uuid: Add 'uuid=?' and use it.

* gnu/system/uuid.scm (uuid=?): New procedure.
* tests/uuid.scm ("uuid=?"): New test.
* gnu/build/file-systems.scm (partition-uuid-predicate)
(luks-partition-uuid-predicate): Use it instead of 'bytevector=?'.

gnu/build/file-systems.scm

@@ -415,12 +415,12 @@ (define partition-label-predicate
   (partition-predicate read-partition-label string=?))
 
 (define partition-uuid-predicate
-  (partition-predicate read-partition-uuid bytevector=?))
+  (partition-predicate read-partition-uuid uuid=?))
 
 (define luks-partition-uuid-predicate
   (partition-predicate
    (partition-field-reader read-luks-header luks-header-uuid)
-   bytevector=?))
+   uuid=?))
 
 (define (find-partition predicate)
   "Return the first partition found that matches PREDICATE, or #f if none

gnu/system/uuid.scm

@@ -29,6 +29,7 @@ (define-module (gnu system uuid)
             uuid?
             uuid-type
             uuid-bytevector
+            uuid=?
 
             bytevector->uuid
 
@@ -281,3 +282,15 @@ (define uuid->string
        ((_ . (? procedure? unparse)) (unparse bv))))
     (((? uuid? uuid))
      (uuid->string (uuid-bytevector uuid) (uuid-type uuid)))))
+
+(define uuid=?
+  ;; Return true if A is equal to B, comparing only the actual bits.
+  (match-lambda*
+    (((? bytevector? a) (? bytevector? b))
+     (bytevector=? a b))
+    (((? uuid? a) (? bytevector? b))
+     (bytevector=? (uuid-bytevector a) b))
+    (((? uuid? a) (? uuid? b))
+     (bytevector=? (uuid-bytevector a) (uuid-bytevector b)))
+    ((a b)
+     (uuid=? b a))))

tests/uuid.scm

@@ -57,4 +57,10 @@ (define-module (test-uuid)
   "1234-ABCD"
   (uuid->string (uuid "1234-abcd" 'fat32)))
 
+(test-equal "uuid=?"
+  (and (uuid=? (uuid-bytevector (uuid "1234-abcd" 'fat32))
+               (uuid "1234-abcd" 'fat32))
+       (uuid=? (uuid "1234-abcd" 'fat32)
+               (uuid "1234-abcd" 'fat))))
+
 (test-end)