Re: [libvirt] [PATCH v3] Add host UUID (to libvirt capabilities)
On 05/25/2010 08:26 AM, Daniel P. Berrange wrote:
+
+# UUID of the host:
+# Provide the UUID of the host here in case the command
+# 'dmidecode -s system-uuid' does not provide a valid uuid. In case
+# 'dmidecode' does not provide a valid UUID and none is provided here, a
+# temporary UUID will be generated.
+# Keep the format of the example UUID below. UUID must not have all digits
+# be the same.
+
+#host_uuid = "8510b1a1-1afa-4da6-8111-785fae202c1e"
What's the likelihood that people just uncomment this line, and this
becomes a very common "uuid" that is no longer unique?
http://www.snopes.com/business/taxes/woolworth.asp
The sample is worthwhile, to show the locations where - must appear, but
is it any better to write the sample as a known-invalid string, with all
digits the same?
+
+/**
+ * virUUIDIsValid
+ *
+ * @uuid: The UUID to test
+ *
+ * Do some basic tests to check whether the given UUID is
+ * valid as a host UUID.
+ * Basic tests:
+ * - Not all of the digits may be equal
+ */
+int
+virUUIDIsValid(unsigned char *uuid)
+{
+ unsigned int i, ctr = 1;
+ unsigned char c;
+
+ if (!uuid)
+ return 0;
+
+ c = uuid[0];
+
+ for (i = 1; i < VIR_UUID_BUFLEN; i++)
+ if (uuid[i] == c)
+ ctr++;
+
+ return (ctr != VIR_UUID_BUFLEN);
Is it worth the micro-optimization of breaking out of the loop on the
first uuid[i] != c, rather than parsing the entire string? That way,
you would only need two or three comparisons on the common case, rather
than a full 32.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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