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Bug #77828 SplFileObject::seek problems on custom stream wrappers
Submitted: 2019-03-31 22:32 UTC Modified: 2019-04-01 08:36 UTC
Avg. Score:3.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: alexey dot khokhryakov at gmail dot com Assigned:
Status: Open Package: SPL related
PHP Version: 7.2.16 OS:
Private report: No CVE-ID: None
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From: alexey dot khokhryakov at gmail dot com
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 [2019-03-31 22:32 UTC] alexey dot khokhryakov at gmail dot com
SplFileObject::seek() works wrong for custom stream wrappers. It should work exactly the same as for native files.

In my example I created simple stream wrapper which just proxies all calls to native fopen/fread/ftell/feof/fseek/stat functions which demonstrates the problem.

Test script:
file_put_contents($tmpFilename = tempnam(sys_get_temp_dir(), 'test'), "one line\r\n");
stream_wrapper_register('foo', FooStreamWrapper::class);

foreach ([$tmpFilename, "foo:/{$tmpFilename}"] as $filename) {
    $file = new SplFileObject($filename, 'r');

class FooStreamWrapper {
    private $r;
    public function stream_open($path, $mode) { $this->r = fopen(str_replace('foo:/', '', $path), $mode); return true; }
    public function stream_read($count) { return fread($this->r, $count); }
    public function stream_tell() { return ftell($this->r); }
    public function stream_eof() { return feof($this->r); }
    public function stream_seek($offset, $whence) { return fseek($this->r, $offset, $whence) === 0; }
    public function url_stat($path) { return stat(str_replace('foo:/', '', $path)); }

Expected result:

Actual result:


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 [2019-03-31 23:19 UTC]
It's not SplFileObject but your stream wrapper. PHP's file wrapper is reading lines, yours is reading bytes. If you edit yours to read lines as well
  public function stream_read($count) { return fgets($this->r, $count); }
then it works as expected.

Not sure the best way to fix this.
 [2019-04-01 07:38 UTC] alexey dot khokhryakov at gmail dot com, I don't think so.

If wrapper::stream_read() proxies calls to fgets() then SplFileObject::fread($count) becomes inconsistent because PHP's file wrapper returns $count of data including linebreaks.
 [2019-04-01 08:12 UTC]
Try the change I said, see what happens.
 [2019-04-01 08:21 UTC] alexey dot khokhryakov at gmail dot com
I tried and I see that my test script works but it breaks SplFileObject::fread() functionality as I said.

file_put_contents($tmpFilename = tempnam(sys_get_temp_dir(), 'test'), "one\r\ntwo\r\n");
stream_wrapper_register('foo', FooStreamWrapper::class);
$file = new SplFileObject("foo:/{$tmpFilename}", 'r');

string(10) "one

string(5) "one
 [2019-04-01 08:36 UTC]
I know it's not correct. I'm saying, you can see the line reading/byte reading behavior if you switch the stream to read lines. There is a bug here.
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