It was not me who wrote this code, it was the previous programmer. However, I noticed he didn't provide a decryption algorithm, rendering the encryption useless.
How can I decrypt this?
function Encrypt(jstr: String): String;
var
I: Integer;
A: Real;
begin
if Length(jstr) = 0 Then begin
Result := '';
Exit;
end;
A := 0;
for I := 0 To Length(jstr) do
A := A + (Ord(jstr[I]) * Pos(jstr[I],jstr)) / 33;
Result := FormatFloat('0000000000.0000000000',A);
if Pos(',',Result) > 0 then begin
Insert('.',Result,Pos(',',Result));
Delete(Result,Pos(',',Result),1);
end;
end;
Thanks!
It looks like a one way hash and hence is not reversible. For example, is the string is very big the result is still a string representation of a float.
That function cannot be reversed. Since it takes input of arbitrary length and returns output of finite length, simple information theory tells you the futility of attempting to write a general inverse. Even for shorter input strings it seems to me that different input strings can result in the same encrypted string.
Even as a hash this function seems very brittle to me due to the bizarre use of floating point code. If I were you I would replace this function with something more fit for purpose.
Finally, I recommend that you undertake a review of all code produced by this developer. The low quality of this code and algorithm suggests to me that everything that this developer touched is liable to have defects.
Related
I'm looking for an easy/quick way to identify and extract hashtags from a string, and temporarily store them separately - e.g.:
If I have the following string:
2017-08-31 This is a useless sentence being used as an example. #Example #Date:2017-09-01 #NothingWow (and then some more text for good measure).
Then I want to be able to get this:
#Example
#Date:2017-09-01
#NothingWow
I figured storing it in a TStringList should be sufficient until I'm done. I just need to store them outside of the original string for easier cross referencing, then if the original string changes, add them back at the end.
(but that's easy - its the extracting part I'm having trouble with)
It should start at the # and end/break when it encounters a [space].
The way I initially planned it was to use Boolean flags (defaulted to False), then check for the different hashtags, set them to true if found, and extract anything after a [:] separately.
(but I'm sure there is a better way of doing it)
Any advice will be greatly appreciated.
The following shows a simple console application which you could use as the basis
for a solution. It works because assigning your input string to the DelimitedText property of a StringList causes the StringList to parse the input into a series of space-limited lines. It is then a simple matter to look for the ones which start with a #.
The code is written as a Delphi console application but should be trivial to convert to Lazarus/FPC.
Code:
program HashTags;
{$APPTYPE CONSOLE}
uses
Classes, SysUtils;
procedure TestHashTags;
var
TL : TStringList;
S : String;
i : Integer;
begin
TL := TStringList.Create;
try
S := '2017-08-31 This is a useless sentence being used as an example. #Example #Date:2017-09-01 #NothingWow (and then some more text for good measure)';
TL.DelimitedText := S;
for i := 0 to TL.Count - 1 do begin
if Pos('#', TL[i]) = 1 then
writeln(i, ' ', TL[i]);
end;
finally
TL.Free;
end;
readln;
end;
begin
TestHashTags;
end.
In the example below, I am wondering, why line 17 does not work, but line 18? Can I not convert a System.Address directly to an Integer (see line 17)?
main.adb
with Ada.Text_IO;
with Ada.Unchecked_Conversion;
with System.Storage_Elements;
procedure Main is
package SSE renames System.Storage_Elements;
type Integer_Access is access Integer;
I1_Access : Integer_Access := new Integer'(42);
I1_Address : System.Address := I1_Access.all'Address;
function Convert1 is new Ada.Unchecked_Conversion (System.Address, Integer);
function Convert2 is new Ada.Unchecked_Conversion (System.Address, Integer_Access);
begin
Ada.Text_IO.Put_Line (SSE.To_Integer (I1_Access'Address)'Img);
Ada.Text_IO.Put_Line (SSE.To_Integer (I1_Access.all'Address)'Img);
Ada.Text_IO.Put_Line (I1_Access.all'Img);
Ada.Text_IO.Put_Line (Convert1 (I1_Address)'Img); -- why does this NOT work?
