[feature] add per-uri dereferencer locks (#2291)

vendor/github.com/klauspost/compress/s2/dict.go

@@ -106,6 +106,25 @@ func MakeDict(data []byte, searchStart []byte) *Dict {
 	return &d
 }
 
+// MakeDictManual will create a dictionary.
+// 'data' must be at least MinDictSize and less than or equal to MaxDictSize.
+// A manual first repeat index into data must be provided.
+// It must be less than len(data)-8.
+func MakeDictManual(data []byte, firstIdx uint16) *Dict {
+	if len(data) < MinDictSize || int(firstIdx) >= len(data)-8 || len(data) > MaxDictSize {
+		return nil
+	}
+	var d Dict
+	dict := data
+	d.dict = dict
+	if cap(d.dict) < len(d.dict)+16 {
+		d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
+	}
+
+	d.repeat = int(firstIdx)
+	return &d
+}
+
 // Encode returns the encoded form of src. The returned slice may be a sub-
 // slice of dst if dst was large enough to hold the entire encoded block.
 // Otherwise, a newly allocated slice will be returned.