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authorArseny Kapoulkine <arseny.kapoulkine@gmail.com>2015-03-05 12:50:29 -0800
committerArseny Kapoulkine <arseny.kapoulkine@gmail.com>2015-03-05 13:02:05 -0800
commit23060d095447ca7c47a9c0698ec731197cebc80b (patch)
tree9536f45a6e9bd86ad7317e48a3b8defbb356f9f8 /src/pugixml.cpp
parent12e137d12fe6e6492e669cfa6c333f4a8911b1b2 (diff)
Use more efficient encoding for string headers
Since all string allocations are pointer-aligned to avoid aligning more frequent node allocations, we can rely on that in string encoding. Encoding page offset and block size in sizeof(void*) units increases the maximum memory page size from 64k to 256k on 32-bit and 512k on 64-bit platforms. Fixes #35.
Diffstat (limited to 'src/pugixml.cpp')
-rw-r--r--src/pugixml.cpp18
1 files changed, 11 insertions, 7 deletions
diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index fa41058..6c88d55 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -400,7 +400,9 @@ PUGI__NS_BEGIN
char_t* allocate_string(size_t length)
{
- PUGI__STATIC_ASSERT(xml_memory_page_size <= (1 << 16));
+ static const size_t max_encoded_offset = (1 << 16) * sizeof(void*);
+
+ PUGI__STATIC_ASSERT(xml_memory_page_size <= max_encoded_offset);
// allocate memory for string and header block
size_t size = sizeof(xml_memory_string_header) + length * sizeof(char_t);
@@ -416,12 +418,14 @@ PUGI__NS_BEGIN
// setup header
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);
+ assert(page_offset % sizeof(void*) == 0);
+ assert(page_offset >= 0 && static_cast<size_t>(page_offset) < max_encoded_offset);
+ header->page_offset = static_cast<uint16_t>(static_cast<size_t>(page_offset) / sizeof(void*));
// 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 = static_cast<uint16_t>(full_size < (1 << 16) ? full_size : 0);
+ assert(full_size % sizeof(void*) == 0);
+ assert(full_size < max_encoded_offset || (page->busy_size == full_size && page_offset == 0));
+ header->full_size = static_cast<uint16_t>(full_size < max_encoded_offset ? full_size / sizeof(void*) : 0);
// round-trip through void* to avoid 'cast increases required alignment of target type' warning
// header is guaranteed a pointer-sized alignment, which should be enough for char_t
@@ -438,11 +442,11 @@ PUGI__NS_BEGIN
assert(header);
// deallocate
- size_t page_offset = sizeof(xml_memory_page) + header->page_offset;
+ size_t page_offset = sizeof(xml_memory_page) + header->page_offset * sizeof(void*);
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
- size_t full_size = header->full_size == 0 ? page->busy_size : header->full_size;
+ size_t full_size = header->full_size == 0 ? page->busy_size : header->full_size * sizeof(void*);
deallocate_memory(header, full_size, page);
}