求一个函数，判断输入的字符串是否是合法IP

Question

求一个函数，判断输入的字符串是否是合法IP

Answer 1

有很多的，这个比较好一点function IsValidIP(astrIP:String):Boolean;
var
  iCount:Integer;
  iIPLength:Integer;
  iFieldLength:Integer;
  iFieldStart:Integer;
  iDotCount:Integer;
  strTemp:String;
begin
  iIPLength:=Length(astrIP);
  if (iIPLength>15)or(iIPLength<7)then
    begin
    Result:=False;//合法IPv4长度在7和15之间
    Exit;
    end;  iDotCount:=0;
  iFieldLength:=0;
  iFieldStart:=1;
  for iCount:=1 to iIPLength do
    begin
    case astrIP[iCount] of
      "0","1","2","3","4","5","6","7","8","9":
         begin
         iFieldLength:=iFieldLength+1;
         if (3<iFieldLength) then
            begin
            Result:=False;//IP的单域长度超过3
            Exit;
            end;
         end;
      "."
         begin
         if 0=iFieldLength then
            begin
            Result:=False;//"."在开头或连续两个"."，或在结尾
            Exit;
            end;
         strTemp:=copy(astrIp,iFieldStart,iCount-iFieldStart);
         if(255<StrToInt(strTemp))then
            begin
            Result:=False;//单域值>255
            Exit;
            end;
         iDotCount:=iDotCount+1;
         if 3<iDotCount then
            begin
            Result:=False;//超过4个域 
            Exit;
            end;
         iFieldLength:=0;
         iFieldStart:=iCount+1;
         end;
      else
         begin
         Result:=False;//非法字符 
         Exit;
         end;
    end;   Result:=True;
end;

Answer 2

uses
  IdStack;
GStack.IsIP(StrIP)