diff options
Diffstat (limited to 'thirdparty/harfbuzz/src/hb-repacker.hh')
| -rw-r--r-- | thirdparty/harfbuzz/src/hb-repacker.hh | 737 |
1 files changed, 581 insertions, 156 deletions
diff --git a/thirdparty/harfbuzz/src/hb-repacker.hh b/thirdparty/harfbuzz/src/hb-repacker.hh index b02128b5c4..26faa56ea8 100644 --- a/thirdparty/harfbuzz/src/hb-repacker.hh +++ b/thirdparty/harfbuzz/src/hb-repacker.hh @@ -33,6 +33,10 @@ #include "hb-serialize.hh" #include "hb-vector.hh" +/* + * For a detailed writeup on the overflow resolution algorithm see: + * docs/repacker.md + */ struct graph_t { @@ -40,23 +44,58 @@ struct graph_t { vertex_t () : distance (0), - incoming_edges (0), + space (0), + parents (), start (0), end (0), priority(0) {} - void fini () { obj.fini (); } + void fini () { + obj.fini (); + parents.fini (); + } hb_serialize_context_t::object_t obj; int64_t distance; - unsigned incoming_edges; + int64_t space; + hb_vector_t<unsigned> parents; unsigned start; unsigned end; unsigned priority; bool is_shared () const { - return incoming_edges > 1; + return parents.length > 1; + } + + unsigned incoming_edges () const + { + return parents.length; + } + + void remove_parent (unsigned parent_index) + { + for (unsigned i = 0; i < parents.length; i++) + { + if (parents[i] != parent_index) continue; + parents.remove (i); + break; + } + } + + void remap_parents (const hb_vector_t<unsigned>& id_map) + { + for (unsigned i = 0; i < parents.length; i++) + parents[i] = id_map[parents[i]]; + } + + void remap_parent (unsigned old_index, unsigned new_index) + { + for (unsigned i = 0; i < parents.length; i++) + { + if (parents[i] == old_index) + parents[i] = new_index; + } } bool is_leaf () const @@ -77,7 +116,7 @@ struct graph_t int64_t modified_distance = hb_min (hb_max(distance + distance_modifier (), 0), 0x7FFFFFFFFF); - return (modified_distance << 24) | (0x00FFFFFF & order); + return (modified_distance << 22) | (0x003FFFFF & order); } int64_t distance_modifier () const @@ -91,34 +130,7 @@ struct graph_t struct overflow_record_t { unsigned parent; - const hb_serialize_context_t::object_t::link_t* link; - }; - - struct clone_buffer_t - { - clone_buffer_t () : head (nullptr), tail (nullptr) {} - - bool copy (const hb_serialize_context_t::object_t& object) - { - fini (); - unsigned size = object.tail - object.head; - head = (char*) hb_malloc (size); - if (!head) return false; - - memcpy (head, object.head, size); - tail = head + size; - return true; - } - - char* head; - char* tail; - - void fini () - { - if (!head) return; - hb_free (head); - head = nullptr; - } + unsigned child; }; /* @@ -129,11 +141,12 @@ struct graph_t * serializer */ graph_t (const hb_vector_t<hb_serialize_context_t::object_t *>& objects) - : edge_count_invalid (true), + : parents_invalid (true), distance_invalid (true), positions_invalid (true), successful (true) { + num_roots_for_space_.push (1); bool removed_nil = false; for (unsigned i = 0; i < objects.length; i++) { @@ -160,12 +173,13 @@ struct graph_t ~graph_t () { vertices_.fini_deep (); - clone_buffers_.fini_deep (); } bool in_error () const { - return !successful || vertices_.in_error () || clone_buffers_.in_error (); + return !successful || + vertices_.in_error () || + num_roots_for_space_.in_error (); } const vertex_t& root () const @@ -226,12 +240,13 @@ struct graph_t hb_vector_t<unsigned> queue; hb_vector_t<vertex_t> sorted_graph; + if (unlikely (!check_success (sorted_graph.resize (vertices_.length)))) return; hb_vector_t<unsigned> id_map; if (unlikely (!check_success (id_map.resize (vertices_.length)))) return; hb_vector_t<unsigned> removed_edges; if (unlikely (!check_success (removed_edges.resize (vertices_.length)))) return; - update_incoming_edge_count (); + update_parents (); queue.push (root_idx ()); int new_id = vertices_.length - 1; @@ -242,12 +257,12 @@ struct graph_t queue.remove (0); vertex_t& next = vertices_[next_id]; - sorted_graph.push (next); + sorted_graph[new_id] = next; id_map[next_id] = new_id--; for (const auto& link : next.obj.links) { removed_edges[link.objidx]++; - if (!