Depend on struct instead of lpack

[ntd]

The struct module is actually available either for Lua 5.1 and 5.2.
lpack was the only dependency preventing lua-websocket to be compiled
for Lua 5.2.

[lipp]

would be nice to have struct.pack in a local, eg: local spack = struct.pack local sunpack = struct.unpack

[ntd]

I'm personally against it: I'd have to jump up and down to understand the code. Anyway no problems: if I have to jump, I jump.

[lipp]

i am a bit performance paranoid. the local is for saving table accesses at spots which are supposedly run very often. sometimes i even do it for table/object methods, e.g.

#!/usr/bin/env lua
local socket = require'socket'

local s = 'hello'
local n = 10000000

print('with table access')
do
  local t1 = socket.gettime()
  for i=1,n do
    s:upper()
  end
  local dt = socket.gettime() - t1
  print('dt=',dt)
end

print('---------------------')
print('without table access')
do
  local supper = s.upper
  local t1 = socket.gettime()
  for i=1,n do
    supper(s)
  end
  local dt = socket.gettime() - t1
  print('dt=',dt)
end

On my macbook, the second variant is about 25% percent faster, even using luajit!

[ntd]

Yes, I am aware locals in tight loops can improve performances but here it is not the case. I am also aware you have only 200 slots for locals on either standard Lua and LuaJIT. Try to run this:

local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z
local a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z

I think this has more to do with habits, a bit like the correct™ indentation to adopt.

[lipp]

@ntd Awesome work! Thanks a lot!