move implementation to internal/ directory (#828)

internal/zfs/property/property.go

@@ -0,0 +1,33 @@
+package property
+
+import (
+	"fmt"
+	"regexp"
+)
+
+type Property string
+
+// Check property name conforms to zfsprops(8), section "User Properties"
+// Keep regex and error message in sync!
+var (
+	propertyValidNameChars    = regexp.MustCompile(`^[0-9a-zA-Z-_\.:]+$`)
+	propertyValidNameCharsErr = fmt.Errorf("property name must only contain alphanumeric chars and any in %q", "-_.:")
+)
+
+func (p Property) Validate() error {
+	const PROPERTYNAMEMAXLEN int = 256
+
+	if len(p) < 1 {
+		return fmt.Errorf("property name cannot be empty")
+	}
+	if len(p) > PROPERTYNAMEMAXLEN {
+		return fmt.Errorf("property name longer than %d characters", PROPERTYNAMEMAXLEN)
+	}
+	if p[0] == '-' {
+		return fmt.Errorf("property name cannot start with '-'")
+	}
+	if !propertyValidNameChars.MatchString(string(p)) {
+		return propertyValidNameCharsErr
+	}
+	return nil
+}