util.dbuffer: Add efficient shortcuts for discard() in certain cases
If the buffer is already empty, nothing to do. If we're throwing away the
whole buffer, we can just empty it and avoid read_chunk() (which in turn
may collapse()). These shortcuts are much more efficient.
local function parse(arg, config)
local short_params = config and config.short_params or {};
local value_params = config and config.value_params or {};
local parsed_opts = {};
if #arg == 0 then
return parsed_opts;
end
while true do
local raw_param = arg[1];
if not raw_param then
break;
end
local prefix = raw_param:match("^%-%-?");
if not prefix then
break;
elseif prefix == "--" and raw_param == "--" then
table.remove(arg, 1);
break;
end
local param = table.remove(arg, 1):sub(#prefix+1);
if #param == 1 and short_params then
param = short_params[param];
end
if not param then
return nil, "param-not-found", raw_param;
end
local param_k, param_v;
if value_params[param] then
param_k, param_v = param, table.remove(arg, 1);
if not param_v then
return nil, "missing-value", raw_param;
end
else
param_k, param_v = param:match("^([^=]+)=(.+)$");
if not param_k then
if param:match("^no%-") then
param_k, param_v = param:sub(4), false;
else
param_k, param_v = param, true;
end
end
end
parsed_opts[param_k] = param_v;
end
for i = 1, #arg do
parsed_opts[i] = arg[i];
end
return parsed_opts;
end
return {
parse = parse;
}