prevent preg_replace() calls when cache is not enabled

src/Composer/Cache.php

@@ -71,12 +71,14 @@ class Cache
 
     public function read($file)
     {
+        if ($this->enabled) {
             $file = preg_replace('{[^'.$this->whitelist.']}i', '-', $file);
-        if ($this->enabled && file_exists($this->root . $file)) {
+            if (file_exists($this->root . $file)) {
                 $this->io->writeError('Reading '.$this->root . $file.' from cache', true, IOInterface::DEBUG);
 
                 return file_get_contents($this->root . $file);
             }
+        }
 
         return false;
     }
@@ -142,8 +144,9 @@ class Cache
      */
     public function copyTo($file, $target)
     {
+        if ($this->enabled) {
             $file = preg_replace('{[^'.$this->whitelist.']}i', '-', $file);
-        if ($this->enabled && file_exists($this->root . $file)) {
+            if (file_exists($this->root . $file)) {
                 try {
                     touch($this->root . $file, filemtime($this->root . $file), time());
                 } catch (\ErrorException $e) {
@@ -156,6 +159,7 @@ class Cache
 
                 return copy($this->root . $file, $target);
             }
+        }
 
         return false;
     }
@@ -167,10 +171,12 @@ class Cache
 
     public function remove($file)
     {
+        if ($this->enabled) {
             $file = preg_replace('{[^'.$this->whitelist.']}i', '-', $file);
-        if ($this->enabled && file_exists($this->root . $file)) {
+            if (file_exists($this->root . $file)) {
                 return $this->filesystem->unlink($this->root . $file);
             }
+        }
 
         return false;
     }
@@ -216,20 +222,24 @@ class Cache
 
     public function sha1($file)
     {
+        if ($this->enabled) {
             $file = preg_replace('{[^'.$this->whitelist.']}i', '-', $file);
-        if ($this->enabled && file_exists($this->root . $file)) {
+            if (file_exists($this->root . $file)) {
                 return sha1_file($this->root . $file);
             }
+        }
 
         return false;
     }
 
     public function sha256($file)
     {
+        if ($this->enabled) {
             $file = preg_replace('{[^'.$this->whitelist.']}i', '-', $file);
-        if ($this->enabled && file_exists($this->root . $file)) {
+            if (file_exists($this->root . $file)) {
                 return hash_file('sha256', $this->root . $file);
             }
+        }
 
         return false;
     }