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GHashTable: Add a note about hash collisions

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Matthias Clasen 2012-01-24 21:11:13 -05:00
parent a3b91b3691
commit 030b3f25e3
1 changed files with 13 additions and 5 deletions
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18
glib/ghash.c
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@ -151,11 +151,19 @@
* g_direct_hash() is also the appropriate hash function for keys
* of the form <literal>GINT_TO_POINTER (n)</literal> (or similar macros).
*
* <!-- FIXME: Need more here. --> The hash values should be evenly
* distributed over a fairly large range? The modulus is taken with the
* hash table size (a prime number) to find the 'bucket' to place each
* key into. The function should also be very fast, since it is called
* for each key lookup.
* <!-- FIXME: Need more here. --> A good hash functions should produce
* hash values that are evenly distributed over a fairly large range.
* The modulus is taken with the hash table size (a prime number) to
* find the 'bucket' to place each key into. The function should also
* be very fast, since it is called for each key lookup.
*
* Note that the hash functions provided by GLib have these qualities,
* but are not particularly robust against manufactured keys that
* cause hash collisions. Therefore, you should consider choosing
* a more secure hash function when using a GHashTable with keys
* that originate in untrusted data (such as HTTP requests).
* Using g_str_hash() in that situation might make your application
* vulerable to <ulink url="https://lwn.net/Articles/474912/">Algorithmic Complexity Attacks</ulink>.
*
* Returns: the hash value corresponding to the key
*/