Decode base64/quoted-printable a block at a time#62
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Transfer-decoding during extraction ran one byte through two function pointers (the per-char filter function and its output callback) and a smart_string append for every output byte. For a multi-megabyte base64 or quoted-printable body that is millions of indirect calls. Add buffer-at-a-time decoders that consume a whole input block in one loop and append decoded bytes straight to the work buffer, using the filter's status/cache as the carry state between blocks. The output is byte-for-byte identical to the per-char path. php_mimepart_decoder_feed and _finish now use these; the now-unused filter_into_work_buffer output callback is removed. The per-char encode path used by mailparse_stream_encode is unchanged.
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Transfer-decoding during extraction ran every input byte through two function pointers (the per-char filter function and its output callback) plus a
smart_stringappend per output byte. For a multi-megabyte base64 or quoted-printable body that is millions of indirect calls.This adds buffer-at-a-time decoders (
mb_convert_filter_feed_block/_flush_block) that consume a whole input block in one tight loop and append decoded bytes straight to the work buffer, reusing the filter'sstatus/cacheas the carry state between blocks. The decoded output is byte-for-byte identical to the per-char path.php_mimepart_decoder_feed/_finishnow use them, and the now-unusedfilter_into_work_bufferoutput callback is removed. The per-char encode path used bymailparse_stream_encodeis unchanged.Verified byte-identical output against the current
masterbuild across 61 base64/QP cases (padding variants, embedded whitespace, invalid chars, partial quartets, soft line breaks, lower/upper hex, all 256 byte values), plus 4000 random round-trips. Decoding a 16 MB base64 body in a debug build went from 349 ms to 197 ms (~1.8x).