All i need to do is parse a single bye file to read the contents to the screen but i dont know how to parse could someone please give me some rough coding i could enter file addresses in or any idea on how to parse?
this is where i currently am at
program Reordering;
uses crt;
var f, i: text;
s: string;
skyf: array [1..256] of byte;
j: integer;
result: array [1..256] of char;
begin
assign(f, 'C:\Users\Peter John Arnold\Documents\Coding\EDID1.LOG_JVC_TV_Model_LT19DK8ZJ.file');
j := 1;
Assign(i, 'C:\Users\Peter John Arnold\Documents\Coding\TV File\TvFile.txt');
rewrite(f);
reset(f);
rewrite(i);
repeat
readln(f, skyf[j]);
Result[j] := char(skyf[j]);
Append(i);
write(i, (skyf[j]));
j := j + 1;
until EOF(f);
close(f);
close(i);
s := result[1..256];
write(s);
readln();
end.
For parsing the binary file:
Read byte array from file (How to read and change a binary file)
Convert byte array obtained from file to string (every byte to
corresponding ASCII char - "chr"-function)
Use existing parsing libraries (e.g. "regexpr" unit)
Note: use "AnsiString" type
Related
I don't work with Pascal very often so I apologise if this question is basic. I am working on a binary file program that writes an array of custom made records to a binary file.
Eventually I want it to be able to write multiple arrays of different custom record types to one single binary file.
For that reason I thought I would write an integer first being the number of bytes that the next array will be in total. Then I write the array itself. I can then read the first integer type block - to tell me the size of the next blocks to read in directly to an array.
For example - when writing the binary file I would do something like this:
assignfile(f,MasterFileName);
{$I-}
reset(f,1);
{$I+}
n := IOResult;
if n<> 0 then
begin
{$I-}
rewrite(f);
{$I+}
end;
n:= IOResult;
If n <> 0 then
begin
writeln('Error creating file: ', n);
end
else
begin
SetLength(MyArray, 2);
MyArray[0].ID := 101;
MyArray[0].Att1 := 'Hi';
MyArray[0].Att2 := 'MyArray 0 - Att2';
MyArray[0].Value := 1;
MyArray[1].ID := 102;
MyArray[1].Att1:= 'Hi again';
MyArray[1].Att2:= MyArray 1 - Att2';
MyArray[1].Value:= 5;
SizeOfArray := sizeOf(MyArray);
writeln('Size of character array: ', SizeOfArray);
writeln('Size of integer var: ', sizeof(SizeOfArray));
blockwrite(f,sizeOfArray,sizeof(SizeOfArray),actual);
blockwrite(f,MyArray,SizeOfArray,actual);
Close(f);
Then you could re-read the file with something like this:
Assign(f, MasterFileName);
Reset(f,1);
blockread(f,SizeOfArray,sizeof(SizeOfArray),actual);
blockread(f,MyArray,SizeOfArray,actual);
Close(f);
This has the idea that after these blocks have been read that you can then have a new integer recorded and a new array then saved etc.
It reads the integer parts of the records in but nothing for the strings. The record would be something like this:
TMyType = record
ID : Integer;
att1 : string;
att2 : String;
Value : Integer;
end;
Any help gratefully received!!
TMyType = record
ID : Integer;
att1 : string; // <- your problem
That field att1 declared as string that way means that the record contains a pointer to the actual string data (att1 is really a pointer). The compiler manages this pointer and the memory for the associated data, and the string can be any (reasonable) length.
A quick fix for you would be to declare att1 something like string[64], for example: a string which can be at maximum 64 chars long. That would eliminate the pointer and use the memory of the record (the att1 field itself, which now is a special static array) as buffer for string characters. Declaring the maximum length of the string, of course, can be slightly dangerous: if you try to assign the string a string too long, it will be truncated.
To be really complete: it depends on the compiler; some have a switch to make your declaration "string" usable, making it an alias for "string[255]". This is not the default though. Consider also that using string[...] is faster and wastes memory.
You have a few mistakes.
MyArray is a dynamic array, a reference type (a pointer), so SizeOf(MyArray) is the size of a pointer, not the size of the array. To get the length of the array, use Length(MyArray).
But the bigger problem is saving long strings (AnsiStrings -- the usual type to which string maps --, WideStrings, UnicodeStrings). These are reference types too, so you can't just save them together with the record. You will have to save the parts of the record one by one, and for strings, you will have to use a function like:
procedure SaveStr(var F: File; const S: AnsiString);
var
Actual: Integer;
Len: Integer;
begin
Len := Length(S);
BlockWrite(F, Len, SizeOf(Len), Actual);
if Len > 0 then
begin
BlockWrite(F, S[1], Len * SizeOf(AnsiChar), Actual);
end;
end;
Of course you should normally check Actual and do appropriate error handling, but I left that out, for simplicity.
