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strcpy_insitu improvements: empty string forces deallocation, memory is reclaimed if waste is too great (small string is copied to the large buffer)

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git-svn-id: http://pugixml.googlecode.com/svn/trunk@654 99668b35-9821-0410-8761-19e4c4f06640
This commit is contained in:
arseny.kapoulkine 2010-08-29 15:19:22 +00:00
parent 9ec7db4c0c
commit bc5901dd28
1 changed files with 33 additions and 1 deletions
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34
src/pugixml.cpp
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@ -1327,12 +1327,40 @@ namespace
}
#endif
inline bool strcpy_insitu_allow(size_t length, uintptr_t allocated, char_t* target)
{
assert(target);
size_t target_length = impl::strlen(target);
// always reuse document buffer memory if possible
if (!allocated) return target_length >= length;
// reuse heap memory if waste is not too great
const size_t reuse_threshold = 32;
return target_length >= length && (target_length < reuse_threshold || target_length - length < target_length / 2);
}
bool strcpy_insitu(char_t*& dest, uintptr_t& header, uintptr_t header_mask, const char_t* source)
{
size_t source_length = impl::strlen(source);
if (dest && impl::strlen(dest) >= source_length)
if (source_length == 0)
{
// empty string and null pointer are equivalent, so just deallocate old memory
xml_allocator* alloc = reinterpret_cast<xml_memory_page*>(header & xml_memory_page_pointer_mask)->allocator;
if (header & header_mask) alloc->deallocate_string(dest);
// mark the string as not allocated
dest = 0;
header &= ~header_mask;
return true;
}
else if (dest && strcpy_insitu_allow(source_length, header & header_mask, dest))
{
// we can reuse old buffer, so just copy the new data (including zero terminator)
memcpy(dest, source, (source_length + 1) * sizeof(char_t));
return true;
@ -1341,13 +1369,17 @@ namespace
{
xml_allocator* alloc = reinterpret_cast<xml_memory_page*>(header & xml_memory_page_pointer_mask)->allocator;
// allocate new buffer
char_t* buf = alloc->allocate_string(source_length + 1);
if (!buf) return false;
// copy the string (including zero terminator)
memcpy(buf, source, (source_length + 1) * sizeof(char_t));
// deallocate old buffer (*after* the above to protect against overlapping memory and/or allocation failures)
if (header & header_mask) alloc->deallocate_string(dest);
// the string is now allocated, so set the flag
dest = buf;
header |= header_mask;