C# FuncDef类代码示例

    public override Null Visit(FuncDef node)
    {
        // Define the function
        node.symbol = new Symbol {
            kind = SymbolKind.Func,
            isStatic = node.isStatic,
            def = node,
            type = new ErrorType()
        };
        scope.Define(node.symbol);

        // Visit the children differently than base.Visit(node) because we
        // want to define arguments in the body scope, not the parent scope.
        // Note that we don't visit the body, that's for ComputeTypesPass.
        node.returnType.Accept(this);
        if (node.block != null) {
            // Define arguments in the scope of the body
            node.block.scope = new Scope(scope, log, ScopeKind.Func);
            scope = node.block.scope;
            foreach (VarDef argDef in node.argDefs)
                argDef.Accept(this);
            scope = scope.parent;
        } else {
            // Define arguments in a temporary scope if no body is present
            scope = new Scope(scope, log, ScopeKind.Func);
            foreach (VarDef argDef in node.argDefs)
                argDef.Accept(this);
            scope = scope.parent;
        }

        return null;
    }

        /*
        ** The first parameter (pDef) is a function implementation.  The
        ** second parameter (pExpr) is the first argument to this function.
        ** If pExpr is a column in a virtual table, then let the virtual
        ** table implementation have an opportunity to overload the function.
        **
        ** This routine is used to allow virtual table implementations to
        ** overload MATCH, LIKE, GLOB, and REGEXP operators.
        **
        ** Return either the pDef argument (indicating no change) or a
        ** new FuncDef structure that is marked as ephemeral using the
        ** SQLITE_FUNC_EPHEM flag.
        */
        FuncDef *sqlite3VtabOverloadFunction(
            sqlite3 *db,    /* Database connection for reporting malloc problems */
            FuncDef *pDef,  /* Function to possibly overload */
            int nArg,       /* Number of arguments to the function */
            Expr *pExpr     /* First argument to the function */
            )
        {
            Table *pTab;
              sqlite3_vtab *pVtab;
              sqlite3_module *pMod;
              void (*xFunc)(sqlite3_context*,int,sqlite3_value**) = 0;
              void *pArg = 0;
              FuncDef *pNew;
              int rc = 0;
              char *zLowerName;
              unsigned char *z;

              /* Check to see the left operand is a column in a virtual table */
              if( NEVER(pExpr==0) ) return pDef;
              if( pExpr->op!=TK_COLUMN ) return pDef;
              pTab = pExpr->pTab;
              if( NEVER(pTab==0) ) return pDef;
              if( (pTab->tabFlags & TF_Virtual)==0 ) return pDef;
              pVtab = sqlite3GetVTable(db, pTab)->pVtab;
              assert( pVtab!=0 );
              assert( pVtab->pModule!=0 );
              pMod = (sqlite3_module *)pVtab->pModule;
              if( pMod->xFindFunction==0 ) return pDef;

              /* Call the xFindFunction method on the virtual table implementation
              ** to see if the implementation wants to overload this function
              */
              zLowerName = sqlite3DbStrDup(db, pDef->zName);
              if( zLowerName ){
            for(z=(unsigned char*)zLowerName; *z; z++){
              *z = sqlite3UpperToLower[*z];
            }
            rc = pMod->xFindFunction(pVtab, nArg, zLowerName, &xFunc, &pArg);
            sqlite3DbFree(db, zLowerName);
              }
              if( rc==0 ){
            return pDef;
              }

              /* Create a new ephemeral function definition for the overloaded
              ** function */
              pNew = sqlite3DbMallocZero(db, sizeof(*pNew)
                             + sqlite3Strlen30(pDef->zName) + 1);
              if( pNew==0 ){
            return pDef;
              }
              *pNew = *pDef;
              pNew->zName = (char *)&pNew[1];
              memcpy(pNew->zName, pDef->zName, sqlite3Strlen30(pDef->zName)+1);
              pNew->xFunc = xFunc;
              pNew->pUserData = pArg;
              pNew->flags |= SQLITE_FUNC_EPHEM;
              return pNew;
        }

    public override Null Visit(FuncDef node)
    {
        // Don't visit the body, that's for ComputeTypesPass
        node.returnType.Accept(this);
        foreach (VarDef argDef in node.argDefs) {
            argDef.Accept(this);
        }

