Category Archives: programming

Space efficient source code storage

23.03.2016 – 23:28

During implementation of DistTest I faced with necessity of building a lot of different linux kernel versions. As a first solution I chose downloading archives from kernel.org for each used version. But I soon realized that about 1000 versions of sources with size 0.5-1GB each would consume a lot of disk space. It’s also impossible to build kernel with exact commit precision using this approach.
Set of base versions with corresponding patches can save disk space, but uses a lot of random I/O during applying patches, so it’s slow on HDD and consume finite rewrite resource of SSD. Temporary nature of sources leads to conclusion “use tmpfs”. But aufs offers much less RAM consuming method – store in RAM only diffs.

Yuriy Nazarov | Permalink | Comment (0)

Selfmade dyndns

10.01.2015 – 02:38

Dyn.com stopped providing free dyndns hosting some time ago. It were sad news.
However most necessary functionality can be implemented in 70 lines of code.
To dynamically update dns records we must find a way to:

get current ip
update DNS record
schedule script for execution

1. Getting current ip address

Many ISP use NAT for security and money saving reasons. Also NAS used in routers. So, to get your IP address you need to ask your IP address from service located outside your network.
For example internet.yandex.ru web page ask resource http://ipv4.internet.yandex.ru/api/v0/ip to determine IP address. So, let’s use it.

use constant IP_API_URI         => 'http://ipv4.internet.yandex.ru/api/v0/ip';
sub get_ip($) {
	my ($ua) = @_;
	my $response = get($ua, IP_API_URI);
	return substr $response, 1, length($response)-2; #clean out quotes
}

use constant IP_API_URI => 'http://ipv4.internet.yandex.ru/api/v0/ip';

sub get_ip($) {

my ($ua) = @_;

my $response = get($ua, IP_API_URI);

return substr $response, 1, length($response)-2; #clean out quotes

}

2. Updating DNS record

Yandex provide API for DNS records management for domains parked in yandex. ~~API reference should be located here but link is currently broken :-(.~~ UPD: API reference.
In two words you should send POST request with token in header and data in request’s body to https://pddimp.yandex.ru/api2/admin/dns/edit url.
It should looks like following snippet:

use constant DNS_API_URI_PREFIX => 'https://pddimp.yandex.ru/api2/admin/dns/';
sub post($$$%){
	my ($ua, $url, $data, %headers) = @_;
	my $req = HTTP::Request->new(POST => $url);
	$req->header(%headers) if keys %headers;
	$req->content_type('application/x-www-form-urlencoded');
	$req->content($data);
	my $res = $ua->request($req);
	return $res->content if $res->is_success;
	return undef;
}
sub set_domain_ip($$$$$$){
	my ($ua, $token, $domain, $subdomain, $record_id , $ip) = @_;
	return decode_json post($ua, DNS_API_URI_PREFIX."edit", "domain=$domain&record_id=$record_id&subdomain=$subdomain&ttl=14400&content=$ip", PddToken => $token);
}

use constant DNS_API_URI_PREFIX => 'https://pddimp.yandex.ru/api2/admin/dns/';

sub post($$$%){

my ($ua, $url, $data, %headers) = @_;

my $req = HTTP::Request->new(POST => $url);

$req->header(%headers) if keys %headers;

$req->content_type('application/x-www-form-urlencoded');

$req->content($data);

my $res = $ua->request($req);

return $res->content if $res->is_success;

return undef;

}

sub set_domain_ip($$$$$$){

my ($ua, $token, $domain, $subdomain, $record_id , $ip) = @_;

return decode_json post($ua, DNS_API_URI_PREFIX."edit", "domain=$domain&record_id=$record_id&subdomain=$subdomain&ttl=14400&content=$ip", PddToken => $token);

}

3. Scheduling dns records updating

Use the cron, Luke :-) I mean that adding following line to cronjobs would be a simplies way to schedule updating of our dns records:

* * * * * ( token=123 /home/user/yandex_dns.pl --domain=domain.com --subdomain=subdomain )

1	* * * * * ( token=123 /home/user/yandex_dns.pl --domain=domain.com --subdomain=subdomain )

That’s all. Complete script on github.

