Lua binding to libcurl

##Status

This module include three layer

1. lcurl module provide low level pure C binding to libcurl.
   Almost ready and needs tests. I have no plans to change this API.

2. cURL module provide compatibility for Lua-cURLv2 API.
   Almost ready and needs tests.

3. cURL module provide new high level API.
   In fact for now it provide lcurl API directly and needed to redesign.
   

Documentation

lcurl API
Lua-cURLv2 API
Lua-cURLv3 API

Original Lua-cURLv2 binding has several problems:

• it can not return error codes but just raise Lua errors (Fixed. use cURL.safe module)
• it raise Lua error from callback that may result resource leak in libcurl (Fixed.)
• it does not provide building multipart/formdata explicitly (Fixed.)
• it has memory leak when send multipart/formdata (Fixed.)
• it does not save string for curl options that may result crush in libcurl (Fixed.)
• there no way to get result for operations in multi interface (e.g. if one of easy operation fail you can not get result code/error message) (Fixed. But it does not very handy interface.)
• you can not use your own callback function to perform operation with multi interface (Could not be fixed without changing API.)
• you can not pass your context to callback functions (Could not be fixed without changing API.)

Installation

Using LuaRocks:

luarocks install Lua-cURL

Install current master:

luarocks install Lua-cURL --server=https://rocks.moonscript.org/dev

List of incompatibility with original Lua-cURLv2

• objects are tables
• multi:perform() also returns ("done",code), ("error",error) and ("response",code) records
• writer callback does not recv string len (just string itself)
• on Lua > 5.2 errors are objects but not strings

Usage

-- HTTP Get
curl.easy()
  :setopt_url('http://httpbin.org/get')
  :setopt_httpheader{
    "X-Test-Header1: Header-Data1",
    "X-Test-Header2: Header-Data2",
  }
  :setopt_writefunction(io.stderr) -- use io.stderr:write()
  :perform()
:close()

-- HTTP Post
curl.easy()
  :setopt_url('http://posttestserver.com/post.php')
  :setopt_writefunction(io.write)
  :setopt_httppost(curl.form() -- Lua-cURL guarantee that form will be alive
    :add_content("test_content", "some data", {
      "MyHeader: SomeValue"
    })
    :add_buffer("test_file", "filename", "text data", "text/plain", {
      "Description: my file description"
    })
    :add_file("test_file2", "BuildLog.htm", "application/octet-stream", {
      "Description: my file description"
    })
  )
  :perform()
:close()

-- FTP Upload
local function get_bin_by(str,n)
  local pos = 1 - n
  return function()
    pos = pos + n
    return (str:sub(pos,pos+n-1))
  end
end

curl.easy()
  :setopt_url("ftp://moteus:123456@127.0.0.1/test.dat")
  :setopt_upload(true)
  :setopt_readfunction(
    get_bin_by(("0123456789"):rep(4), 9)
  )
  :perform()
:close()

-- Multi FTP Upload

-- We get error E_LOGIN_DENIED for this operation
e1 = curl.easy{url = "ftp://moteus:999999@127.0.0.1/test1.dat", upload = true}
  :setopt_readfunction(
    function(t) return table.remove(t) end, {"1111", "2222"}
  )

e2 = curl.easy{url = "ftp://moteus:123456@127.0.0.1/test2.dat", upload = true}
  :setopt_readfunction(get_bin_by(("e"):rep(1000), 5))

m = curl.multi()
m:add_handle(e1)
m:add_handle(e2)

while m:perform() > 0 do m:wait() end

while true do
  h, ok, err = m:info_read()
  if h == 0 then break end

  if h == e1 then 
    assert(ok == nil)
    assert(err:name() == "LOGIN_DENIED")
    assert(err:no() == curl.E_LOGIN_DENIED)
  end

  if h == e2 then 
    assert(ok == true)
  end
end