SQLite

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(Cursor*, int , const unsigned char*, int*);
int sqlite3VdbeIdxRowid(BtCursor *, i64 *);
int sqlite3MemCompare(const Mem*, const Mem*, const CollSeq*);
int sqlite3VdbeKeyCompare(void*,int,const void*,int, const void*);
int sqlite3VdbeRowCompare(void*,int,const void*,int, const void*);

int sqlite3VdbeExec(Vdbe*);
int sqlite3VdbeList(Vdbe*);
int sqlite3VdbeChangeEncoding(Mem *, int);
int sqlite3VdbeMemCopy(Mem*, const Mem*);
int sqlite3VdbeMemNulTerminate(Mem*);
int sqlite3VdbeMemSetStr(Mem*, const char*, int, u8, int);
void sqlite3VdbeMemSetInt64(Mem*, long long int);
void sqlite3VdbeMemSetDouble(Mem*, double);
void sqlite3VdbeMemSetNull(Mem*);
int sqlite3VdbeMemMakeWriteable(Mem*);
int sqlite3VdbeMemDynamicify(Mem*);
int sqlite3VdbeMemStringify(Mem*, int);
int sqlite3VdbeMemIntegerify(Mem*);
int sqlite3VdbeMemRealify(Mem*);

#ifndef NDEBUG
void sqlite3VdbeMemSanity(Mem*, u8);
#endif

** compared to.
*/
int sqlite3VdbeKeyCompare(
  void *userData,
  int nKey1, const void *pKey1, 
  int nKey2, const void *pKey2
){
  KeyInfo *pKeyInfo = (KeyInfo*)userData;
  int offset1 = 0;
  int offset2 = 0;
  int i = 0;
  int rc = 0;
  const unsigned char *aKey1 = (const unsigned char *)pKey1;
  const unsigned char *aKey2 = (const unsigned char *)pKey2;
  
  assert( pKeyInfo!=0 );
  while( offset1<nKey1 && offset2<nKey2 ){
    Mem mem1;
    Mem mem2;
    u32 serial_type1;
    u32 serial_type2;

    /* Read the serial types for the next element in each key. */
    offset1 += sqlite3GetVarint32(&aKey1[offset1], &serial_type1);
    offset2 += sqlite3GetVarint32(&aKey2[offset2], &serial_type2);

    /* If either of the varints just read in are 0 (not a type), then
    ** this is the end of the keys. The remaining data in each key is
    ** the varint rowid. Compare these as signed integers and return
    ** the result.
    */
    if( !serial_type1 || !serial_type2 ){
      assert( !serial_type1 && !serial_type2 );
      sqlite3GetVarint32(&aKey1[offset1], &serial_type1);
      sqlite3GetVarint32(&aKey2[offset2], &serial_type2);
      if( serial_type1 < serial_type2 ){
        rc = -1;
      }else if( serial_type1 > serial_type2 ){
        rc = +1;
      }else{
        rc = 0;
      }
      return rc;
    }

    assert( i<pKeyInfo->nField );

    /* Assert that there is enough space left in each key for the blob of
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    offset1 += sqlite3VdbeSerialGet(&aKey1[offset1], serial_type1, &mem1);
    offset2 += sqlite3VdbeSerialGet(&aKey2[offset2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2, pKeyInfo->aColl[i]);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){
      break;
    }
    i++;
  }

  /* One of the keys ran out of fields, but all the fields up to that point
  ** were equal. If the incrKey flag is true, then the second key is
  ** treated as larger.
  */
  if( rc==0 ){
    if( pKeyInfo->incrKey ){
      assert( offset2==nKey2 );
      rc = -1;
    }else if( offset1<nKey1 ){
      rc = 1;
    }else if( offset2<nKey2 ){
      rc = -1;
    }
  }

  if( pKeyInfo->aSortOrder && i<pKeyInfo->nField && pKeyInfo->aSortOrder[i] ){
    rc = -rc;
  }

  return rc;
}

/*
** This function compares the two table row records specified by 
** {nKey1, pKey1} and {nKey2, pKey2}, returning a negative, zero
** or positive integer if {nKey1, pKey1} is less than, equal to or 
** greater than {nKey2, pKey2}.

  const unsigned char *aKey2 = (const unsigned char *)pKey2;
  
  idx1 = sqlite3GetVarint32(pKey1, &szHdr1);
  d1 = szHdr1;
  idx2 = sqlite3GetVarint32(pKey2, &szHdr2);
  d2 = szHdr2;
  nField = pKeyInfo->nField;
  while( idx1<szHdr1 && idx2<szHdr2 && d1<nKey1 && d2<nKey2 && i<nField ){
    Mem mem1;
    Mem mem2;
    u32 serial_type1;
    u32 serial_type2;

