FileRead

[exodus300]

I have program which loads and saves file. When saving, I use the following:

AnsiString Text = "bla bla bla";
int TextSize = Text.Length();
int FileHandle = FileCreate("c:\\something.txt");
FileWrite(FileHandle, (char *)&TextSize, sizeof(TextSize));
FileWrite(FileHandle, Text.c_str(), TextSize);
FileClose(FileHandle);

This stores the size of the text, then the text itself. This works OK, but how do I read the text again into an AnsiString? eg.

AnsiString RetrievedText;
int TextSize;
int FileHandle = FileOpen("c:\\something.txt", fmOpenRead);
FileRead(FileHandle, (char *)&TextSize, sizeof(TextSize));
//What goes here to read the string into RetrievedText?
FileClose(FileHandle);

I have tried various methods, but I get either blank strings or access violations. Please help.

 

[MrProgrammer]

First try to use
FileRead(FileHandle, (char *)&Text, sizeof(TextSize)-1);

If It does not work, I think your problem results from using a parameter of AnsiString type. If you use FileRead function as below, It must work.

int FileHandle;
int TextSize;
int iBytesRead;
char *Buffer;

FileHandle = FileOpen("c:\\something.txt", fmOpenRead);

FileSeek(FileHandle,0,0);
Buffer = new char[TextSize];
iBytesRead = FileRead(FileHandle, Buffer, TextSize-1);
FileClose(FileHandle);

 

[exodus300]

THANK YOU!
This is working, but I still have problems. In my file I have an int (32-bits or 4 bytes) showing the length of the string. Immediately after that is the actual string. My program is reading the number right (I tested this with a ShowMessage, and each time the for loop repeats, it shows the correct number), but the strings have 'junk' characters at the end of them. And I know FileRead is reading the right number of bytes, because the part of the strings that is not garbled chars is correct. I converted the strings to AnsiString using AnsiString(char *Whatever), but this isn't the problem because it also happens with Application->MessageBox, which takes a char*.
What must I do to get this right????

(If you like, I can give you an extract of my source code [the relevent parts] and a copy of the file I am trying to read from, if this will help you help me....)


In the end it will probably be the simplest, most obvious thing I was doing wrong...

 

[MrProgrammer]

Ok, Send it to alpertufek@ixir.com

 

[butthead]

Just a guess, but when I have a problem
with strings I first look at the size of
the buffer I am saving them in. You might
try increasing the size of the buffer by 1
or decreasing it by one. If you have already
consideered this well never mind.

 

[exodus300]

I tried decreasing it , but not increasing. I will have a look....
In the end it will probably be the simplest, most obvious thing that I was doing wrong...

 

[exodus300]

HMMM... I WAS just about to send you my source when I noticed something VERY strange... The "problem code" is written in a DLL function. I copied the code into a regular exe project, and realised that the problem had magically disappeared.

Could the fact that it's in a DLL be anything to do with it?

Anyways, here's my source... (Put it in a new project, then a DLL... see for yourself!)


NOTE: You need certain header files #included to compile this.. I don't know which one, but it is one of the following:

vcl.h
Classes.hpp
Controls.hpp
StdCtrls.hpp
Forms.hpp
ComCtrls.hpp

    int iFileHandle = FileOpen(FileName, fmOpenRead);
    if (iFileHandle == -1) {
    	Application->MessageBox("Error: Unable to create file handle.", "Error",
        	MB_ICONERROR);
        return false;
        }

    AnsiString AppVersion;
    int iAppVerSize;

    FileRead(iFileHandle, (char *)&iAppVerSize, sizeof(iAppVerSize));

    char *pszBuffer = new char[iAppVerSize];
    FileRead(iFileHandle, pszBuffer, iAppVerSize);
    AppVersion = AnsiString(pszBuffer);
    delete pszBuffer;

    Application->MessageBox(AppVersion.c_str(), "Version", MB_ICONINFORMATION);
    // This is where the prob is - has an extra symbol (usually &) appended to the string
    // (BUT only when this code is in a DLL, not in a regular project)

    /*
    MORE CODE...
    .
    .
    .
    */

    FileClose(iFileHandle);

In the end it will probably be the simplest, most obvious thing that I was doing wrong...

[tt]One is glad to be of service
- Bicentennial man[/red][/tt]