从资源创建流

时间:2018-03-30 12:50:46

标签: php stream fopen psr-7 php-stream-wrappers

我知道我可以使用PHP stream函数从文件名(真实的或URL)创建fopen

$stream = fopen('php://temp', 'r');

结果流($stream)是"流" 类型的资源,由网址{{1}创建}。

但我如何从资源中创建如上所述的流?

我为什么要问这个?

我正在使用PSR-7库,我使用php://temp类实现了PSR-7 StreamInterface。为了创建Stream个实例,我决定实现Stream。其界面StreamFactoryPSR-17 (HTTP Factories)提案中定义。

StreamFactoryInterface定义了一个名为StreamFactoryInterface的方法,该方法符合其官方评论 - 应该:

  

从现有资源创建新流。

     

流必须是可读的并且可以是可写的。

因此工厂方法接收资源作为参数。并且,在其具体实现中,创建了一个新的createStreamFromResource对象 - 它也接收资源作为参数。

以下是问题:

为简单起见,我们假设Stream类仅适用于流,例如:使用" stream" 类型的资源。如果它收到的资源不属于" stream" ,则拒绝该资源。

那么,如果Stream的资源参数不是" stream" 类型的资源,该怎么办?如何将其转换为流,例如进入" stream" 类型的资源,以便我可以进一步传递它,以便用它来创建一个新的createStreamFromResource对象?是否有实现此任务的方法(PHP方法,函数或可能的转换函数)?

备注:

  • 为了清楚起见,我准备了一个完整的例子(Stream),说明我如何创建一个流,例如一个testStream.php实例,有三种方式:一次直接,两次使用流工厂。
  • 我还发布了工厂界面的具体实现:类Stream和方法StreamFactory。调用此方法应该是我在createStreamFromResource中创建流的第四种方式。
  • 此外,我提供了课程testStream.phpStream,以便您可以直接测试所有课程,如果您愿意的话。这两个类是我真实代码的一个非常简化的版本。
  • 在我的代码中,我使用 " @ ask" 标记了两个提问地点。

非常感谢您的时间和耐心!

testStream.php(测试页面)

Response

StreamFactory类(因为我有它,所以没有简化)

<?php

use Tests\Stream;
use Tests\Response;
use Tests\StreamFactory;

/*
 * ================================================
 * Option 1: Create a stream by a stream name
 * (like "php://temp") with read and write rights.
 * ================================================
 */
$stream = new Stream('php://temp', 'w+b');

$response = new Response($stream);
$response->getBody()->write(
        'Stream 1: Created directly.<br/><br/>'
);
echo $response->getBody();

/*
 * ================================================
 * Option 2: Create a stream by a stream name
 * (like "php://temp"), using a stream factory.
 * ================================================
 */
$streamFactory = new StreamFactory();
$stream = $streamFactory->createStreamFromFile('php://temp', 'w+b');

$response = new Response($stream);
$response->getBody()->write(
        'Stream 2: Created by a stream name, with a stream factory.<br/><br/>'
);
echo $response->getBody();

/*
 * ================================================
 * Option 3: Create a stream from a string, using a
 * stream factory.
 * ================================================
 */
$streamFactory = new StreamFactory();
$stream = $streamFactory->createStream(
        'Stream 3: Created from a string, with a stream factory.<br/><br/>'
);

$response = new Response($stream);
echo $response->getBody();

/*
 * ================================================
 * Option 4: Create a stream from an existing
 * resource, using a stream factory.
 * ================================================
 * 
 * @asking How can I create a stream by calling the
 * the factory method ServerFactory::createStreamFromResource
 * with a resource which is not of type "stream"?
 */
//...

Stream类(非常简化)

<?php

namespace Tests;

use Tests\Stream;
use Psr\Http\Message\StreamInterface;
use Psr\Http\Message\StreamFactoryInterface;

class StreamFactory implements StreamFactoryInterface {

    /**
     * Create a new stream from an existing resource.
     *
     * The stream MUST be readable and may be writable.
     *
     * @param resource $resource
     *
     * @return StreamInterface
     * @throws \InvalidArgumentException
     */
    public function createStreamFromResource($resource) {
        /*
         * @asking What if $resource is not already a resource of type *"stream"*? 
         * How can I transform it into a stream, e.g. into a resource of type *"stream"*, 
         * so that I can pass it further, to the call for creating a new `Stream` object 
         * with it? Is there a way (a PHP method, a function, or maybe a casting function) 
         * of achieving this task?
         */
         //...

        return new Stream($resource, 'w+b');
    }

    /**
     * Create a new stream from a string.
     *
     * The stream SHOULD be created with a temporary resource.
     *
     * @param string $content
     *
     * @return StreamInterface
     * @throws \InvalidArgumentException
     */
    public function createStream($content = '') {
        if (!isset($content) || !is_string($content)) {
            throw new \InvalidArgumentException('For creating a stream, a content string must be provided!');
        }

        $stream = $this->createStreamFromFile('php://temp', 'w+b');

        $stream->write($content);

        return $stream;
    }

    /**
     * Create a stream from an existing file.
     *
     * The file MUST be opened using the given mode, which may be any mode
     * supported by the `fopen` function.
     *
     * The `$filename` MAY be any string supported by `fopen()`.
     *
     * @param string $filename
     * @param string $mode
     *
     * @return StreamInterface
     */
    public function createStreamFromFile($filename, $mode = 'r') {
        return new Stream($filename, $mode);
    }

