traefik/pkg/middlewares/compress/acceptencoding.go

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package compress
import (
"slices"
"strconv"
"strings"
)
const acceptEncodingHeader = "Accept-Encoding"
const (
brotliName = "br"
gzipName = "gzip"
zstdName = "zstd"
identityName = "identity"
wildcardName = "*"
notAcceptable = "not_acceptable"
)
type Encoding struct {
Type string
Weight *float64
}
func getCompressionType(acceptEncoding []string, defaultType string) string {
if defaultType == "" {
// Keeps the pre-existing default inside Traefik.
defaultType = brotliName
}
encodings, hasWeight := parseAcceptEncoding(acceptEncoding)
if hasWeight {
if len(encodings) == 0 {
return identityName
}
encoding := encodings[0]
if encoding.Type == identityName && encoding.Weight != nil && *encoding.Weight == 0 {
return notAcceptable
}
if encoding.Type == wildcardName && encoding.Weight != nil && *encoding.Weight == 0 {
return notAcceptable
}
if encoding.Type == wildcardName {
return defaultType
}
return encoding.Type
}
for _, dt := range []string{zstdName, brotliName, gzipName} {
if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == dt }) {
return dt
}
}
if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == wildcardName }) {
return defaultType
}
return identityName
}
func parseAcceptEncoding(acceptEncoding []string) ([]Encoding, bool) {
var encodings []Encoding
var hasWeight bool
for _, line := range acceptEncoding {
for _, item := range strings.Split(strings.ReplaceAll(line, " ", ""), ",") {
parsed := strings.SplitN(item, ";", 2)
if len(parsed) == 0 {
continue
}
switch parsed[0] {
case zstdName, brotliName, gzipName, identityName, wildcardName:
// supported encoding
default:
continue
}
var weight *float64
if len(parsed) > 1 && strings.HasPrefix(parsed[1], "q=") {
w, _ := strconv.ParseFloat(strings.TrimPrefix(parsed[1], "q="), 64)
weight = &w
hasWeight = true
}
encodings = append(encodings, Encoding{
Type: parsed[0],
Weight: weight,
})
}
}
slices.SortFunc(encodings, compareEncoding)
return encodings, hasWeight
}
func compareEncoding(a, b Encoding) int {
lhs, rhs := a.Weight, b.Weight
if lhs == nil && rhs == nil {
return 0
}
if lhs == nil && *rhs == 0 {
return -1
}
if lhs == nil {
return 1
}
if rhs == nil && *lhs == 0 {
return 1
}
if rhs == nil {
return -1
}
if *lhs < *rhs {
return 1
}
if *lhs > *rhs {
return -1
}
return 0
}