initial commit, 4.5 stable

thirdparty/harfbuzz/src/graph/serialize.hh

@@ -0,0 +1,277 @@
+/*
+ * Copyright © 2022  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): Garret Rieger
+ */
+
+#ifndef GRAPH_SERIALIZE_HH
+#define GRAPH_SERIALIZE_HH
+
+namespace graph {
+
+struct overflow_record_t
+{
+  unsigned parent;
+  unsigned child;
+
+  bool operator != (const overflow_record_t o) const
+  { return !(*this == o); }
+
+  inline bool operator == (const overflow_record_t& o) const
+  {
+    return parent == o.parent &&
+        child == o.child;
+  }
+
+  inline uint32_t hash () const
+  {
+    uint32_t current = 0;
+    current = current * 31 + hb_hash (parent);
+    current = current * 31 + hb_hash (child);
+    return current;
+  }
+};
+
+inline
+int64_t compute_offset (
+    const graph_t& graph,
+    unsigned parent_idx,
+    const hb_serialize_context_t::object_t::link_t& link)
+{
+  const auto& parent = graph.vertices_[parent_idx];
+  const auto& child = graph.vertices_[link.objidx];
+  int64_t offset = 0;
+  switch ((hb_serialize_context_t::whence_t) link.whence) {
+    case hb_serialize_context_t::whence_t::Head:
+      offset = child.start - parent.start; break;
+    case hb_serialize_context_t::whence_t::Tail:
+      offset = child.start - parent.end; break;
+    case hb_serialize_context_t::whence_t::Absolute:
+      offset = child.start; break;
+  }
+
+  assert (offset >= link.bias);
+  offset -= link.bias;
+  return offset;
+}
+
+inline
+bool is_valid_offset (int64_t offset,
+                      const hb_serialize_context_t::object_t::link_t& link)
+{
+  if (unlikely (!link.width))
+    // Virtual links can't overflow.
+    return link.is_signed || offset >= 0;
+
+  if (link.is_signed)
+  {
+    if (link.width == 4)
+      return offset >= -((int64_t) 1 << 31) && offset < ((int64_t) 1 << 31);
+    else
+      return offset >= -(1 << 15) && offset < (1 << 15);
+  }
+  else
+  {
+    if (link.width == 4)
+      return offset >= 0 && offset < ((int64_t) 1 << 32);
+    else if (link.width == 3)
+      return offset >= 0 && offset < ((int32_t) 1 << 24);
+    else
+      return offset >= 0 && offset < (1 << 16);
+  }
+}
+
+/*
+ * Will any offsets overflow on graph when it's serialized?
+ */
+inline bool
+will_overflow (graph_t& graph,
+               hb_vector_t<overflow_record_t>* overflows = nullptr)
+{
+  if (overflows) overflows->resize (0);
+  graph.update_positions ();
+
+  hb_hashmap_t<overflow_record_t*, bool> record_set;
+  const auto& vertices = graph.vertices_;
+  for (int parent_idx = vertices.length - 1; parent_idx >= 0; parent_idx--)
+  {
+    // Don't need to check virtual links for overflow
+    for (const auto& link : vertices.arrayZ[parent_idx].obj.real_links)
+    {
+      int64_t offset = compute_offset (graph, parent_idx, link);
+      if (likely (is_valid_offset (offset, link)))
+        continue;
+
+      if (!overflows) return true;
+
+      overflow_record_t r;
+      r.parent = parent_idx;
+      r.child = link.objidx;
+      if (record_set.has(&r)) continue; // don't keep duplicate overflows.
