Tanks a lot for a detailed answer :-)
Dominique

Den 2. aug. 2011 05.18 skrev "Wayne Meissner" <wmeissner@gmail.com> følgende:
> 2D arrays in structs are not supported by FFI - there's an issue for it
> (issue #18), but its not exactly a high priority, since only 2 people have
> asked for it in the last 2 years.
>
> You can work around it by declaring a struct type for the array width, then
> declaring an array of that struct type.
> e.g.
>
> #require 'rubygems'
> require 'ffi'
>
> class DataArray < FFI::Struct
> layout :array, [ :uchar, 178 ]
>
> def [](idx)
> if idx.is_a?(Integer)
> self[:array][idx]
> else
> super(idx)
> end
> end
>
> def []=(idx, val)
> if idx.is_a?(Integer)
> self[:array][idx] = val
> else
> super(idx, val)
> end
> end
> end
>
> class Array2D < FFI::Struct
> layout :encoded_data, [ DataArray, 143 ]
> end
>
> ary = Array2D.new
> ary[:encoded_data][0][0] = 0x1
> ary[:encoded_data][0][1] = 0x2
> ary[:encoded_data][0][2] = 0x3
> ary[:encoded_data][1][0] = 0x4
> ary[:encoded_data][2][0] = 0x5
> ary[:encoded_data][3][0] = 0x6
>
>
> puts "ary[:encoded_data][0][0]=#{ary[:encoded_data][0][0]}"
> puts "ary[:encoded_data][0][1]=#{ary[:encoded_data][0][1]}"
> puts "ary[:encoded_data][1][0]=#{ary[:encoded_data][1][0]}"
> # idx=178 should correspond to ary[:encoded_data][1][0]
> puts "ary.pointer.get_char(178)=#{ary.pointer.get_char(178)}"
> # idx=356 should correspond to ary[:encoded_data][2][0]
> puts "ary.pointer.get_char(356)=#{ary.pointer.get_char(356)}"
>
>