Copy SEEK_END behavior from fseek

Author: jeskew

src/CachingStream.php

@@ -52,8 +52,7 @@ public function seek($offset, $whence = SEEK_SET)
             if ($size === null) {
                 $size = $this->cacheEntireStream();
             }
-            // Because 0 is the first byte, we seek to size - 1.
-            $byte = $size - 1 - $offset;
+            $byte = $size + $offset;
         } else {
             throw new \InvalidArgumentException('Invalid whence');
         }

tests/CachingStreamTest.php

@@ -44,9 +44,9 @@ public function testCanSeekNearEndWithSeekEnd()
     {
         $baseStream = Psr7\stream_for(implode('', range('a', 'z')));
         $cached = new CachingStream($baseStream);
-        $cached->seek(1, SEEK_END);
-        $this->assertEquals(24, $baseStream->tell());
-        $this->assertEquals('y', $cached->read(1));
+        $cached->seek(-1, SEEK_END);
+        $this->assertEquals(25, $baseStream->tell());
+        $this->assertEquals('z', $cached->read(1));
         $this->assertEquals(26, $cached->getSize());
     }
 
@@ -55,8 +55,8 @@ public function testCanSeekToEndWithSeekEnd()
         $baseStream = Psr7\stream_for(implode('', range('a', 'z')));
         $cached = new CachingStream($baseStream);
         $cached->seek(0, SEEK_END);
-        $this->assertEquals(25, $baseStream->tell());
-        $this->assertEquals('z', $cached->read(1));
+        $this->assertEquals(26, $baseStream->tell());
+        $this->assertEquals('', $cached->read(1));
         $this->assertEquals(26, $cached->getSize());
     }
 
@@ -67,8 +67,8 @@ public function testCanUseSeekEndWithUnknownSize()
             'getSize' => function () { return null; }
         ]);
         $cached = new CachingStream($decorated);
-        $cached->seek(1, SEEK_END);
-        $this->assertEquals('ng', $cached->read(2));
+        $cached->seek(-1, SEEK_END);
+        $this->assertEquals('g', $cached->read(1));
     }
 
     public function testRewindUsesSeek()