109 lines
2.2 KiB
Go
109 lines
2.2 KiB
Go
package compress
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import (
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"cmp"
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"slices"
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"strconv"
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"strings"
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)
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const acceptEncodingHeader = "Accept-Encoding"
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const (
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brotliName = "br"
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gzipName = "gzip"
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zstdName = "zstd"
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identityName = "identity"
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wildcardName = "*"
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notAcceptable = "not_acceptable"
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)
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type Encoding struct {
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Type string
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Weight float64
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}
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func getCompressionType(acceptEncoding []string, defaultType string) string {
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if defaultType == "" {
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// Keeps the pre-existing default inside Traefik.
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defaultType = brotliName
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}
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encodings, hasWeight := parseAcceptEncoding(acceptEncoding)
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if hasWeight {
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if len(encodings) == 0 {
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return identityName
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}
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encoding := encodings[0]
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if encoding.Type == identityName && encoding.Weight == 0 {
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return notAcceptable
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}
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if encoding.Type == wildcardName && encoding.Weight == 0 {
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return notAcceptable
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}
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if encoding.Type == wildcardName {
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return defaultType
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}
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return encoding.Type
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}
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for _, dt := range []string{zstdName, brotliName, gzipName} {
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if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == dt }) {
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return dt
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}
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}
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if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == wildcardName }) {
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return defaultType
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}
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return identityName
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}
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func parseAcceptEncoding(acceptEncoding []string) ([]Encoding, bool) {
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var encodings []Encoding
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var hasWeight bool
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for _, line := range acceptEncoding {
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for _, item := range strings.Split(strings.ReplaceAll(line, " ", ""), ",") {
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parsed := strings.SplitN(item, ";", 2)
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if len(parsed) == 0 {
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continue
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}
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switch parsed[0] {
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case zstdName, brotliName, gzipName, identityName, wildcardName:
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// supported encoding
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default:
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continue
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}
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// If no "q" parameter is present, the default weight is 1.
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// https://www.rfc-editor.org/rfc/rfc9110.html#name-quality-values
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weight := 1.0
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if len(parsed) > 1 && strings.HasPrefix(parsed[1], "q=") {
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w, _ := strconv.ParseFloat(strings.TrimPrefix(parsed[1], "q="), 64)
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weight = w
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hasWeight = true
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}
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encodings = append(encodings, Encoding{
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Type: parsed[0],
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Weight: weight,
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})
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}
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}
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slices.SortFunc(encodings, func(a, b Encoding) int {
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return cmp.Compare(b.Weight, a.Weight)
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})
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return encodings, hasWeight
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}
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