dynamic space allocation problem

[Barok]

hello peeps,

i just startet to coding in c, and dont have a big background.

now i have a problem witch i dont understand. i hope you guys can help me out here.

the problem is malloc. i try to allocate space for a padded string.i get the lenght of the new string with strlen and then try to allocate space with that value.but this does not work.the buffer had the size of 16 instead of 8, or 24 instead of 16 and so on.


this is my code:

int tfis()
{
    ERRCODES Status = 0;
    int I;
    const char PaddingByte = 0x24;     //dollar sign
    char TestString[30] = "AAAAXAAA";
    int StringLength = strlen(TestString);
    unsigned int StringLengthNew;
    unsigned short int TheCounter = 0;
    char C;
    unsigned char *StringTable = 0;
 
 
    for(I=0; I<=StringLength; I++)   
    {
        C = TestString[i];
 
        if(! (C == 0))
        {
            printf("%c", C);
        }
        else 
        {
            printf(" End of File..\n");
            if((I%8 == 0)&&(I != 0))
            {
                //add at least 8 bytes..
                printf("1. the string had a length of %d bytes\n", I );
                printf("1. padding not needed, add at least 8 bytes\n");
                do
                {
                    TestString[i] = PaddingByte;
                    printf("%s\n", TestString);
                    I++;
                    TheCounter++;
                }while(I%8 != 0);
            }
            else 
            {
                //add ++ bytes
                printf("2. the string had a length of %d bytes\n", I);
                printf("2. padding needed, add ++ bytes\n");
                do
                {
                    TestString[i] = PaddingByte;
                    printf("%s\n", TestString);
                    I++;
                    TheCounter++;
                }while(I%8 != 0);
            }
        }
    }
 
    StringLengthNew = strlen(TestString);
 
    printf("the new string has a length of %d bytes. the value: %s\n", StringLengthNew, TestString);
    printf("%d bytes added..\n", TheCounter);
 
    TheCounter = 0;
    StringTable = malloc(StringLengthNew);             //allocate space for the new output buffer
    printf("output size: %d\n", strlen(StringTable));
 
 
    if(! StringTable)
    {
        printf("error..\n");
        Status = BUFFER_SIZE;
        return Status;
    }
    else
    {
        printf("success..\n");
        strncpy(StringTable, TestString, StringLengthNew);  //copy the value to the new buffer
        printf("Output String: %s\n", StringTable);
    }
 
    free(StringTable);
    StringTable = 0xc;
 
    return Status;
}
 

[weaknessforcats]

First, strlen returns the number of characters in the string. Your initial string is
"AAAAXAAA" which is 8 characters. strlen will return 8.

However, you loop:

for(I=0; I<=StringLength; I++)
{
C = TestString[i];
etc...

will cycle 9 times.

Your array is 30. Don't you mean to cycle 30 times??

for(I=0; I<30; I++)   
    {
        C = TestString[i];
 etc...
 

Can you use your debugger?? If you can you can see that your array phas been padded correctly without relying on a bunch of printf() statements that may not tell you what you need to know.