added example package

vendor/github.com/IncSW/geoip2/reader_isp.go

@@ -0,0 +1,71 @@
+package geoip2
+
+import (
+	"errors"
+	"io/ioutil"
+	"net"
+	"strconv"
+)
+
+type ISPReader struct {
+	*reader
+}
+
+func (r *ISPReader) Lookup(ip net.IP) (*ISP, error) {
+	offset, err := r.getOffset(ip)
+	if err != nil {
+		return nil, err
+	}
+	dataType, size, offset, err := readControl(r.decoderBuffer, offset)
+	if err != nil {
+		return nil, err
+	}
+	result := &ISP{}
+	switch dataType {
+	case dataTypeMap:
+		_, err = readISPMap(result, r.decoderBuffer, size, offset)
+		if err != nil {
+			return nil, err
+		}
+	case dataTypePointer:
+		pointer, _, err := readPointer(r.decoderBuffer, size, offset)
+		if err != nil {
+			return nil, err
+		}
+		dataType, size, offset, err := readControl(r.decoderBuffer, pointer)
+		if err != nil {
+			return nil, err
+		}
+		if dataType != dataTypeMap {
+			return nil, errors.New("invalid ISP pointer type: " + strconv.Itoa(int(dataType)))
+		}
+		_, err = readISPMap(result, r.decoderBuffer, size, offset)
+		if err != nil {
+			return nil, err
+		}
+	default:
+		return nil, errors.New("invalid ISP type: " + strconv.Itoa(int(dataType)))
+	}
+	return result, nil
+}
+
+func NewISPReader(buffer []byte) (*ISPReader, error) {
+	reader, err := newReader(buffer)
+	if err != nil {
+		return nil, err
+	}
+	if reader.metadata.DatabaseType != "GeoIP2-ISP" {
+		return nil, errors.New("wrong MaxMind DB ISP type: " + reader.metadata.DatabaseType)
+	}
+	return &ISPReader{
+		reader: reader,
+	}, nil
+}
+
+func NewISPReaderFromFile(filename string) (*ISPReader, error) {
+	buffer, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return NewISPReader(buffer)
+}