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Overview
Comment:Remove the use of htonl() in the previous check-in due to linkage issues. Add the get2byteAligned() macro and use it for access to the cell offsets on btree pages for about a 1% performance gain.
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SHA1: 79ff36b7170c9e7e7a9935c8b9d1665867771087
User & Date: drh 2015-06-30 13:28:18
Context
2015-06-30
14:01
Only use __builtin_bswap16() with GCC 4.8 and later. (Closed-Leaf check-in: ce8177e3 user: drh tags: bswap-functions)
13:28
Remove the use of htonl() in the previous check-in due to linkage issues. Add the get2byteAligned() macro and use it for access to the cell offsets on btree pages for about a 1% performance gain. (check-in: 79ff36b7 user: drh tags: bswap-functions)
12:47
Make use of htonl() and __builtin_bswap32() for faster implementations of sqlite3Get4byte() and sqlite3Put4byte(). (check-in: bc27ebd7 user: drh tags: bswap-functions)
Changes
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Changes to src/btree.c. 

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**
** findCellPastPtr() does the same except it skips past the initial
** 4-byte child pointer found on interior pages, if there is one.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
  ((P)->aData + ((P)->maskPage & get2byte(&(P)->aCellIdx[2*(I)])))
#define findCellPastPtr(P,I) \
  ((P)->aDataOfst + ((P)->maskPage & get2byte(&(P)->aCellIdx[2*(I)])))


/*
** This is common tail processing for btreeParseCellPtr() and
** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
** on a single B-tree page.  Make necessary adjustments to the CellInfo
** structure.
................................................................................
    iCellLast = usableSize - 4;
    if( pBt->db->flags & SQLITE_CellSizeCk ){
      int i;            /* Index into the cell pointer array */
      int sz;           /* Size of a cell */

      if( !pPage->leaf ) iCellLast--;
      for(i=0; i<pPage->nCell; i++){
        pc = get2byte(&data[cellOffset+i*2]);
        testcase( pc==iCellFirst );
        testcase( pc==iCellLast );
        if( pc<iCellFirst || pc>iCellLast ){
          return SQLITE_CORRUPT_BKPT;
        }
        sz = pPage->xCellSize(pPage, &data[pc]);
        testcase( pc+sz==usableSize );
................................................................................

  put2byte(&aData[hdr+3], pPg->nCell);
  put2byte(&aData[hdr+5], pData - aData);

#ifdef SQLITE_DEBUG
  for(i=0; i<nNew && !CORRUPT_DB; i++){
    u8 *pCell = pCArray->apCell[i+iNew];
    int iOff = get2byte(&pPg->aCellIdx[i*2]);
    if( pCell>=aData && pCell<&aData[pPg->pBt->usableSize] ){
      pCell = &pTmp[pCell - aData];
    }
    assert( 0==memcmp(pCell, &aData[iOff],
            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
  }
#endif
................................................................................
    ** first.
    */
    memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*limit);
    if( pOld->nOverflow>0 ){
      memset(&b.szCell[b.nCell+limit], 0, sizeof(b.szCell[0])*pOld->nOverflow);
      limit = pOld->aiOvfl[0];
      for(j=0; j<limit; j++){
        b.apCell[b.nCell] = aData + (maskPage & get2byte(piCell));
        piCell += 2;
        b.nCell++;
      }
      for(k=0; k<pOld->nOverflow; k++){
        assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
        b.apCell[b.nCell] = pOld->apOvfl[k];
        b.nCell++;
      }
    }
    piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
    while( piCell<piEnd ){
      assert( b.nCell<nMaxCells );
      b.apCell[b.nCell] = aData + (maskPage & get2byte(piCell));
      piCell += 2;
      b.nCell++;
    }

    cntOld[i] = b.nCell;
    if( i<nOld-1 && !leafData){
      u16 sz = (u16)szNew[i];
................................................................................
    nCell = get2byte(&data[hdr+3]);
    /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
    ** immediately follows the b-tree page header. */
    cellStart = hdr + 12 - 4*pPage->leaf;
    /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
    ** integer offsets to the cell contents. */
    for(i=0; i<nCell; i++){
      int pc = get2byte(&data[cellStart+i*2]);
      u32 size = 65536;
      if( pc<=usableSize-4 ){
        size = pPage->xCellSize(pPage, &data[pc]);
      }
      if( (int)(pc+size-1)>=usableSize ){
        pCheck->zPfx = 0;
        checkAppendMsg(pCheck,








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**
** findCellPastPtr() does the same except it skips past the initial
** 4-byte child pointer found on interior pages, if there is one.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
  ((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
#define findCellPastPtr(P,I) \
  ((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))


/*
** This is common tail processing for btreeParseCellPtr() and
** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
** on a single B-tree page.  Make necessary adjustments to the CellInfo
** structure.
................................................................................
    iCellLast = usableSize - 4;
    if( pBt->db->flags & SQLITE_CellSizeCk ){
      int i;            /* Index into the cell pointer array */
      int sz;           /* Size of a cell */

      if( !pPage->leaf ) iCellLast--;
      for(i=0; i<pPage->nCell; i++){
        pc = get2byteAligned(&data[cellOffset+i*2]);
        testcase( pc==iCellFirst );
        testcase( pc==iCellLast );
        if( pc<iCellFirst || pc>iCellLast ){
          return SQLITE_CORRUPT_BKPT;
        }
        sz = pPage->xCellSize(pPage, &data[pc]);
        testcase( pc+sz==usableSize );
................................................................................

