bench_gen.jl

using Base.Meta
using FixedPointNumbers
using Compat

"Generate read (unpack) method for structs."
function generate_read(T::Type)
    fc = fieldcount(T)
    types = [fieldtype(T, i) for i = 1:fc]

    # Create unpack function expression
    function_expression = :(function Base.read(io::IO, t::Type{$T}) end)

    # Create Type call expression and add parameters
    type_expression = :(($T)())
    for t in types
        read_expression = :(read(io, $t))
        append!(type_expression.args, 0)  # dummy with known length
        type_expression.args[end] = read_expression
    end

    # Replace empty function body with Type call
    function_expression.args[2] = type_expression

    eval(function_expression)
end


function generate_io(T::Type)
    generate_read(T)
end

"""Generate IO expressions macro."""
macro gen_io(typ::Expr)
    T = typ.args[2]
    if isexpr(T, :(<:))
        T = T.args[1]
    end
    if isexpr(T, :curly)
        T = T.args[1]
    end

    ret = Expr(:toplevel, :(Base.@__doc__ $(typ)))
    push!(ret.args, :(generate_io($T)))
    return esc(ret)
end

"ASPRS LAS point data record format 2"
@gen_io struct LasPoint0
    x::Int32
    y::Int32
    z::Int32
    intensity::UInt16
    flag_byte::UInt8
    raw_classification::UInt8
    scan_angle::Int8
    user_data::UInt8
    pt_src_id::UInt16
end



function read_old(io::IO, ::Type{LasPoint0})
    x = read(io, Int32)
    y = read(io, Int32)
    z = read(io, Int32)
    intensity = read(io, UInt16)
    flag_byte = read(io, UInt8)
    raw_classification = read(io, UInt8)
    scan_angle = read(io, UInt8)
    user_data = read(io, UInt8)
    pt_src_id = read(io, UInt16)
    LasPoint0(
        x,
        y,
        z,
        intensity,
        flag_byte,
        raw_classification,
        scan_angle,
        user_data,
        pt_src_id
    )
end

# Extend base by enabling reading/writing relevant FixedPointNumbers from IO.
Base.read(io::IO, ::Type{N0f16}) = reinterpret(N0f16, read(io, UInt16))
Base.write(io::IO, t::N0f16) = write(io, reinterpret(UInt16, t))

@inline function test()
    io = IOBuffer(read(open("test/libLAS_1.2.las")))
    println("----")

    seek(io, 227)
    print("Old:   ")
    @time for _ in 1:497536
        pp = read_old(io, LasPoint0)
    end


    seek(io, 227)
    print("New:   ")
    @time for _ in 1:497536
        p = read(io, LasPoint0)
    end

end

test()