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Support movement of cached objects.
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@tmadden
tmadden committed Oct 1, 2020
1 parent 680ab00 commit 109205f
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Showing 2 changed files with 120 additions and 27 deletions.
91 changes: 75 additions & 16 deletions src/alia/flow/object_trees.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,8 +53,16 @@ struct tree_node : noncopyable
next->prev_ = &this->next_;
}

// prev_ points to whatever pointer anchors this node in the tree.
// If this node is the first child amongst its siblings, then this will
// point back to its parent's children_ pointer.
// Otherwise, this points to the previous sibling's next_ pointer.
tree_node** prev_ = nullptr;

// next_ points to the next sibling in this node's sibling list (if any).
tree_node* next_ = nullptr;

// children_ points to this node's first child (if any).
tree_node* children_ = nullptr;
};

Expand Down Expand Up @@ -226,7 +234,6 @@ template<class Object>
struct tree_caching_data
{
captured_id content_id;
tree_node<Object>** predecessor = nullptr;
tree_node<Object>* subtree_head = nullptr;
tree_node<Object>** subtree_tail = nullptr;
tree_node<Object>* last_sibling = nullptr;
Expand Down Expand Up @@ -267,13 +274,6 @@ struct scoped_tree_cacher
if (!data.content_id.matches(content_id))
content_traversal_required_ = true;

// Check to see that we're inserting this where it's expected.
// If not, traverse the contents. (It's not technically necessary to do
// this. We could instead move the cached contents here, but this is
// easier and fine for now.)
if (data.predecessor != traversal.next_ptr)
content_traversal_required_ = true;

if (content_traversal_required_)
{
// If we're updating the contents, capture the content ID now
Expand All @@ -283,12 +283,72 @@ struct scoped_tree_cacher
// Also record the current value of the tree traversal's next_ptr.
predecessor_ = traversal.next_ptr;
}
else
else if (data.subtree_head)
{
// And if we're not updating the contents, just splice it in.
*traversal.next_ptr = data.subtree_head;
traversal.next_ptr = data.subtree_tail;
traversal.last_sibling = data.last_sibling;
// There's no need to refresh, but we have cached content, so we
// need to splice it in...

// Check to see if we're inserting this where we expected.
if (data.subtree_head->prev_ == traversal.next_ptr)
{
// If so, the objects are already in place, so we just need to
// update the traversal state to skip over them.
*traversal.next_ptr = data.subtree_head;
traversal.next_ptr = data.subtree_tail;
traversal.last_sibling = data.last_sibling;
}
else
{
// If not, we need to relocate all the top-level cached objects
// to the new position in the object tree...

// Remove the whole cached subtree from wherever it is in the
// object tree.
{
tree_node<Object>** prev = data.subtree_head->prev_;
tree_node<Object>* next = *data.subtree_tail;
if (next)
next->prev_ = prev;
if (prev)
*prev = next;
}

// Relocate all the actual objects.
tree_node<Object>* last_sibling = traversal.last_sibling;
{
tree_node<Object>* expected_node = *traversal.next_ptr;
Object* node_after
= expected_node ? &expected_node->object : nullptr;
tree_node<Object>* current_node = data.subtree_head;
tree_node<Object>** next_ptr = nullptr;
while (next_ptr != data.subtree_tail)
{
current_node->object.relocate(
traversal.active_parent->object,
last_sibling ? &last_sibling->object : nullptr,
node_after);
last_sibling = current_node;
next_ptr = &current_node->next_;
current_node = current_node->next_;
}
}

// Splice the subtree into its new place in the object tree.
{
tree_node<Object>* expected_node = *traversal.next_ptr;

data.subtree_head->prev_ = traversal.next_ptr;
*traversal.next_ptr = data.subtree_head;

last_sibling->next_ = expected_node;
if (expected_node)
expected_node->prev_ = &last_sibling->next_;
}

// Update the traversal state.
traversal.last_sibling = data.last_sibling;
traversal.next_ptr = data.subtree_tail;
}
}
}

Expand All @@ -297,11 +357,10 @@ struct scoped_tree_cacher
{
if (traversal_)
{
// If the subtree was traversed, record the head and tail of it so
// we can splice it in on future passes.
// If the subtree was traversed, record the head and tail of it
// so we can splice it in on future passes.
if (content_traversal_required_)
{
data_->predecessor = predecessor_;
data_->subtree_head = *predecessor_;
data_->subtree_tail = traversal_->next_ptr;
data_->last_sibling = traversal_->last_sibling;
Expand Down
56 changes: 45 additions & 11 deletions unit_tests/flow/object_trees.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -449,6 +449,15 @@ TEST_CASE("object tree caching", "[flow][object_trees]")
}
ALIA_END

// Objects inside named blocks aren't necessarily deleted in order, so
// this tests different code paths.
naming_context nc(ctx);
if (n & 32)
{
named_block nb(nc, make_id(32));
do_object(ctx, "bit5");
}

auto& caching_data
= get_cached_data<tree_caching_data<test_object>>(ctx);
scoped_tree_cacher<test_object> cacher(
Expand Down Expand Up @@ -496,27 +505,24 @@ TEST_CASE("object tree caching", "[flow][object_trees]")
}
});

n = 0;
n = 0b000000;
refresh_system(sys);
check_log("traversing cached content; ");
REQUIRE(root.object.to_string() == "root()");

n = 3;
n = 0b000011;
refresh_system(sys);
check_log(
"relocating bit0 into root; "
"relocating bit1 into root after bit0; "
// This happens because the caching system can't currently handle
// moving the cached content.
"traversing cached content; ");
"relocating bit1 into root after bit0; ");
REQUIRE(root.object.to_string() == "root(bit0();bit1();)");

n = 2;
n = 0b000010;
refresh_system(sys);
check_log("removing bit0; ");
REQUIRE(root.object.to_string() == "root(bit1();)");

n = 15;
n = 0b001111;
refresh_system(sys);
check_log(
"relocating bit0 into root; "
Expand All @@ -525,15 +531,43 @@ TEST_CASE("object tree caching", "[flow][object_trees]")
"relocating bit3 into root after bit2; ");
REQUIRE(root.object.to_string() == "root(bit0();bit1();bit2();bit3();)");

n = 14;
n = 0b001110;
refresh_system(sys);
check_log("removing bit0; ");
REQUIRE(root.object.to_string() == "root(bit1();bit2();bit3();)");

n = 6;
n = 0b101110;
refresh_system(sys);
check_log("relocating bit5 into root after bit1; ");
REQUIRE(root.object.to_string() == "root(bit1();bit5();bit2();bit3();)");

n = 0b101100;
refresh_system(sys);
check_log("removing bit1; ");
REQUIRE(root.object.to_string() == "root(bit5();bit2();bit3();)");

n = 0b101101;
refresh_system(sys);
check_log("relocating bit0 into root; ");
REQUIRE(root.object.to_string() == "root(bit0();bit5();bit2();bit3();)");

n = 0b001101;
refresh_system(sys);
check_log(
"relocating bit2 into root after bit0; "
"relocating bit3 into root after bit2; "
"removing bit5; ");
REQUIRE(root.object.to_string() == "root(bit0();bit2();bit3();)");

n = 0b000101;
refresh_system(sys);
check_log(
"traversing cached content; "
"removing bit3; ");
REQUIRE(root.object.to_string() == "root(bit1();bit2();)");
REQUIRE(root.object.to_string() == "root(bit0();bit2();)");

n = 0b100100;
refresh_system(sys);
check_log("removing bit0; relocating bit5 into root; ");
REQUIRE(root.object.to_string() == "root(bit5();bit2();)");
}

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