Fix #66828: iconv_mime_encode Q-encoding longer than it should be #3492
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Before the fix for bug 48289 has been applied, the algorithm to construct a Q-encoded-word has been optimistic, i.e. try to encode as many bytes that *may* fit in the remaining space, calculate the actual length of the Q-encoded word, and if it's too long, try again with a reduced size. However, the fix for the mentioned bug replaced this by a pessimistic algorithm, which always terminates[1] the for loop[2] during the first iteration (which renders the following 3 lines as dead code), and as such easily produces unnecessarily short encoded-words. Instead the proper fix for the bug would have been to make sure that `out_size` is always decremented, if the space isn't sufficient for the encoded-word. With this further insight, the fix for bug 53891 should be reinvestigated. [1] <https://github.com/php/php-src/blob/php-7.3.0beta3/ext/iconv/iconv.c#L1421> [2] <https://github.com/php/php-src/blob/php-7.3.0beta3/ext/iconv/iconv.c#L1360>
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@LawnGnome @moriyoshi Since you've fixed bug #48289 back then, could you please review this PR? Note to potential merger: the expectation of bug53891.phpt has to be adjusted to this patch (PHP-7.3+ only). |
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The test failure is unrelated to this patch. |
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I've just did, and that bugfix is necessary in addition to this PR. Anyhow, unless there are objections, I'm going to merge this PR on next weekend (i.e. in a week). |
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Comment on behalf of cmb at php.net: Applied via 9cbe128. |
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Before the fix for bug 48289 has been applied, the algorithm to
construct a Q-encoded-word has been optimistic, i.e. try to encode as
many bytes that may fit in the remaining space, calculate the actual
length of the Q-encoded word, and if it's too long, try again with a
reduced size. However, the fix for the mentioned bug replaced this by
a pessimistic algorithm, which always terminates[1] the for loop[2]
during the first iteration (which renders the following 3 lines as dead
code), and as such easily produces unnecessarily short encoded-words.
Instead the proper fix for the bug would have been to make sure that
out_sizeis always decremented, if the space isn't sufficient for theencoded-word.
With this further insight, the fix for bug 53891 should be
reinvestigated.
[1] https://github.com/php/php-src/blob/php-7.3.0beta3/ext/iconv/iconv.c#L1421
[2] https://github.com/php/php-src/blob/php-7.3.0beta3/ext/iconv/iconv.c#L1360