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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Further enhancements to the showdb utility: A page number followed by "b" causes a btree decoding to occur on the page.
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SHA1: 2ff824e58ce8b8f605c809ac960dcbfc51c30e30
User & Date: drh 2010-04-26 16:47:13
Context
2010-04-26
17:30
Identify the SQLite version meta-value entry in the db-header output of showdb. check-in: 245d934b user: drh tags: trunk
16:47
Further enhancements to the showdb utility: A page number followed by "b" causes a btree decoding to occur on the page. check-in: 2ff824e5 user: drh tags: trunk
15:44
Enhancements to the showdb.c utility program. Automatically detect the page size and adjust the display accordingly. Add the "dbheader" display option. check-in: 23eb408b user: drh tags: trunk
Changes
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Changes to tool/showdb.c.

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typedef long long int i64;      /* Datatype for 64-bit integers */


/*
** Convert the var-int format into i64.  Return the number of bytes
** in the var-int.  Write the var-int value into *pVal.
*/
static int decodeVarint(const char *z, i64 *pVal){
  i64 v = 0;
  int i = 0;
  while( i<8 ){
    v = (v<<7) + (z[i]&0x7f);
    if( (z[i]&0x80)==0 ){ *pVal = v; return i+1; }
  }
  v = (v<<8) + (z[i]&0xff);
  *pVal = v;
  return 9;
}
................................................................................
    }else{
      sprintf(&zBuf[i], " %02x", aData[ofst+j]);
      val = val*256 + aData[ofst+j];
    }
    i += strlen(&zBuf[i]);
  }
  sprintf(&zBuf[i], "   %9d", val);
  printf(" %s  %s\n", zBuf, zMsg);
}

/*
** Decode the database header.
*/
static print_db_header(void){
  unsigned char *aData;
  aData = print_byte_range(0, 100, 0);
  printf("Decoded:\n");
  print_decode_line(aData, 16, 2, "Database page size");
  print_decode_line(aData, 18, 1, "File format write version");
  print_decode_line(aData, 19, 1, "File format read version");
  print_decode_line(aData, 20, 1, "Reserved space at end of page");
................................................................................
  print_decode_line(aData, 76, 4, "meta[9]");
  print_decode_line(aData, 80, 4, "meta[10]");
  print_decode_line(aData, 84, 4, "meta[11]");
  print_decode_line(aData, 88, 4, "meta[12]");
  print_decode_line(aData, 92, 4, "meta[13]");
  print_decode_line(aData, 96, 4, "meta[14]");
}










































































int main(int argc, char **argv){
  struct stat sbuf;
  unsigned char zPgSz[2];
  if( argc<2 ){
    fprintf(stderr,"Usage: %s FILENAME ?PAGE? ...\n", argv[0]);
    exit(1);
................................................................................
        continue;
      }
      iStart = strtol(argv[i], &zLeft, 0);
      if( zLeft && strcmp(zLeft,"..end")==0 ){
        iEnd = mxPage;
      }else if( zLeft && zLeft[0]=='.' && zLeft[1]=='.' ){
        iEnd = strtol(&zLeft[2], 0, 0);















      }else{
        iEnd = iStart;
      }
      if( iStart<1 || iEnd<iStart || iEnd>mxPage ){
        fprintf(stderr,
          "Page argument should be LOWER?..UPPER?.  Range 1 to %d\n",
          mxPage);







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typedef long long int i64;      /* Datatype for 64-bit integers */


/*
** Convert the var-int format into i64.  Return the number of bytes
** in the var-int.  Write the var-int value into *pVal.
*/
static int decodeVarint(const unsigned char *z, i64 *pVal){
  i64 v = 0;
  int i;
  for(i=0; i<8; i++){
    v = (v<<7) + (z[i]&0x7f);
    if( (z[i]&0x80)==0 ){ *pVal = v; return i+1; }
  }
  v = (v<<8) + (z[i]&0xff);
  *pVal = v;
  return 9;
}
................................................................................
    }else{
      sprintf(&zBuf[i], " %02x", aData[ofst+j]);
      val = val*256 + aData[ofst+j];
    }
    i += strlen(&zBuf[i]);
  }
  sprintf(&zBuf[i], "   %9d", val);
  printf("%s  %s\n", zBuf, zMsg);
}

