Initial Bitbucket→GitHub migration commit, based on release v2.0.0.

ifid.go

@@ -0,0 +1,85 @@
+/*
+	Copyright © 2014–2019 Thomas Michael Edwards. All rights reserved.
+	Use of this source code is governed by a Simplified BSD License which
+	can be found in the LICENSE file.
+*/
+
+package main
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// IFIDs are defined in The Treaty of Babel.
+//   SEE: http://babel.ifarchive.org/
+//
+// Most IFIDs, and certainly those generated by Tweego, are simply the
+// string form of a v4 random UUID.
+
+// newIFID generates a new IFID (UUID v4).
+func newIFID() (string, error) {
+	var uuid [16]byte
+	if _, err := io.ReadFull(rand.Reader, uuid[:]); err != nil {
+		return "", err
+	}
+
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // version 4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // variant 10
+
+	return fmt.Sprintf("%X-%X-%X-%X-%X", uuid[0:4], uuid[4:6], uuid[6:8], uuid[8:10], uuid[10:]), nil
+}
+
+// validateIFID validates ifid or returns an error.
+func validateIFID(ifid string) error {
+	switch len(ifid) {
+	case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36 + 9: // UUID://xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx//
+		if strings.ToUpper(ifid[:7]) != "UUID://" || ifid[43:] != "//" {
+			return fmt.Errorf("invalid IFID UUID://…// format")
+		}
+		ifid = ifid[7:43]
+
+	default:
+		return fmt.Errorf("invalid IFID length: %d", len(ifid))
+	}
+
+	b := []byte(ifid)
+	for i := 0; i < len(b); i++ {
+		switch i {
+		// hyphens
+		case 8, 13, 18, 23:
+			if b[i] != '-' {
+				return fmt.Errorf("invalid IFID character %#U at position %d", b[i], i+1)
+			}
+
+		// version
+		case 14:
+			if '1' > b[i] || b[i] > '5' {
+				return fmt.Errorf("invalid version %#U at position %d", b[i], i+1)
+			}
+
+		// variant
+		case 19:
+			switch b[i] {
+			case '8', '9', 'a', 'A', 'b', 'B':
+			default:
+				return fmt.Errorf("invalid variant %#U at position %d", b[i], i+1)
+			}
+
+		// regular hex character
+		default:
+			switch {
+			case '0' <= b[i] && b[i] <= '9':
+			case 'a' <= b[i] && b[i] <= 'f':
+			case 'A' <= b[i] && b[i] <= 'F':
+			default:
+				return fmt.Errorf("invalid IFID hex value %#U at position %d", b[i], i+1)
+			}
+		}
+	}
+
+	return nil
+}