# cachecontrol: HTTP Caching Parser and Interpretation
[](https://pkg.go.dev/github.com/pquerna/cachecontrol?tab=doc)[](https://travis-ci.org/pquerna/cachecontrol)
`cachecontrol` implements [RFC 7234](http://tools.ietf.org/html/rfc7234) __Hypertext Transfer Protocol (HTTP/1.1): Caching__. It does this by parsing the `Cache-Control` and other headers, providing information about requests and responses -- but `cachecontrol` does not implement an actual cache backend, just the control plane to make decisions about if a particular response is cachable.
# Usage
`cachecontrol.CachableResponse` returns an array of [reasons](https://godoc.org/github.com/pquerna/cachecontrol/cacheobject#Reason) why a response should not be cached and when it expires. In the case that `len(reasons) == 0`, the response is cachable according to the RFC. However, some people want non-compliant caches for various business use cases, so each reason is specifically named, so if your cache wants to cache `POST` requests, it can easily do that, but still be RFC compliant in other situations.
# Examples
## Can you cache Example.com?
```go
package main
import (
"github.com/pquerna/cachecontrol"
"fmt"
"io/ioutil"
"net/http"
)
func main() {
req, _ := http.NewRequest("GET", "http://www.example.com/", nil)
res, _ := http.DefaultClient.Do(req)
_, _ = ioutil.ReadAll(res.Body)
reasons, expires, _ := cachecontrol.CachableResponse(req, res, cachecontrol.Options{})
fmt.Println("Reasons to not cache: ", reasons)
fmt.Println("Expiration: ", expires.String())
}
```
## Can I use this in a high performance caching server?
`cachecontrol` is divided into two packages: `cachecontrol` with a high level API, and a lower level `cacheobject` package. Use [Object](https://godoc.org/github.com/pquerna/cachecontrol/cacheobject#Object) in a high performance use case where you have previously parsed headers containing dates or would like to avoid memory allocations.
```go
package main
import (
"github.com/pquerna/cachecontrol/cacheobject"
"fmt"
"io/ioutil"
"net/http"
)
func main() {
req, _ := http.NewRequest("GET", "http://www.example.com/", nil)
res, _ := http.DefaultClient.Do(req)
_, _ = ioutil.ReadAll(res.Body)
reqDir, _ := cacheobject.ParseRequestCacheControl(req.Header.Get("Cache-Control"))
resDir, _ := cacheobject.ParseResponseCacheControl(res.Header.Get("Cache-Control"))
expiresHeader, _ := http.ParseTime(res.Header.Get("Expires"))
dateHeader, _ := http.ParseTime(res.Header.Get("Date"))
lastModifiedHeader, _ := http.ParseTime(res.Header.Get("Last-Modified"))
obj := cacheobject.Object{
RespDirectives: resDir,
RespHeaders: res.Header,
RespStatusCode: res.StatusCode,
RespExpiresHeader: expiresHeader,
RespDateHeader: dateHeader,
RespLastModifiedHeader: lastModifiedHeader,
ReqDirectives: reqDir,
ReqHeaders: req.Header,
ReqMethod: req.Method,
NowUTC: time.Now().UTC(),
}
rv := cacheobject.ObjectResults{}
cacheobject.CachableObject(&obj, &rv)
cacheobject.ExpirationObject(&obj, &rv)
fmt.Println("Errors: ", rv.OutErr)
fmt.Println("Reasons to not cache: ", rv.OutReasons)
fmt.Println("Warning headers to add: ", rv.OutWarnings)
fmt.Println("Expiration: ", rv.OutExpirationTime.String())
}
```
## Improvements, bugs, adding features, and taking cachecontrol new directions!
Please [open issues in Github](https://github.com/pquerna/cachecontrol/issues) for ideas, bugs, and general thoughts. Pull requests are of course preferred :)
# Credits
`cachecontrol` has recieved significant contributions from:
* [Paul Querna](https://github.com/pquerna)
## License
`cachecontrol` is licensed under the [Apache License, Version 2.0](./LICENSE)
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