Problems with file input/output

[Hodge4ever]

Just to give you some background, I am trying to write an encryption algorithmn, so the options are -e to encrypt or -d to decrypt. During the encryption process an array of characters is written to a file called asciivalue.txt and stored for later use. This part of the program appears to work fine, HOWEVER when I try to read back from the file during the decryption process the input I am getting is not what I expected. The input file contains "YYYYYNYYYYY" but when I read from the file into the array (chartestarray) it appears as random characters i.e. smilie faces, spaces etc......

I have read other inputs/outputs in the same program using the same logic and coding and and they work perfectly, so I am really confused why this isn't working!?!

The way I am doing it at the moment is:

FILE *asciivalue_file;
asciivalue_file = fopen("asciivalue.txt","w");
fseek(asciivalue_file, 0, SEEK_SET);
char chartestarray[charcount];
//Charcount is devised elsewhere and works fine
 
int readin = 2;
int i = 0;
 
while (readin != 7)
//Very crude way of repeating I know
{
     lc = fgetc(asciivalue_file);
     if (lc == EOF)
          break;
     else
          if (lc != EOF)
          {
               chartestarray[i] = lc;
               i++;
          }
}
 

Hope that makes sense :(

[Cucumber]

After taking a fast look, should not you be opening the file in read mode rather than write mode?

FILE *asciivalue_file;
asciivalue_file = fopen("asciivalue.txt","w");//<--- should be "r"
 

Also, when reading the characters and saving them into the array of characters, you should add the end of string.

i=0;
while (i != 7)
{
     lc = fgetc(asciivalue_file);
     if (lc == EOF)
          break;
     chartestarray[i++] = lc;
     chartestarray[i]=0;
}
 

[Hodge4ever]

Many thanks, your first point pointed me in the right direction.

I was opening asciivalue.txt using write because if the user chooses -e (to encrypt) then an array of characters is written to that file. If they choose -d (to decrypt) then the characters are read from the file to an array of characters.

I was declaring this at the start of the program along with my variables, I assumed that if I opened it as write then it would also read i.e. work O.K in both functions. I'm guessing that opening with WRITE access does not necessarily give the user READ access?

I have now ameneded the code so that it the user chooses -e then asciivalue.txt is opened with write access, however if they choose -d then asciivalue.txt is opened with read access. It is now functioning as expected.

[Cucumber]

Correct, if using "w" you can only write, is using "r" you can only read. I dont know whether there is a way to open files in Read and Write mode using C standard file functions.

Win32 file functions allow opening files in read AND write mode though.