Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 213 insertions, 0 deletions

diff --git a/gfx/harfbuzz/src/hb-set-digest.hh b/gfx/harfbuzz/src/hb-set-digest.hh
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+++ b/gfx/harfbuzz/src/hb-set-digest.hh
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+/*
+ * 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_HH
+#define HB_SET_DIGEST_HH
+
+#include "hb.hh"
+#include "hb-machinery.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 way these are used is that the filter is first populated by
+ * a lookup's or subtable's Coverage table(s), and then when we
+ * want to apply the lookup or subtable to a glyph, before trying
+ * to apply, we ask the filter if the glyph may be covered. If it's
+ * not, we return early.  We can also match a digest against another
+ * digest.
+ *
+ * We use these filters at three levels:
+ *   - If the digest for all the glyphs in the buffer as a whole
+ *     does not match the digest for the lookup, skip the lookup.
+ *   - For each glyph, if it doesn't match the lookup digest,
+ *     skip it.
+ *   - For each glyph, if it doesn't match the subtable digest,
+ *     skip it.
+ *
+ * The main filter we use is a combination of three bits-pattern
+ * filters. A bits-pattern filter checks a number of bits (5 or 6)
+ * of the input number (glyph-id in this case) and checks whether
+ * its pattern is amongst the patterns of any of the accepted values.
+ * The accepted patterns are represented as a "long" integer. The
+ * check is done using four bitwise operations only.
+ */
+
+template <typename mask_t, unsigned int shift>
+struct hb_set_digest_bits_pattern_t
+{
+  static constexpr unsigned mask_bytes = sizeof (mask_t);
+  static constexpr unsigned mask_bits = sizeof (mask_t) * 8;
+  static constexpr unsigned 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), "");
+
+  void init () { mask = 0; }
+
+  void add (const hb_set_digest_bits_pattern_t &o) { mask |= o.mask; }
+
+  void add (hb_codepoint_t g) { mask |= mask_for (g); }
+
+  bool 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);
+    }
+    return true;
+  }
+
+  template <typename T>
+  void add_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    for (unsigned int i = 0; i < count; i++)
+    {
+      add (*array);
+      array = &StructAtOffsetUnaligned<T> ((const void *) array, stride);
+    }
+  }
+  template <typename T>
+  void add_array (const hb_array_t<const T>& arr) { add_array (&arr, arr.len ()); }
+  template <typename T>
+  bool add_sorted_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    add_array (array, count, stride);
+    return true;
+  }
+  template <typename T>
+  bool add_sorted_array (const hb_sorted_array_t<const T>& arr) { return add_sorted_array (&arr, arr.len ()); }
+
+  bool may_have (const hb_set_digest_bits_pattern_t &o) const
+  { return mask & o.mask; }
+
+  bool may_have (hb_codepoint_t g) const
+  { return mask & mask_for (g); }
+
+  private:
+
+  static mask_t mask_for (hb_codepoint_t g)
+  { return ((mask_t) 1) << ((g >> shift) & (mask_bits - 1)); }
+  mask_t mask;
+};
+
+template <typename head_t, typename tail_t>
+struct hb_set_digest_combiner_t
+{
+  void init ()
+  {
+    head.init ();
+    tail.init ();
+  }
+
+  void add (const hb_set_digest_combiner_t &o)
+  {
+    head.add (o.head);
+    tail.add (o.tail);
+  }
+
+  void add (hb_codepoint_t g)
+  {
+    head.add (g);
+    tail.add (g);
+  }
+
+  bool add_range (hb_codepoint_t a, hb_codepoint_t b)
+  {
+    return head.add_range (a, b) &&
+	   tail.add_range (a, b);
+  }
+  template <typename T>
+  void add_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    head.add_array (array, count, stride);
+    tail.add_array (array, count, stride);
+  }
+  template <typename T>
+  void add_array (const hb_array_t<const T>& arr) { add_array (&arr, arr.len ()); }
+  template <typename T>
+  bool add_sorted_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    return head.add_sorted_array (array, count, stride) &&
+	   tail.add_sorted_array (array, count, stride);
+  }
+  template <typename T>
+  bool add_sorted_array (const hb_sorted_array_t<const T>& arr) { return add_sorted_array (&arr, arr.len ()); }
+
+  bool may_have (const hb_set_digest_combiner_t &o) const
+  {
+    return head.may_have (o.head) && tail.may_have (o.tail);
+  }
+
+  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.
+ */
+using hb_set_digest_t =
+  hb_set_digest_combiner_t
+  <
+    hb_set_digest_bits_pattern_t<unsigned long, 4>,
+    hb_set_digest_combiner_t
+    <
+      hb_set_digest_bits_pattern_t<unsigned long, 0>,
+      hb_set_digest_bits_pattern_t<unsigned long, 9>
+    >
+  >
+;
+
+
+#endif /* HB_SET_DIGEST_HH */