Name
====

lua-resty-upload - Streaming reader and parser for HTTP file uploading based on ngx_lua cosocket

Table of Contents
=================

* [Name](#name)
* [Status](#status)
* [Description](#description)
* [Synopsis](#synopsis)
* [Author](#author)
* [Copyright and License](#copyright-and-license)
* [See Also](#see-also)

Status
======

This library is considered production ready.

Description
===========

This Lua library is a streaming file uploading API for the ngx_lua nginx module:

http://wiki.nginx.org/HttpLuaModule

The multipart/form-data MIME type is supported.

The API of this library just returns tokens one by one. The user just needs to call the `read` method repeatedly until a nil token type is returned. For each token returned from the `read` method, just check the first return value for the current token type. The token type can be `header`, `body`, and `part end`. Each `multipart/form-data` form field parsed consists of several `header` tokens holding each field header, several `body` tokens holding each body data chunk, and a `part end` flag indicating the field end.

This is how streaming reading works. Even for giga bytes of file data input, the memory used in the lua land can be small and constant, as long as the user does not accumulate the input data chunks herself.

This Lua library takes advantage of ngx_lua's cosocket API, which ensures
100% nonblocking behavior.

Note that at least [ngx_lua 0.7.9](https://github.com/chaoslawful/lua-nginx-module/tags) or [OpenResty 1.2.4.14](http://openresty.org/#Download) is required.

Synopsis
========

```lua
    lua_package_path "/path/to/lua-resty-redis/lib/?.lua;;";

    server {
        location /test {
            content_by_lua '
                local upload = require "resty.upload"
                local cjson = require "cjson"

                local chunk_size = 5 -- should be set to 4096 or 8192
                                     -- for real-world settings

                local form, err = upload:new(chunk_size)
                if not form then
                    ngx.log(ngx.ERR, "failed to new upload: ", err)
                    ngx.exit(500)
                end

                form:set_timeout(1000) -- 1 sec

                while true do
                    local typ, res, err = form:read()
                    if not typ then
                        ngx.say("failed to read: ", err)
                        return
                    end

                    ngx.say("read: ", cjson.encode({typ, res}))

                    if typ == "eof" then
                        break
                    end
                end

                local typ, res, err = form:read()
                ngx.say("read: ", cjson.encode({typ, res}))
            ';
        }
    }
```

A typical output of the /test location defined above is:

    read: ["header",["Content-Disposition","form-data; name=\"file1\"; filename=\"a.txt\"","Content-Disposition: form-data; name=\"file1\"; filename=\"a.txt\""]]
    read: ["header",["Content-Type","text\/plain","Content-Type: text\/plain"]]
    read: ["body","Hello"]
    read: ["body",", wor"]
    read: ["body","ld"]
    read: ["part_end"]
    read: ["header",["Content-Disposition","form-data; name=\"test\"","Content-Disposition: form-data; name=\"test\""]]
    read: ["body","value"]
    read: ["body","\r\n"]
    read: ["part_end"]
    read: ["eof"]
    read: ["eof"]

You can use the [lua-resty-string](https://github.com/agentzh/lua-resty-string) library to compute SHA-1 and MD5 digest of the file data incrementally. Here is such an example:

```lua
    local resty_sha1 = require "resty.sha1"
    local upload = require "resty.upload"

    local chunk_size = 4096
    local form = upload:new(chunk_size)
    local sha1 = resty_sha1:new()
    local file
    while true do
        local typ, res, err = form:read()

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

        if typ == "header" then
            local file_name = my_get_file_name(res)
            if file_name then
                file = io.open(file_name, "w+")
                if not file then
                    ngx.say("failed to open file ", file_name)
                    return
                end
            end

         elseif typ == "body" then
            if file then
                file:write(res)
                sha1:update(res)
            end

        elseif typ == "part_end" then
            file:close()
            file = nil
            local sha1_sum = sha1:final()
            sha1:reset()
            my_save_sha1_sum(sha1_sum)

        elseif typ == "eof" then
            break

        else
            -- do nothing
        end
    end
```

If you want to compute MD5 sums for the uploaded files, just use the
resty.md5 module shipped by the [lua-resty-string](https://github.com/agentzh/lua-resty-string) library. It has
a similar API as resty.sha1.

For big file uploading, it is important not to buffer all the data in memory.
That is, you should never accumulate data chunks either in a huge Lua string or
in a huge Lua table. You must write the data chunk into files as soon as possible and
throw away the data chunk immediately (to let the Lua GC free it up).

Instead of writing the data chunk into files (as shown in the example above),
you can also write the data chunks to upstream cosocket connections if you do
not want to save the data on local file systems.

[Back to TOC](#table-of-contents)

Author
======

Yichun "agentzh" Zhang (章亦春) <agentzh@gmail.com>, CloudFlare Inc.

[Back to TOC](#table-of-contents)

Copyright and License
=====================

This module is licensed under the BSD license.

Copyright (C) 2012-2016, by Yichun "agentzh" Zhang (章亦春) <agentzh@gmail.com>, CloudFlare Inc.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[Back to TOC](#table-of-contents)

See Also
========
* the [ngx_lua module](http://wiki.nginx.org/HttpLuaModule)
* the [lua-resty-string](https://github.com/agentzh/lua-resty-string) library
* the [lua-resty-memcached](https://github.com/agentzh/lua-resty-memcached) library
* the [lua-resty-redis](https://github.com/agentzh/lua-resty-redis) library
* the [lua-resty-mysql](https://github.com/agentzh/lua-resty-mysql) library

[Back to TOC](#table-of-contents)

