Re: [Qemu-devel] [PATCH] util: add is_equal to UUID API

[Thomas Huth]

On 24.11.2017 15:32, Roman Kagan wrote:
> It's going to be useful, in particular, in VMBus code massively using
> uuids aka GUIDs.
> 
> Signed-off-by: Roman Kagan <address@hidden>
> ---
>  include/qemu/uuid.h |  2 ++
>  tests/test-uuid.c   | 24 ++++++++++++++++++++++++
>  util/uuid.c         |  7 ++++++-
>  3 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h
> index afe4840296..09489ce5c5 100644
> --- a/include/qemu/uuid.h
> +++ b/include/qemu/uuid.h
> @@ -48,6 +48,8 @@ void qemu_uuid_generate(QemuUUID *out);
>  
>  int qemu_uuid_is_null(const QemuUUID *uu);
>  
> +int qemu_uuid_is_equal(const QemuUUID *lhv, const QemuUUID *rhv);
> +
>  void qemu_uuid_unparse(const QemuUUID *uuid, char *out);
>  
>  char *qemu_uuid_unparse_strdup(const QemuUUID *uuid);
> diff --git a/tests/test-uuid.c b/tests/test-uuid.c
> index d3a2791fd4..c6c8148117 100644
> --- a/tests/test-uuid.c
> +++ b/tests/test-uuid.c
> @@ -116,6 +116,29 @@ static void test_uuid_is_null(void)
>      g_assert_false(qemu_uuid_is_null(&uuid_not_null_2));
>  }
>  
> +static void test_uuid_is_equal(void)
> +{
> +    int i;
> +    QemuUUID uuid;
> +    QemuUUID uuid_null = { };
> +    QemuUUID uuid_not_null = { { {
> +        0x58, 0x6e, 0xce, 0x27, 0x7f, 0x09, 0x41, 0xe0,
> +        0x9e, 0x74, 0xe9, 0x01, 0x31, 0x7e, 0x9d, 0x42
> +    } } };
> +    QemuUUID uuid_null_2 = uuid_null;
> +    QemuUUID uuid_not_null_2 = uuid_not_null;
> +
> +    g_assert(qemu_uuid_is_equal(&uuid_null, &uuid_null_2));
> +    g_assert(qemu_uuid_is_equal(&uuid_not_null, &uuid_not_null_2));
> +    g_assert_false(qemu_uuid_is_equal(&uuid_null, &uuid_not_null));
> +
> +    for (i = 0; i < 100; ++i) {
> +        qemu_uuid_generate(&uuid);
> +        g_assert_false(qemu_uuid_is_equal(&uuid_null, &uuid));
> +        g_assert_false(qemu_uuid_is_equal(&uuid_not_null, &uuid));

Isn't there a very low chance that the last line triggers by accident?
Or uuid_no_null guaranteed to not match the generated one? In the latter
case, a comment with a short explanation might be helpful here...

 Thomas