Re: Use "ropes" for string concatenation

Hey Sent from my iPhone > On Mar 24, 2015, at 5:11 PM, Nikita Popov <nikita.ppv@gmail.com> wrote: > >> On Mon, Mar 23, 2015 at 11:41 PM, Dmitry Stogov <dmitry@zend.com> wrote: >> Hi, >> >> Recently, Xinchen and me worked on optimization that eliminates useless reallocations and >> copying during string concatenation (ZEND_ADD_STRING and family + ZEND_CONCAT). >> >> The idea comes from ropes, but adopted especially for our needs. >> Rope is popular data structure in languages with immutable strings. >> http://en.wikipedia.org/wiki/Rope_%28data_structure%29 >> >> We don't try to use ropes everywhere in the engine (at least it's too later for >> 7.0), only for concatenation. >> >> The first branch uses ropes only instead of ZEND_ADD_STRING and family. This must be safe. >> The only problem is possible memory leaks on exception (but we already have this problem anyway). >> The simplest way to understand the patch - read code for new opcodes in zend_vm_def.h. >> >> https://github.com/php/php-src/pull/1194/files >> >> The second branch in addition uses ropes for series of ZEND_CONCAT. It disables calls to >> do_operation(ZEND_CONCAT) handler of custom internal classes.. >> >> https://github.com/php/php-src/pull/1195/files >> >> Both make slight speed improvement (first +0.3%, second +0.6% on wordpress home page). >> >> We don't currently use ability to override CONCAT behavior in internal classes, and >> I'm not sure if it may be useful at all. (For example Lua doesn't provide concat >> meta-method). May be remove it? > > Overloading concat operator will be useful in the future for the implementation of the UString > class, for example. > then we can implement is in rope_end handler, and don't convert op to string in rope add var handler. Thanks > Nikita