Implement Buffer

refs #13623

library/Icinga/Util/Buffer.php

@@ -0,0 +1,176 @@
+<?php
+/* Icinga Web 2 | (c) 2016 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Util;
+
+use Icinga\Exception\IcingaException;
+
+/**
+ * Stores data in memory or a temporary file not to get out of memory
+ */
+class Buffer
+{
+    /**
+     * The actual buffer
+     *
+     * @var resource
+     */
+    protected $handle;
+
+    /**
+     * The amount of bytes currently stored in the buffer
+     *
+     * @var int
+     */
+    protected $size = 0;
+
+    /**
+     * Whether the current position of {@link handle} is the end of file
+     *
+     * @var bool
+     */
+    protected $atEOF = true;
+
+    /**
+     * Buffer constructor
+     */
+    public function __construct()
+    {
+        $this->handle = fopen('php://temp', 'w+b');
+    }
+
+    /**
+     * Append the given data to the buffer
+     *
+     * @param   string  $data
+     */
+    public function append($data)
+    {
+        $strlen = strlen($data);
+        if ($strlen) {
+            $this->seekToEnd();
+            $this->fwrite($this->handle, $data);
+            $this->size += $strlen;
+        }
+    }
+
+    /**
+     * Get size
+     *
+     * @return int
+     */
+    public function getSize()
+    {
+        return $this->size;
+    }
+
+    /**
+     * Get the data stored in the buffer
+     *
+     * @return  string
+     *
+     * @throws  IcingaException     In case of an error
+     */
+    public function __toString()
+    {
+        $result = '';
+
+        if ($this->size) {
+            $this->seekToBegin();
+            for (;;) {
+                $buf = fread($this->handle, $this->size);
+                if ($buf === '') {
+                    break;
+                }
+                $result .= $buf;
+            }
+
+            if (strlen($result) !== $this->size) {
+                throw new IcingaException('Couldn\'t read all data from the buffer');
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * Pass the data stored in the buffer to the user agent (as with {@link fpassthru()})
+     */
+    public function fpassthru()
+    {
+        if ($this->size) {
+            $this->seekToBegin();
+            // fpassthru() returns the amount of bytes passed so we could perform
+            // the same error check as in __toString(), but throwing exceptions here
+            // makes no sense as we're already writing the response body
+            fpassthru($this->handle);
+        }
+    }
+
+    /**
+     * fseek({@link handle}) to the begin of the buffer if not already done
+     */
+    protected function seekToBegin()
+    {
+        if ($this->atEOF) {
+            if ($this->size) {
+                $this->fseek($this->handle, 0);
+            }
+            $this->atEOF = false;
+        }
+    }
+
+    /**
+     * fseek({@link handle}) to the end of the buffer if not already done
+     */
+    protected function seekToEnd()
+    {
+        if (! $this->atEOF) {
+            if ($this->size) {
+                $this->fseek($this->handle, 0, SEEK_END);
+            }
+            $this->atEOF = true;
+        }
+    }
+
+    /**
+     * Forwards all passed parameters to {@link fseek()}
+     *
+     * @throws  IcingaException     In case of an error
+     */
+    protected function fseek()
+    {
+        if (call_user_func_array('fseek', func_get_args()) === -1) {
+            $this->reportFunctionCallError('fseek', func_get_args());
+        }
+    }
+
+    /**
+     * Forwards all passed parameters to {@link fwrite()}
+     *
+     * @throws  IcingaException     In case of an error
+     */
+    protected function fwrite()
+    {
+        if (call_user_func_array('fwrite', func_get_args()) === 0) {
+            $this->reportFunctionCallError('fwrite', func_get_args());
+        }
+    }
+
+    /**
+     * Throw an exception telling that the given function call didn't succeed
+     *
+     * @param   string  $functionName
+     * @param   array   $passedArgs
+     *
+     * @throws  IcingaException     unconditional
+     */
+    protected function reportFunctionCallError($functionName, array $passedArgs)
+    {
+        $args = array();
+        foreach ($passedArgs as $arg) {
+            $args[] = print_r($arg, true);
+        }
+        throw new IcingaException('Couldn\'t ' . $functionName . '(' . implode(', ', $args) . ')');
+    }
+}