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package middleware
import (
"net/http"
"strings"
)
// ContentCharset generates a handler that writes a 415 Unsupported Media Type response if none of the charsets match.
// An empty charset will allow requests with no Content-Type header or no specified charset.
func ContentCharset(charsets ...string) func(next http.Handler) http.Handler {
for i, c := range charsets {
charsets[i] = strings.ToLower(c)
}
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if !contentEncoding(r.Header.Get("Content-Type"), charsets...) {
w.WriteHeader(http.StatusUnsupportedMediaType)
return
}
next.ServeHTTP(w, r)
})
}
}
// Check the content encoding against a list of acceptable values.
func contentEncoding(ce string, charsets ...string) bool {
_, ce = split(strings.ToLower(ce), ";")
_, ce = split(ce, "charset=")
ce, _ = split(ce, ";")
for _, c := range charsets {
if ce == c {
return true
}
}
return false
}
// Split a string in two parts, cleaning any whitespace.
func split(str, sep string) (string, string) {
var a, b string
var parts = strings.SplitN(str, sep, 2)
a = strings.TrimSpace(parts[0])
if len(parts) == 2 {
b = strings.TrimSpace(parts[1])
}
return a, b
}
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