    /* Read the serial types for the next element in each key. */
    idx1 += sqlite3GetVarint32(&aKey1[idx1], &serial_type1);

    idx2 += sqlite3GetVarint32(&aKey2[idx2], &serial_type2);


    /* Assert that there is enough space left in each key for the blob of
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    d1 += sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
    d2 += sqlite3VdbeSerialGet(&aKey2[d2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2, pKeyInfo->aColl[i]);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){
      break;
    }
    i++;
  }

  /* One of the keys ran out of fields, but all the fields up to that point
  ** were equal. If the incrKey flag is true, then the second key is
  ** treated as larger.
  */
  if( rc==0 ){
    if( pKeyInfo->incrKey ){
      assert( d2==nKey2 );
      rc = -1;
    }else if( d1<nKey1 ){
      rc = 1;
    }else if( d2<nKey2 ){
      rc = -1;
    }
  }

  if( pKeyInfo->aSortOrder && i<pKeyInfo->nField && pKeyInfo->aSortOrder[i] ){
    rc = -rc;
  }

  return rc;
}













  

/*
** pCur points at an index entry. Read the rowid (varint occuring at
** the end of the entry and store it in *rowid. Return SQLITE_OK if
** everything works, or an error code otherwise.
*/
int sqlite3VdbeIdxRowid(BtCursor *pCur, i64 *rowid){
  i64 sz;
  int rc;
  char buf[10];

  int len;
  u64 r;

  rc = sqlite3BtreeKeySize(pCur, &sz);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  len = ((sz>10)?10:sz);

  /* If there are less than 2 bytes in the key, this cannot be
  ** a valid index entry. In practice this comes up for a query
  ** of the sort "SELECT max(x) FROM t1;" when t1 is an empty table
  ** with an index on x. In this case just call the rowid 0.
  */
  if( len<2 ){
    *rowid = 0;
    return SQLITE_OK;
  }

  rc = sqlite3BtreeKey(pCur, sz-len, len, buf);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  len--;
  while( buf[len-1] && --len );

  sqlite3GetVarint(&buf[len], &r);

  *rowid = r;



  return SQLITE_OK;
}

/*
** Compare the key of the index entry that cursor pC is point to against
** the key string in pKey (of length nKey).  Write into *pRes a number
** that is negative, zero, or positive if pC is less than, equal to,
** or greater than pKey.  Return SQLITE_OK on success.
**
** pKey might contain fewer terms than the cursor.


*/
int sqlite3VdbeIdxKeyCompare(
  Cursor *pC,                 /* The cursor to compare against */
  int nKey, const u8 *pKey,   /* The key to compare */
  int *res                    /* Write the comparison result here */
){
  unsigned char *pCellKey;
  u64 nCellKey;
  int freeCellKey = 0;
  int rc;
  int len;
  BtCursor *pCur = pC->pCursor;



  sqlite3BtreeKeySize(pCur, &nCellKey);
  if( nCellKey<=0 ){
    *res = 0;
    return SQLITE_OK;
  }

  pCellKey = (unsigned char *)sqlite3BtreeKeyFetch(pCur, nCellKey);
  if( !pCellKey ){
    pCellKey = (unsigned char *)sqliteMallocRaw(nCellKey);
    if( !pCellKey ){
      return SQLITE_NOMEM;
    }
    freeCellKey = 1;
    rc = sqlite3BtreeKey(pCur, 0, nCellKey, pCellKey);
    if( rc!=SQLITE_OK ){
      sqliteFree(pCellKey);
      return rc;
    }
  }
 
  len = nCellKey-2;
  while( pCellKey[len] && --len );

  *res = sqlite3VdbeKeyCompare(pC->pKeyInfo, len, pCellKey, nKey, pKey);
  
  if( freeCellKey ){
    sqliteFree(pCellKey);
  }
  return SQLITE_OK;
}

  */
  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( rc==0 ){
    rc = pMem1->n - pMem2->n;
  }
  return rc;
}



































































#ifndef NDEBUG
/*
** Perform various checks on the memory cell pMem. An assert() will
** fail if pMem is internally inconsistent.
*/
void sqlite3VdbeMemSanity(Mem *pMem, u8 db_enc){

    assert( (pMem->flags & (MEM_Static|MEM_Dyn|MEM_Ephem|MEM_Short))==0 );
  }
  /* MEM_Null excludes all other types */
  assert( (pMem->flags&(MEM_Str|MEM_Int|MEM_Real|MEM_Blob))==0
          || (pMem->flags&MEM_Null)==0 );
}
#endif