}

Response类(非常简化)

<?php

namespace Tests;

use Psr\Http\Message\StreamInterface;

class Stream implements StreamInterface {

    /**
     * Stream (resource).
     *
     * @var resource
     */
    private $stream;

    /**
     *
     * @param string|resource $stream Stream name, or resource.
     * @param string $accessMode (optional) Access mode.
     * @throws \InvalidArgumentException
     */
    public function __construct($stream, string $accessMode = 'r') {
        if (
                !isset($stream) ||
                (!is_string($stream) && !is_resource($stream))
        ) {
            throw new \InvalidArgumentException(
                'The provided stream must be a filename, or an opened resource of type "stream"!'
            );
        }

        if (is_string($stream)) {
            $this->stream = fopen($stream, $accessMode);
        } elseif (is_resource($stream)) {
            if ('stream' !== get_resource_type($stream)) {
                throw new \InvalidArgumentException('The provided resource must be of type "stream"!');
            }

            $this->stream = $stream;
        }
    }

    /**
     * Write data to the stream.
     *
     * @param string $string The string that is to be written.
     * @return int Returns the number of bytes written to the stream.
     * @throws \RuntimeException on failure.
     */
    public function write($string) {
        return fwrite($this->stream, $string);
    }

    /**
     * Reads all data from the stream into a string, from the beginning to end.
     *
     * @return string
     */
    public function __toString() {
        try {
            // Rewind the stream.
            fseek($this->stream, 0);

            // Get the stream contents as string.
            $contents = stream_get_contents($this->stream);

            return $contents;
        } catch (\RuntimeException $exc) {
            return '';
        }
    }

    public function close() {}
    public function detach() {}
    public function eof() {}
    public function getContents() {}
    public function getMetadata($key = null) {}
    public function getSize() {}
    public function isReadable() {}
    public function isSeekable() {}
    public function isWritable() {}
    public function read($length) {}
    public function rewind() {}
    public function seek($offset, $whence = SEEK_SET) {}
    public function tell() {}

}

3 个答案:

答案 0 :(得分:1)

您可以按照自己喜欢的方式实现它,但此方法实际上只是预生成资源的包装器。

在大多数情况下,你的Stream可能会接受一个字符串,可能还有一个settings / options数组,并根据信息创建一个流(可能在途中某处有一个fopen('http://...')

createStreamFromResource($ resource)将接收预先生成的资源(例如,来自fopen的返回资源值而不是执行fopen的数据):

class Stream implements StreamInterface {

    // ...

    public function __construct($url, $opt = null) {

        // ...

        if( is_resource( $url ) ) {

            /*
             * Check that the $resource is a valid resource
             * (e.g. an http request from an fopen call vs a mysql resource.)
             * or possibly a stream context that still needs to create a
             * request...
             */

            if( !$isValid ) {
                return false;
            }

            $this->resource = $resource;

        } else {

            // ...

            $this->resource = fopen($url, $modifiedOpt);

            // ...

        }

    }

    // ...

    /* createStreamFromResource would call Stream::fromResource($r)
     * or possibly Stream($resource) directly, your call.
     */
    static function fromResource($resource) {
        return new static($resource);
    }

}

您的工厂方法可能很简单:

public function createStreamFromResource($resource) {
    return Stream::fromResource($resource);
}

答案 1 :(得分:1)

PSR-7有很多很好的实现StreamInterface我建议先看一下。您可能会了解需要进行何种验证和逻辑。

<强>更新: 在查看所有这些链接后,我发现了您当前代码的一些问题:

  • 您必须在构造函数中检查资源类型。例如,它可能是一个MySQL资源,你不想写它:

    public function __construct($stream, string $accessMode = 'r') {
    
        if (is_string($stream)) {
            $stream = fopen($stream, $accessMode);
        }
    
        if (! is_resource($stream) || 'stream' !== get_resource_type($stream)) {
            throw new InvalidArgumentException(
                'Invalid stream provided; must be a string stream identifier or stream resource'
            );
        }
    
        $this->stream = $stream;
    }
    
  • 写入流时,检查流是否实际可写。您必须先实施isWritable方法,然后在write函数中调用它。此示例取自zend-diactoros库:

    public function isWritable()
    {
        if (! $this->resource) {
            return false;
        }
        $meta = stream_get_meta_data($this->resource);
        $mode = $meta['mode'];
        return (
            strstr($mode, 'x')
            || strstr($mode, 'w')
            || strstr($mode, 'c')
            || strstr($mode, 'a')
            || strstr($mode, '+')
        );
    }
    
  • readseek功能相同,您必须首先实施isSeekableisReadable

  • __toString还应检查流是否可读且可搜索:

    public function __toString()
    {
        if (! $this->isReadable()) {
            return '';
        }
        try {
            if ($this->isSeekable()) {
                $this->rewind();
            }
            return $this->getContents();
        } catch (RuntimeException $e) {
            return '';
        }
    } 
    

希望这会有所帮助。祝你的新图书馆好运。

答案 2 :(得分:1)

如何处理传递的参数取决于您的最终实现。如果你的代码需要一个流参数,那么它应该在它没有检测到这种情况时停止。但是,如果您的代码需要处理该问题,那么您可以尝试创建一个流。

修改

从一开始就没有得到它,但看起来问题是如果有可能转换资源变量。根据{{​​3}},这是不可能的,没有意义。