Add geosite protocol

common/geosite/writer.go

@@ -0,0 +1,64 @@
+package geosite
+
+import (
+	"bytes"
+	"io"
+	"sort"
+
+	"github.com/sagernet/sing/common/rw"
+)
+
+func Write(writer io.Writer, domains map[string][]Item) error {
+	keys := make([]string, 0, len(domains))
+	for code := range domains {
+		keys = append(keys, code)
+	}
+	sort.Strings(keys)
+
+	content := &bytes.Buffer{}
+	index := make(map[string]int)
+	for _, code := range keys {
+		index[code] = content.Len()
+		for _, domain := range domains[code] {
+			err := rw.WriteByte(content, byte(domain.Type))
+			if err != nil {
+				return err
+			}
+			if err = rw.WriteVString(content, domain.Value); err != nil {
+				return err
+			}
+		}
+	}
+
+	err := rw.WriteByte(writer, 0)
+	if err != nil {
+		return err
+	}
+
+	err = rw.WriteUVariant(writer, uint64(len(keys)))
+	if err != nil {
+		return err
+	}
+
+	for _, code := range keys {
+		err = rw.WriteVString(writer, code)
+		if err != nil {
+			return err
+		}
+		err = rw.WriteUVariant(writer, uint64(index[code]))
+		if err != nil {
+			return err
+		}
+		err = rw.WriteUVariant(writer, uint64(len(domains[code])))
+		if err != nil {
+			return err
+		}
+	}
+
+	_, err = writer.Write(content.Bytes())
+	if err != nil {
+		return err
+	}
+
+	return nil
+}