Monday, April 25, 2011

Damn Data::UUID

The Data::UUID module has the annoying behavior that it will not fail if you provide an invalid namespace when creating a v3 UUID. It will generate a UUID, but depending on the circumstances it may generate a different UUID in subsequent calls. Consider the following example:

use strict;
use warnings;

use Data::UUID;
use UUID::Tiny;

sub v3_data_uuid {
    my $namespace = shift;
    my $name = shift;
    my $ug = shift;
    $ug = new Data::UUID unless defined $ug; 
    return lc($ug->create_from_name_str($namespace, $name));

sub v3_uuid_tiny {
    my $namespace = shift;
    my $name = shift;
    return UUID_to_string(create_UUID(UUID_V3, $namespace, $name));

# Generate a v3 UUID using Data::UUID
print "Data::UUID\n";
my $ug = new Data::UUID;
print '  1. ', lc($ug->create_from_name_str(UUID_NS_DNS, 'abc')), "\n";
print '  2. ', lc($ug->create_from_name_str(UUID_NS_DNS, 'abc')), "\n";
print '  3. ', v3_data_uuid(UUID_NS_DNS, 'abc'), "\n";
print '  4. ', v3_data_uuid(UUID_NS_DNS, 'abc'), "\n";
print '  5. ', v3_data_uuid(UUID_NS_DNS, 'abc', $ug), "\n";

# Generate a v3 UUID using UUID::Tiny
print "UUID::Tiny\n";
print '  1. ', UUID_to_string(create_UUID(UUID_V3, UUID_NS_DNS, 'abc')), "\n";
print '  2. ', UUID_to_string(create_UUID(UUID_V3, UUID_NS_DNS, 'abc')), "\n";
print '  3. ', v3_uuid_tiny(UUID_NS_DNS, 'abc'), "\n";
print '  4. ', v3_uuid_tiny(UUID_NS_DNS, 'abc'), "\n";

# Generate a v3 UUID using Data::UUID with an invalid namespace
print "Data::UUID - bad namespace\n";
my $namespace = 'namespace';
print '  1. ', lc($ug->create_from_name_str($namespace, 'abc')), "\n";
print '  2. ', lc($ug->create_from_name_str($namespace, 'abc')), "\n";
print '  3. ', v3_data_uuid($namespace, 'abc'), "\n";
print '  4. ', v3_data_uuid($namespace, 'abc'), "\n";
print '  5. ', v3_data_uuid($namespace, 'abc', $ug), "\n";

# Generate a v3 UUID using UUID::Tiny with an invalid namespace
print "UUID::Tiny - bad namespace\n";
print '  1. ', UUID_to_string(create_UUID(UUID_V3, $namespace, 'abc')), "\n";
This example also uses UUID::Tiny as a point of comparison. The output that I get when running this example is:
$ ./ 
  1. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  2. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  3. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  4. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  5. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  1. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  2. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  3. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  4. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
Data::UUID - bad namespace
  1. 15da4c6e-29ae-3f6c-a7ed-ec36373d4e5d
  2. 15da4c6e-29ae-3f6c-a7ed-ec36373d4e5d
  3. 8fa130be-2517-3e29-a087-c7d75545a62c
  4. 8fa130be-2517-3e29-a087-c7d75545a62c
  5. 8fa130be-2517-3e29-a087-c7d75545a62c
UUID::Tiny - bad namespace
UUID::Tiny::string_to_uuid(): 'namespace' is no UUID string! at ./ line 50
When a valid UUID is used for the namespace, Data::UUID consistently generates the same value. However, if I pass in a bad value such as the string literal namespace, then I get different values depending on how/where/when it is called. UUID::Tiny on the other hand dies with a nice error message telling me exactly what is wrong.

Polls and Research on Public Acceptance of Evolution

It was brought to my attention that my post on the acceptance of evolution by state was cited in an ASA article Polls and Research on Public Acceptance of Evolution. The article provides a summary of around 50 sites discussing the public acceptance of evolution. The ASA, American Scientific Affiliation, is an organization of Christian scientists so I would guess they have some bias towards creationism. That said, this is the first time I have heard of the ASA and their article seems to provide a fair summary of the findings presented.