hash_32bit
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| + | # $EPIC: hash_32bit.txt,v 1.3 2007/03/02 02:32:04 jnelson Exp $ | ||
| + | ======Synopsis:====== | ||
| + | $__hash_32bit__(<word> <length>) | ||
| + | |||
| + | ======Technical:====== | ||
| + | * The <word> and <length> arguments are [[what is a word|dwords]], which is different from most function arguments. | ||
| + | * If the <word> argument is omitted the empty string is returned | ||
| + | * If the <length> argument is omitted it defaults to 0 | ||
| + | * If the <length> argument is a negative number of is greater than 64, it is changed to 20. | ||
| + | * The return value of this function is a 32 bit signed integer that is a "hash" of the first <length> characters in <word>. | ||
| + | * Analytically speaking, hashing is a specific type of lossy compression. | ||
| + | * All lossy compression techniques suffer from "collisions". A collision occurs when two different <word>s yield the same return value. If you must avoid collisions, use $[[encode]]() instead. | ||
| + | * The inverse of this principle is that all lossy compression techniques are irreversible. You cannot take the return value of this function and determine what <word> was. If you must be able to recreate <word>, use $[[encode]]() instead. | ||
| + | * The return value of this function is deterministic within the lifetime of the client. The algorithm used to compute this value is subject to change in the future; you should not "save" the return value of this function to a file for use in future versions in epic. | ||
| + | |||
| + | ======Practical:====== | ||
| + | You can use $__hash_32bit__() to convert an arbitrary string (perhaps | ||
| + | containing characters that cannot be used in alias names) into a 32 bit signed | ||
| + | integer value which you can use as part of an alias name. Collisions will | ||
| + | occur. You cannot recover the original <word> from the output of this | ||
| + | function. Please keep these in mind when using this function. | ||
| + | |||
| + | ======Returns:====== | ||
| + | A 32 bit signed integer (it can be either negative or positive) that | ||
| + | is deterministically derived from the first <length> characters in <word>. | ||
| + | |||
| + | ======Examples:====== | ||
| + | $hash_32bit("hello there") returns 51439 | ||
hash_32bit.txt ยท Last modified: 2007/03/02 02:32 (external edit)
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