Format
sha1(T)sha1(F)
Returns
text or null.
Args
T: A text string.F: A file.
This proc implements SHA1 hashing. A hash function is a one-way process that compacts information to a short value: a hash. The same value will always have the same hash. Among other uses, most computers use hashing to store passwords. By storing just the hash, the password file contains very little sensitive information, but the password can still be verified by confirming that sha1(password)==hash. SHA1 is a widely-used hash function.
mob/var/hash
mob/Read(savefile/S)
..()
// hash was saved in the file along with other values
if(sha1("[level]/[exp]/[exp_needed]") != hash)
src << "Cheater!"
del(src)In the example, a few vars belonging to a mob were saved along with a hash of those values. When the mob is loaded again, the game compares the hash to the values to make sure it’s still accurate. If the values or hash had been changed by a sneaky player, they wouldn’t match. (But a sneaky player could still calculate hash themselves if they knew the exact text used to make it, so this should be kept secret.)
If the argument is a file, sha1() will read the file and return the SHA1 hash of the file’s entire contents. If the file doesn’t exist, it returns null. The file may be a cache file or an external file.
Examples:
var/hash = "(insert hash value here)" // Compute this ahead of time
// Check that the cached default icon is still the same
if (sha1('default.dmi') != hash)
world << "The default icon has been modified!"
// Or check that the entire game resource file is pristine
if (sha1(file("mygame.rsc")) != hash)
world << "The game resources have been modified!"Note that you must pass the result of file() in order to compute the hash of an external file’s contents at runtime. Otherwise sha1() will treat the filename as text and return the hash of the name only.
If T is anything but a text string or file, the proc returns null.