c_extensions/c_structs.rb

tests/_examples/c_extensions/c_structs.rb in the metorex repository.

# A C extension defining Struct and Data classes, making and reading their
# instances, and filling in instances that were only allocated.
require "tmpdir"
require_relative "build_helper"

directory = Dir.mktmpdir
require(build_extension("c_structs.c", "c_structs", directory))
structs = CStructs.new

named = structs.define("Pair")
p(named)
p(Struct::Pair.members)
anonymous = structs.define(nil)
p(anonymous.name)
report { structs.define("lower") }
report { structs.define_twice }

module Holder
end
under = structs.define_under(Holder, "Inner")
p(under)
p(structs.define_under(Holder, "Inner").equal?(under))
Holder.const_set(:Plain, Class.new)
report { structs.define_under(Holder, "Plain") }

Shape = structs.define_data(nil)
shape = Shape
p(shape.superclass)
base = Class.new(Data)
p(structs.define_data(base).superclass.equal?(base))
report { structs.define_data([]) }
report { structs.define_data_twice }

pair = structs.make(named, 1, 2)
p(pair)
p(structs.make_with(named, [3]))
p(structs.class_members(named))
p(structs.members(pair))
p(structs.size(pair))
p([structs.read(pair, :left), structs.read(pair, "right"), structs.read(pair, 1)])
p(structs.write(pair, :left, 10))
p(pair.left)
report { structs.read(pair, :missing) }
report { structs.read(pair, 2) }
report { structs.read(pair, -3) }
p(structs.member(pair, :right))
report { structs.member(pair, :missing) }

p(structs.fill(pair, [7, 8]))
p(pair)
report { structs.fill(pair, [1, 2, 3]) }
pair.freeze
report { structs.fill(pair, [1]) }

empty = shape.allocate
p(structs.fill(empty, [4]))
p([empty.width, empty.height, empty.frozen?])
report { structs.fill(empty, [1, 2]) }
report { structs.fill(shape.allocate, [1, 2, 3]) }

FileUtils.rm_rf(directory)

Output:

Struct::Pair
[:left, :right]
nil
NameError: identifier lower needs to be constant
ArgumentError: duplicate member: same
Holder::Inner
true
TypeError: superclass mismatch for class Holder::Plain (Struct is given but was Object)
Data
true
TypeError: wrong argument type Array (expected Class)
ArgumentError: duplicate member: width
#<struct Struct::Pair left=1, right=2>
#<struct Struct::Pair left=3, right=nil>
[:left, :right]
[:left, :right]
2
[1, 2, 2]
10
10
NameError: no member 'missing' in struct
IndexError: offset 2 too large for struct(size:2)
IndexError: offset -3 too small for struct(size:2)
2
NameError: 'missing' is not a struct member
nil
#<struct Struct::Pair left=7, right=8>
ArgumentError: struct size differs
FrozenError: can't modify frozen Struct::Pair: #<struct Struct::Pair left=7, right=8>
nil
[4, nil, true]
FrozenError: can't modify frozen Shape: #<data Shape width=4, height=nil>
ArgumentError: struct size differs