(vertices_[link.objidx].incoming_edges - removed_edges[link.objidx])) + if (!(vertices_[link.objidx].incoming_edges () - removed_edges[link.objidx])) queue.push (link.objidx); } } @@ -255,14 +270,11 @@ struct graph_t check_success (!queue.in_error ()); check_success (!sorted_graph.in_error ()); if (!check_success (new_id == -1)) - DEBUG_MSG (SUBSET_REPACK, nullptr, "Graph is not fully connected."); - - remap_obj_indices (id_map, &sorted_graph); + print_orphaned_nodes (); - sorted_graph.as_array ().reverse (); + remap_all_obj_indices (id_map, &sorted_graph); - vertices_.fini_deep (); - vertices_ = sorted_graph; + hb_swap (vertices_, sorted_graph); sorted_graph.fini_deep (); } @@ -283,12 +295,13 @@ struct graph_t hb_priority_queue_t queue; hb_vector_t<vertex_t> sorted_graph; + if (unlikely (!check_success (sorted_graph.resize (vertices_.length)))) return; hb_vector_t<unsigned> id_map; if (unlikely (!check_success (id_map.resize (vertices_.length)))) return; hb_vector_t<unsigned> removed_edges; if (unlikely (!check_success (removed_edges.resize (vertices_.length)))) return; - update_incoming_edge_count (); + update_parents (); queue.insert (root ().modified_distance (0), root_idx ()); int new_id = root_idx (); @@ -298,12 +311,12 @@ struct graph_t unsigned next_id = queue.pop_minimum().second; vertex_t& next = vertices_[next_id]; - sorted_graph.push (next); + sorted_graph[new_id] = next; id_map[next_id] = new_id--; for (const auto& link : next.obj.links) { removed_edges[link.objidx]++; - if (!(vertices_[link.objidx].incoming_edges - removed_edges[link.objidx])) + if (!(vertices_[link.objidx].incoming_edges () - removed_edges[link.objidx])) // Add the order that the links were encountered to the priority. // This ensures that ties between priorities objects are broken in a consistent // way. More specifically this is set up so that if a set of objects have the same @@ -317,66 +330,264 @@ struct graph_t check_success (!queue.in_error ()); check_success (!sorted_graph.in_error ()); if (!check_success (new_id == -1)) - DEBUG_MSG (SUBSET_REPACK, nullptr, "Graph is not fully connected."); - - remap_obj_indices (id_map, &sorted_graph); + print_orphaned_nodes (); - sorted_graph.as_array ().reverse (); + remap_all_obj_indices (id_map, &sorted_graph); - vertices_.fini_deep (); - vertices_ = sorted_graph; + hb_swap (vertices_, sorted_graph); sorted_graph.fini_deep (); } /* - * Creates a copy of child and re-assigns the link from - * parent to the clone. The copy is a shallow copy, objects - * linked from child are not duplicated. + * Assign unique space numbers to each connected subgraph of 32 bit offset(s). */ - void duplicate (unsigned parent_idx, unsigned child_idx) + bool assign_32bit_spaces () { - DEBUG_MSG (SUBSET_REPACK, nullptr, " Duplicating %d => %d", - parent_idx, child_idx); + unsigned root_index = root_idx (); + hb_set_t visited; + hb_set_t roots; + for (unsigned i = 0; i <= root_index; i++) + { + for (auto& l : vertices_[i].obj.links) + { + if (l.width == 4 && !l.is_signed) + { + roots.add (l.objidx); + find_subgraph (l.objidx, visited); + } + } + } + + // Mark everything not in the subgraphs of 32 bit roots as visited. + // This prevents 32 bit subgraphs from being connected via nodes not in