Apologies for this question but I am a bit of a noob with Delphi. I am using Dejan TComport component to get data from a serial port. A box of equipment connected to the port sends about 100 bytes of binary data to the serial port. What I want to do is extract the bytes as numerical values into an array so that I can perform calculations on them.
TComport has a method Read(buffer,Count) which reads DATA from input buffer.
function Read(var Buffer; Count: Integer): Integer;
The help says the Buffer variable must be large enough to hold Count bytes but does not provide any example of how to use this function. I can see that the Count variable holds the number of bytes received but I can't find a way to access the bytes in Buffer.
TComport also has a methord Readstr which reads data from input buffer into a STRING variable.
function ReadStr(var Str: String; Count: Integer): Integer;
Again the Count variable shows the number of bytes received and I can use Memo1.Text:=str to display some information but obviously Memo1 has problems displaying the control characters. I have tried various ways to try and extract the byte data from Str but so far without success.
I am sure it must be easy. Here's hoping.
In this function
function Read(var Buffer; Count: Integer): Integer;
The Count parameter is the number of bytes you expect to read.
While the function return value is actually read bytes.
If you have a Buffer defined as an array of 100 bytes you can code
x := Read(Buffer, 100);
and if the input is only 70 bytes then x will be 70.
That way you can read while x > 0
// I use a timer to read a weight coming in on the Serial Port
// but the routing could also be triggered by OnRXChar (received data event)
// or OnRXBufferFull event.
var
WeightString: String; //global
procedure TfmUDF.tmScaleTimer(Sender: TObject);
var
Data: AnsiString;
begin
ReadStr(Data,Count); //the individual bytes can be read Data[n].....
WeightData:=WeightData+Data; //just keeps adding the incoming data
end;
Does this help?
Related
I tried to read the FIFO buffer in FT2332H and it was successful but the to data is coming is a format make it difficult to process or plot it .. Here is the example ... I use ftd2xx library
while True:
rxn = d.getQueueStatus()
if (rxn>1024):
print(bytearray(d.read(1024)))
The output is as below .. Each 4 is a byte received from the buffer .. How to get each
bytearray(b'4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444')
This is the result without bytearray
print((d.read(1024)))
b'4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444'
Assuming this is python:
You can index each individual byte in the byte array with []
my_buffer = bytearray(d.read(1024)
now my_buffer[0] holds the value of the first byte in your byte array, represented as an integer with value 0-255. You will need to additionally cast this integer to a character to create a character array / string. ASCII is the typical correlation between an integer value and its character representation. The order of the bytes in your FIFO buffer is dependent on what is putting bytes into the FIFO on the not-USB side of the FT232. Many devices send data most-significant first, but you should verify this against that device's data sheet.
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 try to read a GUID value stored as a binary value in registry in Delphi.
When I read it with BintoHex, but the result is in reverse order.
It seems that I have to swap bytes but I thought BinToHex would do it.
I refered to this thread but I can't find the right solution :
how to convert byte array to its hex representation in Delphi
It seems that it is due to little Eendian.
Below, you can see the GUID stored in registry
Here is my code :
var
s : string;
buffer : pointer;
...
begin
getmem(buffer, 1024*1024);
....
reg.ReadBinaryData(iValueOfregistry, buffer^, 1024*1024);
....
bintohex(pointer(longint(buffer)+14), PChar(s), 32);
Output for s :
90E24D373F126545916439C4925E467B
GUID should be FOLDERID_Downloads GUID :
{374DE290-123F-4565-9164-39C4925E467B}
Please help
A GUID in binary form is best thought of as a record. Indeed in Delphi the record already exists – it is TGUID.
All you need to do is to copy the relevant bytes directly into a variable of type TGUID and your job is done. If you want a string representation, use GUIDToString.
var
GUID: TGUID;
strGUID: string;
....
GUID := PGUID(PAnsiChar(buffer)+14)^;
strGUID := GUIDToString(GUID);
This will take care of all the endian issues automatically. Let's take a look at the declaration of TGUID:
TGUID = packed record
D1: LongWord;
D2: Word;
D3: Word;
D4: array[0..7] of Byte;
end;
Your code treats this as a straight array of bytes. However, in the record, D1, D2 and D3 are integral types on a little endian machine. So your code reverses the first 4 bytes, those belonging to D1. It then reverses the two bytes of D2, and also the two bytes of D3. The array of 8 bytes at the end of the GUID are not reversed, of course.
So, whilst you could readily do all the byte swapping yourself, it's far better to use a record to do so, and take advantage of the helper function that converts a binary GUID record to a properly formatted GUID string.
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.
I am trying to learn Free Pascal using Lazarus and one of my pet projects involves reading the 64 byte headers of a particular set of untyped files that cannot be read and displayed using text or ASCII related procedures (so cannot be outputted directly to Memo boxes etc).
So far, I have devised the following code which does, I think, read in the 64 bytes of the header and I am using TStreams and a "Select Directory" dialog box to do this, based on advice received via the Lazarus IRC. My question though is how to actually USE the data that is read into the buffer from the header? For example, in the headers, there are sequences of 8 bytes, then 16 bytes, then 2 bytes and so on that I want to "work on" to generate other output that will eventually be converted to a string to go into my string grid.
Some of what I have so far is based on what I found here written by Mason Wheeler near the end (http://stackoverflow.com/questions/455790/fast-read-write-from-file-in-delphi) but it only shows how to read it in, not how to use it. I also read this (http://stackoverflow.com/questions/4309739/best-way-to-read-parse-a-untyped-binary-file-in-delphi) but again, it shows you how to READ the data too, but not subsequently USE the data. Any guidance wamrly received! So far, the code below just outputs single value integer numbers to the edit box, as opposed to, say, a range of 8 hexadecimal values.
PS - I am new to programming so please be gentle! Nothing too complex.
procedure TForm1.ProbeFile(FileIterator: TFileIterator);
type
TMyHeader = Array[1..64] of packed record
First8Bytes,
Next16Bytes,
Next2Bytes: byte;
end;
var
FI : TFileIterator; //File Iterator class
SG : TStringGrid;
NumRead : SmallInt;
FileToProbe: TStream;
header: TMyHeader;
begin
FI := TFileIterator.Create;
SG := TStringGrid.Create(self);
// Open the file and read the header
FileToProbe := TFileStream.Create(FileIterator.FileName, fmOpenRead);
try
FileToProbe.seek(0, soFromBeginning);
FileToProbe.ReadBuffer(header, SizeOf(header));
edit1.text := IntToStr(header[0].First8Bytes); // Just outputs '0' to the field? If I try '10' it ooutputs '29' and so on
finally
FileToProbe.Free;
end;
Please forgive me if I misunderstood your question.
As I understand it there is a header of 64 bytes. The first 8 bytes belong together, then the next 16 bytes and finally another 2 bytes.
To me it seems the declaration for this header should be:
TMyHeader = packed record
First8Bytes: array[0..7] of byte;
Next16Bytes: array [0..15] of byte;
Next2Bytes: array [0..1] of byte;
// add more if you like
end;
This recordtype has a size of 8+16+2 = 26 bytes.
Your code that reads the header looks ok to me, So I won't repeat that.
The next16bytes in your header can be retrieved, for example, like this:
edit1.text:= '';
// needs a declaration of a variable "i" as integer
for i:= 0 to 15 do
edit1.text:= edit1.text + IntToStr(header.next16bytes[i]) + '-';
Change the value of the first byte in the next2bytes part of your header as follows (again as an example):
header.next2bytes[0]:= 123;
Finally, you could write your changes back to the header of the file with help of the filetoprobe.writebuffer method.