Calculate ZIP Size (maennchen#241)

Calculates the resulting file size with the minimal amount of work
that is required.

Fixes maennchen#89

Author: maennchen

guides/ContentLength.rst

@@ -1,85 +1,47 @@
 Adding Content-Length header
 =============
 
-Adding a ``Content-Length`` header for ``ZipStream`` is not trivial since the
-size is not known beforehand.
+Adding a ``Content-Length`` header for ``ZipStream`` can be achieved by
+using the options ``SIMULATION_STRICT`` or ``SIMULATION_LAX`` in the
+``operationMode`` parameter.
 
-The following workaround adds an approximated header:
+In the ``SIMULATION_STRICT`` mode, ``ZipStream`` will not allow to calculate the
+size based on reading the whole file. ``SIMULATION_LAX`` will read the whole
+file if neccessary.
 
-.. code-block:: php
+``SIMULATION_STRICT`` is therefore useful to make sure that the size can be
+calculated efficiently.
 
-    use ZipStream\CompressionMethod;
+.. code-block:: php
+    use ZipStream\OperationMode;
     use ZipStream\ZipStream;
 
-    class Zip
-        {
-        private $files = [];
-
-        public function __construct(
-            private readonly string $name
-        ) { }
-
-        public function addFile(
-            string $name,
-            string $data,
-        ): void {
-            $this->files[] = ['type' => 'addFile', 'name' => $name, 'data' => $data];
-        }
-
-        public function addFileFromPath(
-            string $name,
-            string $path,
-        ): void {
-            $this->files[] = ['type' => 'addFileFromPath', 'name' => $name, 'path' => $path];
+    $zip = new ZipStream(
+        operationMode: OperationMode::SIMULATE_STRICT, // or SIMULATE_LAX
+        defaultEnableZeroHeader: false,
+        sendHttpHeaders: true,
+        outputStream: $stream,
+    );
+
+    // Normally add files
+    $zip->addFile('sample.txt', 'Sample String Data');
+
+    // Use addFileFromCallback and exactSize if you want to defer opening of
+    // the file resource
+    $zip->addFileFromCallback(
+        'sample.txt',
+        exactSize: 18,
+        callback: function () {
+            return fopen('...');
         }
+    );
 
-        public function getEstimate(): int {
-            $estimate = 22;
-            foreach ($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());
-            $zip = new ZipStream(
-                outputName: $this->name,
-                SendHttpHeaders: true,
-                enableZip64: false,
-                defaultCompressionMethod: CompressionMethod::STORE,
-            );
-
-            foreach ($this->files as $file) {
-                if ($file['type'] === 'addFile') {
-                    $zip->addFile(
-                        fileName: $file['name'],
-                        data: $file['data'],
-                    );
-                }
-                if ($file['type'] === 'addFileFromPath') {
-                    $zip->addFileFromPath(
-                        fileName: $file['name'],
-                        path: $file['path'],
-                    );
-                }
-            }
-            $zip->finish();
-        }
-    }
-
-It only works with the following constraints:
-
-- All file content is known beforehand.
-- Content Deflation is disabled
+    // Read resulting file size
+    $size = $zip->finish();
+    
+    // Tell it to the browser
+    header('Content-Length: '. $size);
+    
+    // Execute the Simulation and stream the actual zip to the client
+    $zip->executeSimulation();
 
-Thanks to
-`partiellkorrekt <https://github.com/maennchen/ZipStream-PHP/issues/89#issuecomment-1047949274>`_
-for this workaround.

psalm.xml

@@ -18,5 +18,6 @@
         <!-- Turn off dead code warnings for externally called functions -->
         <PossiblyUnusedProperty errorLevel="suppress" />
         <PossiblyUnusedMethod errorLevel="suppress" />
+        <PossiblyUnusedReturnValue errorLevel="suppress" />
     </issueHandlers>
 </psalm>

src/Exception/FileSizeIncorrectException.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ZipStream\Exception;
+
+use ZipStream\Exception;
+
+/**
+ * This Exception gets invoked if a file is not as large as it was specified.
+ */
+class FileSizeIncorrectException extends Exception
+{
+    /**
+     * @internal
+     */
+    public function __construct(
+        public readonly int $expectedSize,
+        public readonly int $actualSize
+    ) {
+        parent::__construct("File is {$actualSize} instead of {$expectedSize} bytes large. Adjust `exactSize` parameter.");
+    }
+}

src/Exception/SimulationFileUnknownException.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ZipStream\Exception;
+
+use ZipStream\Exception;
+
+/**
+ * This Exception gets invoked if a strict simulation is executed and the file
+ * information can't be determined without reading the entire file.
+ */
+class SimulationFileUnknownException extends Exception
+{
+    public function __construct()
+    {
+        parent::__construct('The details of the strict simulation file could not be determined without reading the entire file.');
+    }
+}