the 32 bit subgraphs. + visited.invert (); + + if (!roots) return false; + + while (roots) + { + unsigned next = HB_SET_VALUE_INVALID; + if (!roots.next (&next)) break; + + hb_set_t connected_roots; + find_connected_nodes (next, roots, visited, connected_roots); + isolate_subgraph (connected_roots); + + unsigned next_space = this->next_space (); + num_roots_for_space_.push (0); + for (unsigned root : connected_roots) + { + DEBUG_MSG (SUBSET_REPACK, nullptr, "Subgraph %u gets space %u", root, next_space); + vertices_[root].space = next_space; + num_roots_for_space_[next_space] = num_roots_for_space_[next_space] + 1; + distance_invalid = true; + positions_invalid = true; + } + + // TODO(grieger): special case for GSUB/GPOS use extension promotions to move 16 bit space + // into the 32 bit space as needed, instead of using isolation. + } + + return true; + } + + /* + * Isolates the subgraph of nodes reachable from root. Any links to nodes in the subgraph + * that originate from outside of the subgraph will be removed by duplicating the linked to + * object. + * + * Indices stored in roots will be updated if any of the roots are duplicated to new indices. + */ + bool isolate_subgraph (hb_set_t& roots) + { + update_parents (); + hb_hashmap_t<unsigned, unsigned> subgraph; + + // incoming edges to root_idx should be all 32 bit in length so we don't need to de-dup these + // set the subgraph incoming edge count to match all of root_idx's incoming edges + hb_set_t parents; + for (unsigned root_idx : roots) + { + subgraph.set (root_idx, wide_parents (root_idx, parents)); + find_subgraph (root_idx, subgraph); + } + + unsigned original_root_idx = root_idx (); + hb_hashmap_t<unsigned, unsigned> index_map; + bool made_changes = false; + for (auto entry : subgraph.iter ()) + { + const auto& node = vertices_[entry.first]; + unsigned subgraph_incoming_edges = entry.second; + + if (subgraph_incoming_edges < node.incoming_edges ()) + { + // Only de-dup objects with incoming links from outside the subgraph. + made_changes = true; + duplicate_subgraph (entry.first, index_map); + } + } + + if (!made_changes) + return false; + if (original_root_idx != root_idx () + && parents.has (original_root_idx)) + { + // If the root idx has changed since parents was determined, update root idx in parents + parents.add (root_idx ()); + parents.del (original_root_idx); + } + + auto new_subgraph = + + subgraph.keys () + | hb_map([&] (unsigned node_idx) { + if (index_map.has (node_idx)) return index_map[node_idx]; + return node_idx; + }) + ; + + remap_obj_indices (index_map, new_subgraph); + remap_obj_indices (index_map, parents.iter (), true); + + // Update roots set with new indices as needed. + unsigned next = HB_SET_VALUE_INVALID; + while (roots.next (&next)) + { + if (index_map.has (next)) + { + roots.del (next); + roots.add (index_map[next]); + } + } + + return true; + } + + void find_subgraph (unsigned node_idx, hb_hashmap_t<unsigned, unsigned>& subgraph) + { + for (const auto& link : vertices_[node_idx].obj.links) + { + if (subgraph.has (link.objidx)) + { + subgraph.set (link.objidx, subgraph[link.objidx] + 1); + continue; + } + subgraph.set (link.objidx, 1); + find_subgraph (link.objidx, subgraph); + } + } + + void find_subgraph (unsigned node_idx, hb_set_t& subgraph) + { + if (subgraph.has (node_idx)) return; + subgraph.add (node_idx); + for (const auto& link : vertices_[node_idx].obj.links) + find_subgraph (link.objidx, subgraph); + } + + /* + * duplicates all nodes in the subgraph reachable from node_idx. Does not re-assign + * links. index_map is updated with mappings from old id to new id. If a duplication has already + * been