SQLite

** Read content from the file.
**
** Space to hold the content is obtained from malloc() and needs to be
** freed by the caller.
*/
static unsigned char *getContent(int ofst, int nByte){
  unsigned char *aData;
  aData = malloc(nByte+32);
  if( aData==0 ) out_of_memory();
  lseek(db, ofst, SEEK_SET);
  read(db, aData, nByte);
  return aData;
}

/*

  print_decode_line(aData, 96, 4, "SQLite version number");
}

/*
** Describe cell content.
*/
static int describeContent(
  unsigned char *a,       /* Cell content */
  int nLocal,             /* Bytes in a[] */
  char *zDesc             /* Write description here */
){
  int nDesc = 0;
  int n, i, j;
  i64 x, v;
  const unsigned char *pData;
  const unsigned char *pLimit;
  char sep = ' ';

  pLimit = &a[nLocal];
  n = decodeVarint(a, &x);
  pData = &a[x];
  a += n;
  i = x - n;
  while( i>0 && pData<=pLimit ){
    n = decodeVarint(a, &x);
    a += n;
    i -= n;
    nLocal -= n;
    zDesc[0] = sep;
    sep = ',';
    nDesc++;
    zDesc++;
    if( x==0 ){
      sprintf(zDesc, "*");     /* NULL is a "*" */
    }else if( x>=1 && x<=6 ){
      v = (signed char)pData[0];
      pData++;
      switch( x ){
        case 6:  v = (v<<16) + (pData[0]<<8) + pData[1];  pData += 2;
        case 5:  v = (v<<16) + (pData[0]<<8) + pData[1];  pData += 2;
        case 4:  v = (v<<8) + pData[0];  pData++;

    }else if( x==9 ){
      sprintf(zDesc, "1");
    }else if( x>=12 ){
      int size = (x-12)/2;
      if( (x&1)==0 ){
        sprintf(zDesc, "blob(%d)", size);
      }else{
        sprintf(zDesc, "txt(%d)", size);
      }
      pData += size;
    }
    j = strlen(zDesc);
    zDesc += j;
    nDesc += j;
  }
  return nDesc;
}

/*
** Compute the local payload size given the total payload size and
** the page size.
*/
static int localPayload(i64 nPayload, char cType){
  int maxLocal;
  int minLocal;
  int surplus;
  int nLocal;
  if( cType==13 ){
    /* Table leaf */
    maxLocal = pagesize-35;
    minLocal = (pagesize-12)*32/255-23;
  }else{
    maxLocal = (pagesize-12)*64/255-23;
    minLocal = (pagesize-12)*32/255-23;
  }
  if( nPayload>maxLocal ){
    surplus = minLocal + (nPayload-minLocal)%(pagesize-4);
    if( surplus<=maxLocal ){
      nLocal = surplus;
    }else{
      nLocal = minLocal;
    }
  }else{
    nLocal = nPayload;
  }
  return nLocal;
}
  

/*
** Create a description for a single cell.
**
** The return value is the local cell size.
*/
static int describeCell(
  unsigned char cType,    /* Page type */
  unsigned char *a,       /* Cell content */
  int showCellContent,    /* Show cell content if true */
  char **pzDesc           /* Store description here */
){

  }
  if( cType!=5 ){
    i = decodeVarint(a, &nPayload);
    a += i;
    n += i;
    sprintf(&zDesc[nDesc], "n: %lld ", nPayload);
    nDesc += strlen(&zDesc[nDesc]);
    nLocal = localPayload(nPayload, cType);
  }else{
    nPayload = nLocal = 0;
  }
  if( cType==5 || cType==13 ){
    i = decodeVarint(a, &rowid);
    a += i;
    n += i;
    sprintf(&zDesc[nDesc], "r: %lld ", rowid);
    nDesc += strlen(&zDesc[nDesc]);
  }
  if( showCellContent && cType!=5 ){
    nDesc += describeContent(a, nLocal, &zDesc[nDesc-1]);
  }
  *pzDesc = zDesc;
  return nLocal+n;
}

/*
** Decode a btree page
*/
static void decode_btree_page(
  unsigned char *a,   /* Page content */
  int pgno,           /* Page number */
  int hdrSize,        /* Size of the page header.  0 or 100 */
  char *zArgs         /* Flags to control formatting */
){
  const char *zType = "unknown";
  int nCell;
  int i, j;
  int iCellPtr;
  int showCellContent = 0;
  int showMap = 0;
  char *zMap = 0;
  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;
  }
  while( zArgs[0] ){
    switch( zArgs[0] ){
      case 'c': showCellContent = 1;  break;
      case 'm': showMap = 1;          break;
    }
    zArgs++;
  }
  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;
  }
  if( nCell>0 ){
    printf(" key: lx=left-child n=payload-size r=rowid\n");
  }
  if( showMap ){
    zMap = malloc(pagesize);
    memset(zMap, '.', pagesize);
    memset(zMap, '1', hdrSize);
    memset(&zMap[hdrSize], 'H', iCellPtr);
    memset(&zMap[hdrSize+iCellPtr], 'P', 2*nCell);
  }
  for(i=0; i<nCell; i++){
    int cofst = iCellPtr + i*2;
    char *zDesc;
    int n;

    cofst = a[cofst]*256 + a[cofst+1];
    n = describeCell(a[0], &a[cofst-hdrSize], showCellContent, &zDesc);
    if( showMap ){
      char zBuf[30];
      memset(&zMap[cofst], '*', n);
      zMap[cofst] = '[';
      zMap[cofst+n-1] = ']';
      sprintf(zBuf, "%d", i);
      j = strlen(zBuf);
      if( j<=n-2 ) memcpy(&zMap[cofst+1], zBuf, j);
    }
    printf(" %03x: cell[%d] %s\n", cofst, i, zDesc);
  }
  if( showMap ){
    for(i=0; i<pagesize; i+=64){
      printf(" %03x: %.64s\n", i, &zMap[i]);
    }
    free(zMap);
  }  
}

/*
** Decode a freelist trunk page.
*/
static void decode_trunk_page(
  int pgno,             /* The page number */

  fprintf(stderr, "Usage %s FILENAME ?args...?\n\n", argv0);
  fprintf(stderr,
    "args:\n"
    "    dbheader        Show database header\n"
    "    NNN..MMM        Show hex of pages NNN through MMM\n"
    "    NNN..end        Show hex of pages NNN through end of file\n"
    "    NNNb            Decode btree page NNN\n"
    "    NNNbc           Decode btree page NNN and show content\n"
    "    NNNbm           Decode btree page NNN and show a layout map\n"
    "    NNNt            Decode freelist trunk page NNN\n"
    "    NNNtd           Show leave freelist pages on the decode\n"
    "    NNNtr           Recurisvely decode freelist starting at NNN\n"
  );
}

int main(int argc, char **argv){