fix base32 encode/decode

[live627]

test script

<?php

declare(strict_types=1);

use SMF\Uuid;

require_once __DIR__ . '/Uuid.php';

/**
 * Verify equality.
 */
function assertEqual(
	mixed $expected,
	mixed $actual,
	string $message
): void {
	if ($expected !== $actual) {
		throw new RuntimeException(
			$message .
			PHP_EOL .
			'Expected: ' . var_export($expected, true) .
			PHP_EOL .
			'Actual:   ' . var_export($actual, true)
		);
	}
}

/******************************************************************************
 * Base32 encode/decode correctness tests
 *****************************************************************************/

echo PHP_EOL;
echo "Running Base32 correctness tests..." . PHP_EOL;

/**
 * Test vectors.
 */
$vectors = [

	/******************************************************************************
	 * Nil UUID
	 *****************************************************************************/

	'00000000-0000-0000-0000-000000000000',

	/******************************************************************************
	 * Max UUID
	 *****************************************************************************/

	'ffffffff-ffff-ffff-ffff-ffffffffffff',

	/******************************************************************************
	 * RFC example UUIDs
	 *****************************************************************************/

	'6ba7b810-9dad-11d1-80b4-00c04fd430c8',
	'6ba7b811-9dad-11d1-80b4-00c04fd430c8',
	'6ba7b812-9dad-11d1-80b4-00c04fd430c8',

	/******************************************************************************
	 * Random fixed UUIDs
	 *****************************************************************************/

	'019e0e2e-4a3a-7fb1-8754-29d817add942',
	'12345678-1234-5678-9abc-def012345678',
	'aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee',
	'deadbeef-cafe-babe-face-0123456789ab',

	/******************************************************************************
	 * Leading zero stress
	 *****************************************************************************/

	'00000001-0000-0000-0000-000000000000',
	'00000000-0000-0000-0000-000000000001',
	'00000000-0000-0000-0000-ffffffffffff',

	/******************************************************************************
	 * Trailing bit stress
	 *****************************************************************************/

	'ffffffff-ffff-ffff-ffff-fffffffffffe',
	'ffffffff-ffff-ffff-ffff-ffffffffffff',
];

/******************************************************************************
 * Test both implementations
 *****************************************************************************/

echo PHP_EOL;
echo "Testing {Uuid}" . PHP_EOL;

foreach ($vectors as $uuid) {

	/******************************************************************************
	 * Encode
	 *****************************************************************************/

	$b32 = Uuid::compress(
		$uuid,
		Uuid::COMPRESS_BASE32
	);

	/******************************************************************************
	 * Length check
	 *****************************************************************************/

	assertEqual(
		26,
		strlen($b32),
		"Base32 length mismatch for {$uuid}"
	);

	/******************************************************************************
	 * Character set check
	 *****************************************************************************/

	if (
		strspn(
			$b32,
			Uuid::BASE32_ALT
		) !== 26
	) {
		throw new RuntimeException(
			"Invalid Base32 chars for {$uuid}: {$b32}"
		);
	}

	/******************************************************************************
	 * Decode
	 *****************************************************************************/

	$expanded = Uuid::expand($b32);

	/******************************************************************************
	 * Roundtrip check
	 *****************************************************************************/

	assertEqual(
		strtolower($uuid),
		strtolower($expanded),
		"Base32 roundtrip failed"
	);

	/******************************************************************************
	 * Stability check
	 *****************************************************************************/

	$b32_2 = Uuid::compress(
		$expanded,
		Uuid::COMPRESS_BASE32
	);

	assertEqual(
		$b32,
		$b32_2,
		"Base32 stability failed"
	);
}

echo "  OK" . PHP_EOL;

/******************************************************************************
 * Random fuzz tests
 *****************************************************************************/

echo PHP_EOL;
echo "Running Base32 fuzz tests..." . PHP_EOL;

for ($i = 0; $i < 10000; $i++) {

	/******************************************************************************
	 * Generate UUID
	 *****************************************************************************/

	$uuid = (string) new Uuid(7);

	/******************************************************************************
	 * Encode/decode
	 *****************************************************************************/

	$b32 = Uuid::compress(
		$uuid,
		Uuid::COMPRESS_BASE32
	);

	$expanded = Uuid::expand($b32);

	/******************************************************************************
	 * Verify exact roundtrip
	 *****************************************************************************/

	assertEqual(
		strtolower($uuid),
		strtolower($expanded),
		"Fuzz roundtrip failed at iteration {$i}"
	);
}

echo "Fuzz tests passed." . PHP_EOL;

[Sesquipedalian]

Dang. After further testing, I realized that this actually produces incorrect output, @live627. That's because your algorithm proceeds from the first byte to the last byte, but it actually needs to proceed from the last byte to the first byte. I'm going to have to revert this.