        // Construct a function type from the parsed return and argument types
        node.symbol.type = new FuncType {
            returnType = GetInstanceType(node.returnType, true),
            argTypes = node.argDefs.ConvertAll(arg => GetInstanceType(arg.type, false))
        };

        return null;
    }

    public override Null Visit(FuncDef node)
    {
        // Forbid default arguments for the moment
        foreach (VarDef arg in node.argDefs) {
            if (arg.value != null) {
                log.ErrorDefaultArgNotAllowed(arg.location);
            }
        }

        // Validate the presence of the function body
        if (node.info.inExternal != (node.block == null)) {
            log.ErrorFunctionBody(node.location, node.info.inExternal);
        }

        base.Visit(node);
        return null;
    }

    /*
    ** The first parameter (pDef) is a function implementation.  The
    ** second parameter (pExpr) is the first argument to this function.
    ** If pExpr is a column in a virtual table, then let the virtual
    ** table implementation have an opportunity to overload the function.
    **
    ** This routine is used to allow virtual table implementations to
    ** overload MATCH, LIKE, GLOB, and REGEXP operators.
    **
    ** Return either the pDef argument (indicating no change) or a
    ** new FuncDef structure that is marked as ephemeral using the
    ** SQLITE_FUNC_EPHEM flag.
    */
    static FuncDef sqlite3VtabOverloadFunction(
      sqlite3 db,    /* Database connection for reporting malloc problems */
      FuncDef pDef,  /* Function to possibly overload */
      int nArg,      /* Number of arguments to the function */
      Expr pExpr     /* First argument to the function */
    )
    {
      Table pTab;
      sqlite3_vtab pVtab;
      sqlite3_module pMod;
      dxFunc xFunc = null;//void (*xFunc)(sqlite3_context*,int,sqlite3_value*) = 0;
      object pArg = null;
      FuncDef pNew;
      int rc = 0;
      string zLowerName;
      string z;

      /* Check to see the left operand is a column in a virtual table */
      if ( NEVER( pExpr == null ) )
        return pDef;
      if ( pExpr.op != TK_COLUMN )
        return pDef;
      pTab = pExpr.pTab;
      if ( NEVER( pTab == null ) )
        return pDef;
      if ( ( pTab.tabFlags & TF_Virtual ) == 0 )
        return pDef;
      pVtab = sqlite3GetVTable( db, pTab ).pVtab;
      Debug.Assert( pVtab != null );
      Debug.Assert( pVtab.pModule != null );
      pMod = (sqlite3_module)pVtab.pModule;
      if ( pMod.xFindFunction == null )
        return pDef;

      /* Call the xFindFunction method on the virtual table implementation
      ** to see if the implementation wants to overload this function
      */
      zLowerName = pDef.zName;//sqlite3DbStrDup(db, pDef.zName);
      if ( zLowerName != null )
      {
        //for(z=(unsigned char)zLowerName; *z; z++){
        //  *z = sqlite3UpperToLower[*z];
        //}
        rc = pMod.xFindFunction( pVtab, nArg, zLowerName.ToLowerInvariant(), ref xFunc, ref pArg );
        sqlite3DbFree( db, ref zLowerName );
      }
      if ( rc == 0 )
      {
        return pDef;
      }

      /* Create a new ephemeral function definition for the overloaded
      ** function */
      //sqlite3DbMallocZero(db, sizeof(*pNew)
      //      + sqlite3Strlen30(pDef.zName) + 1);
      //if ( pNew == null )
      //{
      //  return pDef;
      //}
      pNew = pDef.Copy();
      pNew.zName = pDef.zName;
      //pNew.zName = (char )&pNew[1];
      //memcpy(pNew.zName, pDef.zName, sqlite3Strlen30(pDef.zName)+1);
      pNew.xFunc = xFunc;
      pNew.pUserData = pArg;
      pNew.flags |= SQLITE_FUNC_EPHEM;
      return pNew;
    }

 /*
 ** If the input FuncDef structure is ephemeral, then free it.  If
 ** the FuncDef is not ephermal, then do nothing.
 */
 static void freeEphemeralFunction( sqlite3 db, FuncDef pDef )
 {
   if ( ALWAYS( pDef ) && ( pDef.flags & SQLITE_FUNC_EPHEM ) != 0 )
   {
     pDef = null;
     sqlite3DbFree( db, ref pDef );
   }
 }

