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diff --git a/vendor/maennchen/zipstream-php/guides/ContentLength.rst b/vendor/maennchen/zipstream-php/guides/ContentLength.rst
new file mode 100644
index 0000000..e51e692
--- /dev/null
+++ b/vendor/maennchen/zipstream-php/guides/ContentLength.rst
@@ -0,0 +1,79 @@
+Adding Content-Length header
+=============
+
+Adding a ``Content-Length`` header for ``ZipStream`` is not trivial since the
+size is not known beforehand.
+
+The following workaround adds an approximated header:
+
+.. code-block:: php
+
+    class Zip
+    {
+        /** @var string */
+        private $name;
+
+        private $files = [];
+
+        public function __construct($name)
+        {
+            $this->name = $name;
+        }
+
+        public function addFile($name, $data)
+        {
+            $this->files[] = ['type' => 'addFile', 'name' => $name, 'data' => $data];
+        }
+
+        public function addFileFromPath($name, $path)
+        {
+            $this->files[] = ['type' => 'addFileFromPath', 'name' => $name, 'path' => $path];
+        }
+
+        public function getEstimate()
+        {
+            $estimate = 22;
+            foreach ($this->files as $file) {
+            $estimate += 76 + 2 * strlen($file['name']);
+            if ($file['type'] === 'addFile') {
+                $estimate += strlen($file['data']);
+            }
+            if ($file['type'] === 'addFileFromPath') {
+                $estimate += filesize($file['path']);
+            }
+            }
+            return $estimate;
+        }
+
+        public function finish()
+        {
+            header('Content-Length: ' . $this->getEstimate());
+            $options = new \ZipStream\Option\Archive();
+            $options->setSendHttpHeaders(true);
+            $options->setEnableZip64(false);
+            $options->setDeflateLevel(-1);
+            $zip = new \ZipStream\ZipStream($this->name, $options);
+
+            $fileOptions = new \ZipStream\Option\File();
+            $fileOptions->setMethod(\ZipStream\Option\Method::STORE());
+            foreach ($this->files as $file) {
+            if ($file['type'] === 'addFile') {
+                $zip->addFile($file['name'], $file['data'], $fileOptions);
+            }
+            if ($file['type'] === 'addFileFromPath') {
+                $zip->addFileFromPath($file['name'], $file['path'], $fileOptions);
+            }
+            }
+            $zip->finish();
+            exit;
+        }
+    }
+
+It only works with the following constraints:
+
+- All file content is known beforehand.
+- Content Deflation is disabled
+
+Thanks to
+`partiellkorrekt <https://github.com/maennchen/ZipStream-PHP/issues/89#issuecomment-1047949274>`_
+for this workaround.
+\ No newline at end of file