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Reorganize xml_memory_page structure

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The page no longer contains 'data' field to use sizeof everywhere instead
of offsetof/sizeof inconsistency (that is required because some compilers
don't recognize offsetof as compile-time constant).

The page no longer contains 'memory' field that is now encoded as an
offset byte before the page - this allows us to save one pointer from the
static page in the document to keep the size the same as in v1.2 (binary
compatibility).

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1046 99668b35-9821-0410-8761-19e4c4f06640
This commit is contained in:
Arseny Kapoulkine 2014-10-03 05:18:03 +00:00
parent daa48183f9
commit c4ecc406d2
2 changed files with 21 additions and 20 deletions
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38
src/pugixml.cpp
View File

@ -288,7 +288,6 @@ PUGI__NS_BEGIN
xml_memory_page* result = static_cast<xml_memory_page*>(memory);
result->allocator = 0;
result->memory = 0;
result->prev = 0;
result->next = 0;
result->busy_size = 0;
@ -299,15 +298,11 @@ PUGI__NS_BEGIN
xml_allocator* allocator;
void* memory;
xml_memory_page* prev;
xml_memory_page* next;
size_t busy_size;
size_t freed_size;
char data[1];
};
struct xml_memory_string_header
@ -324,28 +319,32 @@ PUGI__NS_BEGIN
xml_memory_page* allocate_page(size_t data_size)
{
size_t size = offsetof(xml_memory_page, data) + data_size;
size_t size = sizeof(xml_memory_page) + data_size;
// allocate block with some alignment, leaving memory for worst-case padding
void* memory = xml_memory::allocate(size + xml_memory_page_alignment);
if (!memory) return 0;
// align upwards to page boundary
void* page_memory = reinterpret_cast<void*>((reinterpret_cast<uintptr_t>(memory) + (xml_memory_page_alignment - 1)) & ~(xml_memory_page_alignment - 1));
// align upwards to page boundary (note: this guarantees at least 1 usable byte before the page)
char* page_memory = reinterpret_cast<char*>((reinterpret_cast<uintptr_t>(memory) + xml_memory_page_alignment) & ~(xml_memory_page_alignment - 1));
// prepare page structure
xml_memory_page* page = xml_memory_page::construct(page_memory);
assert(page);
page->memory = memory;
page->allocator = _root->allocator;
// record the offset for freeing the memory block
page_memory[-1] = static_cast<char>(page_memory - static_cast<char*>(memory));
return page;
}
static void deallocate_page(xml_memory_page* page)
{
xml_memory::deallocate(page->memory);
char* page_memory = reinterpret_cast<char*>(page);
xml_memory::deallocate(page_memory - page_memory[-1]);
}
void* allocate_memory_oob(size_t size, xml_memory_page*& out_page);
@ -354,7 +353,7 @@ PUGI__NS_BEGIN
{
if (_busy_size + size > xml_memory_page_size) return allocate_memory_oob(size, out_page);
void* buf = _root->data + _busy_size;
void* buf = reinterpret_cast<char*>(_root) + sizeof(xml_memory_page) + _busy_size;
_busy_size += size;
@ -367,7 +366,7 @@ PUGI__NS_BEGIN
{
if (page == _root) page->busy_size = _busy_size;
assert(ptr >= page->data && ptr < page->data + page->busy_size);
assert(ptr >= reinterpret_cast<char*>(page) + sizeof(xml_memory_page) && ptr < reinterpret_cast<char*>(page) + sizeof(xml_memory_page) + page->busy_size);
(void)!ptr;
page->freed_size += size;
@ -412,7 +411,7 @@ PUGI__NS_BEGIN
if (!header) return 0;
// setup header
ptrdiff_t page_offset = reinterpret_cast<char*>(header) - page->data;
ptrdiff_t page_offset = reinterpret_cast<char*>(header) - reinterpret_cast<char*>(page) - sizeof(xml_memory_page);
assert(page_offset >= 0 && page_offset < (1 << 16));
header->page_offset = static_cast<uint16_t>(page_offset);
@ -435,7 +434,7 @@ PUGI__NS_BEGIN
xml_memory_string_header* header = static_cast<xml_memory_string_header*>(static_cast<void*>(string)) - 1;
// deallocate
size_t page_offset = offsetof(xml_memory_page, data) + header->page_offset;
size_t page_offset = sizeof(xml_memory_page) + header->page_offset;
xml_memory_page* page = reinterpret_cast<xml_memory_page*>(static_cast<void*>(reinterpret_cast<char*>(header) - page_offset));
// if full_size == 0 then this string occupies the whole page
@ -484,7 +483,7 @@ PUGI__NS_BEGIN
// allocate inside page
page->busy_size = size;
return page->data;
return reinterpret_cast<char*>(page) + sizeof(xml_memory_page);
}
PUGI__NS_END
@ -5872,7 +5871,7 @@ namespace pugi
assert(!_root);
// initialize sentinel page
PUGI__STATIC_ASSERT(sizeof(impl::xml_memory_page) + sizeof(impl::xml_document_struct) + impl::xml_memory_page_alignment <= sizeof(_memory));
PUGI__STATIC_ASSERT(sizeof(impl::xml_memory_page) + sizeof(impl::xml_document_struct) + impl::xml_memory_page_alignment - sizeof(void*) <= sizeof(_memory));
// align upwards to page boundary
void* page_memory = reinterpret_cast<void*>((reinterpret_cast<uintptr_t>(_memory) + (impl::xml_memory_page_alignment - 1)) & ~(impl::xml_memory_page_alignment - 1));
@ -5884,11 +5883,14 @@ namespace pugi
page->busy_size = impl::xml_memory_page_size;
// allocate new root
_root = new (page->data) impl::xml_document_struct(page);
_root = new (reinterpret_cast<char*>(page) + sizeof(impl::xml_memory_page)) impl::xml_document_struct(page);
_root->prev_sibling_c = _root;
// setup sentinel page
page->allocator = static_cast<impl::xml_document_struct*>(_root);
// verify the document allocation
assert(reinterpret_cast<char*>(_root) + sizeof(impl::xml_document_struct) <= _memory + sizeof(_memory));
}
PUGI__FN void xml_document::destroy()
@ -5910,7 +5912,7 @@ namespace pugi
// destroy dynamic storage, leave sentinel page (it's in static memory)
impl::xml_memory_page* root_page = reinterpret_cast<impl::xml_memory_page*>(_root->header & impl::xml_memory_page_pointer_mask);
assert(root_page && !root_page->prev && !root_page->memory);
assert(root_page && !root_page->prev);
for (impl::xml_memory_page* page = root_page->next; page; )
{

3
src/pugixml.hpp
View File

@ -926,8 +926,7 @@ namespace pugi
private:
char_t* _buffer;
// sizeof(xml_memory_page) + sizeof(xml_document_struct) + xml_memory_page_alignment
char _memory[sizeof(void*) * 20 + 64];
char _memory[192];
// Non-copyable semantics
xml_document(const xml_document&);