  put2byte(&aData[hdr+3], pPg->nCell);
  put2byte(&aData[hdr+5], pData - aData);

#ifdef SQLITE_DEBUG
  for(i=0; i<nNew && !CORRUPT_DB; i++){
    u8 *pCell = pCArray->apCell[i+iNew];
    int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
    if( pCell>=aData && pCell<&aData[pPg->pBt->usableSize] ){
      pCell = &pTmp[pCell - aData];
    }
    assert( 0==memcmp(pCell, &aData[iOff],
            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
  }
#endif
................................................................................
    ** first.
    */
    memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*limit);
    if( pOld->nOverflow>0 ){
      memset(&b.szCell[b.nCell+limit], 0, sizeof(b.szCell[0])*pOld->nOverflow);
      limit = pOld->aiOvfl[0];
      for(j=0; j<limit; j++){
        b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
        piCell += 2;
        b.nCell++;
      }
      for(k=0; k<pOld->nOverflow; k++){
        assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
        b.apCell[b.nCell] = pOld->apOvfl[k];
        b.nCell++;
      }
    }
    piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
    while( piCell<piEnd ){
      assert( b.nCell<nMaxCells );
      b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
      piCell += 2;
      b.nCell++;
    }

    cntOld[i] = b.nCell;
    if( i<nOld-1 && !leafData){
      u16 sz = (u16)szNew[i];
................................................................................
    nCell = get2byte(&data[hdr+3]);
    /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
    ** immediately follows the b-tree page header. */
    cellStart = hdr + 12 - 4*pPage->leaf;
    /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
    ** integer offsets to the cell contents. */
    for(i=0; i<nCell; i++){
      int pc = get2byteAligned(&data[cellStart+i*2]);
      u32 size = 65536;
      if( pc<=usableSize-4 ){
        size = pPage->xCellSize(pPage, &data[pc]);
      }
      if( (int)(pc+size-1)>=usableSize ){
        pCheck->zPfx = 0;
        checkAppendMsg(pCheck,

Changes to src/btreeInt.h. 

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/*
** Routines to read or write a two- and four-byte big-endian integer values.
*/
#define get2byte(x)   ((x)[0]<<8 | (x)[1])
#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
#define get4byte sqlite3Get4byte
#define put4byte sqlite3Put4byte





















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/*
** Routines to read or write a two- and four-byte big-endian integer values.
*/
#define get2byte(x)   ((x)[0]<<8 | (x)[1])
#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
#define get4byte sqlite3Get4byte
#define put4byte sqlite3Put4byte

/*
** get2byteAligned(), unlike get2byte(), requires that its argument point to a
** two-byte aligned address.  get2bytea() is only used for accessing the
** cell addresses in a btree header.
*/
#if SQLITE_BYTEORDER==4321
# define get2byteAligned(x)  (*(u16*)(x))
#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__)
# define get2byteAligned(x)  __builtin_bswap16(*(u16*)(x))
#else
# define get2byteAligned(x)  ((x)[0]<<8 | (x)[1])
#endif

Changes to src/util.c. 

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** Read or write a four-byte big-endian integer value.
*/
u32 sqlite3Get4byte(const u8 *p){
#if SQLITE_BYTEORDER==4321
  u32 x;
  memcpy(&x,p,4);
  return x;
#elif defined(_MSC_VER)
  u32 x;
  memcpy(&x,p,4);
  return htonl(x);
#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__)
  u32 x;
  memcpy(&x,p,4);
  return __builtin_bswap32(x);
#else
  testcase( p[0]&0x80 );
  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
#endif
}
void sqlite3Put4byte(unsigned char *p, u32 v){
#if SQLITE_BYTEORDER==4321
  memcpy(p,&v,4);
#elif defined(_MSC_VER)
  u32 x = htonl(v);
  memcpy(&x,p,4);
#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__)
  u32 x = __builtin_bswap32(v);
  memcpy(p,&x,4);
#else
  p[0] = (u8)(v>>24);
  p[1] = (u8)(v>>16);
  p[2] = (u8)(v>>8);








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** Read or write a four-byte big-endian integer value.
*/
u32 sqlite3Get4byte(const u8 *p){
#if SQLITE_BYTEORDER==4321
  u32 x;
  memcpy(&x,p,4);
  return x;




#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__)
  u32 x;
  memcpy(&x,p,4);
  return __builtin_bswap32(x);
#else
  testcase( p[0]&0x80 );
  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
#endif
}
void sqlite3Put4byte(unsigned char *p, u32 v){
#if SQLITE_BYTEORDER==4321
  memcpy(p,&v,4);



#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__)
  u32 x = __builtin_bswap32(v);
  memcpy(p,&x,4);
#else
  p[0] = (u8)(v>>24);
  p[1] = (u8)(v>>16);
  p[2] = (u8)(v>>8);

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