Module: BinData::BitField
- Defined in:
- lib/bindata/bits.rb
Overview
Defines a number of classes that contain a bit based integer. The integer is defined by endian and number of bits.
Class Method Summary collapse
- .create_clamp_code(nbits, signed) ⇒ Object
- .create_do_num_bytes_code(nbits) ⇒ Object
- .create_dynamic_clamp_code(nbits, signed) ⇒ Object
- .create_fixed_clamp_code(nbits, signed) ⇒ Object
- .create_int2uint_code(nbits, signed) ⇒ Object
- .create_nbits_code(nbits) ⇒ Object
- .create_params_code(nbits) ⇒ Object
- .create_uint2int_code(nbits, signed) ⇒ Object
- .define_class(name, nbits, endian, signed = :unsigned) ⇒ Object
- .define_methods(bit_class, nbits, endian, signed) ⇒ Object
Class Method Details
.create_clamp_code(nbits, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 84 def create_clamp_code(nbits, signed) if nbits == :nbits create_dynamic_clamp_code(nbits, signed) else create_fixed_clamp_code(nbits, signed) end end |
.create_do_num_bytes_code(nbits) ⇒ Object
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# File 'lib/bindata/bits.rb', line 76 def create_do_num_bytes_code(nbits) if nbits == :nbits "nbits / 8.0" else nbits / 8.0 end end |
.create_dynamic_clamp_code(nbits, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 92 def create_dynamic_clamp_code(nbits, signed) if signed == :signed max = "max = (1 << (nbits - 1)) - 1" min = "min = -(max + 1)" else max = "max = (1 << nbits) - 1" min = "min = 0" end "#{max}; #{min}; val = (val < min) ? min : (val > max) ? max : val" end |
.create_fixed_clamp_code(nbits, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 104 def create_fixed_clamp_code(nbits, signed) if nbits == 1 and signed == :signed raise "signed bitfield must have more than one bit" end if signed == :signed max = (1 << (nbits - 1)) - 1 min = -(max + 1) else min = 0 max = (1 << nbits) - 1 end clamp = "(val < #{min}) ? #{min} : (val > #{max}) ? #{max} : val" if nbits == 1 # allow single bits to be used as booleans clamp = "(val == true) ? 1 : (not val) ? 0 : #{clamp}" end "val = #{clamp}" end |
.create_int2uint_code(nbits, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 127 def create_int2uint_code(nbits, signed) if signed != :signed "" elsif nbits == :nbits "val &= (1 << nbits) - 1" else "val &= #{(1 << nbits) - 1}" end end |
.create_nbits_code(nbits) ⇒ Object
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# File 'lib/bindata/bits.rb', line 68 def create_nbits_code(nbits) if nbits == :nbits "nbits = eval_parameter(:nbits)" else "" end end |
.create_params_code(nbits) ⇒ Object
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# File 'lib/bindata/bits.rb', line 60 def create_params_code(nbits) if nbits == :nbits "mandatory_parameter :nbits" else "" end end |
.create_uint2int_code(nbits, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 137 def create_uint2int_code(nbits, signed) if signed != :signed "" elsif nbits == :nbits "val -= (1 << nbits) if (val >= (1 << (nbits - 1)))" else "val -= #{1 << nbits} if (val >= #{1 << (nbits - 1)})" end end |
.define_class(name, nbits, endian, signed = :unsigned) ⇒ Object
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# File 'lib/bindata/bits.rb', line 9 def define_class(name, nbits, endian, signed = :unsigned) unless BinData.const_defined?(name) BinData.module_eval <<-END class #{name} < BinData::BasePrimitive BitField.define_methods(self, #{nbits.inspect}, #{endian.inspect}, #{signed.inspect}) end END end BinData.const_get(name) end |
.define_methods(bit_class, nbits, endian, signed) ⇒ Object
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# File 'lib/bindata/bits.rb', line 21 def define_methods(bit_class, nbits, endian, signed) bit_class.module_eval <<-END #{create_params_code(nbits)} def assign(val) #{create_nbits_code(nbits)} #{create_clamp_code(nbits, signed)} super(val) end def do_write(io) #{create_nbits_code(nbits)} val = _value #{create_int2uint_code(nbits, signed)} io.writebits(val, #{nbits}, :#{endian}) end def do_num_bytes #{create_nbits_code(nbits)} #{create_do_num_bytes_code(nbits)} end #--------------- private def read_and_return_value(io) #{create_nbits_code(nbits)} val = io.readbits(#{nbits}, :#{endian}) #{create_uint2int_code(nbits, signed)} val end def sensible_default 0 end END end |