performed for a given index, then it will be skipped. + */ + void duplicate_subgraph (unsigned node_idx, hb_hashmap_t<unsigned, unsigned>& index_map) + { + if (index_map.has (node_idx)) + return; + + index_map.set (node_idx, duplicate (node_idx)); + for (const auto& l : object (node_idx).links) { + duplicate_subgraph (l.objidx, index_map); + } + } + + /* + * Creates a copy of node_idx and returns it's new index. + */ + unsigned duplicate (unsigned node_idx) + { positions_invalid = true; + distance_invalid = true; auto* clone = vertices_.push (); - auto& child = vertices_[child_idx]; - clone_buffer_t* buffer = clone_buffers_.push (); - if (vertices_.in_error () - || clone_buffers_.in_error () - || !check_success (buffer->copy (child.obj))) { - return; + auto& child = vertices_[node_idx]; + if (vertices_.in_error ()) { + return -1; } - clone->obj.head = buffer->head; - clone->obj.tail = buffer->tail; + clone->obj.head = child.obj.head; + clone->obj.tail = child.obj.tail; clone->distance = child.distance; + clone->space = child.space; + clone->parents.reset (); + unsigned clone_idx = vertices_.length - 2; for (const auto& l : child.obj.links) + { clone->obj.links.push (l); + vertices_[l.objidx].parents.push (clone_idx); + } check_success (!clone->obj.links.in_error ()); + // The last object is the root of the graph, so swap back the root to the end. + // The root's obj idx does change, however since it's root nothing else refers to it. + // all other obj idx's will be unaffected. + vertex_t root = vertices_[vertices_.length - 2]; + vertices_[clone_idx] = *clone; + vertices_[vertices_.length - 1] = root; + + // Since the root moved, update the parents arrays of all children on the root. + for (const auto& l : root.obj.links) + vertices_[l.objidx].remap_parent (root_idx () - 1, root_idx ()); + + return clone_idx; + } + + /* + * Creates a copy of child and re-assigns the link from + * parent to the clone. The copy is a shallow copy, objects + * linked from child are not duplicated. + */ + bool duplicate (unsigned parent_idx, unsigned child_idx) + { + update_parents (); + + unsigned links_to_child = 0; + for (const auto& l : vertices_[parent_idx].obj.links) + { + if (l.objidx == child_idx) links_to_child++; + } + + if (vertices_[child_idx].incoming_edges () <= links_to_child) + { + // Can't duplicate this node, doing so would orphan the original one as all remaining links + // to child are from parent. + DEBUG_MSG (SUBSET_REPACK, nullptr, " Not duplicating %d => %d", + parent_idx, child_idx); + return false; + } + + DEBUG_MSG (SUBSET_REPACK, nullptr, " Duplicating %d => %d", + parent_idx, child_idx); + + unsigned clone_idx = duplicate (child_idx); + if (clone_idx == (unsigned) -1) return false; + // duplicate shifts the root node idx, so if parent_idx was root update it. + if (parent_idx == clone_idx) parent_idx++; + auto& parent = vertices_[parent_idx]; - unsigned clone_idx = vertices_.length - 2; for (unsigned i = 0; i < parent.obj.links.length; i++) { auto& l = parent.obj.links[i]; - if (l.objidx == child_idx) - { - l.objidx = clone_idx; - clone->incoming_edges++; - child.incoming_edges--; - } + if (l.objidx != child_idx) + continue; + + reassign_link (l, parent_idx, clone_idx); } - // The last object is the root of the graph, so swap back the root to the end. - // The root's obj idx does change, however since it's root nothing else refers to it. - // all other obj idx's will be unaffected. - vertex_t root = vertices_[vertices_.length - 2]; - vertices_[vertices_.length - 2] = *clone; - vertices_[vertices_.length - 1] = root; + return true; } /* @@ -414,7 +625,7 @@ struct graph_t overflow_record_t r; r.parent = parent_idx; - r.link = &link; + r.child = link.objidx; overflows->push (r); } } @@ -423,48 +634,134 @@ struct graph_t return overflows->length; } + void print_orphaned_nodes () + { + if (!DEBUG_ENABLED(SUBSET_REPACK)) return; + + DEBUG_MSG (SUBSET_REPACK, nullptr, "Graph is not fully connected."); + parents_invalid = true; + update_parents(); + + for (unsigned i = 0; i < root_idx (); i++) + { + const auto& v = vertices_[i]; + if (!v.parents) + DEBUG_MSG (SUBSET_REPACK, nullptr, "Node %u is orphaned.", i); + } + } + void print_overflows (const hb_vector_t<overflow_record_t>& overflows) { if (!DEBUG_ENABLED(SUBSET_REPACK)) return; - update_incoming_edge_count (); + update_parents (); for (const auto& o : overflows) { - const auto& child = vertices_[o.link->objidx]; - DEBUG_MSG (SUBSET_REPACK, nullptr, " overflow from %d => %d (%d incoming , %d outgoing)", + const auto& parent = vertices_[o.parent]; + const auto& child = vertices_[o.child]; + DEBUG_MSG (SUBSET_REPACK, nullptr, + " overflow from " + "%4d (%4d in, %4d out, space %2d) => " + "%4d (%4d in, %4d out, space %2d)", o.parent, - o.link->objidx, - child.incoming_edges, - child.obj.links.length); + parent.incoming_edges (), + parent.obj.links.length, + space_for (o.parent), + o.child, + child.incoming_edges (), + child.obj.links.length, + space_for (o.child)); } } + unsigned num_roots_for_space (unsigned space) const + { + return num_roots_for_space_[space]; + } + + unsigned next_space () const + { + return num_roots_for_space_.length; + } + + void move_to_new_space (unsigned index) + { + auto& node = vertices_[index]; + num_roots_for_space_.push (1); + num_roots_for_space_[node.space] = num_roots_for_space_[node.space] - 1; + node.space = num_roots_for_space_.length - 1; + } + + unsigned space_for (unsigned index, unsigned* root = nullptr) const + { + const auto& node = vertices_[index]; + if (node.space) + { + if (root != nullptr) + *root = index; + return node.space; + } + + if (!node.parents) + { + if (root) + *root = index; + return 0; + } + + return space_for (node.parents[0], root); + } + void err_other_error () { this->successful = false; } private: + /* + * Returns the numbers of incoming edges that are 32bits wide. + */ + unsigned wide_parents (unsigned node_idx, hb_set_t& parents) const + { + unsigned count = 0; + hb_set_t visited; + for (unsigned p : vertices_[node_idx].parents) + { + if (visited.has (p)) continue; + visited.add (p); + + for (const auto& l : vertices_[p].obj.links) + { + if (l.objidx == node_idx && l.width == 4 && !l.is_signed) + { + count++; + parents.add (p); + } + } + } + return count; + } + bool check_success (bool success) { return this->successful && (success || (err_other_error (), false)); } /* * Creates a map from objid to # of incoming edges. */ - void update_incoming_edge_count () + void update_parents () { - if (!edge_count_invalid) return; + if (!parents_invalid) return; for (unsigned i = 0; i < vertices_.length; i++) - vertices_[i].incoming_edges = 0; + vertices_[i].parents.reset (); - for (const vertex_t& v : vertices_) + for (unsigned p = 0; p < vertices_.length; p++) { - for (auto& l : v.obj.links) + for (auto& l : vertices_[p].obj.links) { - vertices_[l.objidx].incoming_edges++; + vertices_[l.objidx].parents.push (p); } } - edge_count_invalid = false; + parents_invalid = false; } /* @@ -515,23 +812,25 @@ struct graph_t hb_priority_queue_t queue; queue.insert (0, vertices_.length - 1); - hb_set_t visited; + hb_vector_t<bool> visited; + visited.resize (vertices_.length); while (!queue.in_error () && !queue.is_empty ()) { unsigned next_idx = queue.pop_minimum ().second; - if (visited.has (next_idx)) continue; + if (visited[next_idx]) continue; const auto& next = vertices_[next_idx]; int64_t next_distance = vertices_[next_idx].distance; - visited.add (next_idx); + visited[next_idx] = true; for (const auto& link : next.obj.links) { - if (visited.has (link.objidx)) continue; + if (visited[link.objidx]) continue; const auto& child = vertices_[link.objidx].obj; - int64_t child_weight = child.tail - child.head + - ((int64_t) 1 << (link.width * 8)); + unsigned link_width = link.width ? link.width : 4; // treat virtual offsets as 32 bits wide + int64_t child_weight = (child.tail - child.head) + + ((int64_t) 1 << (link_width * 8)) * (vertices_[link.objidx].space + 1); int64_t child_distance = next_distance + child_weight; if (child_distance < vertices_[link.objidx].distance) @@ -545,7 +844,7 @@ struct graph_t check_success (!queue.in_error ()); if (!check_success (queue.is_empty ())) { - DEBUG_MSG (SUBSET_REPACK, nullptr, "Graph is not fully connected."); + print_orphaned_nodes (); return; } @@ -576,6 +875,10 @@ struct graph_t bool is_valid_offset (int64_t offset, const hb_serialize_context_t::object_t::link_t& link) const { + if (unlikely (!link.width)) + // Virtual links can't overflow. + return link.is_signed || offset >= 0; + if (link.is_signed) { if (link.width == 4) @@ -595,13 +898,50 @@ struct graph_t } /* + * Updates a link in the graph to point to a different object. Corrects the + * parents vector on the previous and new child nodes. + */ + void reassign_link (hb_serialize_context_t::object_t::link_t& link, + unsigned parent_idx, + unsigned new_idx) + { + unsigned old_idx = link.objidx; + link.objidx = new_idx; + vertices_[old_idx].remove_parent (parent_idx); + vertices_[new_idx].parents.push (parent_idx); + } + + /* + * Updates all objidx's in all links using the provided mapping. Corrects incoming edge counts. + */ + template<typename Iterator, hb_requires (hb_is_iterator (Iterator))> + void remap_obj_indices (const hb_hashmap_t<unsigned, unsigned>& id_map, + Iterator subgraph, + bool only_wide = false) + { + if (!id_map) return; + for (unsigned i : subgraph) + { + for (unsigned j = 0; j < vertices_[i].obj.links.length; j++) + { + auto& link = vertices_[i].obj.links[j]; + if (!id_map.has (link.objidx)) continue; + if (only_wide && !(link.width == 4 && !link.is_signed)) continue; + + reassign_link (link, i, id_map[link.objidx]); + } + } + } + + /* * Updates all objidx's in all links using the provided mapping. */ - void remap_obj_indices (const hb_vector_t<unsigned>& id_map, - hb_vector_t<vertex_t>* sorted_graph) const + void remap_all_obj_indices (const hb_vector_t<unsigned>& id_map, + hb_vector_t<vertex_t>* sorted_graph) const { for (unsigned i = 0; i < sorted_graph->length; i++) { + (*sorted_graph)[i].remap_parents (id_map); for (unsigned j = 0; j < (*sorted_graph)[i].obj.links.length; j++) { auto& link = (*sorted_graph)[i].obj.links[j]; @@ -631,6 +971,9 @@ struct graph_t { switch (link.width) { + case 0: + // Virtual links aren't serialized. + return; case 4: if (link.is_signed) { @@ -656,17 +999,120 @@ struct graph_t } } + /* + * Finds all nodes in targets that are reachable from start_idx, nodes in visited will be skipped. + * For this search the graph is treated as being undirected. + * + * Connected targets will be added to connected and removed from targets. All visited nodes + * will be added to visited. + */ + void find_connected_nodes (unsigned start_idx, + hb_set_t& targets, + hb_set_t& visited, + hb_set_t& connected) + { + if (visited.has (start_idx)) return; + visited.add (start_idx); + + if (targets.has (start_idx)) + { + targets.del (start_idx); + connected.add (start_idx); + } + + const