Description:
------------
Passing length of -1 to stream_get_contents() with the file position indicator of resource near the end of file still loads the entire file into memory. Passing a fixed length to stream_get_contents() does not produce the same behaviour.

Note: when running test script set memory_limit=64M

Test script:
---------------
<?php

$resource = fopen('/tmp/file1', 'a+');

for ($i = 0; $i < 64; ++$i)
{
    $data = random_bytes(1024 * 1024);
    $position = ftell($resource);
    fwrite($resource, $data);
    fseek($resource, $position);
    stream_get_contents($resource, strlen($data));
}

$resource = fopen('/tmp/file2', 'a+');

for ($i = 0; $i < 64; ++$i)
{
    $data = random_bytes(1024 * 1024);
    $position = ftell($resource);
    fwrite($resource, $data);
    fseek($resource, $position);
    stream_get_contents($resource, -1);
}


Actual result:
--------------
PHP Fatal error:  Allowed memory size of 67108864 bytes exhausted (tried to allocate 62922784 bytes) in script.php on line 22