Moved shared structs to package

1 files changed, 91 insertions, 0 deletions

diff --git a/models/infohash.go b/models/infohash.go
new file mode 100644
index 0000000..e8db422
--- /dev/null
+++ b/models/infohash.go
@@ -0,0 +1,91 @@
+package models
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"math/rand"
+	"time"
+)
+
+const InfohashLength = 20
+
+// Infohash is a 160 bit (20 byte) value
+type Infohash []byte
+
+// InfohashFromString converts a 40 digit hexadecimal string to an Infohash
+func InfohashFromString(s string) (*Infohash, error) {
+	switch len(s) {
+	case 20:
+		// Binary string
+		ih := Infohash([]byte(s))
+		return &ih, nil
+	case 40:
+		// Hex string
+		b, err := hex.DecodeString(s)
+		if err != nil {
+			return nil, err
+		}
+		ih := Infohash(b)
+		return &ih, nil
+	default:
+		return nil, fmt.Errorf("invalid length %d", len(s))
+	}
+}
+
+func (ih Infohash) String() string {
+	return hex.EncodeToString(ih)
+}
+func (ih Infohash) Valid() bool {
+	// TODO
+	return len(ih) == 20
+}
+
+func (ih Infohash) Equal(other Infohash) bool {
+	if len(ih) != len(other) {
+		return false
+	}
+	for i := 0; i < len(ih); i++ {
+		if ih[i] != other[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// Distance determines the distance to another infohash as an integer
+func (ih Infohash) Distance(other Infohash) int {
+	i := 0
+	for ; i < 20; i++ {
+		if ih[i] != other[i] {
+			break
+		}
+	}
+
+	if i == 20 {
+		return 160
+	}
+
+	xor := ih[i] ^ other[i]
+
+	j := 0
+	for (xor & 0x80) == 0 {
+		xor <<= 1
+		j++
+	}
+	return 8*i + j
+}
+
+func GenerateNeighbour(first, second Infohash) Infohash {
+	s := append(second[:10], first[10:]...)
+	return Infohash(s)
+}
+
+func GenInfohash() (ih Infohash) {
+	random := rand.New(rand.NewSource(time.Now().UnixNano()))
+	hash := sha1.New()
+	io.WriteString(hash, time.Now().String())
+	io.WriteString(hash, string(random.Int()))
+	return Infohash(hash.Sum(nil))
+}