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authorarseny.kapoulkine <arseny.kapoulkine@99668b35-9821-0410-8761-19e4c4f06640>2010-08-29 15:18:22 +0000
committerarseny.kapoulkine <arseny.kapoulkine@99668b35-9821-0410-8761-19e4c4f06640>2010-08-29 15:18:22 +0000
commit9ec7db4c0cdf945eddb30a1630dcc96fd3763b1c (patch)
treea9ed13eaba520ab48eb1d82f95a2432dd306456e
parent40e6900b0feec0a39f9b71f3e5bacb82b20d0259 (diff)
Reduced allocation header for strings from 8/16 to 4 bytes
git-svn-id: http://pugixml.googlecode.com/svn/trunk@653 99668b35-9821-0410-8761-19e4c4f06640
-rw-r--r--src/pugixml.cpp30
1 files changed, 21 insertions, 9 deletions
diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index f093a8b..c9b0046 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -277,8 +277,8 @@ namespace pugi
struct xml_memory_string_header
{
- xml_memory_page* page;
- size_t full_size;
+ uint16_t page_offset; // offset from page->data
+ uint16_t full_size; // 0 if string occupies whole page
};
struct xml_allocator
@@ -364,11 +364,11 @@ namespace pugi
char_t* allocate_string(size_t length)
{
- // get actual size, rounded up to pointer alignment boundary
- size_t size = ((length * sizeof(char_t)) + (sizeof(void*) - 1)) & ~(sizeof(void*) - 1);
-
// allocate memory for string and header block
- size_t full_size = sizeof(xml_memory_string_header) + size;
+ size_t size = sizeof(xml_memory_string_header) + length * sizeof(char_t);
+
+ // round size up to pointer alignment boundary
+ size_t full_size = (size + (sizeof(void*) - 1)) & ~(sizeof(void*) - 1);
xml_memory_page* page;
xml_memory_string_header* header = static_cast<xml_memory_string_header*>(allocate_memory(full_size, page));
@@ -376,8 +376,14 @@ namespace pugi
if (!header) return 0;
// setup header
- header->page = page;
- header->full_size = full_size;
+ ptrdiff_t page_offset = reinterpret_cast<char*>(header) - page->data;
+
+ assert(page_offset >= 0 && page_offset < (1 << 16));
+ header->page_offset = static_cast<uint16_t>(page_offset);
+
+ // full_size == 0 for large strings that occupy the whole page
+ assert(full_size < (1 << 16) || (page->busy_size == full_size && page_offset == 0));
+ header->full_size = full_size < (1 << 16) ? static_cast<uint16_t>(full_size) : 0;
return reinterpret_cast<char_t*>(header + 1);
}
@@ -388,7 +394,13 @@ namespace pugi
xml_memory_string_header* header = reinterpret_cast<xml_memory_string_header*>(string) - 1;
// deallocate
- deallocate_memory(header, header->full_size, header->page);
+ size_t page_offset = offsetof(xml_memory_page, data) + header->page_offset;
+ xml_memory_page* page = reinterpret_cast<xml_memory_page*>(reinterpret_cast<char*>(header) - page_offset);
+
+ // if full_size == 0 then this string occupies the whole page
+ size_t full_size = header->full_size == 0 ? page->busy_size : header->full_size;
+
+ deallocate_memory(header, full_size, page);
}
xml_memory_page* _root;