Ada.Text_IO.Put_Line (Convert2 (I1_Address).all'Img); -- why does this work?
end Main;
Result
140734773254664
140243203260416
42
-363855872
42
If I compile your code on this Mac with -gnatwa (most warnings) and -gnatl (generate a listing) I get (excerpted)
12. function Convert1 is new Ada.Unchecked_Conversion (System.Address, Integer);
|
>>> warning: types for unchecked conversion have different sizes
because Integer is 32-bits while System.Address (and most access types) are 64-bits. Your machine is evidently similar.
So the reason you get a weird 5th output line (I got -490720512, by the way) is that it’s only looking at the bottom 32 bits of the actual address.
You might look at System.Address_To_Access_Conversions (ARM 13.7.2) for the supported way to do this.
It does work. Apparently it's doing something other than what you expected.
You can convert a System.Address to an Integer using Unchecked_Conversion, but the result isn't necessarily going to be meaningful. You'll get an integer representing the (probably virtual) address held in the System.Address value -- not the value of whatever object it points to. And if System.Address and Integer aren't the same size, the result will be even less meaningful.
Ada.Text_IO.Put_Line (Convert1 (I1_Address)'Img);
This prints an Integer representation of a memory address. It's not particularly meaningful. (Typically you'd want to see such an address in hexadecimal.)
Ada.Text_IO.Put_Line (Convert2 (I1_Address).all'Img);
This prints the Integer value, 42, of the object at the memory location indicated by the value of I1_Address. It's just a roundabout way of printing I1_Access.all.
If you only want to print the value of an image, as in your example, consider using the function System.Address_Image. This is not good for pointer arithmetic, but leads to better output (hexadecimal, for instance)
I developed the following sorting algorithm but there are some run time errors that I cant figure out. The program terminates when it comes to the part of filling the array. I'm still a beginner in ada so I couldn't figure out where the problem is...
With Ada.Text_IO;
With Ada.Integer_Text_IO;
Use Ada.Integer_Text_IO;
Use Ada.Text_IO;
Procedure sort is
n,i,x : Integer;
-- Max_Heapify Function...
Procedure Max_Heapify ( i, n : integer) is
j, Temp : Integer;
begin
Temp:=Int_Acc(i);
j:=2*i;
if Temp>Int_Acc(j) then
elsif Temp<=Int_Acc(j) then
Int_Acc(j/2):=Int_Acc(j);
j:=2*j;
end if;
end loop;
Int_Acc(j/2):=Temp;
end Max_Heapify;
begin
Get(n);
for i in MyArr'range loop
Put_Line("Enter Element " & Integer'Image(i));
Get(MyArr(i));
end loop;
end;
end sort;
Thanks in advance :)
Your Problem is that you are insisting on writing Ada code using c - Style programming paradigms.
Firstly:
The declarations:
Type Arr is array(1..20) of Integer;
Type int_access is access Arr;
MyArr : int_access;
Where you use Int_Acc : in out int_access as parameters to procedures are useless in Ada. You are trying to pass a pointer to an array in (which you are doing!), but you should just pass your Type Arr as in out - The Ada compiler knows to do this as a pointer!
Secondly:
I cannot see where you actually allocate any memory to MyArr. This is a possible source of your runtime error. (when you write to or index an array that does not exist, i would expect to have a problem!)
Thirdly:
You seem to be mixing fixed length arrays with variable length input. If N > 20, you will have a problem.
Fourthly:
Insulting the language is not the best way of getting help from those who like it.
NWS has nailed it : there is a pointer, but no array there.
But it's clear that you have learned C, which leaves you with a lot to learn about other languages including Ada. There really are better ways of doing many things, that aren't taught to C programmers because C doesn't allow them.
