[Uid] Ensure ULIDs are monotonic even when the time goes backward

nicolas-grekas · nicolas-grekas · commit ceb74346f0d9 · 2022-09-08T20:46:13.000+02:00
diff --git a/src/Symfony/Component/Uid/Tests/UlidTest.php b/src/Symfony/Component/Uid/Tests/UlidTest.php
@@ -26,11 +26,16 @@ public function testGenerate()
     {
         $a = new Ulid();
         $b = new Ulid();
+        usleep(-10000);
+        $c = new Ulid();
 
         $this->assertSame(0, strncmp($a, $b, 20));
+        $this->assertSame(0, strncmp($a, $c, 20));
         $a = base_convert(strtr(substr($a, -6), 'ABCDEFGHJKMNPQRSTVWXYZ', 'abcdefghijklmnopqrstuv'), 32, 10);
         $b = base_convert(strtr(substr($b, -6), 'ABCDEFGHJKMNPQRSTVWXYZ', 'abcdefghijklmnopqrstuv'), 32, 10);
+        $c = base_convert(strtr(substr($c, -6), 'ABCDEFGHJKMNPQRSTVWXYZ', 'abcdefghijklmnopqrstuv'), 32, 10);
         $this->assertSame(1, $b - $a);
+        $this->assertSame(1, $c - $b);
     }
 
     public function testWithInvalidUlid()
diff --git a/src/Symfony/Component/Uid/Ulid.php b/src/Symfony/Component/Uid/Ulid.php
@@ -137,7 +137,7 @@ public function getDateTime(): \DateTimeImmutable
         }
 
         if (4 > \strlen($time)) {
-            $time = str_pad($time, 4, '0', \STR_PAD_LEFT);
+            $time = '000'.$time;
         }
 
         return \DateTimeImmutable::createFromFormat('U.u', substr_replace($time, '.', -3, 0));
@@ -149,7 +149,7 @@ public static function generate(\DateTimeInterface $time = null): string
             return self::doGenerate();
         }
 
-        if (0 > $time = substr($time->format('Uu'), 0, -3)) {
+        if (0 > $time = $time->format('Uv')) {
             throw new \InvalidArgumentException('The timestamp must be positive.');
         }
 
@@ -163,7 +163,7 @@ private static function doGenerate(string $mtime = null): string
             $time = substr($time, 11).substr($time, 2, 3);
         }
 
-        if ($time !== self::$time) {
+        if ($time > self::$time || (null !== $mtime && $time !== self::$time)) {
             $r = unpack('nr1/nr2/nr3/nr4/nr', random_bytes(10));
             $r['r1'] |= ($r['r'] <<= 4) & 0xF0000;
             $r['r2'] |= ($r['r'] <<= 4) & 0xF0000;
@@ -186,6 +186,7 @@ private static function doGenerate(string $mtime = null): string
             }
 
             ++self::$rand[$i];
+            $time = self::$time;
         }
 
         if (\PHP_INT_SIZE >= 8) {

Original file line number	Diff line number	Diff line change
`@@ -137,7 +137,7 @@ public function getDateTime(): \DateTimeImmutable`
`137`	`137`	`}`
`138`	`138`
`139`	`139`	`if (4 > \strlen($time)) {`
`140`		`- $time = str_pad($time, 4, '0', \STR_PAD_LEFT);`
	`140`	`+ $time = '000'.$time;`
`141`	`141`	`}`
`142`	`142`
`143`	`143`	`return \DateTimeImmutable::createFromFormat('U.u', substr_replace($time, '.', -3, 0));`
`@@ -149,7 +149,7 @@ public static function generate(\DateTimeInterface $time = null): string`
`149`	`149`	`return self::doGenerate();`
`150`	`150`	`}`
`151`	`151`
`152`		`- if (0 > $time = substr($time->format('Uu'), 0, -3)) {`
	`152`	`+ if (0 > $time = $time->format('Uv')) {`
`153`	`153`	`throw new \InvalidArgumentException('The timestamp must be positive.');`
`154`	`154`	`}`
`155`	`155`
`@@ -163,7 +163,7 @@ private static function doGenerate(string $mtime = null): string`
`163`	`163`	`$time = substr($time, 11).substr($time, 2, 3);`
`164`	`164`	`}`
`165`	`165`
`166`		`- if ($time !== self::$time) {`
	`166`	`+ if ($time > self::$time \|\| (null !== $mtime && $time !== self::$time)) {`
`167`	`167`	`$r = unpack('nr1/nr2/nr3/nr4/nr', random_bytes(10));`
`168`	`168`	`$r['r1'] \|= ($r['r'] <<= 4) & 0xF0000;`
`169`	`169`	`$r['r2'] \|= ($r['r'] <<= 4) & 0xF0000;`
`@@ -186,6 +186,7 @@ private static function doGenerate(string $mtime = null): string`
`186`	`186`	`}`
`187`	`187`
`188`	`188`	`++self::$rand[$i];`
	`189`	`+ $time = self::$time;`
`189`	`190`	`}`
`190`	`191`
`191`	`192`	`if (\PHP_INT_SIZE >= 8) {`