Mime header

RFC reference

Implementation of mime types and Accept header support (RFC 2616 Sec 14.1).

Motivation

This library created to help people to parse media type data, like headers, and store and match it. The main features of the library are to:

• Save a type as a structure (it can help pass mime type as an argument to a function or use as a field of a structure)
• Match mime types by a wildcard. It can be helpful for Accept header negotiation
• MUST be covered by tests to provide guarantees it works well
• Zero dependencies

Examples

Match a header with text

package main

import (
    "fmt"

    "github.com/aohorodnyk/mimeheader"
)

// Content-Type - application/json;q=0.9;p=2
func parse(contentType string) {
    mtype, err := mimeheader.ParseMediaType(contentType)

    fmt.Println(err)                                 // nil
    fmt.Println(mtype.MatchText("application/json; param=1")) // true
    fmt.Println(mtype.MatchText("application/xml; param=1"))  // false
    fmt.Println(mtype.MatchText("*/plain; param=1"))          // false
    fmt.Println(mtype.MatchText("text/plain; param=1"))       // false
}

Match accept header

package main

import (
    "fmt"

    "github.com/aohorodnyk/mimeheader"
)

// Accept - application/json;q=1.0,*/*;q=1.0; param=wild,image/png;q=1.0;param=test
func parse(acceptHeader string) {
    ah := mimeheader.ParseAcceptHeader(acceptHeader)

    fmt.Println(ah.Negotiate([]string{"application/json;param=1", "image/png"}, "text/javascript")) // image/png, image/png, true
}

Accept header HTTP middleware

OWASP suggests using this middleware in all applications.

package main

import (
    "context"
    "log"
    "net/http"

    "github.com/aohorodnyk/mimeheader"
)

func main() {
    r := http.NewServeMux()

    r.HandleFunc("/", acceptHeaderMiddleware([]string{"application/json", "text/html"})(handlerTestFunc))

    err := http.ListenAndServe(":8080", r)
    if err != nil {
        log.Fatalln(err)
    }
}

func acceptHeaderMiddleware(acceptMimeTypes []string) func(http.HandlerFunc) http.HandlerFunc {
    return func(next http.HandlerFunc) http.HandlerFunc {
        return func(rw http.ResponseWriter, r *http.Request) {
            header := r.Header.Get("Accept")
            ah := mimeheader.ParseAcceptHeader(header)

            // We do not need default mime type.
            _, mtype, m := ah.Negotiate(acceptMimeTypes, "")
            if !m {
                // If not matched accept mim type, return 406.
                rw.WriteHeader(http.StatusNotAcceptable)

                return
            }

            // Add matched mime type to context.
            ctx := context.WithValue(r.Context(), "resp_content_type", mtype)
            // New requet from new context.
            rc := r.WithContext(ctx)

            // Call next middleware or handler.
            next(rw, rc)
        }
    }
}

func handlerTestFunc(rw http.ResponseWriter, r *http.Request) {
    mtype := r.Context().Value("resp_content_type").(string)
    rw.Write([]byte(mtype))
}

Requests example

GET http://localhost:8080/
Accept: text/*; q=0.9,application/json; q=1;

# HTTP/1.1 200 OK
# Date: Sat, 03 Jul 2021 19:14:58 GMT
# Content-Length: 16
# Content-Type: text/plain; charset=utf-8
# Connection: close

# application/json

###

GET http://localhost:8080/
Accept: text/*; q=1,application/json; q=1;

# HTTP/1.1 200 OK
# Date: Sat, 03 Jul 2021 19:15:51 GMT
# Content-Length: 16
# Content-Type: text/plain; charset=utf-8
# Connection: close

# application/json

###
GET http://localhost:8080/
Accept: text/html; q=1,application/*; q=1;

# HTTP/1.1 200 OK
# Date: Sat, 03 Jul 2021 19:16:15 GMT
# Content-Length: 9
# Content-Type: text/plain; charset=utf-8
# Connection: close

# text/html

###
GET http://localhost:8080/
Accept: text/*; q=1,application/*; q=0.9;

# HTTP/1.1 200 OK
# Date: Sat, 03 Jul 2021 19:16:48 GMT
# Content-Length: 9
# Content-Type: text/plain; charset=utf-8
# Connection: close

# text/html

###
GET http://localhost:8080/
Accept: text/plain; q=1,application/xml; q=1;

# HTTP/1.1 406 Not Acceptable
# Date: Sat, 03 Jul 2021 19:17:28 GMT
# Content-Length: 0
# Connection: close

Current benchmark results

$ go test -bench=.
goos: darwin
goarch: arm64
pkg: github.com/aohorodnyk/mimeheader
BenchmarkParseAcceptHeaderLong-8                              595474          1979 ns/op        1672 B/op         16 allocs/op
BenchmarkParseAcceptHeaderThreeWithWights-8                   879034          1364 ns/op        1480 B/op         14 allocs/op
BenchmarkParseAcceptHeaderOne-8                              4268950           279.7 ns/op       232 B/op          7 allocs/op
BenchmarkParseAcceptHeaderAndCompareLong-8                    295642          4052 ns/op        2344 B/op         34 allocs/op
BenchmarkParseAcceptHeaderAndCompareThreeWithWights-8         408138          2943 ns/op        1992 B/op         28 allocs/op
BenchmarkParseAcceptHeaderAndCompareOne-8                    1399750           856.0 ns/op       411 B/op         13 allocs/op
PASS
ok      github.com/aohorodnyk/mimeheader    9.252s

Contributing

All contributions have to follow the CONTRIBUTING.md document If you have any questions/issues/feature requests do not hesitate to create a ticket.