auto& v = vertices_[start_idx]; + + // Graph is treated as undirected so search children and parents of start_idx + for (const auto& l : v.obj.links) + find_connected_nodes (l.objidx, targets, visited, connected); + + for (unsigned p : v.parents) + find_connected_nodes (p, targets, visited, connected); + } + public: // TODO(garretrieger): make private, will need to move most of offset overflow code into graph. hb_vector_t<vertex_t> vertices_; private: - hb_vector_t<clone_buffer_t> clone_buffers_; - bool edge_count_invalid; + bool parents_invalid; bool distance_invalid; bool positions_invalid; bool successful; + hb_vector_t<unsigned> num_roots_for_space_; }; +static bool _try_isolating_subgraphs (const hb_vector_t<graph_t::overflow_record_t>& overflows, + graph_t& sorted_graph) +{ + for (int i = overflows.length - 1; i >= 0; i--) + { + const graph_t::overflow_record_t& r = overflows[i]; + unsigned root = 0; + unsigned space = sorted_graph.space_for (r.parent, &root); + if (!space) continue; + if (sorted_graph.num_roots_for_space (space) <= 1) continue; + + DEBUG_MSG (SUBSET_REPACK, nullptr, "Overflow in space %d moving subgraph %d to space %d.", + space, + root, + sorted_graph.next_space ()); + + hb_set_t roots; + roots.add (root); + sorted_graph.isolate_subgraph (roots); + for (unsigned new_root : roots) + sorted_graph.move_to_new_space (new_root); + return true; + } + return false; +} + +static bool _process_overflows (const hb_vector_t<graph_t::overflow_record_t>& overflows, + hb_set_t& priority_bumped_parents, + graph_t& sorted_graph) +{ + bool resolution_attempted = false; + + // Try resolving the furthest overflows first. + for (int i = overflows.length - 1; i >= 0; i--) + { + const graph_t::overflow_record_t& r = overflows[i]; + const auto& child = sorted_graph.vertices_[r.child]; + if (child.is_shared ()) + { + // The child object is shared, we may be able to eliminate the overflow + // by duplicating it. + if (!sorted_graph.duplicate (r.parent, r.child)) continue; + return true; + } + + if (child.is_leaf () && !priority_bumped_parents.has (r.parent)) + { + // This object is too far from it's parent, attempt to move it closer. + // + // TODO(garretrieger): initially limiting this to leaf's since they can be + // moved closer with fewer consequences. However, this can + // likely can be used for non-leafs as well. + // TODO(garretrieger): add a maximum priority, don't try to raise past this. + // TODO(garretrieger): also try lowering priority of the parent. Make it + // get placed further up in the ordering, closer to it's children. + // this is probably preferable if the total size of the parent object + // is < then the total size of the children (and the parent can be moved). + // Since in that case moving the parent will cause a smaller increase in + // the length of other offsets. + sorted_graph.raise_childrens_priority (r.parent); + priority_bumped_parents.add (r.parent); + resolution_attempted = true; + continue; + } + + // TODO(garretrieger): add additional offset resolution strategies + // - Promotion to extension lookups. + // - Table splitting. + } + + return resolution_attempted; +} /* * Attempts to modify the topological sorting of the provided object graph to @@ -677,10 +1123,15 @@ struct graph_t * If necessary the structure of the graph may be modified in ways that do not * affect the functionality of the graph. For example shared objects may be * duplicated. + * + * For a detailed writeup describing how the algorithm operates see: + * docs/repacker.md */ inline void hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& packed, - hb_serialize_context_t* c) { + hb_tag_t