<?php



namespace Psr\Http\Message;



/**

 * Describes a data stream.

 *

 * Typically, an instance will wrap a PHP stream; this interface provides

 * a wrapper around the most common operations, including serialization of

 * the entire stream to a string.

 */

interface StreamInterface

{

    /**

     * Reads all data from the stream into a string, from the beginning to end.

     *

     * This method MUST attempt to seek to the beginning of the stream before

     * reading data and read the stream until the end is reached.

     *

     * Warning: This could attempt to load a large amount of data into memory.

     *

     * This method MUST NOT raise an exception in order to conform with PHP's

     * string casting operations.

     *

     * @see http://php.net/manual/en/language.oop5.magic.php#object.tostring

     * @return string

     */

    public function __toString();



    /**

     * Closes the stream and any underlying resources.

     *

     * @return void

     */

    public function close();



    /**

     * Separates any underlying resources from the stream.

     *

     * After the stream has been detached, the stream is in an unusable state.

     *

     * @return resource|null Underlying PHP stream, if any

     */

    public function detach();



    /**

     * Get the size of the stream if known.

     *

     * @return int|null Returns the size in bytes if known, or null if unknown.

     */

    public function getSize();



    /**

     * Returns the current position of the file read/write pointer

     *

     * @return int Position of the file pointer

     * @throws \RuntimeException on error.

     */

    public function tell();



    /**

     * Returns true if the stream is at the end of the stream.

     *

     * @return bool

     */

    public function eof();



    /**

     * Returns whether or not the stream is seekable.

     *

     * @return bool

     */

    public function isSeekable();



    /**

     * Seek to a position in the stream.

     *

     * @link http://www.php.net/manual/en/function.fseek.php

     * @param int $offset Stream offset

     * @param int $whence Specifies how the cursor position will be calculated

     *     based on the seek offset. Valid values are identical to the built-in

     *     PHP $whence values for `fseek()`.  SEEK_SET: Set position equal to

     *     offset bytes SEEK_CUR: Set position to current location plus offset

     *     SEEK_END: Set position to end-of-stream plus offset.

     * @throws \RuntimeException on failure.

     */

    public function seek($offset, $whence = SEEK_SET);



    /**

     * Seek to the beginning of the stream.

     *

     * If the stream is not seekable, this method will raise an exception;

     * otherwise, it will perform a seek(0).

     *

     * @see seek()

     * @link http://www.php.net/manual/en/function.fseek.php

     * @throws \RuntimeException on failure.

     */

    public function rewind();



    /**

     * Returns whether or not the stream is writable.

     *

     * @return bool

     */

    public function isWritable();



    /**

     * 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);



    /**

     * Returns whether or not the stream is readable.

     *

     * @return bool

     */

    public function isReadable();



    /**

     * Read data from the stream.

     *

     * @param int $length Read up to $length bytes from the object and return

     *     them. Fewer than $length bytes may be returned if underlying stream

     *     call returns fewer bytes.

     * @return string Returns the data read from the stream, or an empty string

     *     if no bytes are available.

     * @throws \RuntimeException if an error occurs.

     */

    public function read($length);



    /**

     * Returns the remaining contents in a string

     *

     * @return string

     * @throws \RuntimeException if unable to read or an error occurs while

     *     reading.

     */

    public function getContents();



    /**

     * Get stream metadata as an associative array or retrieve a specific key.

     *

     * The keys returned are identical to the keys returned from PHP's

     * stream_get_meta_data() function.

     *

     * @link http://php.net/manual/en/function.stream-get-meta-data.php

     * @param string $key Specific metadata to retrieve.

     * @return array|mixed|null Returns an associative array if no key is

     *     provided. Returns a specific key value if a key is provided and the

     *     value is found, or null if the key is not found.

     */

    public function getMetadata($key = null);

}

