SQLite

    /* This call is a request for the "docid" column. Since "docid" is an 
    ** alias for "rowid", use the xRowid() method to obtain the value.
    */
    sqlite3_result_int64(pCtx, pCsr->iPrevId);
  }else if( iCol==p->nColumn ){
    /* The extra column whose name is the same as the table.
    ** Return a blob which is a pointer to the cursor.  */
    sqlite3_result_pointer(pCtx, pCsr);
  }else if( iCol==p->nColumn+2 && pCsr->pExpr ){
    sqlite3_result_int64(pCtx, pCsr->iLangid);
  }else{
    /* The requested column is either a user column (one that contains 
    ** indexed data), or the language-id column.  */
    rc = fts3CursorSeek(0, pCsr);

*/
static int fts3FunctionArg(
  sqlite3_context *pContext,      /* SQL function call context */
  const char *zFunc,              /* Function name */
  sqlite3_value *pVal,            /* argv[0] passed to function */
  Fts3Cursor **ppCsr              /* OUT: Store cursor handle here */
){
  Fts3Cursor *pRet = (Fts3Cursor*)sqlite3_value_pointer(pVal);


  if( pRet==0 ){
    char *zErr = sqlite3_mprintf("illegal first argument to %s", zFunc);
    sqlite3_result_error(pContext, zErr, -1);
    sqlite3_free(zErr);
    return SQLITE_ERROR;
  }

  *ppCsr = pRet;
  return SQLITE_OK;
}

/*
** Implementation of the snippet() function for FTS3
*/

*/
const void *sqlite3_value_blob(sqlite3_value*);
int sqlite3_value_bytes(sqlite3_value*);
int sqlite3_value_bytes16(sqlite3_value*);
double sqlite3_value_double(sqlite3_value*);
int sqlite3_value_int(sqlite3_value*);
sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
void *sqlite3_value_pointer(sqlite3_value*);
const unsigned char *sqlite3_value_text(sqlite3_value*);
const void *sqlite3_value_text16(sqlite3_value*);
const void *sqlite3_value_text16le(sqlite3_value*);
const void *sqlite3_value_text16be(sqlite3_value*);
int sqlite3_value_type(sqlite3_value*);
int sqlite3_value_numeric_type(sqlite3_value*);

void sqlite3_result_error16(sqlite3_context*, const void*, int);
void sqlite3_result_error_toobig(sqlite3_context*);
void sqlite3_result_error_nomem(sqlite3_context*);
void sqlite3_result_error_code(sqlite3_context*, int);
void sqlite3_result_int(sqlite3_context*, int);
void sqlite3_result_int64(sqlite3_context*, sqlite3_int64);
void sqlite3_result_null(sqlite3_context*);
void sqlite3_result_pointer(sqlite3_context*, void*);
void sqlite3_result_text(sqlite3_context*, const char*, int, void(*)(void*));
void sqlite3_result_text16(sqlite3_context*, const void*, int, void(*)(void*));
void sqlite3_result_text16le(sqlite3_context*, const void*, int,void(*)(void*));
void sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
void sqlite3_result_zeroblob(sqlite3_context*, int n);

struct Mem {
  sqlite3 *db;        /* The associated database connection */
  char *z;            /* String or BLOB value */
  double r;           /* Real value */
  union {
    i64 i;              /* Integer value used when MEM_Int is set in flags */
    int nZero;          /* Used when bit MEM_Zero is set in flags */
    void *pPtr;         /* Pointer when flags==MEM_Ptr|MEM_Null */
    FuncDef *pDef;      /* Used only when flags==MEM_Agg */
    RowSet *pRowSet;    /* Used only when flags==MEM_RowSet */
    VdbeFrame *pFrame;  /* Used when flags==MEM_Frame */
  } u;
  int n;              /* Number of characters in string value, excluding '\0' */
  u16 flags;          /* Some combination of MEM_Null, MEM_Str, MEM_Dyn, etc. */
  u8  type;           /* One of SQLITE_NULL, SQLITE_TEXT, SQLITE_INTEGER, etc */

#define MEM_TypeMask  0x00ff   /* Mask of type bits */

/* Whenever Mem contains a valid string or blob representation, one of
** the following flags must be set to determine the memory management
** policy for Mem.z.  The MEM_Term flag tells us whether or not the
** string is \000 or \u0000 terminated
*/
#define MEM_Ptr       0x8000   /* u.pPtr is valid if type==SQLITE_NULL */
#define MEM_Term      0x0200   /* String rep is nul terminated */
#define MEM_Dyn       0x0400   /* Need to call sqliteFree() on Mem.z */
#define MEM_Static    0x0800   /* Mem.z points to a static string */
#define MEM_Ephem     0x1000   /* Mem.z points to an ephemeral string */
#define MEM_Agg       0x2000   /* Mem.z points to an agg function context */
#define MEM_Zero      0x4000   /* Mem.i contains count of 0s appended to blob */
#ifdef SQLITE_OMIT_INCRBLOB
  #undef MEM_Zero
  #define MEM_Zero 0x0000
#endif

/*
** Clear any existing type flags from a Mem and replace them with f
*/
#define MemSetTypeFlag(p, f) \
   ((p)->flags = ((p)->flags&~(MEM_TypeMask|MEM_Zero|MEM_Ptr))|f)

/*
** Return true if a memory cell is not marked as invalid.  This macro
** is for use inside assert() statements only.
*/
#ifdef SQLITE_DEBUG
#define memIsValid(M)  ((M)->flags & MEM_Invalid)==0

  return sqlite3VdbeRealValue((Mem*)pVal);
}
int sqlite3_value_int(sqlite3_value *pVal){
  return (int)sqlite3VdbeIntValue((Mem*)pVal);
}
sqlite_int64 sqlite3_value_int64(sqlite3_value *pVal){
  return sqlite3VdbeIntValue((Mem*)pVal);
}
void *sqlite3_value_pointer(sqlite3_value *pVal){
  Mem *p = (Mem*)pVal;
  if( (p->flags&(MEM_TypeMask|MEM_Ptr))==(MEM_Null|MEM_Ptr) ) return p->u.pPtr;
  return 0;
}
const unsigned char *sqlite3_value_text(sqlite3_value *pVal){
  return (const unsigned char *)sqlite3ValueText(pVal, SQLITE_UTF8);
}
#ifndef SQLITE_OMIT_UTF16
const void *sqlite3_value_text16(sqlite3_value* pVal){
  return sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);

void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
}
void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
}
void sqlite3_result_pointer(sqlite3_context *pCtx, void *pPtr){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetNull(&pCtx->s);
  assert( (pCtx->s.flags & (MEM_TypeMask|MEM_Ptr))==MEM_Null );
  pCtx->s.flags |= MEM_Ptr;
  pCtx->s.u.pPtr = pPtr;
}
void sqlite3_result_null(sqlite3_context *pCtx){
  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
  sqlite3VdbeMemSetNull(&pCtx->s);
}
void sqlite3_result_text(
  sqlite3_context *pCtx,