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sot: simplify the storage stream FAT item cache

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Change-Id: Icb6fe9341244dfd53300f58ac85560604f53558a
This commit is contained in:
Michael Meeks 2012-05-11 19:49:27 +01:00
parent e4450c54ae
commit 7ed1e9aa17
2 changed files with 38 additions and 72 deletions
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109
sot/source/sdstor/stgstrms.cxx
View file

@ -334,27 +334,12 @@ void StgStrm::SetEntry( StgDirEntry& r )
r.SetDirty();
}
namespace lcl
{
#if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
using std::is_sorted;
#else
template <typename iter> bool is_sorted(iter aStart, iter aEnd)
{
if (aStart == aEnd)
return true;
for (iter aNext = aStart + 1; aNext != aEnd; aStart = aNext, ++aNext)
{
if (*aNext < *aStart)
return false;
}
return true;
}
#endif
}
/*
* The page chain, is basically a singly linked list of slots each
* point to the next page. Instead of traversing the file structure
* for this each time build a simple flat in-memory vector list
* of pages.
*/
bool StgStrm::buildPageChainCache()
{
if (nSize > 0)
@ -370,10 +355,6 @@ bool StgStrm::buildPageChainCache()
return false;
}
m_bSortedPageChain = lcl::is_sorted(m_aPagesCache.begin(), m_aPagesCache.end());
SAL_WARN_IF(!m_bSortedPageChain, "sot", "unsorted page chain, that's suspicious");
return true;
}
@ -382,7 +363,7 @@ bool StgStrm::buildPageChainCache()
//
//There's a cost to building a page cache, so only build one if the number of
//pages to seek through hits some sufficiently high value where it's worth it.
#define ARBITRARY_LARGE_AMOUNT_OF_PAGES 256
#define ARBITRARY_LARGE_AMOUNT_OF_PAGES 8 * 512
// Compute page number and offset for the given byte position.
// If the position is behind the size, set the stream right
@ -403,6 +384,32 @@ sal_Bool StgStrm::Pos2Page( sal_Int32 nBytePos )
nPos = nBytePos;
if( nOld == nNew )
return sal_True;
if (m_aPagesCache.empty() && nNew > ARBITRARY_LARGE_AMOUNT_OF_PAGES)
{
SAL_WARN("sot", "kicking off large seek helper\n");
buildPageChainCache();
}
if (!m_aPagesCache.empty())
{
size_t nIdx = nNew / nPageSize;
// special case: seek to 1st byte of new, unallocated page
// (in case the file size is a multiple of the page size)
if( nBytePos == nSize && !nOffset && nIdx == m_aPagesCache.size() )
{
nIdx--;
nOffset = nPageSize;
}
if (nIdx < m_aPagesCache.size())
{
nPage = m_aPagesCache[ nIdx ];
return sal_Bool( nPage >= 0 );
}
}
if( nNew > nOld )
{
// the new position is after the current, so an incremental
@ -421,58 +428,18 @@ sal_Bool StgStrm::Pos2Page( sal_Int32 nBytePos )
nRel /= nPageSize;
sal_Int32 nLast = STG_EOF;
if (m_aPagesCache.empty() && nRel < ARBITRARY_LARGE_AMOUNT_OF_PAGES)
while (nRel && nBgn >= 0)
{
while (nRel && nBgn >= 0)
{
nLast = nBgn;
nBgn = pFat->GetNextPage( nBgn );
nRel--;
}
}
else if (nBgn >= 0)
{
//Seeking large distances is slow, so if we're starting seeking (some
//fairly arbitrary) large distances, build a cache and re-use it for
//subsequent seeks
if (m_aPagesCache.empty())
{
SAL_WARN("sot", "kicking off large seek helper\n");
buildPageChainCache();
}
std::vector<sal_Int32>::iterator aI;
if (m_bSortedPageChain)
aI = std::lower_bound(m_aPagesCache.begin(), m_aPagesCache.end(), nBgn);
else
aI = std::find(m_aPagesCache.begin(), m_aPagesCache.end(), nBgn);
if (aI == m_aPagesCache.end())
{
SAL_WARN("sot", "Unknown page position");
nBgn = STG_EOF;
}
else
{
size_t nBgnIndex = std::distance(m_aPagesCache.begin(), aI);
size_t nIndex = nBgnIndex + nRel;
if (nIndex >= m_aPagesCache.size())
nIndex = m_aPagesCache.size() - 1;
size_t nSuccessfulStepsTaken = nIndex - nBgnIndex;
nRel -= nSuccessfulStepsTaken;
nLast = nIndex ? m_aPagesCache[nIndex - 1] : STG_EOF;
nBgn = m_aPagesCache[nIndex];
}
nLast = nBgn;
nBgn = pFat->GetNextPage( nBgn );
nRel--;
}
// special case: seek to 1st byte of new, unallocated page
// (in case the file size is a multiple of the page size)
if( nBytePos == nSize && nBgn == STG_EOF && !nRel && !nOffset )
nBgn = nLast, nOffset = nPageSize;
if( nBgn < 0 && nBgn != STG_EOF )
{
rIo.SetError( SVSTREAM_FILEFORMAT_ERROR );

1
sot/source/sdstor/stgstrms.hxx
View file

@ -79,7 +79,6 @@ protected:
short nOffset; // offset into current page
short nPageSize; // logical page size
std::vector<sal_Int32> m_aPagesCache;
bool m_bSortedPageChain;
bool buildPageChainCache();
sal_Bool Copy( sal_Int32 nFrom, sal_Int32 nBytes );
StgStrm( StgIo& );