<?php
  /**
   * Copyright (c) 2014 Andreas Fischer <bantu@owncloud.com>
   * This file is licensed under the Affero General Public License version 3 or
   * later.
   * See the COPYING-README file.
   */
  
  namespace OC;
  
  /**
   * Helper class for large files on 32-bit platforms.
   */
  class LargeFileHelper {
  	/**
  	* pow(2, 53) as a base-10 string.
  	* @var string
  	*/
  	const POW_2_53 = '9007199254740992';
  
  	/**
  	* pow(2, 53) - 1 as a base-10 string.
  	* @var string
  	*/
  	const POW_2_53_MINUS_1 = '9007199254740991';
  
  	/**
  	* @brief Checks whether our assumptions hold on the PHP platform we are on.
  	*
  	* @throws \RunTimeException if our assumptions do not hold on the current
  	*                           PHP platform.
  	*/
  	public function __construct() {
  		$pow_2_53 = floatval(self::POW_2_53_MINUS_1) + 1.0;
  		if ($this->formatUnsignedInteger($pow_2_53) !== self::POW_2_53) {
  			throw new \RunTimeException(
  				'This class assumes floats to be double precision or "better".'
  			);
  		}
  	}
  
  	/**
  	* @brief Formats a signed integer or float as an unsigned integer base-10
  	*        string. Passed strings will be checked for being base-10.
  	*
  	* @param int|float|string $number Number containing unsigned integer data
  	*
  	* @throws \UnexpectedValueException if $number is not a float, not an int
  	*                                   and not a base-10 string.
  	*
  	* @return string Unsigned integer base-10 string
  	*/
  	public function formatUnsignedInteger($number) {
  		if (is_float($number)) {
  			// Undo the effect of the php.ini setting 'precision'.
  			return number_format($number, 0, '', '');
  		} else if (is_string($number) && ctype_digit($number)) {
  			return $number;
  		} else if (is_int($number)) {
  			// Interpret signed integer as unsigned integer.
  			return sprintf('%u', $number);
  		} else {
  			throw new \UnexpectedValueException(
  				'Expected int, float or base-10 string'
  			);
  		}
  	}
  
  	/**
  	* @brief Tries to get the size of a file via various workarounds that
  	*        even work for large files on 32-bit platforms.
  	*
  	* @param string $filename Path to the file.
  	*
  	* @return null|int|float Number of bytes as number (float or int) or
  	*                        null on failure.
  	*/
  	public function getFileSize($filename) {
  		$fileSize = $this->getFileSizeViaCurl($filename);
  		if (!is_null($fileSize)) {
  			return $fileSize;
  		}
  		$fileSize = $this->getFileSizeViaCOM($filename);
  		if (!is_null($fileSize)) {
  			return $fileSize;
  		}
  		$fileSize = $this->getFileSizeViaExec($filename);
  		if (!is_null($fileSize)) {
  			return $fileSize;
  		}
  		return $this->getFileSizeNative($filename);
  	}
  
  	/**
  	* @brief Tries to get the size of a file via a CURL HEAD request.
  	*
  	* @param string $filename Path to the file.
  	*
  	* @return null|int|float Number of bytes as number (float or int) or
  	*                        null on failure.
  	*/
  	public function getFileSizeViaCurl($filename) {
  		if (function_exists('curl_init')) {
  			$ch = curl_init("file://$filename");
  			curl_setopt($ch, CURLOPT_NOBODY, true);
  			curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  			curl_setopt($ch, CURLOPT_HEADER, true);
  			$data = curl_exec($ch);
  			curl_close($ch);
  			if ($data !== false) {
  				$matches = array();
  				preg_match('/Content-Length: (\d+)/', $data, $matches);
  				if (isset($matches[1])) {
  					return 0 + $matches[1];
  				}
  			}
  		}
  		return null;
  	}
  
  	/**
  	* @brief Tries to get the size of a file via the Windows DOM extension.
  	*
  	* @param string $filename Path to the file.
  	*
  	* @return null|int|float Number of bytes as number (float or int) or
  	*                        null on failure.
  	*/
  	public function getFileSizeViaCOM($filename) {
  		if (class_exists('COM')) {
  			$fsobj = new \COM("Scripting.FileSystemObject");
  			$file = $fsobj->GetFile($filename);
  			return 0 + $file->Size;
  		}
  		return null;
  	}
  
  	/**
  	* @brief Tries to get the size of a file via an exec() call.
  	*
  	* @param string $filename Path to the file.
  	*
  	* @return null|int|float Number of bytes as number (float or int) or
  	*                        null on failure.
  	*/
  	public function getFileSizeViaExec($filename) {
  		if (\OC_Helper::is_function_enabled('exec')) {
  			$os = strtolower(php_uname('s'));
  			$arg = escapeshellarg($filename);
  			$result = '';
  			if (strpos($os, 'linux') !== false) {
  				$result = $this->exec("stat -c %s $arg");
  			} else if (strpos($os, 'bsd') !== false) {
  				$result = $this->exec("stat -f %z $arg");
  			} else if (strpos($os, 'win') !== false) {
  				$result = $this->exec("for %F in ($arg) do @echo %~zF");
  				if (is_null($result)) {
  					// PowerShell
  					$result = $this->exec("(Get-Item $arg).length");
  				}
  			}
  			return $result;
  		}
  		return null;
  	}
  
  	/**
  	* @brief Gets the size of a file via a filesize() call and converts
  	*        negative signed int to positive float. As the result of filesize()
  	*        will wrap around after a file size of 2^32 bytes = 4 GiB, this
  	*        should only be used as a last resort.
  	*
  	* @param string $filename Path to the file.
  	*
  	* @return int|float Number of bytes as number (float or int).
  	*/
  	public function getFileSizeNative($filename) {
  		$result = filesize($filename);
  		if ($result < 0) {
  			// For file sizes between 2 GiB and 4 GiB, filesize() will return a
  			// negative int, as the PHP data type int is signed. Interpret the
  			// returned int as an unsigned integer and put it into a float.
  			return (float) sprintf('%u', $result);
  		}
  		return $result;
  	}
  
  	protected function exec($cmd) {
  		$result = trim(exec($cmd));
  		return ctype_digit($result) ? 0 + $result : null;
  	}
  }