| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  | namespace Thruster\Component\HttpMessage; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  | use Psr\Http\Message\StreamInterface; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  |  * Class BufferStream | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  |  * @package Thruster\Component\HttpMessage | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  |  * @author  Aurimas Niekis <[email protected]> | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | class BufferStream implements StreamInterface | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |      * @var int | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |     private $hwm; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |      * @var string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |     private $buffer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |      * @param int $hwm High water mark, representing the preferred maximum | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |      *                 buffer size. If the size of the buffer exceeds the high | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |      *                 water mark, then calls to write will continue to succeed | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |      *                 but will return false to inform writers to slow down | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |      *                 until the buffer has been drained by reading from it. | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 31 |  |  |      */ | 
            
                                                                        
                            
            
                                    
            
            
                | 32 | 11 |  |     public function __construct($hwm = 16384) | 
            
                                                                        
                            
            
                                    
            
            
                | 33 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 34 | 11 |  |         $this->buffer = ''; | 
            
                                                                        
                            
            
                                    
            
            
                | 35 | 11 |  |         $this->hwm = $hwm; | 
            
                                                                        
                            
            
                                    
            
            
                | 36 | 11 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 | 2 |  |     public function __toString() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 | 2 |  |         return $this->getContents(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 | 2 |  |     public function getContents() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 | 2 |  |         $buffer = $this->buffer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 | 2 |  |         $this->buffer = ''; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 | 2 |  |         return $buffer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 | 1 |  |     public function close() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 | 1 |  |         $this->buffer = ''; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 | 1 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 | 1 |  |     public function detach() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 | 1 |  |         $this->close(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 | 1 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 | 2 |  |     public function getSize() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 | 2 |  |         return strlen($this->buffer); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 | 1 |  |     public function isReadable() : bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 | 1 |  |         return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 | 1 |  |     public function isWritable() : bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 | 1 |  |         return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 74 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 75 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 76 | 2 |  |     public function isSeekable() : bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 77 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 78 | 2 |  |         return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 80 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 81 |  |  |     public function rewind() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 82 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 83 |  |  |         $this->seek(0); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 84 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 85 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 86 |  |  |     public function seek($offset, $whence = SEEK_SET) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 87 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 88 |  |  |         throw new \RuntimeException('Cannot seek a BufferStream'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 89 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 90 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 91 | 3 |  |     public function eof() : bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 92 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 93 | 3 |  |         return strlen($this->buffer) === 0; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 94 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 95 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 96 | 1 |  |     public function tell() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 97 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 98 | 1 |  |         throw new \RuntimeException('Cannot determine the position of a BufferStream'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 99 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 100 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 101 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 102 |  |  |      * Reads data from the buffer. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 103 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 104 | 8 |  |     public function read($length) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 105 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 106 | 8 |  |         $currentLength = strlen($this->buffer); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 107 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 108 | 8 |  |         if ($length >= $currentLength) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 109 |  |  |             // No need to slice the buffer because we don't have enough data. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 110 | 7 |  |             $result = $this->buffer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 111 | 7 |  |             $this->buffer = ''; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 112 |  |  |         } else { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 113 |  |  |             // Slice up the result to provide a subset of the buffer. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 114 | 2 |  |             $result = substr($this->buffer, 0, $length); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 115 | 2 |  |             $this->buffer = substr($this->buffer, $length); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 116 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 117 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 118 | 8 |  |         return $result; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 119 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 120 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 121 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 122 |  |  |      * Writes data to the buffer. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 123 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 124 | 8 |  |     public function write($string) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 125 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 126 | 8 |  |         $this->buffer .= $string; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 127 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 128 |  |  |         // TODO: What should happen here? | 
            
                                                                                                            
                            
            
                                    
            
            
                | 129 | 8 |  |         if (strlen($this->buffer) >= $this->hwm) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 130 | 1 |  |             return false; | 
                            
                    |  |  |  | 
                                                                                        
                                                                                     | 
            
                                                                                                            
                            
            
                                    
            
            
                | 131 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 132 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 133 | 8 |  |         return strlen($string); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 134 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 135 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 136 | 1 |  |     public function getMetadata($key = null) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 137 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 138 | 1 |  |         if ($key == 'hwm') { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 139 | 1 |  |             return $this->hwm; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 140 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 141 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 142 | 1 |  |         return $key ? null : []; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 143 |  |  |     } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 144 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 145 |  |  |  | 
            
                        
If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.