/*
** Decode the database header.
*/
static void print_db_header(void){
  unsigned char *aData;
  aData = print_byte_range(0, 100, 0);
  printf("Decoded:\n");
  print_decode_line(aData, 16, 2, "Database page size");
  print_decode_line(aData, 18, 1, "File format write version");
  print_decode_line(aData, 19, 1, "File format read version");
  print_decode_line(aData, 20, 1, "Reserved space at end of page");
................................................................................
  print_decode_line(aData, 76, 4, "meta[9]");
  print_decode_line(aData, 80, 4, "meta[10]");
  print_decode_line(aData, 84, 4, "meta[11]");
  print_decode_line(aData, 88, 4, "meta[12]");
  print_decode_line(aData, 92, 4, "meta[13]");
  print_decode_line(aData, 96, 4, "meta[14]");
}

/*
** Create a description for a single cell.
*/
static int describeCell(unsigned char cType, unsigned char *a, char **pzDesc){
  int i;
  int nDesc = 0;
  int n = 0;
  int leftChild;
  i64 nPayload;
  i64 rowid;
  static char zDesc[100];
  i = 0;
  if( cType<=5 ){
    leftChild = ((a[0]*256 + a[1])*256 + a[2])*256 + a[3];
    a += 4;
    n += 4;
    sprintf(zDesc, "left-child: %d ", leftChild);
    nDesc = strlen(zDesc);
  }
  if( cType!=5 ){
    i = decodeVarint(a, &nPayload);
    a += i;
    n += i;
    sprintf(&zDesc[nDesc], "sz: %lld ", nPayload);
    nDesc += strlen(&zDesc[nDesc]);
  }
  if( cType==5 || cType==13 ){
    i = decodeVarint(a, &rowid);
    a += i;
    n += i;
    sprintf(&zDesc[nDesc], "rowid: %lld ", rowid);
    nDesc += strlen(&zDesc[nDesc]);
  }
  *pzDesc = zDesc;
  return n;
}

/*
** Decode a btree page
*/
static void decode_btree_page(unsigned char *a, int pgno, int hdrSize){
  const char *zType = "unknown";
  int nCell;
  int i;
  int iCellPtr;
  switch( a[0] ){
    case 2:  zType = "index interior node";  break;
    case 5:  zType = "table interior node";  break;
    case 10: zType = "index leaf";           break;
    case 13: zType = "table leaf";           break;
  }
  printf("Decode of btree page %d:\n", pgno);
  print_decode_line(a, 0, 1, zType);
  print_decode_line(a, 1, 2, "Offset to first freeblock");
  print_decode_line(a, 3, 2, "Number of cells on this page");
  nCell = a[3]*256 + a[4];
  print_decode_line(a, 5, 2, "Offset to cell content area");
  print_decode_line(a, 7, 1, "Fragmented byte count");
  if( a[0]==2 || a[0]==5 ){
    print_decode_line(a, 8, 4, "Right child");
    iCellPtr = 12;
  }else{
    iCellPtr = 8;
  }
  for(i=0; i<nCell; i++){
    int cofst = iCellPtr + i*2;
    char *zDesc;
    cofst = a[cofst]*256 + a[cofst+1];
    describeCell(a[0], &a[cofst-hdrSize], &zDesc);
    printf(" %03x: cell[%d] %s\n", cofst, i, zDesc);
  }
}

int main(int argc, char **argv){
  struct stat sbuf;
  unsigned char zPgSz[2];
  if( argc<2 ){
    fprintf(stderr,"Usage: %s FILENAME ?PAGE? ...\n", argv[0]);
    exit(1);
................................................................................
        continue;
      }
      iStart = strtol(argv[i], &zLeft, 0);
      if( zLeft && strcmp(zLeft,"..end")==0 ){
        iEnd = mxPage;
      }else if( zLeft && zLeft[0]=='.' && zLeft[1]=='.' ){
        iEnd = strtol(&zLeft[2], 0, 0);
      }else if( zLeft && zLeft[0]=='b' ){
        int ofst, nByte, hdrSize;
        unsigned char *a;
        if( iStart==1 ){
          ofst = hdrSize = 100;
          nByte = pagesize-100;
        }else{
          hdrSize = 0;
          ofst = (iStart-1)*pagesize;
          nByte = pagesize;
        }
        a = getContent(ofst, nByte);
        decode_btree_page(a, iStart, hdrSize);
        free(a);
        continue;
      }else{
        iEnd = iStart;
      }
      if( iStart<1 || iEnd<iStart || iEnd>mxPage ){
        fprintf(stderr,
          "Page argument should be LOWER?..UPPER?.  Range 1 to %d\n",
          mxPage);