Hi
I think it would probably need to be a static rather than per-document, because
you won’t always have a reference to an owner document when dictionaries are
being modified.
class PdfName
{
static Map< std::string, PdfName> s_nameTable;
}
That would mean keys are always valid (the name table would only be destroyed
when the app exits)
One issue is threading – I’m not sure what guarantees PoDoFo gives around
threading, but this makes dictionary operations non-thread safe unless locking
is added.
Current memory layout in 32-bit windows is:
class PoDoFo::PdfName size(36):
0 (base class PoDoFo::PdfDataType)
0 {vfptr} (size=4)
4 m_bImmutable (size=1)
| <alignment member> (size=3)
8 std::string m_Data (size =24)
plus
8 bytes HeapAlloc overhead
8 bytes malloc overhead
Total: 36+8+8 =52 bytes per dictionary key
If the std::string was changed to a ref counted pointer this would change to
something like:
class PoDoFo::PdfName size(16):
0 (base class PoDoFo::PdfDataType)
0 {vfptr} (size=4)
4 m_bImmutable (size=1)
| <alignment member> (size=3)
8 std::string* m_Data (size =4)
plus
8 bytes HeapAlloc overhead
8 bytes malloc overhead
Total: 31+8+8 =32 bytes per dictionary key
If the dictionary keys are changed to PdfName& or PdfName* then it changes to
Total: 4 bytes per dictionary key (Sizeof(PdfName*) = sizeof(void*) = 4 bytes)
with no heap overhead
Best Regards
Mark
Mark Rogers - [email protected]
PowerMapper Software Ltd - www.powermapper.com
Registered in Scotland No 362274 Quartermile 2 Edinburgh EH3 9GL
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