php_stream_seek()
repositions the internal position of
stream
. The new position is determined by adding the
offset
to the position indicated by
whence
. If
whence
is set to
SEEK_SET
,
SEEK_CUR
or
SEEK_END
the offset is relative to the start of the stream, the current
position or the end of the stream, respectively.
php_stream_seek()
returns 0 on success, but -1 if there was an error.
注意 Not all streams support seeking, although the streams API will emulate a seek if whence is set to SEEK_CUR and offset is positive, by calling php_stream_read() to read (and discard) offset bytes.
The emulation is only applied when the underlying stream implementation does not support seeking. If the stream is (for example) a file based stream that is wrapping a non-seekable pipe, the streams api will not apply emulation because the file based stream implements a seek operation; the seek will fail and an error result will be returned to the caller.