Skip to content

Instantly share code, notes, and snippets.

View virtualsafety's full-sized avatar

virtualsafety virtualsafety

View GitHub Profile
@kkc
kkc / elasticsearch.md
Last active December 29, 2023 00:39
Elasticsearch performance tuning

##TUNING##

Configuration

System: set file descriptors to 32K or 64K

vim /etc/security/limit.conf

@chmarr
chmarr / blocked.sql
Created November 5, 2015 18:30
PostgreSQL query to display blocked and blocking queries. Updated from PG Wiki.
SELECT blocked_locks.pid AS blocked_pid,
blocked_activity.usename AS blocked_user,
now() - blocked_activity.query_start
AS blocked_duration,
blocking_locks.pid AS blocking_pid,
blocking_activity.usename AS blocking_user,
now() - blocking_activity.query_start
AS blocking_duration,
blocked_activity.query AS blocked_statement,
blocking_activity.query AS blocking_statement
@shaheemirza
shaheemirza / sniff.py
Created February 18, 2016 12:04
Packet sniffer in python for Linux
#Packet sniffer in python for Linux
#Sniffs only incoming TCP packet
import socket, sys
from struct import *
#create an INET, STREAMing socket
try:
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
except socket.error , msg:
@pathikrit
pathikrit / NQueen.scala
Last active January 19, 2023 21:30
O(n!) solution to the n-Queen puzzle (https://en.wikipedia.org/wiki/Eight_queens_puzzle)
/**
* Solves the n-Queen puzzle in O(n!)
* Let p[r] be the column of the queen on the rth row (must be exactly 1 queen per row)
* There also must be exactly 1 queen per column and hence p must be a permuation of (0 until n)
* There must be n distinct (col + diag) and n distinct (col - diag) for each queen (else bishop attacks)
* @return returns a Iterator of solutions
* Each solution is an array p of length n such that p[i] is the column of the queen on the ith row
*/
def nQueens(n: Int): Iterator[Seq[Int]] =
(0 until n)
@tomykaira
tomykaira / Base64.h
Last active April 23, 2025 22:58
C++ single header base64 decode/encoder for C++ 11 and above.
#ifndef _MACARON_BASE64_H_
#define _MACARON_BASE64_H_
/**
* The MIT License (MIT)
* Copyright (c) 2016-2024 tomykaira
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
@derofim
derofim / codestyle.md
Last active December 11, 2025 06:46
C++ code style sample

Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x
@oinopion
oinopion / read-access.sql
Created October 5, 2016 13:00
How to create read only user in PostgreSQL
-- Create a group
CREATE ROLE readaccess;
-- Grant access to existing tables
GRANT USAGE ON SCHEMA public TO readaccess;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;
-- Grant access to future tables
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;
@yydai
yydai / Calc.java
Last active July 7, 2025 21:46
chapter4 of antlr4---Building a Calculator Using a Visitor
/***
* Excerpted from "The Definitive ANTLR 4 Reference",
* published by The Pragmatic Bookshelf.
* Copyrights apply to this code. It may not be used to create training material,
* courses, books, articles, and the like. Contact us if you are in doubt.
* We make no guarantees that this code is fit for any purpose.
* Visit http://www.pragmaticprogrammer.com/titles/tpantlr2 for more book information.
***/
import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.ParseTree;
@jdtournier
jdtournier / README.md
Last active February 11, 2023 07:26
short demo of explicit instantiation of templates, and avoiding parsing the full definition in every compilation unit

A short demo showing the explicit instantiation of templates, and how to avoid parsing the full definition(s) in every compilation unit. The limitation is that it will only be possible to use the specific specialisations explicitly instantiated in the cpp file.