Reading back is similar: first read the length, then use SetLength to set the string to that size and then read the rest.
So now you do something like:
Len := Length(MyArray);
BlockWrite(F, Len, SizeOf(Len), Actual);
for I := Low(MyArray) to High(MyArray) do
begin
BlockWrite(F, MyArray[I].ID, SizeOf(Integer), Actual);
SaveStr(F, MyArray[I].att1);
SaveStr(F, MyArray[I].att2);
BlockWrite(F, MyArray[I].Value, SizeOf(Integer), Actual);
end;
// etc...
Note that I can't currently test the code, so it may have some little errors. I'll try this later on, when I have access to a compiler, if that is necessary.
Update
As Marco van de Voort commented, you may have to do:
rewrite(f, 1);
instead of a simple
rewrite(f);
But as I replied to him, if you can, use streams. They are easier to use (IMO) and provide a more consistent interface, no matter to what exactly you try to write or read. There are streams for many different kinds of I/O, and all derive from (and are thus compatible with) the same basic abstract TStream class.
I have tried the following code (and varients) without any sucess, nor can I find any examples of how to call these Windows Functions from Delphi out there. Any clues would be very gratefully received.
The CryptProtectMemory does appear to produce some possibly encrypted result, but the unprotect does not change that result at all.I suspect I have done something charactisticly stupid, but I havent found it all day...
function WinMemEnc(PlnTxt: String): String;
var
Enc: Pointer;
j: Integer;
EncSze: Cardinal;
ws: String;
const
CRYPTPROTECTMEMORY_SAME_PROCESS: Cardinal = 0;
EncryptionBlockSize: Integer = 8;
begin
if Length(PlnTxt) mod EncryptionBlockSize = 0 then
j := Length(PlnTxt)
else
j := ((Length(PlnTxt) div 8) + 1) * 8;
ws := StringofChar(' ', j);
Move(PlnTxt[1], ws[1], j);
Enc := Pointer(ws);
EncSze := j * 2;
if CryptProtectMemory(Enc, EncSze, CRYPTPROTECTMEMORY_SAME_PROCESS) then
begin
Setlength(Result, j);
Move(Enc, Result[1], EncSze);
end;
end;
function WinMemDcr(EncInp: String): String;
var
Enc: Pointer;
j: Integer;
EncSze: Cardinal;
ws: String;
const
CRYPTPROTECTMEMORY_SAME_PROCESS: Cardinal = 0;
begin
j := Length(EncInp);
EncSze := j * 2;
ws := EncInp;
Enc := Pointer(ws);
if CryptUnprotectMemory(Enc, EncSze, CRYPTPROTECTMEMORY_SAME_PROCESS) then
begin
Setlength(Result, j);
Move(Enc, Result[1], EncSze);
end;
end;
You have set EncryptionBlockSize := 8; while in my library CRYPTPROTECTMEMORY_BLOCK_SIZE = 16.
You also mistakenly move only half of the input string to ws, because j holds the length of the string while Move() moves Count number of bytes. A Unicode Char is 2 bytes.
As said in the comments, encryption/decryption works on bytes and storing an encryption in a string is a potential disaster.
So here's my suggestion for a encryption/decryption of a string with encrypted storage in TBytes.
function MemEncrypt(const StrInp: String): TBytes;
begin
Result := TEncoding.Unicode.GetBytes(StrInp);
if Length(Result) mod CRYPTPROTECTMEMORY_BLOCK_SIZE <> 0 then
SetLength(Result, ((Length(Result) div CRYPTPROTECTMEMORY_BLOCK_SIZE) + 1) * CRYPTPROTECTMEMORY_BLOCK_SIZE);
if not CryptProtectMemory(Result, Length(Result), CRYPTPROTECTMEMORY_SAME_PROCESS) then
raise Exception.Create('Error Message: '+IntToStr(GetLastError));
end;
function MemDecrypt(const EncInp: TBytes): String;
var
EncTmp: TBytes;
begin
EncTmp := Copy(EncInp);
if CryptUnprotectMemory(EncTmp, Length(EncTmp), CRYPTPROTECTMEMORY_SAME_PROCESS) then
result := TEncoding.Unicode.GetString(EncTmp)
else
raise Exception.Create('Error Message: '+IntToStr(GetLastError));
end;
In the decryption a copy of the input TBytes is made to preserve the encrypted data.
