        int2uint = nil, uint2int = nil)
  # define methods in the given class
  klass.module_eval <<-END
    def value=(val)
      #{clamp}
      super(val)
    end

    def _num_bytes(ignored)
      #{nbytes}
    end

    #---------------
    private

    def sensible_default
      0
    end

    def val_to_str(val)
      #{clamp}
      #{int2uint unless int2uint.nil?}
      #{to_s}
    end

    def read_val(io)
      val = #{read}
      #{uint2int unless uint2int.nil?}
    end
  END
end