PSET6 Server - Parse function (requesting two files in a row)

Question

I'm currently working on PSET6 and have implemented the parse() and lookup() functions. When I try to test my code using CS50 (the first part), I get all checks minus the last one, "Requesting two files in a row (cat.html then cat.jpg) succeeds"

Doesn't the server request files one at a time? I figured it would run the parse function every time a file is needed. If you think I'm going in the wrong direction or want to offer any criticism, I'm all ears. Thanks in advance!

---

bool parse(const char* line, char* abs_path, char* query)
{
    // check if method is of type GET
    if (strncmp(line, "GET ", 4) != 0)
    {
        error(405);
        return false;
    } 

    // check if request-target starts with '/'
    if (line[4] != '/')
    {
        error(501);
        return false;       
    }

    // get request target
    char* haystack = strchr(line, '/');
    char* needle = strchr(haystack, ' ');

    // will be used to check what comes after the request-target
    char* http_version = needle;

    // check for extra targets
    char* errchk = strchr(http_version + 1, ' ');
    if (errchk != NULL)
    {
        error(505);
        return false;   
    }

    char target[needle - haystack];
    strncpy(target, haystack, needle - haystack);
    target[needle - haystack] = '\0'; 

    errchk = strchr(target, '\"');
    if (errchk != NULL)
    {
        error(400);
        return false;
    }

    // parse absolute path
    haystack = target;
    needle = strchr(haystack, '?');

    // check if a query is present
    if (needle == NULL)
    {
        strcpy(abs_path, haystack);
        query[0] = '\0';
    }
    else
    {
        // if so, remove query
        char path[needle - haystack + 1];
        strncpy(path, haystack, needle - haystack);
        path[needle - haystack + 1] = '\0'; 

        strcpy(abs_path, path);

        // parse query
        strcpy(query, needle + 1);
    }

    // check for HTTP version
    needle = strstr(http_version, "HTTP/1.1");

    if (needle == NULL)
    {
        error(505);
        return false;
    }

    return true;
}

Answer 1

I just completed this pset successfully.. I had the same issue and i moved on implementing the next function because if you see in the sandbox link you will find under that error written TODO..which means it will be covered in the remaining TODO functions.

Answer 2

Doesn't the server request files one at a time?

the server does not request files at all. the client (e.g., telnet, curl, a browser, etc) does. and it does request one file at a time.

however, if we take cat.html as an example, you'll find that it has an <img> element with a src attribute whose value is the path to cat.jpg.

so when requesting cat.html with a browser, the browser automatically requests cat.jpg as well after requesting cat.html in order to render cat.jpg in place of the aforementioned <img> tag in cat.html.

regarding your code:

char target[needle - haystack];
strncpy(target, haystack, needle - haystack);
target[needle - haystack] = '\0';

are you sure, target is big enough? are you sure the last available index in an array of length needle - haystack is needle - haystack?

same thing applies for

path[needle - haystack + 1] = '\0';

I recommend you avoid using check50 for now and use a client (perhaps a browser) to test your server, which may be running under gdb. set breakpoints, and check whether you have the values you expect stored in your variables.