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Overview
Comment:Streamline the decodeFlags() routine in btree.c for a small performance increase.
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SHA3-256: 4cb285210b4a2b14c80962bf2ecb35be310d3444c329c15d86b3073096455704
User & Date: drh 2022-11-19 13:09:03.004
Context
2022-11-19
14:18
Improved comments on the pageFreeArray() routine of btree.c. No changes to code. (check-in: 0c2adc6d35 user: drh tags: trunk)
13:09
Streamline the decodeFlags() routine in btree.c for a small performance increase. (check-in: 4cb285210b user: drh tags: trunk)
05:26
Add build of sqlite3.mjs (ES6 module), add a test app for it, and include it in the dist build. (check-in: 2e783670e1 user: stephan tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/btree.c.
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/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported.  Anything different
** indicates a corrupt database files:
**
**         PTF_ZERODATA

**         PTF_ZERODATA | PTF_LEAF
**         PTF_LEAFDATA | PTF_INTKEY
**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
*/
static int decodeFlags(MemPage *pPage, int flagByte){
  BtShared *pBt;     /* A copy of pPage->pBt */

  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pPage->leaf = (u8)(flagByte>>3);  assert( PTF_LEAF == 1<<3 );

  flagByte &= ~PTF_LEAF;
  pPage->childPtrSize = 4-4*pPage->leaf;
  pBt = pPage->pBt;
  if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
    /* EVIDENCE-OF: R-07291-35328 A value of 5 (0x05) means the page is an
    ** interior table b-tree page. */
    assert( (PTF_LEAFDATA|PTF_INTKEY)==5 );
    /* EVIDENCE-OF: R-26900-09176 A value of 13 (0x0d) means the page is a
    ** leaf table b-tree page. */


    assert( (PTF_LEAFDATA|PTF_INTKEY|PTF_LEAF)==13 );

    pPage->intKey = 1;





    if( pPage->leaf ){
      pPage->intKeyLeaf = 1;
      pPage->xCellSize = cellSizePtrTableLeaf;
      pPage->xParseCell = btreeParseCellPtr;


    }else{










      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtrNoPayload;
      pPage->xParseCell = btreeParseCellPtrNoPayload;
    }
    pPage->maxLocal = pBt->maxLeaf;
    pPage->minLocal = pBt->minLeaf;
  }else if( flagByte==PTF_ZERODATA ){
    /* EVIDENCE-OF: R-43316-37308 A value of 2 (0x02) means the page is an
    ** interior index b-tree page. */
    assert( (PTF_ZERODATA)==2 );
    /* EVIDENCE-OF: R-59615-42828 A value of 10 (0x0a) means the page is a
    ** leaf index b-tree page. */
    assert( (PTF_ZERODATA|PTF_LEAF)==10 );
    pPage->intKey = 0;
    pPage->intKeyLeaf = 0;
    pPage->xCellSize = cellSizePtr;
    pPage->xParseCell = btreeParseCellPtrIndex;
    pPage->maxLocal = pBt->maxLocal;
    pPage->minLocal = pBt->minLocal;
  }else{
    /* EVIDENCE-OF: R-47608-56469 Any other value for the b-tree page type is
    ** an error. */
    pPage->intKey = 0;
    pPage->intKeyLeaf = 0;
    pPage->xCellSize = cellSizePtr;
    pPage->xParseCell = btreeParseCellPtrIndex;
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  pPage->max1bytePayload = pBt->max1bytePayload;

  return SQLITE_OK;
}

/*
** Compute the amount of freespace on the page.  In other words, fill
** in the pPage->nFree field.
*/








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/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported.  Anything different
** indicates a corrupt database files:
**
**         PTF_ZERODATA                             (0x02,  2)
**         PTF_LEAFDATA | PTF_INTKEY                (0x05,  5)
**         PTF_ZERODATA | PTF_LEAF                  (0x0a, 10)
**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF     (0x0d, 13)

*/
static int decodeFlags(MemPage *pPage, int flagByte){
  BtShared *pBt;     /* A copy of pPage->pBt */

  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pBt = pPage->pBt;
  pPage->max1bytePayload = pBt->max1bytePayload;
  if( flagByte>=(PTF_ZERODATA | PTF_LEAF) ){
    pPage->childPtrSize = 0;
    pPage->leaf = 1;
    if( flagByte==(PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF) ){

      pPage->intKeyLeaf = 1;
      pPage->xCellSize = cellSizePtrTableLeaf;
      pPage->xParseCell = btreeParseCellPtr;
      pPage->intKey = 1;
      pPage->maxLocal = pBt->maxLeaf;
      pPage->minLocal = pBt->minLeaf;
    }else if( flagByte==(PTF_ZERODATA | PTF_LEAF) ){
      pPage->intKey = 0;
      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtr;
      pPage->xParseCell = btreeParseCellPtrIndex;
      pPage->maxLocal = pBt->maxLocal;
      pPage->minLocal = pBt->minLocal;
    }else{
      pPage->intKey = 0;
      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtr;
      pPage->xParseCell = btreeParseCellPtrIndex;
      return SQLITE_CORRUPT_PAGE(pPage);
    }
  }else{
    pPage->childPtrSize = 4;
    pPage->leaf = 0;
    if( flagByte==(PTF_ZERODATA) ){
      pPage->intKey = 0;
      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtr;
      pPage->xParseCell = btreeParseCellPtrIndex;
      pPage->maxLocal = pBt->maxLocal;
      pPage->minLocal = pBt->minLocal;
    }else if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtrNoPayload;
      pPage->xParseCell = btreeParseCellPtrNoPayload;











      pPage->intKey = 1;


      pPage->maxLocal = pBt->maxLeaf;
      pPage->minLocal = pBt->minLeaf;
    }else{


      pPage->intKey = 0;
      pPage->intKeyLeaf = 0;
      pPage->xCellSize = cellSizePtr;
      pPage->xParseCell = btreeParseCellPtrIndex;
      return SQLITE_CORRUPT_PAGE(pPage);
    }

  }
  return SQLITE_OK;
}

/*
** Compute the amount of freespace on the page.  In other words, fill
** in the pPage->nFree field.
*/
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