send-transform

send-transform

Send-transform is a modified version of the send library for streaming files from the file system as a http response supporting partial responses (Ranges), conditional-GET negotiation, high test coverage, and granular events which may be leveraged to take appropriate actions in your application or framework.

This modified version of send supports specifying a transform function that takes the file stream as input, and produces a new (transformed) stream as ouput. See below for more information.

Looking to serve up entire folders mapped to URLs? Try serve-static.

Installation

$ npm install send-transform

API

var send = require('send-transform')

send(req, path, [options])

Create a new SendStream for the given path to send to a res. The req is the Node.js HTTP request and the path is a urlencoded path to send (urlencoded, not the actual file-system path).

Options

acceptRanges

Enable or disable accepting ranged requests, defaults to true. Disabling this will not send Accept-Ranges and ignore the contents of the Range request header.

cacheControl

Enable or disable setting Cache-Control response header, defaults to true. Disabling this will ignore the maxAge option.

dotfiles

Set how "dotfiles" are treated when encountered. A dotfile is a file or directory that begins with a dot ("."). Note this check is done on the path itself without checking if the path actually exists on the disk. If root is specified, only the dotfiles above the root are checked (i.e. the root itself can be within a dotfile when when set to "deny").

• 'allow' No special treatment for dotfiles.
• 'deny' Send a 403 for any request for a dotfile.
• 'ignore' Pretend like the dotfile does not exist and 404.

The default value is similar to 'ignore', with the exception that this default will not ignore the files within a directory that begins with a dot, for backward-compatibility.

end

Byte offset at which the stream ends, defaults to the length of the file minus 1. The end is inclusive in the stream, meaning end: 3 will include the 4th byte in the stream.

etag

Enable or disable etag generation.

Defaults to true, unless the transform option is set.

extensions

If a given file doesn't exist, try appending one of the given extensions, in the given order. By default, this is disabled (set to false). An example value that will serve extension-less HTML files: ['html', 'htm']. This is skipped if the requested file already has an extension.

index

By default send supports "index.html" files, to disable this set false or to supply a new index pass a string or an array in preferred order.

lastModified

Enable or disable Last-Modified header. Uses the file system's last modified value.

Defaults to true, unless the transform option is set.

maxAge

Provide a max-age in milliseconds for http caching, defaults to 0. This can also be a string accepted by the ms module.

root

Serve files relative to path.

start

Byte offset at which the stream starts, defaults to 0. The start is inclusive, meaning start: 2 will include the 3rd byte in the stream.

transform

A function that consumes the file stream and produces a new (transformed) stream:

function(stream) {return stream.pipe(replaceStream('tobi', 'peter'))}

Multiple transformations are possible:

function(stream) {
  return stream
  .pipe(replaceStream('tobi', 'peter'))
  .pipe(replaceStream('peter', 'hans'))
  .pipe(...)
}

When a transform is specified, the lastModified and etag options default to false, but can be overridden when a transform on the file's stream is expected to always generate the same result.

Events

The SendStream is an event emitter and will emit the following events:

• error an error occurred (err)
• directory a directory was requested
• file a file was requested (path, stat)
• headers the headers are about to be set on a file (res, path, stat)
• stream file streaming has started (stream)
• end streaming has completed

.pipe

The pipe method is used to pipe the response into the Node.js HTTP response object, typically send(req, path, options).pipe(res).

.mime

The mime export is the global instance of of the mime npm module.

This is used to configure the MIME types that are associated with file extensions as well as other options for how to resolve the MIME type of a file (like the default type to use for an unknown file extension).

Error-handling

By default when no error listeners are present an automatic response will be made, otherwise you have full control over the response, aka you may show a 5xx page etc.

Caching

It does not perform internal caching, you should use a reverse proxy cache such as Varnish for this, or those fancy things called CDNs. If your application is small enough that it would benefit from single-node memory caching, it's small enough that it does not need caching at all ;).

Debugging

To enable debug() instrumentation output export DEBUG:

$ DEBUG=send node app

Running tests

$ npm install
$ npm test

Examples

Small example

var http = require('http')
var parseUrl = require('parseurl')
var send = require('send-transform')

var app = http.createServer(function onRequest (req, res) {
  send(req, parseUrl(req).pathname).pipe(res)
}).listen(3000)

Custom file types

var http = require('http')
var parseUrl = require('parseurl')
var send = require('send-transform')

// Default unknown types to text/plain
send.mime.default_type = 'text/plain'

// Add a custom type
send.mime.define({
  'application/x-my-type': ['x-mt', 'x-mtt']
})

var app = http.createServer(function onRequest (req, res) {
  send(req, parseUrl(req).pathname).pipe(res)
}).listen(3000)

Serving from a root directory with custom error-handling

var http = require('http')
var parseUrl = require('parseurl')
var send = require('send')

var app = http.createServer(function onRequest (req, res) {
  // your custom error-handling logic:
  function error (err) {
    res.statusCode = err.status || 500
    res.end(err.message)
  }

  // your custom headers
  function headers (res, path, stat) {
    // serve all files for download
    res.setHeader('Content-Disposition', 'attachment')
  }

  // your custom directory handling logic:
  function redirect () {
    res.statusCode = 301
    res.setHeader('Location', req.url + '/')
    res.end('Redirecting to ' + req.url + '/')
  }

  // transfer arbitrary files from within
  // /www/example.com/public/*
  send(req, parseUrl(req).pathname, {root: '/www/example.com/public'})
  .on('error', error)
  .on('directory', redirect)
  .on('headers', headers)
  .pipe(res);
}).listen(3000)

License

MIT