Question 200628 in Html Question posted in
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Html – HTTP server in C

I wrote a simple http server in C and I was now trying to send html responses. I wrote a function to read the html file and put it in a string but turns out it’s only working on small .txt files.
I was getting seg faults every time I try to read an html file.
Here’s my code:

int file_to_str(char** string, char* filename){
        FILE* mystream = fopen(filename, "r");
        char c;
        int index = 0;

        *string = (char*) malloc(sizeof mystream);
        
        while ((c = getc(mystream)) != EOF){
                if (c == '"') c = ''';
                (*string)[index++] = c;
        }
        fclose(mystream);
        //string will be freed by the caller
}
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2

Answers


  1. 0

    You probably are experiencing buffer overrun, unless you happen to read a file smaller than the buffer malloc returns (it can be internally larger than what you request)

    Try the following:

    int file_to_str(char *&string, char* filename)
{
    FILE* mystream = fopen(filename, "r");
    if (mystream != nullptr)
    {
        fseek(mystream, 0, SEEK_END);
        size_t buf_size = ftell(mystream);
        fseek(mystream, 0, SEEK_SET);
        string = (char *)malloc(buf_size + 10);
        memset(string, 0, buf_size + 10);
        fread(string, sizeof(char), buf_size, mystream);
        fclose(mystream);
    }
}

    Also note: if you aren’t going to return anything, then your return type should be void. Otherwise, you should return a value, maybe the char count? And I used malloc in keeping with your code, but consider an STL container.

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  2. 0

    FYI: Be careful. Your question has a negative score. I’m afraid to ask another question because they ban users with low scores, and this is a great research space. I think your question is valid and I want to help you, but I just want you to be aware.

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