Allocating variable sized arrays without pointers, malloc and free for example...
Type Arr is array(positive range <>) of Integer; -- of any size
begin
Put_Line("Enter Number Of Elements Of Array");
Get(n);
declare -- now we know the size
My_Arr : Arr(1 .. n);
begin -- My_Arr is in scope until the end of this block
...
end;
end sort;
Using the type system better...
Bad programming :
for i in 1 .. n loop
Get(MyArr(i));
end loop;
HeapSort(MyArr,n);
for i in 1 .. n loop
Put_Line(Integer'Image(MyArr(i)));
end loop;
This is bad because it violates the DRY principle : loop bounds repeated, and something that hopefully represents the array size passed around as a separate parameter... a maintenance nightmare if you decide to rename n to something meaningful for example.
better programming : Use the type system. Recognise that merely declaring an array has declared a new subtype of integer, representing the index of the array. You can access it as My_Arr'range, and the high bound as My_Arr'last.
for i in My_Arr'range loop
Get(MyArr(i));
end loop;
HeapSort(MyArr);
for i in My_Arr'range loop
Put_Line(Integer'Image(MyArr(i)));
end loop;
And accidents such as redefining n after the array declaration can no longer generate buffer overflows.
NOTE: Heapsort now gets its range from the array. (Max_Heapify may still need a separate parameter to operate on subsets of the array)
Arguably best - if it makes the intent clearer - name the index datatype explicitly and use it...
declare -- now we know the size
subtype My_Range is positive range 1 .. n;
My_Arr : Arr(My_Range);
begin -- My_Arr is in scope until the end of this block
for i in My_Range loop ...
And lastly, which do you prefer; a Storage_Error exception immediately the bug occurs (writing to memory you forgot to allocate) or something odd happening much later because something scribbled across another variable?
EDIT
Having cleared up the major issues two more subtle ones remain...
If I compile the modified program (in Gnat 4.8) I get several warnings : one of them is important and tells you exactly what the problem is...
Most of the warnings stem from the fact that
for i in My_Arr'range loop
declares its own loop variable i which hides any existing in-scope declaration. So you can tidy up the code by removing the unnecessary declarations.
What remains is:
sort.adb:51:28: warning: loop range may be null
sort.adb:51:28: warning: bounds may be wrong way round
The for loop bounds are empty ranges, reversed...
1 .. 3 declares a subtype with 3 values
reverse 1 .. 3 declares the same subtype and iterates backwards over it.
But 3 .. 1 declares an EMPTY subtype (containing NO valid values) so iterating over it - either way round - does precisely nothing.
Hopefully that is the missing part of the puzzle. I'm not clear why one faulty loop gets this warning while the other (at line 38) doesn't...
if j<n **and then** Int_Acc(j+1)>Int_Acc(j) then
j:=j+1;
I think you want just 'and' instead of 'and then,' although I haven't looked at Ada code in years.
Did that compile?
Functions are obviously less verbose to write than entities. But it implies many drawbacks, including:
No generic keyword equivalent
Only one output possible
It appears that functions can be called recursively. May it not be the case with entities? If so, is there any good reason to use functions except for aesthetic purposes?
Functions can't create hardware directly - they have to exist within an architecture to do so. There's nothing to stop you putting all your functionality into a function (or procedure) and then just calling that within a process though.
Regarding some of your other points:
With procedures you can have multiple inout or out parameters.
Entities can recurse... Consider:
entity recurse is
generic (
depth : integer := 1;
param : integer := 3);
port (
a : in integer;
b : out integer);
end entity recurse;
architecture a1 of recurse is
signal c : integer;
begin
c <= a + 1;
bottom: if depth = param generate
b <= a + 1;
end generate bottom;
mid:if depth /= param generate
recurse_1: entity work.recurse
generic map (
param => param,
depth => depth+1)
port map (
a => c,
b => b);
end generate mid;
end architecture a1;
Not very useful, but it synthesises and simulates just fine.
