Add Spamhaus JSON example to demonstrate blocklist usage

blocklist.go

@@ -35,6 +35,7 @@ type Config struct {
 }
 
 // NewConfig creates a new Config with default values.
+// limit is the maximum number of items to process or validate. 0 means no limit.
 func NewConfig(limit uint) Config {
 	return Config{
 		Limit:          limit,

examples/spamhaus.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"git.kor-elf.net/kor-elf-shield/blocklist"
+	"git.kor-elf.net/kor-elf-shield/blocklist/parser"
+)
+
+/**
+ * An example of how to get a list of bad IP addresses from the service https://www.spamhaus.org/blocklists/do-not-route-or-peer/
+ */
+
+type lineJson struct {
+	IP string `json:"cidr"`
+}
+
+func main() {
+	url := "https://www.spamhaus.org/drop/drop_v4.json"
+	//url := "https://www.spamhaus.org/drop/drop_v6.json"
+	pars, err := parser.NewJsonLines(func(item json.RawMessage) (string, error) {
+		var line lineJson
+		if err := json.Unmarshal(item, &line); err != nil {
+			return "", fmt.Errorf("unmarshal json item: %w", err)
+		}
+		return line.IP, nil
+	})
+	if err != nil {
+		panic(err)
+	}
+	// limit 0 - no limit
+	limit := uint(0)
+	config := blocklist.NewConfig(limit)
+	ips, err := blocklist.Get(url, pars, config)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(ips)
+}