And finally a test procedure:
procedure TForm13.Button2Click(Sender: TObject);
const
Txt = '1234567890123456789012345678901';
var
s: string;
b: TBytes;
begin
s := Txt;
Memo1.Lines.Add(s);
b := MemEncrypt(Txt);
s := MemDecrypt(b);
Memo1.Lines.Add(s);
end;
Without testing it (purely from the looks of your code), I believe the problem lies in the MOVE statement:
Move(Enc, Result[1], EncSze);
You are moving data from the location of the pointer - not from the data that the pointer is pointing to.
You should use
Move(Enc^, Result[1], EncSze);
to move data from the location that is POINTED TO by the pointer, and not from the pointer itself.
To clarify: The Enc variable is - say - located at address $12345678 and the data you are manipulating is located at address $99999999
This means that at address $12345678 is located 4 bytes ($99 $99 $99 and $99). And at address $99999999 is located the data you are manipulating.
The statement
Move(Enc, Result[1], EncSze);
thus moves EncSize bytes from the address $12345678 to the 1st character of the string variable Result. This you do not want, as it will only move 4 bytes of $99 and then whatever follows at address $1234567C and on.
To move data from the address $99999999 you need to tell the compiler, that you want to move data from the location POINTED TO by the pointer, and not from the POINTER itself:
Move(Enc^, Result[1], EncSze);
But other that that, I agree with David. You should stop using strings as storage for non-string data. It'll bite you in the a** at some point. Use a byte array (TBytes) instead.
1.this is my code i want to read a record from a text file into array in pascal my program is about making a hotel helper and i already have a text file with the data of the hotel then i should read it from the text file and store it in array .. but i am facing error 103 exit code (file not open).... any help Please . :)
program Hotel1(input,output);
const max =10; MaxFloor =10;
type
Date = record
day :1..31;
month:1..12;
year:integer;
end;
Booking = record
Guest:string[20];
S_Date:date;
E_date:date;
end;
Booking_Mat= array[1..max] of Booking;
History_Booking = record
B_num:integer;
B_Mat:Booking_Mat;
end;
Room = record
Num:integer;
Bed_num:integer;
Price:integer;
Status:Boolean;
H:History_Booking;
end;
Data = record
Ro:Room;
m:integer;
end;
Data_mat= array [1..max] of Data;
Procedure Read_Data(filename:string; var table:Data_mat);
var df:text; i,j :integer;
n,m,num,GN:integer;
Bed_num,Price:integer;
f:text;
s,e:Date;
Gname:string[20];
ok:boolean;
a:Data_mat;
c:char;
Begin
writeln('Reading ',filename,' records into array.... ');
assign(df,filename);
reset(df);
i:=0;
while (not eof) do
begin
i:=i+1;
Read (f,num);
a[i].Ro.num:=num;
Read (f,Bed_num);
a[i].Ro.Bed_num:=Bed_num;
Read (f,Price);
a[i].Ro.Price:=Price;
Read(f,c);
if (c ='Y') then
a[i].Ro.status:= true
else
a[i].Ro.status:= false;
readln;
End; {while eof}
close(df);
End; {Read_Data}
You've declared two variables of type Text, (df and f) in your var block.
You open df with these lines:
assign(df,filename);
reset(df);
You then read from f (which is not the file you opened above) in several lines, such as this one:
Read (f, num);
It's interesting to note that you actually manage to close the file you really opened, even though you never use it in your loop:
close(df);
The solution to all of these issues is to delete the declaration of either f or df, and then fix the compiler errors you get by correcting the code to use the remaining text variable. (Two important lessons here are
Only declare the variables you actually need.
Use the variables you declare.
Your loop is also invalid, because you're using while not eof with no file provided for which to test the end. Your loop should read while not Eof(df) do instead.
It's also much better to follow the typical naming convention of prefixing types with a T. It makes it clear that it's a type and not a variable, and allows you to read the code more easily. For instance, I'd change your definition of Data to TRoomData, and change the other type declarations accordingly. Here's an example - note that TRoomData now has a field (member) named Room of type TRoom:
TRoomData = record
Room: TRoom;
m: Integer;
end;
TRoom is defined as
TRoom = record
Num: Integer;
Bed_num: Integer;
Price: Integer;
Status: Boolean;
H: THistory_Booking;
end;
And so forth. This allows you to write code more clearly:
var
RoomData: TRoomData;
begin
RoomData.Room.Num := 1;
RoomData.Room.Price := 50;
// etc.
