diff -r e2065f7505eb -r 51772bf1fb0c src/java.desktop/share/native/libfontmanager/harfbuzz/hb-set-digest-private.hh --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-set-digest-private.hh Thu Dec 07 11:55:06 2017 -0800 @@ -0,0 +1,144 @@ +/* + * Copyright © 2012 Google, Inc. + * + * This is part of HarfBuzz, a text shaping library. + * + * Permission is hereby granted, without written agreement and without + * license or royalty fees, to use, copy, modify, and distribute this + * software and its documentation for any purpose, provided that the + * above copyright notice and the following two paragraphs appear in + * all copies of this software. + * + * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR + * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES + * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN + * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH + * DAMAGE. + * + * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, + * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND + * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS + * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO + * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. + * + * Google Author(s): Behdad Esfahbod + */ + +#ifndef HB_SET_DIGEST_PRIVATE_HH +#define HB_SET_DIGEST_PRIVATE_HH + +#include "hb-private.hh" + +/* + * The set digests here implement various "filters" that support + * "approximate member query". Conceptually these are like Bloom + * Filter and Quotient Filter, however, much smaller, faster, and + * designed to fit the requirements of our uses for glyph coverage + * queries. + * + * Our filters are highly accurate if the lookup covers fairly local + * set of glyphs, but fully flooded and ineffective if coverage is + * all over the place. + * + * The frozen-set can be used instead of a digest, to trade more + * memory for 100% accuracy, but in practice, that doesn't look like + * an attractive trade-off. + */ + +template +struct hb_set_digest_lowest_bits_t +{ + ASSERT_POD (); + + static const unsigned int mask_bytes = sizeof (mask_t); + static const unsigned int mask_bits = sizeof (mask_t) * 8; + static const unsigned int num_bits = 0 + + (mask_bytes >= 1 ? 3 : 0) + + (mask_bytes >= 2 ? 1 : 0) + + (mask_bytes >= 4 ? 1 : 0) + + (mask_bytes >= 8 ? 1 : 0) + + (mask_bytes >= 16? 1 : 0) + + 0; + + static_assert ((shift < sizeof (hb_codepoint_t) * 8), ""); + static_assert ((shift + num_bits <= sizeof (hb_codepoint_t) * 8), ""); + + inline void init (void) { + mask = 0; + } + + inline void add (hb_codepoint_t g) { + mask |= mask_for (g); + } + + inline void add_range (hb_codepoint_t a, hb_codepoint_t b) { + if ((b >> shift) - (a >> shift) >= mask_bits - 1) + mask = (mask_t) -1; + else { + mask_t ma = mask_for (a); + mask_t mb = mask_for (b); + mask |= mb + (mb - ma) - (mb < ma); + } + } + + inline bool may_have (hb_codepoint_t g) const { + return !!(mask & mask_for (g)); + } + + private: + + static inline mask_t mask_for (hb_codepoint_t g) { + return ((mask_t) 1) << ((g >> shift) & (mask_bits - 1)); + } + mask_t mask; +}; + +template +struct hb_set_digest_combiner_t +{ + ASSERT_POD (); + + inline void init (void) { + head.init (); + tail.init (); + } + + inline void add (hb_codepoint_t g) { + head.add (g); + tail.add (g); + } + + inline void add_range (hb_codepoint_t a, hb_codepoint_t b) { + head.add_range (a, b); + tail.add_range (a, b); + } + + inline bool may_have (hb_codepoint_t g) const { + return head.may_have (g) && tail.may_have (g); + } + + private: + head_t head; + tail_t tail; +}; + + +/* + * hb_set_digest_t + * + * This is a combination of digests that performs "best". + * There is not much science to this: it's a result of intuition + * and testing. + */ +typedef hb_set_digest_combiner_t +< + hb_set_digest_lowest_bits_t, + hb_set_digest_combiner_t + < + hb_set_digest_lowest_bits_t, + hb_set_digest_lowest_bits_t + > +> hb_set_digest_t; + + +#endif /* HB_SET_DIGEST_PRIVATE_HH */