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Request locking

To reduce opportunity for tampering with requests, a simple locking facility is provided.
If attribute::RequestLock is set, a lock value must be appended to the request, in form of &xxxx , with xxxx being a four digit hex value. This hex value is generated using a simple hashing algorithm applied to the modifiers portion of the request (after the '?' which separates the URL path from the modifiers ). This must be done after the request is fully http-encoded, but before it is (optionally) obfuscated. After de-obfuscating the request, the server will use the same hashing algorithm on the modifier string (excluding the last 5 characters, which contain the lock value). If the generated key does not match the lock, the request is rejected.
C++ sample code to generate the request lock value:
unsigned int lockValue(const char *str) 
    unsigned int sum = 0; 
    if (str == NULL) 
        return sum; 
    for (; *str; ++str) 
        sum = (sum*131 + *str) & 0xffff; 
    return sum;