table_tag, + hb_serialize_context_t* c, + unsigned max_rounds = 10) { // Kahn sort is ~twice as fast as shortest distance sort and works for many fonts // so try it first to save time. graph_t sorted_graph (packed); @@ -693,68 +1144,36 @@ hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& pac sorted_graph.sort_shortest_distance (); + if ((table_tag == HB_OT_TAG_GPOS + || table_tag == HB_OT_TAG_GSUB) + && sorted_graph.will_overflow ()) + { + DEBUG_MSG (SUBSET_REPACK, nullptr, "Assigning spaces to 32 bit subgraphs."); + if (sorted_graph.assign_32bit_spaces ()) + sorted_graph.sort_shortest_distance (); + } + unsigned round = 0; hb_vector_t<graph_t::overflow_record_t> overflows; // TODO(garretrieger): select a good limit for max rounds. while (!sorted_graph.in_error () && sorted_graph.will_overflow (&overflows) - && round++ < 10) { - DEBUG_MSG (SUBSET_REPACK, nullptr, "=== Over flow resolution round %d ===", round); + && round++ < max_rounds) { + DEBUG_MSG (SUBSET_REPACK, nullptr, "=== Overflow resolution round %d ===", round); sorted_graph.print_overflows (overflows); - bool resolution_attempted = false; hb_set_t priority_bumped_parents; - // Try resolving the furthest overflows first. - for (int i = overflows.length - 1; i >= 0; i--) + + if (!_try_isolating_subgraphs (overflows, sorted_graph)) { - const graph_t::overflow_record_t& r = overflows[i]; - const auto& child = sorted_graph.vertices_[r.link->objidx]; - if (child.is_shared ()) + if (!_process_overflows (overflows, priority_bumped_parents, sorted_graph)) { - // The child object is shared, we may be able to eliminate the overflow - // by duplicating it. - sorted_graph.duplicate (r.parent, r.link->objidx); - resolution_attempted = true; - - // Stop processing overflows for this round so that object order can be - // updated to account for the newly added object. + DEBUG_MSG (SUBSET_REPACK, nullptr, "No resolution available :("); break; } - - if (child.is_leaf () && !priority_bumped_parents.has (r.parent)) - { - // This object is too far from it's parent, attempt to move it closer. - // - // TODO(garretrieger): initially limiting this to leaf's since they can be - // moved closer with fewer consequences. However, this can - // likely can be used for non-leafs as well. - // TODO(garretrieger): add a maximum priority, don't try to raise past this. - // TODO(garretrieger): also try lowering priority of the parent. Make it - // get placed further up in the ordering, closer to it's children. - // this is probably preferable if the total size of the parent object - // is < then the total size of the children (and the parent can be moved). - // Since in that case moving the parent will cause a smaller increase in - // the length of other offsets. - sorted_graph.raise_childrens_priority (r.parent); - priority_bumped_parents.add (r.parent); - resolution_attempted = true; - continue; - } - - // TODO(garretrieger): add additional offset resolution strategies - // - Promotion to extension lookups. - // - Table splitting. - } - - if (resolution_attempted) - { - sorted_graph.sort_shortest_distance (); - continue; } - DEBUG_MSG (SUBSET_REPACK, nullptr, "No resolution available :("); - c->err (HB_SERIALIZE_ERROR_OFFSET_OVERFLOW); - return; + sorted_graph.sort_shortest_distance (); } if (sorted_graph.in_error ()) @@ -762,8 +1181,14 @@ hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& pac c->err (HB_SERIALIZE_ERROR_OTHER); return; } + + if (sorted_graph.will_overflow ()) + { + c->err (HB_SERIALIZE_ERROR_OFFSET_OVERFLOW); + DEBUG_MSG (SUBSET_REPACK, nullptr, "Offset overflow resolution failed."); + return; + } sorted_graph.serialize (c); } - #endif /* HB_REPACKER_HH */ |