 //FUNCDEF
 static int sqlite3VdbeAddOp4( Vdbe p, int op, int p1, int p2, int p3, FuncDef pP4, int p4type )
 {
   union_p4 _p4 = new union_p4();
   _p4.pFunc = pP4;
   int addr = sqlite3VdbeAddOp3( p, op, p1, p2, p3 );
   sqlite3VdbeChangeP4( p, addr, _p4, p4type );
   return addr;
 }

 //P4_FUNCDEF
 static void sqlite3VdbeChangeP4( Vdbe p, int addr, FuncDef pFunc, int n )
 {
   union_p4 _p4 = new union_p4();
   _p4.pFunc = pFunc;
   sqlite3VdbeChangeP4( p, addr, _p4, n );
 }

        /// <summary>
        /// This procedure generates VDBE code for a single invocation of either the
        /// sqlite_detach() or sqlite_attach() SQL user functions.
        /// </summary>
        /// <param name='pParse'>
        /// The parser context
        /// </param>
        /// <param name='type'>
        /// Either SQLITE_ATTACH or SQLITE_DETACH
        /// </param>
        /// <param name='pFunc'>
        /// FuncDef wrapper for detachFunc() or attachFunc()
        /// </param>
        /// <param name='pAuthArg'>
        /// Expression to pass to authorization callback 
        /// </param>
        /// <param name='pFilename'>
        /// Name of database file
        /// </param>
        /// <param name='pDbname'>
        /// Name of the database to use internally
        /// </param>
        /// <param name='pKey'>
        /// Database key for encryption extension
        /// </param>
        static void codeAttach(
		Parse pParse,
		int type,
		FuncDef pFunc,
		Expr pAuthArg,
		Expr pFilename,
		Expr pDbname,
		Expr pKey
		)
        {
            NameContext sName;
            Vdbe v;
            sqlite3 db = pParse.db;
            int regArgs;

            sName = new NameContext();// memset( &sName, 0, sizeof(NameContext));
            sName.pParse = pParse;

            if (
            SQLITE_OK != (resolveAttachExpr(sName, pFilename)) ||
            SQLITE_OK != (resolveAttachExpr(sName, pDbname)) ||
            SQLITE_OK != (resolveAttachExpr(sName, pKey))
            )
            {
                pParse.nErr++;
                goto attach_end;
            }

            #if !SQLITE_OMIT_AUTHORIZATION
            if( pAuthArg ){
            char *zAuthArg;
            if( pAuthArg->op==TK_STRING ){
              zAuthArg = pAuthArg->u.zToken;
            }else{
              zAuthArg = 0;
            }
            rc = sqlite3AuthCheck(pParse, type, zAuthArg, 0, 0);
            if(rc!=SQLITE_OK ){
            goto attach_end;
            }
            }
            #endif //* SQLITE_OMIT_AUTHORIZATION */

            v = sqlite3GetVdbe(pParse);
            regArgs = sqlite3GetTempRange(pParse, 4);
            sqlite3ExprCode(pParse, pFilename, regArgs);
            sqlite3ExprCode(pParse, pDbname, regArgs + 1);
            sqlite3ExprCode(pParse, pKey, regArgs + 2);

            Debug.Assert(v != null /*|| db.mallocFailed != 0 */ );
            if (v != null)
            {
                sqlite3VdbeAddOp3(v, OP_Function, 0, regArgs + 3 - pFunc.nArg, regArgs + 3);
                Debug.Assert(pFunc.nArg == -1 || (pFunc.nArg & 0xff) == pFunc.nArg);
                sqlite3VdbeChangeP5(v, (u8)(pFunc.nArg));
                sqlite3VdbeChangeP4(v, -1, pFunc, P4_FUNCDEF);

                /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
                ** statement only). For DETACH, set it to false (expire all existing
                ** statements).
                */
                sqlite3VdbeAddOp1(v, OP_Expire, (type == SQLITE_ATTACH) ? 1 : 0);
            }

            attach_end:
            sqlite3ExprDelete(db, ref pFilename);
            sqlite3ExprDelete(db, ref pDbname);
            sqlite3ExprDelete(db, ref pKey);
        }

