text: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  """
  ffi.py
  
  Created by Stephan Hügel on 2016-08-3
  
  This file is part of simplification.
  
  The MIT License (MIT)
  
  Copyright (c) 2016 Stephan Hügel
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
  
  """
  
  import os
  from sys import platform, version_info
  from ctypes import Structure, POINTER, c_void_p, c_size_t, c_double, cast, cdll
  import numpy as np
  
  __author__ = "Stephan Hügel"
  __version__ = "0.5.21"
  
  file_path = os.path.dirname(__file__)
  
  prefix = {"win32": ""}.get(platform, "lib")
  extension = {"darwin": ".dylib", "win32": ".dll"}.get(platform, ".so")
  fpath = {"darwin": "", "win32": ""}.get(platform, os.path.join(file_path, ".libs"))
  
  # Python 3 check
  if version_info > (3, 0):
      from subprocess import getoutput as spop
  
      py3 = True
  else:
      from subprocess import check_output as spop
  
      py3 = False
  
  try:
      lib = cdll.LoadLibrary(os.path.join(file_path, prefix + "rdp" + extension))
  except OSError:
      # the Rust lib's been grafted by manylinux1
      if not py3:
          fname = spop(["ls", fpath]).split()[0]
      else:
          fname = spop(["ls %s" % fpath]).split()[0]
      lib = cdll.LoadLibrary(os.path.join(file_path, ".libs", fname))
  
  
  class _FFIArray(Structure):
      """
      Convert sequence of float lists to a C-compatible void array
      example: [[1.0, 2.0], [3.0, 4.0]]
  
      """
  
      _fields_ = [("data", c_void_p), ("len", c_size_t)]
  
      @classmethod
      def from_param(cls, seq):
          """  Allow implicit conversions """
          return seq if isinstance(seq, cls) else cls(seq)
  
      def __init__(self, seq, data_type=c_double):
          self.data = cast(
              np.array(seq, dtype=np.float64).ctypes.data_as(POINTER(data_type)), c_void_p
          )
          self.len = len(seq)
  
  
  class _CoordResult(Structure):
      """ Container for returned FFI coordinate data """
  
      _fields_ = [("coords", _FFIArray)]
  
  
  def _void_array_to_nested_list(res, _func, _args):
      """ Dereference the FFI result to a list of coordinates """
      try:
          shape = res.coords.len, 2
          ptr = cast(res.coords.data, POINTER(c_double))
          array = np.ctypeslib.as_array(ptr, shape)
          return array.tolist()
      finally:
          drop_array(res.coords)
  
  
  simplify_coords = lib.simplify_rdp_ffi
  simplify_coords.argtypes = (_FFIArray, c_double)
  simplify_coords.restype = _CoordResult
  simplify_coords.errcheck = _void_array_to_nested_list
  simplify_coords.__doc__ = """
      Simplify a LineString using the Ramer-Douglas-Peucker algorithm.
      Input: a list of lat, lon coordinates, and an epsilon float (Try 1.0 to begin with, reducing by orders of magnitude)
      Output: a simplified list of coordinates
  
      Example:
      simplify_coords([
          [0.0, 0.0], [5.0, 4.0], [11.0, 5.5], [17.3, 3.2], [27.8, 0.1]],
          1.0
      )
      Result: [[0.0, 0.0], [5.0, 4.0], [11.0, 5.5], [27.8, 0.1]]
  
      """
  
  simplify_coords_vw = lib.simplify_visvalingam_ffi
  simplify_coords_vw.argtypes = (_FFIArray, c_double)
  simplify_coords_vw.restype = _CoordResult
  simplify_coords_vw.errcheck = _void_array_to_nested_list
  simplify_coords_vw.__doc__ = """
      Simplify a LineString using the Visvalingam-Whyatt algorithm.
      Input: a list of lat, lon coordinates, and an epsilon float
      Output: a simplified list of coordinates
  
      Example:
      simplify_coords([
          [5.0, 2.0], [3.0, 8.0], [6.0, 20.0], [7.0, 25.0], [10.0, 10.0]],
          30.0
      )
      Result: [[5.0, 2.0], [7.0, 25.0], [10.0, 10.0]]
  
      """
  
  simplify_coords_vwp = lib.simplify_visvalingamp_ffi
  simplify_coords_vwp.argtypes = (_FFIArray, c_double)
  simplify_coords_vwp.restype = _CoordResult
  simplify_coords_vwp.errcheck = _void_array_to_nested_list
  simplify_coords_vwp.__doc__ = """
      Simplify a LineString using a topology-preserving variant of
      the Visvalingam-Whyatt algorithm.
      Input: a list of lat, lon coordinates, and an epsilon float
      Output: a simplified list of coordinates
  
      Example:
      simplify_coords([
          [5.0, 2.0], [3.0, 8.0], [6.0, 20.0], [7.0, 25.0], [10.0, 10.0]],
          30.0
      )
      Result: [[5.0, 2.0], [7.0, 25.0], [10.0, 10.0]]
  
      """
  
  drop_array = lib.drop_float_array
  drop_array.argtypes = (_FFIArray,)
  drop_array.restype = None
  