[wip] Parse args

[mapsam]

This sets up the vtquery.cpp file for parsing arguments before heading into the worker.

TODO

• write validator for the first argument, array of buffer objects

[springmeyer]

It is ideal to check for geometry_utf8_value.length() <= 0 before trying to create a std::string since passing a null string may crash unpredictably (refs mapbox/node-fontnik#124)

[springmeyer]

Actually, while std::string s(nullptr); crashes, std::string s(nullptr,0); does not. So technically this usage is safe. However, it is still ideal to catch geometry_utf8_value.length() <= 0 since a zero length string would be an invalid option value.

[mapsam]

@springmeyer I originally had this check, but since a couple lines down we are checking for string values == point linestring polygon and exiting if they don't, I figured this null string couldn't get too far. Happy to add it back in though!

[springmeyer]

👍 on adding back.

[mapsam]

@springmeyer any idea what a good data structure would be here? A vector that contains maps of buffer, x, y, z values? Like:

std::vector<std::map<...>>

❓

[mapsam]

Or perhaps we create a custom struct that has these values defined, so we could do a vector of structs with the proper values? Something like

std::vector<buf> bufs;

struct buf {
  int z;
  int x;
  int y;
  node::Buffer buffer;
}

// start doing stuff
buf buffer_obj;
buffer_obj.z = 0;
buffer_obj.x = 0;
buffer_obj.y = 0;
node::Buffer real_buffer;
real_buffer = node::Buffer::Data(buffer_data); // defined elsewhere
buffer_obj.buffer = real_buffer;
// stop doing stuff
bufs.push_back(buffer_obj);