    /*
    ** Locate a user function given a name, a number of arguments and a flag
    ** indicating whether the function prefers UTF-16 over UTF-8.  Return a
    ** pointer to the FuncDef structure that defines that function, or return
    ** NULL if the function does not exist.
    **
    ** If the createFlag argument is true, then a new (blank) FuncDef
    ** structure is created and liked into the "db" structure if a
    ** no matching function previously existed.  When createFlag is true
    ** and the nArg parameter is -1, then only a function that accepts
    ** any number of arguments will be returned.
    **
    ** If createFlag is false and nArg is -1, then the first valid
    ** function found is returned.  A function is valid if either xFunc
    ** or xStep is non-zero.
    **
    ** If createFlag is false, then a function with the required name and
    ** number of arguments may be returned even if the eTextRep flag does not
    ** match that requested.
    */

    static FuncDef sqlite3FindFunction(
    sqlite3 db,           /* An open database */
    string zName,         /* Name of the function.  Not null-terminated */
    int nName,            /* Number of characters in the name */
    int nArg,             /* Number of arguments.  -1 means any number */
    u8 enc,              /* Preferred text encoding */
    u8 createFlag       /* Create new entry if true and does not otherwise exist */
    )
    {
      FuncDef p;            /* Iterator variable */
      FuncDef pBest = null; /* Best match found so far */
      int bestScore = 0;
      int h;              /* Hash value */

      Debug.Assert( enc == SQLITE_UTF8 || enc == SQLITE_UTF16LE || enc == SQLITE_UTF16BE );
      h = ( sqlite3UpperToLower[(u8)zName[0]] + nName ) % ArraySize( db.aFunc.a );


      /* First search for a match amongst the application-defined functions.
      */
      p = functionSearch( db.aFunc, h, zName, nName );
      while ( p != null )
      {
        int score = matchQuality( p, nArg, enc );
        if ( score > bestScore )
        {
          pBest = p;
          bestScore = score;

        }
        p = p.pNext;
      }


      /* If no match is found, search the built-in functions.
      **
      ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
      ** functions even if a prior app-defined function was found.  And give
      ** priority to built-in functions.
      **
      ** Except, if createFlag is true, that means that we are trying to
      ** install a new function.  Whatever FuncDef structure is returned it will
      ** have fields overwritten with new information appropriate for the
      ** new function.  But the FuncDefs for built-in functions are read-only.
      ** So we must not search for built-ins when creating a new function.
      */
      if ( 0 == createFlag && ( pBest == null || ( db.flags & SQLITE_PreferBuiltin ) != 0 ) )
      {
#if SQLITE_OMIT_WSD
FuncDefHash pHash = GLOBAL( FuncDefHash, sqlite3GlobalFunctions );
#else
        FuncDefHash pHash = sqlite3GlobalFunctions;
#endif
        bestScore = 0;
        p = functionSearch( pHash, h, zName, nName );
        while ( p != null )
        {
          int score = matchQuality( p, nArg, enc );
          if ( score > bestScore )
          {
            pBest = p;
            bestScore = score;
          }
          p = p.pNext;
        }
      }

      /* If the createFlag parameter is true and the search did not reveal an
      ** exact match for the name, number of arguments and encoding, then add a
      ** new entry to the hash table and return it.
      */
      if ( createFlag != 0 && ( bestScore < 6 || pBest.nArg != nArg ) &&
      ( pBest = new FuncDef() ) != null )
      { //sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
        //pBest.zName = (char *)&pBest[1];
        pBest.nArg = (i16)nArg;
        pBest.iPrefEnc = enc;
        pBest.zName = zName; //memcpy(pBest.zName, zName, nName);
        //pBest.zName[nName] = 0;
//.........这里部分代码省略.........

