FFI and third-party modules

First, FFI

FFI is  LuaJIT an extension library in which allows us to use Lua code to call C language data structures and functions.

The FFI library largely avoids the Lua/C need to write cumbersome manual bindings in C. No need to learn a separate binding language-it parses ordinary C statements! These can be cut and pasted from C header files or reference manuals.

How to call external C library functions?
1. Load the FFI library.
2. Add a C statement to the function.
3. Call the named C function.

Look at a simple example provided by the official:

-- test_ffi.lua

local ffi = require("ffi")
ffi.cdef[[
int printf(const char *fmt, ...);
]]
ffi.C.printf("Hello %s!", "world")

run:

luajit test_ffi.lua

For details, see: http://luajit.org/ext_ffi.html

https://moonbingbing.gitbooks.io/openresty-best-practices/content/lua/FFI.html

Second, add third-party modules

The location of the default resty library:

The principle of using third-party libraries:

There are more stars, more frequent updates, more distributors

Install a third-party http library:

git clone https://github.com/ledgetech/lua-resty-http

Copy the tripartite library lib / resty / * to / opt / openresty / lulib / resty

cp lua-resty-http/lib/resty/* /opt/openresty/lualib/resty

Examples of use:

local http = require "resty.http"
local httpc = http.new()

local res, err = httpc:request_uri("http://example.com/helloworld", {
    method = "POST",
    body = "a=1&b=2",
    headers = {
      ["Content-Type"] = "application/x-www-form-urlencoded",
    },
    keepalive_timeout = 60,
    keepalive_pool = 10
})

if not res then
    ngx.say("failed to request: ", err)
    return
end

ngx.status = res.status

for k,v in pairs(res.headers) do
  --
end

ngx.say(res.body)