This moves unicode conversion to the filter layer
(rather than at the lower streams layer)
unicode_filter.c has been moved from ext/unicode to main/streams
as it's an integral part of the streams unicode conversion process.
There are now three ways to set encoding on a stream:
(1) By context
$ctx = stream_context_create(NULL,array('encoding'=>'latin1'));
$fp = fopen('somefile', 'r+t', false, $ctx);
(2) By stream_encoding()
$fp = fopen('somefile', 'r+');
stream_encoding($fp, 'latin1');
(3) By filter
$fp = fopen('somefile', 'r+');
stream_filter_append($fp, 'unicode.from.latin1', STREAM_FILTER_READ);
stream_filter_append($fp, 'unicode.to.latin1', STREAM_FILTER_WRITE);
Note: Methods 1 and 2 are convenience wrappers around method 3.
