minor #21748 Refactor file constraint logic (greg0ire)

This PR was submitted for the 2.7 branch but it was merged into the 3.3-dev branch instead (closes #21748).

Discussion
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Refactor file constraint logic

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

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These are pedantic changes done in #21747 , which turned out to be useless.

Commits
-------

b717d7c Refactor file constraint logic

src/Symfony/Component/Validator/Constraints/File.php

@@ -88,23 +88,18 @@ public function __get($option)
 
     private function normalizeBinaryFormat($maxSize)
     {
-        $sizeInt = (int) $maxSize;
-
+        $factors = array(
+            'k' => 1000,
+            'ki' => 1 << 10,
+            'm' => 1000000,
+            'mi' => 1 << 20,
+        );
         if (ctype_digit((string) $maxSize)) {
-            $this->maxSize = $sizeInt;
-            $this->binaryFormat = null === $this->binaryFormat ? false : $this->binaryFormat;
-        } elseif (preg_match('/^\d++k$/i', $maxSize)) {
-            $this->maxSize = $sizeInt * 1000;
-            $this->binaryFormat = null === $this->binaryFormat ? false : $this->binaryFormat;
-        } elseif (preg_match('/^\d++M$/i', $maxSize)) {
-            $this->maxSize = $sizeInt * 1000000;
+            $this->maxSize = (int) $maxSize;
             $this->binaryFormat = null === $this->binaryFormat ? false : $this->binaryFormat;
-        } elseif (preg_match('/^\d++Ki$/i', $maxSize)) {
-            $this->maxSize = $sizeInt << 10;
-            $this->binaryFormat = null === $this->binaryFormat ? true : $this->binaryFormat;
-        } elseif (preg_match('/^\d++Mi$/i', $maxSize)) {
-            $this->maxSize = $sizeInt << 20;
-            $this->binaryFormat = null === $this->binaryFormat ? true : $this->binaryFormat;
+        } elseif (preg_match('/^(\d++)('.implode('|', array_keys($factors)).')$/i', $maxSize, $matches)) {
+            $this->maxSize = $matches[1] * $factors[$unit = strtolower($matches[2])];
+            $this->binaryFormat = null === $this->binaryFormat ? 2 === strlen($unit) : $this->binaryFormat;
         } else {
             throw new ConstraintDefinitionException(sprintf('"%s" is not a valid maximum size', $this->maxSize));
         }