class Fiddle::CStructEntity
A pointer to a C structure
Public Class Methods
# File ext/fiddle/lib/fiddle/struct.rb, line 277 def CStructEntity.alignment(types) max = 1 types.each do |type, count = 1| if type.respond_to?(:entity_class) n = type.alignment else n = ALIGN_MAP[type] end max = n if n > max end max end
Allocates a C struct with the types provided.
See Fiddle::Pointer.malloc for memory management issues.
Fiddle::Pointer::malloc
# File ext/fiddle/lib/fiddle/struct.rb, line 293 def CStructEntity.malloc(types, func = nil, size = size(types), &block) if block_given? super(size, func) do |struct| struct.set_ctypes types yield struct end else struct = super(size, func) struct.set_ctypes types struct end end
Wraps the C pointer addr as a C struct with the given types.
When the instance is garbage collected, the C function func is called.
See also Fiddle::Pointer.new
Fiddle::Pointer::new
# File ext/fiddle/lib/fiddle/struct.rb, line 340 def initialize(addr, types, func = nil) if func && addr.is_a?(Pointer) && addr.free raise ArgumentError, 'free function specified on both underlying struct Pointer and when creating a CStructEntity - who do you want to free this?' end set_ctypes(types) super(addr, @size, func) end
Returns the offset for the packed sizes for the given types.
Fiddle::CStructEntity.size( [ Fiddle::TYPE_DOUBLE, Fiddle::TYPE_INT, Fiddle::TYPE_CHAR, Fiddle::TYPE_VOIDP ]) #=> 24
# File ext/fiddle/lib/fiddle/struct.rb, line 313 def CStructEntity.size(types) offset = 0 max_align = types.map { |type, count = 1| last_offset = offset if type.respond_to?(:entity_class) align = type.alignment type_size = type.size else align = PackInfo::ALIGN_MAP[type] type_size = PackInfo::SIZE_MAP[type] end offset = PackInfo.align(last_offset, align) + (type_size * count) align }.max PackInfo.align(offset, max_align) end
Public Instance Methods
Fetch struct member name if only one argument is specified. If two arguments are specified, the first is an offset and the second is a length and this method returns the string of length bytes beginning at offset.
Examples:
my_struct = struct(['int id']).malloc my_struct.id = 1 my_struct['id'] # => 1 my_struct[0, 4] # => "\x01\x00\x00\x00".b
Fiddle::Pointer::[]
# File ext/fiddle/lib/fiddle/struct.rb, line 413 def [](*args) return super(*args) if args.size > 1 name = args[0] idx = @members.index(name) if( idx.nil? ) raise(ArgumentError, "no such member: #{name}") end ty = @ctypes[idx] if( ty.is_a?(Array) ) if ty.first.respond_to?(:entity_class) return @nested_structs[name] else r = super(@offset[idx], SIZE_MAP[ty[0]] * ty[1]) end elsif ty.respond_to?(:entity_class) return @nested_structs[name] else r = super(@offset[idx], SIZE_MAP[ty.abs]) end packer = Packer.new([ty]) val = packer.unpack([r]) case ty when Array case ty[0] when TYPE_VOIDP val = val.collect{|v| Pointer.new(v)} end when TYPE_VOIDP val = Pointer.new(val[0]) else val = val[0] end if( ty.is_a?(Integer) && (ty < 0) ) return unsigned_value(val, ty) elsif( ty.is_a?(Array) && (ty[0] < 0) ) return StructArray.new(self + @offset[idx], ty[0], val) else return val end end
Set struct member name, to value val. If more arguments are specified, writes the string of bytes to the memory at the given offset and length.
Examples:
my_struct = struct(['int id']).malloc my_struct['id'] = 1 my_struct[0, 4] = "\x01\x00\x00\x00".b my_struct.id # => 1
Fiddle::Pointer#[]=
# File ext/fiddle/lib/fiddle/struct.rb, line 465 def []=(*args) return super(*args) if args.size > 2 name, val = *args name = name.to_s if name.is_a?(Symbol) nested_struct = @nested_structs[name] if nested_struct if nested_struct.is_a?(StructArray) if val.nil? nested_struct.each do |s| s.replace(nil) end else val.each_with_index do |v, i| nested_struct[i] = v end end else nested_struct.replace(val) end return val end idx = @members.index(name) if( idx.nil? ) raise(ArgumentError, "no such member: #{name}") end ty = @ctypes[idx] packer = Packer.new([ty]) val = wrap_arg(val, ty, []) buff = packer.pack([val].flatten()) super(@offset[idx], buff.size, buff) if( ty.is_a?(Integer) && (ty < 0) ) return unsigned_value(val, ty) elsif( ty.is_a?(Array) && (ty[0] < 0) ) return val.collect{|v| unsigned_value(v,ty[0])} else return val end end
Set the names of the members in this C struct
# File ext/fiddle/lib/fiddle/struct.rb, line 349 def assign_names(members) @members = [] @nested_structs = {} members.each_with_index do |member, index| if member.is_a?(Array) # nested struct member_name = member[0] struct_type, struct_count = @ctypes[index] if struct_count.nil? struct = struct_type.new(to_i + @offset[index]) else structs = struct_count.times.map do |i| struct_type.new(to_i + @offset[index] + i * struct_type.size) end struct = StructArray.new(to_i + @offset[index], struct_type, structs) end @nested_structs[member_name] = struct else member_name = member end @members << member_name end end
Calculates the offsets and sizes for the given types in the struct.
# File ext/fiddle/lib/fiddle/struct.rb, line 375 def set_ctypes(types) @ctypes = types @offset = [] offset = 0 max_align = types.map { |type, count = 1| orig_offset = offset if type.respond_to?(:entity_class) align = type.alignment type_size = type.size else align = ALIGN_MAP[type] type_size = SIZE_MAP[type] end offset = PackInfo.align(orig_offset, align) @offset << offset offset += (type_size * count) align }.max @size = PackInfo.align(offset, max_align) end