end;
With all that being said, your file does not contain text, and therefore you're using the wrong file type by using df: Text in the first place. You should use a File of TRoomData, allowing you to read and write entire records at a time. Here's an example of doing so:
var
DF: File of TRoomData;
RoomData: TRoomData;
i: Integer;
const
DataFileName = 'D:\TempFiles\RoomData.dat';
Writing it:
// Put some data into the record
RoomData.Room.Num := 1;
RoomData.Room.Bed_num := 1;
RoomData.Room.Price := 40;
RoomData.Room.Status := True;
RoomData.Room.H.B_num := 1;
for i := 1 to Max do
begin
RoomData.Room.H.B_Mat[1].Guest := Format('Guest %d', [i]);
RoomData.Room.H.B_Mat[1].S_Date.Year := 2014;
RoomData.Ro.H.B_Mat[1].S_Date.Month := i;
RoomData.Ro.H.B_Mat[1].S_Date.Day := i;
end;
// Write it out to the file
AssignFile(DF, DataFileName);
try
Rewrite(DF);
Write(DF, RoomData);
finally
CloseFile(DF);
end;
Reading it back in:
AssignFile(DF, DataFileName);
try
Reset(DF);
Read(DF, RoomData);
finally
CloseFile(DF);
end;
(Or, better yet: If the version of Pascal you're using supports it, move away from the old file I/O routines and start using TFileStream instead.)
Last but not least, learn to properly format your code. It makes it much easier to debug and maintain, and it's much easier to read when you can follow the execution path clearly.
I'm writing a custom structure manipulation program, and I've got the following types:
type
StrLen = 0..MaxLen;
Str = ^StrInst;
StrInst = record
length: StrLen;
data: array [StrPos] of char;
end;
Then I've got the following procedure:
procedure ReadStr(var S: Str);
var pos: StrLen;
begin
S^.length:=0;
pos := 0;
writeln('pos before entering:',pos);
writeln;
with S^ do begin
repeat
Inc(pos);
Read(data[pos]);
until (ord(data[pos]) = 13) or (pos > MaxLen+1);
writeln('pos after entering:',pos);
length := pos-1;
end;
end;
Problem is, when I read into the second object of that type, pos variable, and thus the length field, is getting a mysterious increase by 1. The following code
ReadStr(S1);
ReadStr(S2);
outputs (when I input '123' in both cases):
pos before entering:0
123
pos after entering:4
pos before entering:0
123
pos after entering:5
Will be very gladful, if someone clears situation for me. Thank you in advance.
You're missing some possibly relevant parts of the program. In particular, if this is on Windows then (depending on how you are reading the file) you may have an extra character in the second string because you're stopping at a CR and not processing the following LF.
I'm using Pascal. I have a problem when dealing with reading file.
I have a file with integer numbers. My pascal to read the file is:
read(input, arr[i]);
if my file content is 1 2 3 then it's good but if it is 1 2 3 or 1 2 3(enter here) (there is a space or empty line at the end) then my arr will be 1 2 3 0.
From what I can recall read literally reads the file as a stream of characters, of which a blank space and carriage return are, but I believe these should be ignored as you are reading into an integer array. Does your file actually contain a space character between each number?
Another approach would be to use readLn and have the required integers stored as new lines in the file, e.g.
1
2
3
I have tested the problem on Delphi 2009 console applications. Code like this
var
F: Text;
A: array[0..99] of Integer;
I, J: Integer;
begin
Assign(F, 'test.txt');
Reset(F);
I:= -1;
while not EOF(F) do begin
Inc(I);
Read(F, A[I]);
end;
for J:= 0 to I do write(A[J], ' ');
Close(F);
writeln;
readln;
end.
works exactly as you have written. It can be improved using SeekEOLN function that skips all whitespace characters; the next code does not produce wrong additional zero:
var
F: Text;
A: array[0..99] of Integer;
I, J: Integer;
begin
Assign(F, 'test.txt');
Reset(F);
I:= -1;
while not EOF(F) do begin
if not SeekEOLN(F) then begin
Inc(I);
Read(F, A[I]);
end
else Readln(F);
end;
for J:= 0 to I do write(A[J], ' ');
Close(F);
writeln;
readln;
end.
Since all that staff is just a legacy in Delphi, I think it must work in Turbo Pascal.
You could read the string into a temporary and then trim it prior to converting it.
It doesnt hurt to mention basics like what type of Pascal on what platform you're using in order that people can give a specific answer (as the article notes, there isnt a nice way OOTB in many Pascals)
If I recall there was a string function called Val that converts a string to a number...my knowledge of Pascal is a bit rusty (Turbo Pascal v6)
var
num : integer;
str : string;
begin
str := '1234';
Val(str, num); (* This is the line I am not sure of *)
end;
Hope this helps,
Best regards,
Tom.