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Revise marker deletion strategy

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Instead of checking if the object being removed allocated a marker, mark the
marker block as deleted immediately upon allocation. This simplifies the logic
and prevents extra markers from being inserted if we allocate/deallocate the
same node indefinitely.

Also change marker pointer type to uint32_t*.
This commit is contained in:
Arseny Kapoulkine
2015-05-02 15:40:30 -07:00
parent 613301ce51
commit fa8663c066
1 changed files with 22 additions and 29 deletions
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51
src/pugixml.cpp
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@@ -473,7 +473,7 @@ PUGI__NS_BEGIN
#ifdef PUGIXML_COMPACT
char_t* compact_string_base;
void* compact_shared_parent;
char* compact_page_marker;
uint32_t* compact_page_marker;
#endif
};
@@ -556,7 +556,16 @@ PUGI__NS_BEGIN
assert(_root == page);
// top page freed, just reset sizes
page->busy_size = page->freed_size = 0;
page->busy_size = 0;
page->freed_size = 0;
#ifdef PUGIXML_COMPACT
// reset compact state to maximize efficiency
page->compact_string_base = 0;
page->compact_shared_parent = 0;
page->compact_page_marker = 0;
#endif
_busy_size = 0;
}
else
@@ -696,7 +705,7 @@ PUGI__NS_BEGIN
PUGI__STATIC_ASSERT(xml_memory_block_alignment == compact_alignment);
PUGI__STATIC_ASSERT(sizeof(xml_memory_page) + xml_memory_page_size <= (1 << (16 + compact_alignment_log2)));
ptrdiff_t offset = (reinterpret_cast<char*>(this) - page->compact_page_marker);
ptrdiff_t offset = (reinterpret_cast<char*>(this) - reinterpret_cast<char*>(page->compact_page_marker));
assert(offset >= 0 && offset < 256 << compact_alignment_log2);
_page = static_cast<unsigned char>(offset >> compact_alignment_log2);
@@ -725,11 +734,6 @@ PUGI__NS_BEGIN
return const_cast<xml_memory_page*>(reinterpret_cast<const xml_memory_page*>(page_marker - *reinterpret_cast<const uint32_t*>(page_marker)));
}
bool has_marker() const
{
return _page == sizeof(uint32_t) >> compact_alignment_log2;
}
private:
unsigned char _page;
unsigned char _flags;
@@ -1122,13 +1126,17 @@ PUGI__NS_BEGIN
if (!result) return 0;
// adjust for marker
if (PUGI__UNLIKELY(static_cast<uintptr_t>(static_cast<char*>(result) - out_page->compact_page_marker) >= 256 * compact_alignment))
if (PUGI__UNLIKELY(static_cast<uintptr_t>(static_cast<char*>(result) - reinterpret_cast<char*>(out_page->compact_page_marker)) >= 256 * compact_alignment))
{
// insert new marker
uint32_t* marker = static_cast<uint32_t*>(result);
*marker = reinterpret_cast<char*>(marker) - reinterpret_cast<char*>(out_page);
out_page->compact_page_marker = reinterpret_cast<char*>(marker);
out_page->compact_page_marker = marker;
// since we don't reuse the page space until we reallocate it, we can just pretend that we freed the marker block
// this will make sure deallocate_memory correctly tracks the size
out_page->freed_size += sizeof(uint32_t);
return marker + 1;
}
@@ -1140,26 +1148,11 @@ PUGI__NS_BEGIN
return result;
}
}
template <typename T>
inline void deallocate_object(xml_allocator& alloc, T* ptr, size_t size, xml_memory_page* page)
{
// this is very crude... we should be able to do better?
if (ptr->header.has_marker())
page->compact_page_marker = 0;
alloc.deallocate_memory(ptr, size + ptr->header.has_marker() * sizeof(uint32_t), page);
}
#else
inline void* allocate_object(xml_allocator& alloc, size_t size, xml_memory_page*& out_page)
{
return alloc.allocate_memory(size, out_page);
}
inline void deallocate_object(xml_allocator& alloc, void* ptr, size_t size, xml_memory_page* page)
{
alloc.deallocate_memory(ptr, size, page);
}
#endif
inline xml_attribute_struct* allocate_attribute(xml_allocator& alloc)
@@ -1186,7 +1179,7 @@ PUGI__NS_BEGIN
if (a->header & impl::xml_memory_page_value_allocated_mask)
alloc.deallocate_string(a->value);
deallocate_object(alloc, a, sizeof(xml_attribute_struct), PUGI__GETPAGE(a));
alloc.deallocate_memory(a, sizeof(xml_attribute_struct), PUGI__GETPAGE(a));
}
inline void destroy_node(xml_node_struct* n, xml_allocator& alloc)
@@ -1215,7 +1208,7 @@ PUGI__NS_BEGIN
child = next;
}
deallocate_object(alloc, n, sizeof(xml_node_struct), PUGI__GETPAGE(n));
alloc.deallocate_memory(n, sizeof(xml_node_struct), PUGI__GETPAGE(n));
}
inline void append_node(xml_node_struct* child, xml_node_struct* node)
@@ -6725,8 +6718,8 @@ namespace pugi
// setup first page marker
#ifdef PUGIXML_COMPACT
page->compact_page_marker = reinterpret_cast<char*>(page) + sizeof(impl::xml_memory_page);
*reinterpret_cast<uint32_t*>(page->compact_page_marker) = sizeof(impl::xml_memory_page);
page->compact_page_marker = reinterpret_cast<uint32_t*>(reinterpret_cast<char*>(page) + sizeof(impl::xml_memory_page));
*page->compact_page_marker = sizeof(impl::xml_memory_page);
#endif
// allocate new root