And finally, of course you only use functions for aesthetic purposes (assuming you include maintainability and readability into the definition of aesthetic, which most programming types do in my experience). You only use enumerated types, entities, records and a whole host of other language features for 'aesthetic purposes'. Even assembly mnemonics are aesthetic! Maybe should return to toggling DIP switches :)
Functions in vhdl make the code easy to maintain and read. generally architectures are very big and while debugging if something is not working you can easily find the problematic function and correct it and no need to analyse the entire architecture body.
in case of small codes it's useless but in more big machines it makes you better understand if you consider it function wise.
There is no rule for this so all comments are welcome.
in short : the advantage of functions are
overloading
operators definition
overloading of operators therefore
Better Structure of code
I can see why you are confused, another good question would be why there's both procedure and function. (VHDL seems quite inelegant sometimes!)
That being said, I use both procedures and functions all the time, although mostly in testbenches. For example, for a testbench for a firewall system I made a while back I wrote a procedure called pd_tb_send_udp_packet() that I use repeatedly in the main process, e.g.,
pd_tb_send_udp_packet("10.10.10.2", 1234, false);
pd_tb_send_udp_packet("10.10.10.1", 1234, true);
pd_tb_send_udp_packet("10.10.10.1", 1235, false);
pd_tb_send_udp_packet("ff02:100::1", 1234, false);
pd_tb_send_udp_packet("ff02:101::1", 1234, true);
This procedure generates a random UDP packet with the given addr/port and sends it to the firewall system, then tests whether it is forwarded or not based on the final boolean parameter. Here are the first lines of it, where I use functions from a library:
if f_atvtb_is_ipv6_addr(dest_ip_addr) then
v_ipv6 := true;
v_ipv6_addr := f_atvtb_ipv6_addr(dest_ip_addr);
else
v_ipv6 := false;
v_ipv4_addr := f_atvtb_ip_addr(dest_ip_addr);
end if;
The latter two return 128 and 32 bit std_logic_vectors from the string input, respectively.
While I could probably do all this without using procedures and functions somehow, it would definitely be a lot more messy.
This snippet not only causes a runtime error, it makes FPC close if I run it using the debugger.
procedure sortplayersbyscore(var vAux:tplayers);
procedure swap(var a:trplayers;var b:trplayers);
var
rAux:trplayers;
begin
rAux:=a;
a:=b;
b:=rAux;
end;
var
i,j:integer;
sorted:boolean;
begin
vAux:=playersarray;
i:=1;
sorted:=false;
while (i <= MAXPLAYERS -1) and not sorted do
begin
j:=1;
sorted:=true;
while (j <= MAXPLAYERS -i) do
begin
if (vAux[j].score < vAux[j+1].score) then
begin
swap(vAux[j],vAux[j+1]);
sorted:=false;
end;
inc(j);
end;
inc(i);
end;
end;
The code itself is part of a really big source file, I can post the whole thing but the responsible for the error is just that bunch of lines. The debugger terminates at line:
swap(vAux[j],vAux[j+1]);
tplayers is just a type defined as an array of records that contain score (an integer) among a bunch of other variables. trplayers is the type of the aforementioned records. I'm at a total loss; FPC (while not under debugging mode) spits an out-of-range error but under my watches I see that the variables I'm trying to read exist. Any help is really appreciated!
rAux:trplayers; have you typed a wrong symbol or the type here really contains "r" in its name?
It looks valid (other than typos) ... so let's try something simple.
What's the value of "j" when you abort?
If the debugger won't tell you, try adding:
writeln ('j = ', j);
just before the "swap" call.
As Yochai's question implied, your array needs to be dimensioned at least from
1 (or lower) to MAXPLAYERS (or larger). (I.e.: 0..MAXPLAYERS-1 would not work,
but 1..MAXPLAYERS should.)