Squashed commit of the following:
commit d96eab8d79
Author: Francois Laupretre <francois@tekwire.net>
Date: Fri Jun 26 01:23:31 2015 +0200
Use the new 'ZSTR' macros in the rest of the code.
Does not change anything to the generated code (thanks to compat macros) but cleaner.
commit b352643910
Author: Francois Laupretre <francois@tekwire.net>
Date: Thu Jun 25 13:45:06 2015 +0200
Improve zend_string API
Add missing methods
Split off zend_hash_compare_impl into separate function that does
not bother with recursion protection. We had two cases where
UNPROTECT_RECURSION was missing.
New implementation of hashtables introduced a compaction step which is
triggered when a hashtable is full but it contains at least one deleted
bucket. Therefore there is a possibility that a cleverly crafted code can
trigger this compaction step (which takes time proportional to the size of
hashtabe) by executing constatnt number of operations. When the hashtable
is full, deletion and subsequent addition or single element triggers a
table compaction and these two steps can be repeated ad infinitum. This
might be avenue for a DOS attack.
This patch allows compaction to be performed only if the hashtable contains
at least 1/32 deleted elements, otherwise the hashtable is doubled in size.
Linear amount of work caused by compaction is amortized over multiple
malicious additions and deletions.
Removed HashTable->arHash (reduced memory consumption). Now hash slots may be accessed using HT_HASH() macro.
Hash slotas are allocated together with Buckets (before them) and lay in reverse order from HashTable->arData base address (see comments in Zend/zend_types.h)
Indexes in hash table and conflict resolution chains (Z_NEXT) may be stored as indeces or offsets in bytes, depending on system (32 or 64-bit).
HashTable data filelds are reordered to keep the most useful for zend_hash_find() data in the same CPU cache line.
