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Optimize calls to get2byte() in btree.c for almost a one-million cycle

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performance gain and a few bytes less code.

FossilOrigin-Name: 41061f29969dc546c2702f7f412127070a4dd54593827692df93a83c939dfb61
This commit is contained in:
drh
2022-02-23 18:23:15 +00:00
parent eac750e9a6
commit 009a48e0ad
3 changed files with 19 additions and 12 deletions
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17
src/btree.c
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@@ -1586,7 +1586,8 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
const int hdr = pPg->hdrOffset; /* Offset to page header */
u8 * const aData = pPg->aData; /* Page data */
int iAddr = hdr + 1; /* Address of ptr to pc */
int pc = get2byte(&aData[iAddr]); /* Address of a free slot */
u8 *pTmp = &aData[iAddr]; /* Temporary ptr into aData[] */
int pc = get2byte(pTmp); /* Address of a free slot */
int x; /* Excess size of the slot */
int maxPC = pPg->pBt->usableSize - nByte; /* Max address for a usable slot */
int size; /* Size of the free slot */
@@ -1596,7 +1597,8 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
/* EVIDENCE-OF: R-22710-53328 The third and fourth bytes of each
** freeblock form a big-endian integer which is the size of the freeblock
** in bytes, including the 4-byte header. */
size = get2byte(&aData[pc+2]);
pTmp = &aData[pc+2];
size = get2byte(pTmp);
if( (x = size - nByte)>=0 ){
testcase( x==4 );
testcase( x==3 );
@@ -1621,7 +1623,8 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
return &aData[pc + x];
}
iAddr = pc;
pc = get2byte(&aData[pc]);
pTmp = &aData[pc];
pc = get2byte(pTmp);
if( pc<=iAddr+size ){
if( pc ){
/* The next slot in the chain is not past the end of the current slot */
@@ -1655,6 +1658,7 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int top; /* First byte of cell content area */
int rc = SQLITE_OK; /* Integer return code */
u8 *pTmp; /* Temp ptr into data[] */
int gap; /* First byte of gap between cell pointers and cell content */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
@@ -1673,7 +1677,8 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
** then the cell content offset of an empty page wants to be 65536.
** However, that integer is too large to be stored in a 2-byte unsigned
** integer, so a value of 0 is used in its place. */
top = get2byte(&data[hdr+5]);
pTmp = &data[hdr+5];
top = get2byte(pTmp);
assert( top<=(int)pPage->pBt->usableSize ); /* by btreeComputeFreeSpace() */
if( gap>top ){
if( top==0 && pPage->pBt->usableSize==65536 ){
@@ -1755,6 +1760,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
u16 x; /* Offset to cell content area */
u32 iEnd = iStart + iSize; /* First byte past the iStart buffer */
unsigned char *data = pPage->aData; /* Page content */
u8 *pTmp; /* Temporary ptr into data[] */
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
@@ -1817,7 +1823,8 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_PAGE(pPage);
data[hdr+7] -= nFrag;
}
x = get2byte(&data[hdr+5]);
pTmp = &data[hdr+5];
x = get2byte(pTmp);
if( iStart<=x ){
/* The new freeblock is at the beginning of the cell content area,
** so just extend the cell content area rather than create another