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https://github.com/tdewolff/push

Push web resources recursively to the client
https://github.com/tdewolff/push

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Push web resources recursively to the client

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# Push [![Build Status](https://travis-ci.org/tdewolff/push.svg?branch=master)](https://travis-ci.org/tdewolff/push) [![GoDoc](http://godoc.org/github.com/tdewolff/push?status.svg)](http://godoc.org/github.com/tdewolff/push) [![Coverage Status](https://coveralls.io/repos/github/tdewolff/push/badge.svg?branch=master)](https://coveralls.io/github/tdewolff/push?branch=master)

Push is a package that uses HTTP2 to push resources to the client as it parses content. By parsing HTML, CSS and SVG it extracts referenced resource URIs and pushes them towards the client, which is quicker than waiting for the client to parse and request those resources.

## Installation
You need Go1.8 (from tip for example).

Run the following command

go get github.com/tdewolff/push

or add the following import and run the project with `go get`
``` go
import (
"github.com/tdewolff/push"
)
```

## Parsers
### HTML
Parses
- `...` as CSS
- `` as inline CSS
- `...` as HTML
- `...` as SVG

Extracts URIs from
- ``
- ``
- `<img src="...">`
- `<img srcset="..., ...">`
- `<object data="...">`
- `<source src="...">`
- `<audio src="...">`
- `<video src="...">`
- `<track src="...">`
- `<embed src="...">`
- `<input src="...">`
- `<iframe src="...">`

### CSS
Parses
- ~~`url(data:image/svg+xml,...)` as SVG~~ data URI SVGs are not allowed to load external resources

Extracts URIs from
- `url("...")`

### SVG
Parses
- `<style>...</style>` as CSS
- `<x style="...">` as inline CSS

Extracts URIs from
- `<script href="..." xlink:href="...">`
- `<image href="..." xlink:href="...">`
- `<feImage href="..." xlink:href="...">`
- `<color-profile href="..." xlink:href="...">`
- `<use href="..." xlink:href="...">`

## Usage
### Middleware
``` go
fileOpener := push.DefaultFileOpener("resources/")
cache := push.DefaultCache()
p := push.New("example.com/", fileOpener, cache)
http.HandleFunc("/", p.Middleware(func(w http.ResponseWriter, r *http.Request) {
// ...
}))
```

Pass `nil` for `fileOpener` and `cache` to disable recursive parsing and URI caching respectively.

### ResponseWriter
Wrap an existing `http.ResponseWriter` so that it pushes resources automatically:
``` go
fileOpener := push.DefaultFileOpener("resources/")
cache := push.DefaultCache()
p := push.New("example.com/", fileOpener, cache)
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
if pushWriter, err := p.ResponseWriter(w, r); err == nil {
defer pushWriter.Close() // Close returns an error...
w = pushWriter
}

// ...
})
```

Pass `nil` for `fileOpener` and `cache` to disable recursive parsing and URI caching respectively.

### Reader
Wrap a reader and obtain the URIs from a channel:
``` go
func openIndex() io.Reader {
r, _ := os.Open("index.html")

uriHandler := push.URIHandlerFunc(func(uri string) error {
// is called concurrently when using a recursive parser
return nil
})
fileOpener := push.FileOpenerFunc(func(uri string) (io.Reader, string, error) {
// open file for uri
return r, mimetype, nil
})
parser := push.NewParser("example.com/", fileOpener, uriHandler)

return p.Reader(r, parser, "text/html", "/index.html")
}
```

### List
List the resource URIs found:
``` go
r, _ := os.Open("index.html")

uris, err := push.List("example.com/", fileOpener, r, "text/html", "/index.html")
if err != nil {
panic(err)
}
```

### Low-level usage
`Push` pushes resources to `pusher`. It is the underlying functionality of `ResponseWriter`.
``` go
httpPusher, ok := w.(http.Pusher)
if ok {
pusher := NewPusher(httpPusher, &http.PushOptions{"", http.Header{}})

parser, err := push.NewParser("example.com/", nil, pusher)
if err != nil {
panic(err)
}

tr := io.TeeReader(r, w)
err := parser.Parse(r, "text/html", "/index.html")
}
```

## Example
See [example](https://github.com/tdewolff/push/tree/master/example), it shows how a webserver with artificial 50ms delay per request can have the page load time reduced from 1.6s (http) to 0.4s (https).

## License
Released under the [MIT license](LICENSE.md).

[1]: http://golang.org/ "Go Language"