chg: feat: add better magnet processing

magnet/infohash.go

@@ -0,0 +1,80 @@
+package magnet
+
+import (
+	"crypto/sha1"
+	"encoding"
+	"encoding/hex"
+	"fmt"
+)
+
+const Size = 20
+
+// 20-byte SHA1 hash used for info and pieces.
+type T [Size]byte
+
+var _ fmt.Formatter = (*T)(nil)
+
+func (t T) Format(f fmt.State, c rune) {
+	// TODO: I can't figure out a nice way to just override the 'x' rune, since it's meaningless
+	// with the "default" 'v', or .String() already returning the hex.
+	f.Write([]byte(t.HexString()))
+}
+
+func (t T) Bytes() []byte {
+	return t[:]
+}
+
+func (t T) AsString() string {
+	return string(t[:])
+}
+
+func (t T) String() string {
+	return t.HexString()
+}
+
+func (t T) HexString() string {
+	return fmt.Sprintf("%x", t[:])
+}
+
+func (t *T) FromHexString(s string) (err error) {
+	if len(s) != 2*Size {
+		err = fmt.Errorf("hash hex string has bad length: %d", len(s))
+		return
+	}
+	n, err := hex.Decode(t[:], []byte(s))
+	if err != nil {
+		return
+	}
+	if n != Size {
+		panic(n)
+	}
+	return
+}
+
+var (
+	_ encoding.TextUnmarshaler = (*T)(nil)
+	_ encoding.TextMarshaler   = T{}
+)
+
+func (t *T) UnmarshalText(b []byte) error {
+	return t.FromHexString(string(b))
+}
+
+func (t T) MarshalText() (text []byte, err error) {
+	return []byte(t.HexString()), nil
+}
+
+func FromHexString(s string) (h T) {
+	err := h.FromHexString(s)
+	if err != nil {
+		panic(err)
+	}
+	return
+}
+
+func HashBytes(b []byte) (ret T) {
+	hasher := sha1.New()
+	hasher.Write(b)
+	copy(ret[:], hasher.Sum(nil))
+	return
+}