+
+      overflows->push (r);
+      record_set.set(&r, true);
+    }
+  }
+
+  if (!overflows) return false;
+  return overflows->length;
+}
+
+inline
+void print_overflows (graph_t& graph,
+                      const hb_vector_t<overflow_record_t>& overflows)
+{
+  if (!DEBUG_ENABLED(SUBSET_REPACK)) return;
+
+  graph.update_parents ();
+  int limit = 10;
+  for (const auto& o : overflows)
+  {
+    if (!limit--) break;
+    const auto& parent = graph.vertices_[o.parent];
+    const auto& child = graph.vertices_[o.child];
+    DEBUG_MSG (SUBSET_REPACK, nullptr,
+               "  overflow from "
+               "%4u (%4u in, %4u out, space %2u) => "
+               "%4u (%4u in, %4u out, space %2u)",
+               o.parent,
+               parent.incoming_edges (),
+               parent.obj.real_links.length + parent.obj.virtual_links.length,
+               graph.space_for (o.parent),
+               o.child,
+               child.incoming_edges (),
+               child.obj.real_links.length + child.obj.virtual_links.length,
+               graph.space_for (o.child));
+  }
+  if (overflows.length > 10) {
+    DEBUG_MSG (SUBSET_REPACK, nullptr, "  ... plus %u more overflows.", overflows.length - 10);
+  }
+}
+
+template <typename O> inline void
+serialize_link_of_type (const hb_serialize_context_t::object_t::link_t& link,
+                        char* head,
+                        unsigned size,
+                        hb_serialize_context_t* c)
+{
+  assert(link.position + link.width <= size);
+
+  OT::Offset<O>* offset = reinterpret_cast<OT::Offset<O>*> (head + link.position);
+  *offset = 0;
+  c->add_link (*offset,
+               // serializer has an extra nil object at the start of the
+               // object array. So all id's are +1 of what our id's are.
+               link.objidx + 1,
+               (hb_serialize_context_t::whence_t) link.whence,
+               link.bias);
+}
+
+inline
+void serialize_link (const hb_serialize_context_t::object_t::link_t& link,
+                     char* head,
+                     unsigned size,
+                     hb_serialize_context_t* c)
+{
+  switch (link.width)
+  {
+    case 0:
+      // Virtual links aren't serialized.
+      return;
+    case 4:
+      if (link.is_signed)
+      {
+        serialize_link_of_type<OT::HBINT32> (link, head, size, c);
+      } else {
+        serialize_link_of_type<OT::HBUINT32> (link, head, size, c);
+      }
+      return;
+    case 2:
+      if (link.is_signed)
+      {
+        serialize_link_of_type<OT::HBINT16> (link, head, size, c);
+      } else {
+        serialize_link_of_type<OT::HBUINT16> (link, head, size, c);
+      }
+      return;
+    case 3:
+      serialize_link_of_type<OT::HBUINT24> (link, head, size, c);
+      return;
+    default:
+      // Unexpected link width.
+      assert (0);
+  }
+}
+
+/*
+ * serialize graph into the provided serialization buffer.
+ */
+inline hb_blob_t* serialize (const graph_t& graph)
+{
+  hb_vector_t<char> buffer;
+  size_t size = graph.total_size_in_bytes ();
+
+  if (!size) return hb_blob_get_empty ();
+
+  if (!buffer.alloc (size)) {
+    DEBUG_MSG (SUBSET_REPACK, nullptr, "Unable to allocate output buffer.");
+    return nullptr;
+  }
+  hb_serialize_context_t c((void *) buffer, size);
+
+  c.start_serialize<void> ();
+  const auto& vertices = graph.vertices_;
+  for (unsigned i = 0; i < vertices.length; i++) {
+    c.push ();
+
+    size_t size = vertices[i].obj.tail - vertices[i].obj.head;
+    char* start = c.allocate_size <char> (size);
+    if (!start) {
+      DEBUG_MSG (SUBSET_REPACK, nullptr, "Buffer out of space.");
+      return nullptr;
+    }
+
+    hb_memcpy (start, vertices[i].obj.head, size);
+
+    // Only real links needs to be serialized.
+    for (const auto& link : vertices[i].obj.real_links)
+      serialize_link (link, start, size, &c);
+
+    // All duplications are already encoded in the graph, so don't
+    // enable sharing during packing.
+    c.pop_pack (false);
+  }
+  c.end_serialize ();
+
+  if (c.in_error ()) {
+    DEBUG_MSG (SUBSET_REPACK, nullptr, "Error during serialization. Err flag: %d",
+               c.errors);
+    return nullptr;
+  }
+
+  return c.copy_blob ();
+}
+
+} // namespace graph
+
+#endif // GRAPH_SERIALIZE_HH