 /* During the search for the best function definition, this procedure
 ** is called to test how well the function passed as the first argument
 ** matches the request for a function with nArg arguments in a system
 ** that uses encoding enc. The value returned indicates how well the
 ** request is matched. A higher value indicates a better match.
 **
 ** The returned value is always between 0 and 6, as follows:
 **
 ** 0: Not a match, or if nArg<0 and the function is has no implementation.
 ** 1: A variable arguments function that prefers UTF-8 when a UTF-16
 **    encoding is requested, or vice versa.
 ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
 **    requested, or vice versa.
 ** 3: A variable arguments function using the same text encoding.
 ** 4: A function with the exact number of arguments requested that
 **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
 ** 5: A function with the exact number of arguments requested that
 **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
 ** 6: An exact match.
 **
 */
 static int matchQuality( FuncDef p, int nArg, int enc )
 {
   int match = 0;
   if ( p.nArg == -1 || p.nArg == nArg
   || ( nArg == -1 && ( p.xFunc != null || p.xStep != null ) )
   )
   {
     match = 1;
     if ( p.nArg == nArg || nArg == -1 )
     {
       match = 4;
     }
     if ( enc == p.iPrefEnc )
     {
       match += 2;
     }
     else if ( ( enc == SQLITE_UTF16LE && p.iPrefEnc == SQLITE_UTF16BE ) ||
     ( enc == SQLITE_UTF16BE && p.iPrefEnc == SQLITE_UTF16LE ) )
     {
       match += 1;
     }
   }
   return match;
 }

 public override Null Visit(FuncDef node)
 {
     // Don't initialize arguments
     node.block.Accept(this);
     return null;
 }

 /*
 ** Called by the parser to compile an ATTACH statement.
 **
 **     ATTACH p AS pDbname KEY pKey
 */
 static void sqlite3Attach( Parse pParse, Expr p, Expr pDbname, Expr pKey )
 {
   FuncDef attach_func = new FuncDef(
   3,                /* nArg */
   SQLITE_UTF8,      /* iPrefEnc */
   0,                /* flags */
   null,             /* pUserData */
   null,             /* pNext */
   attachFunc,       /* xFunc */
   null,             /* xStep */
   null,             /* xFinalize */
   "sqlite_attach",  /* zName */
   null              /* pHash */
   );
   codeAttach( pParse, SQLITE_ATTACH, attach_func, p, p, pDbname, pKey );
 }

 /*
 ** Called by the parser to compile a DETACH statement.
 **
 **     DETACH pDbname
 */
 static void sqlite3Detach( Parse pParse, Expr pDbname )
 {
   FuncDef detach_func = new FuncDef(
   1,                   /* nArg */
   SQLITE_UTF8,         /* iPrefEnc */
   0,                   /* flags */
   null,                /* pUserData */
   null,                /* pNext */
   detachFunc,          /* xFunc */
   null,                /* xStep */
   null,                /* xFinalize */
   "sqlite_detach",     /* zName */
   null                 /* pHash */
   );
   codeAttach( pParse, SQLITE_DETACH, detach_func, pDbname, null, null, pDbname );
 }

        static void CodeAttach(Parse parse, AUTH type, FuncDef func, Expr authArg, Expr filename, Expr dbName, Expr key)
        {
            Context ctx = parse.Ctx;

            NameContext sName;
            sName = new NameContext();
            sName.Parse = parse;

            if (ResolveAttachExpr(sName, filename) != RC.OK || ResolveAttachExpr(sName, dbName) != RC.OK || ResolveAttachExpr(sName, key) != RC.OK)
            {
                parse.Errs++;
                goto attach_end;
            }

#if !OMIT_AUTHORIZATION
            if (authArg != null)
            {
                string authArgToken = (authArg.OP == TK.STRING ? authArg.u.Token : null);
                ARC arc = Auth.Check(parse, type, authArgToken, null, null);
                if (arc != ARC.OK)
                    goto attach_end;
            }
#endif
            Vdbe v = parse.GetVdbe();
            int regArgs = Expr.GetTempRange(parse, 4);
            Expr.Code(parse, filename, regArgs);
            Expr.Code(parse, dbName, regArgs + 1);
            Expr.Code(parse, key, regArgs + 2);

            Debug.Assert(v != null || ctx.MallocFailed);
            if (v != null)
            {
                v.AddOp3(OP.Function, 0, regArgs + 3 - func.Args, regArgs + 3);
                Debug.Assert(func.Args == -1 || (func.Args & 0xff) == func.Args);
                v.ChangeP5((byte)(func.Args));
                v.ChangeP4(-1, func, Vdbe.P4T.FUNCDEF);

                // Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this statement only). For DETACH, set it to false (expire all existing statements).
                v.AddOp1(OP.Expire, (type == AUTH.ATTACH ? 1 : 0));
            }

        attach_end:
            Expr.Delete(ctx, ref filename);
            Expr.Delete(ctx, ref dbName);
            Expr.Delete(ctx, ref key);
        }