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27 lines
1.5 KiB
Markdown
Executable File
27 lines
1.5 KiB
Markdown
Executable File
## PAC-Script Performance Analysis
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Somewhere in PAC-script you may want:
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```javascript
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if (Is_subdomain_of( host, blocked_hosts ))
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return 'use proxy';
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```
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You have to make `Is_subdomain_of` very fast.
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This check is executed on each request. You should watch memeory consumption too.
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The naive solution is to keep array of blocked ips and check if the host resolves to one of the ips.
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You may do it with `indexOf`, binary search, etc.
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The shortcoming of every ip solution is that __some providers resolve blocked hosts to wrong ips__, so we eventually need list of hosts.
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I have tested different [solutions](https://github.com/ilyaigpetrov/anti-censorship-russia/tree/master/pac-generator/src), and depicted [results](./benchmark/Output.txt) in the following chart:
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![Host Lookup Chart: Time-Memory, Hits-Misses](./chart/host-lookup-chart.png)
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* __IPs indexOf__ – Blocked IP is searched by `indexOf`
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* __IPs binary__ – Blocked IP is searched by binary search. For some reason hit time is slightly increased.
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* __IPs switch__ – Simply `switch(Blocked_IP) { case1: ... caseN: return true }`. Works even better than binary search. Magic.
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* __Hosts switch__ – Radix trie built on `switch`. Comparable to __IPs switch__.
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* __Hosts reversed binary__ – binary search on hosts, but hosts are kept in reversed form: _"gro.evichra"_ instead of _"archive.org"_. It shouldn't really affect anything, but it does, maybe because I also use `dnsDomainIs` instead of `===`.
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