[Libreoffice] An Improvement for libreoffice to access a file in disk

-------------This email and the patch follow  the provisions of GPL 3.
hi,i modified the code of libreoffice to access the file in disk,mainly in
sot module and the speed for libreoffice  to open a ppt file from disk is
25% faster.
My computer :
   cpu:unicore-2 600Mhz,mem:1GB.DDR2
The main change:
   I found that when libreoffice  reads a byte from the file,it will traverse
the list  of sectors and it is slow.So i use an array to save the list.when
reading a byte,we can use the array to obtain the address of this byte in
disk directly.This change wil accelerate  the process of opening a ppt file
from disk.Theorily,it also can improve the perfommance
of libreoffice  running ,but if the file is  changed ,the array will be
failed。Therefore,i add an tag to mark whether the file is modified.If it is
changed,we can use the list,else we use the array.
 The patch :

diff -u orig/sot/source/sdstor/stgdir.cxx optimized/sot/source/sdstor/stgdir.cxx
--- orig/sot/source/sdstor/stgdir.cxx   2010-07-23 11:31:38.046198867 +0800
+++ optimized/sot/source/sdstor/stgdir.cxx      2011-03-12 12:30:07.092985044 +0800
@@ -879,6 +879,7 @@

 BOOL StgDirStrm::Store()
 {
+       Dirty=true;
     if( !pRoot->IsDirty() )
         return TRUE;
     if( !pRoot->StoreStreams( rIo ) )
diff -u orig/sot/source/sdstor/stgstrms.cxx
optimized/sot/source/sdstor/stgstrms.cxx
--- orig/sot/source/sdstor/stgstrms.cxx 2010-07-23 11:31:38.046198867 +0800
+++ optimized/sot/source/sdstor/stgstrms.cxx    2011-03-12 12:41:12.756986414 +0800
@@ -327,6 +327,8 @@
     pEntry  = NULL;
     nPos = nSize = 0;
     nPageSize = rIo.GetPhysPageSize();
+       initFAT=true;
+       Dirty=false;
 }

 StgStrm::~StgStrm()
@@ -350,6 +352,32 @@

 BOOL StgStrm::Pos2Page( INT32 nBytePos )
 {
+       if(initFAT==true)
+       {
+               initFAT=false;
+
+               FAT[0]=nStart;
+               for(INT32 i=1;i<8192;i++)
+                       FAT[i]=-5;
+
+               INT32 nRel,nBgn,currentSuffix;
+               currentSuffix=0;
+               nRel=nSize/nPageSize;
+               if(nRel==0)
+                       FAT[++currentSuffix]=-2;
+               else
+               {
+                       nBgn=nStart;
+
+                       while(nRel && nBgn>=0)
+                       {
+                               nBgn=pFat->GetNextPage(nBgn);
+                               FAT[++currentSuffix]=nBgn;
+                               nRel--;
+                       }
+               }
+       
+       }
     INT32 nRel, nBgn;
     // Values < 0 seek to the end
     if( nBytePos < 0 || nBytePos >= nSize )
@@ -363,7 +391,29 @@
     nPos = nBytePos;
     if( nOld == nNew )
         return TRUE;
-    if( nNew > nOld )
+    if(Dirty==false)
+       {
+               INT32 nDestPage=nNew/nPageSize;
+               INT32 nNewPage=FAT[nDestPage];
+       
+               if(nNewPage!=-5)
+               {
+                       nPage=nNewPage;
+                       if(nBytePos==nSize&&!nOffset)
+                       {
+                               nPage=FAT[nDestPage-1];
+                               nOffset=nPageSize;
+                       }
+                       return BOOL(nPage>=0);
+               }
+               else
+               {
+                       rIo.SetError( SVSTREAM_FILEFORMAT_ERROR );
+                       nPage = STG_EOF;
+                       nOffset = nPageSize;
+               }
+       }
+    if( nNew >= nOld )
     {
         // the new position is behind the current, so an incremental
         // positioning is OK. Set the page relative position
@@ -879,6 +929,7 @@

 INT32 StgDataStrm::Write( const void* pBuf, INT32 n )
 {
+       Dirty=true;
     INT32 nDone = 0;
     if( ( nPos + n ) > nSize )
     {
@@ -1005,6 +1056,7 @@

 INT32 StgSmallStrm::Write( const void* pBuf, INT32 n )
 {
+       Dirty=true;
     // you can safely assume that reads are not huge, since the
     // small stream is likely to be < 64 KBytes.
     short nDone = 0;
diff -u orig/sot/source/sdstor/stgstrms.hxx
optimized/sot/source/sdstor/stgstrms.hxx
--- orig/sot/source/sdstor/stgstrms.hxx 2011-03-12 12:37:52.468985102 +0800
+++ optimized/sot/source/sdstor/stgstrms.hxx    2011-03-12 12:37:49.297042325 +0800
@@ -84,6 +84,9 @@
     BOOL  Copy( INT32 nFrom, INT32 nBytes );
     StgStrm( StgIo& );
 public:
+       INT32 FAT[8192];
+       BOOL  initFAT;
+       BOOL  Dirty;
     virtual ~StgStrm();
     StgIo&  GetIo()            { return rIo;    }
     INT32   GetPos()   { return nPos;   }
@@ -97,7 +100,7 @@
     virtual BOOL SetSize( INT32 );
     virtual BOOL Pos2Page( INT32 nBytePos );
     virtual INT32 Read( void*, INT32 )                   { return 0; }
-    virtual INT32 Write( const void*, INT32 ) { return 0; }
+    virtual INT32 Write( const void*, INT32 ) { Dirty=true; return 0; }
     virtual StgPage* GetPhysPage( INT32 nBytePos, BOOL bForce = FALSE );
     virtual BOOL IsSmallStrm() { return FALSE; }
 };

-- 
Shantong Kang     康善同
Microprocessor R&D Center(MPRC)
Room 1818,Science Building 1,
Peking University,
Beijing, P.R.China, 100871
Tel: 86-010-62763734
Mobile: 86-15210037972