Yuriy Nazarov | Permalink | Comment (0)

programming

Buzz words collection

16.07.2014 – 21:41

My collection of programmers buzz words. I think it will be useful for beginner programmers and Software Engineering students. Will be actively replenished.

Principles

Defensive programming
KISS – Keep it simple, stupid
DRY – Don’t repeat yourself
YAGNI – You Ain’t Gonna Need It
ACID – Atomicity Consistency Isolation Durability
Inversion of control
Uniform Access Principle
Law of Demeter
SOA – Service-oriented architecture
GRASP – General Responsibility Assignment Software Patterns
SOLID
- Single responsibility principle
- Open/closed principle
- Liskov substitution principle
- Interface segregation principle
- Dependency inversion principle

Yuriy Artamonov | Permalink | Comment (0)

programming

Some weekend’s madness

19.08.2013 – 00:18

I’ve just tried to follow intellij idea’s manual and develop some useless plugin. And now my plugin can display “Hello world” program on perl.

You also can view this madness on github.
UPD1. Some new lexical constructions support added.

Yuriy Nazarov | Permalink | Comments (2)

programming

Link assembly and c

01.06.2013 – 12:53

I using nasm to generate object code from assembly source. 3 application required to compile executable:
– nasm
– gcc from gcc--base package (gcc-4.7-base for example)
– ld from binutils package
*package names in ubuntu distribution

To install this packages run following command:

sudo apt-get install nasm binutils gcc-4.7-base

1	sudo apt-get install nasm binutils gcc-4.7-base

Files contents:

global func

section .text
func:
    push   rbp
    mov    rbp, rsp
    mov    rax, 1        ; sys_write
    mov    rdi, 1        ; stdout
    mov    rsi, message  ; message address
    mov    rdx, length   ; message string length
    syscall
    pop rbp
    ret

section .data
    message: db 'Hello, world!',0x0A    ; message and newline
    length:    equ    $-message        ; NASM definition pseudo-instruction

global func

section .text

func:

push rbp

mov rbp, rsp

mov rax, 1 ; sys_write

mov rdi, 1 ; stdout

mov rsi, message ; message address

mov rdx, length ; message string length

syscall

pop rbp

ret

section .data

message: db 'Hello, world!',0x0A ; message and newline

length: equ $-message ; NASM definition pseudo-instruction

void func(); //may be extern void func(); is more true way

int main(){
    func();
    return 0;
}

void func(); //may be extern void func(); is more true way

int main(){

func();

return 0;

}

nasm -f elf64 func.asm
gcc -c use_asm.c
gcc use_asm.o func.o -o use_asm

nasm -f elf64 func.asm

gcc -c use_asm.c

gcc use_asm.o func.o -o use_asm

And finaly:

$ ./use_asm
Hello, world!

1 2	$ ./use_asm Hello, world!

Yuriy Nazarov | Permalink | Comment (0)

programming

Precision of calculation with floating point numbers

25.05.2013 – 14:26

I found some curiosity issues during finding optimal tool for compilation our program. Results of computations be different for different tools and different optimisation flags.
For investigating this issue I write simple code(full sources on github):

	int i;
	long double res;
	for(i=0;i<100000000;i++){
		res += cos(i);
	}

int i;

long double res;

for(i=0;i<100000000;i++){

res += cos(i);

}

In this small test program I can’t reproduce different results for different flags. But 5 different results for so similar programs is enough to demonstrate discovered effect.

Source code and tool	Result	Computation time, s
Assembler	1.53436944477410652787	3.81
gcc long	1.53436944477462278158	4.4
gcc double	1.53436944477389380914	4.4
icc long	1.53436944477397574360	6.88
icc double	1.53436944477334602510	1.50

p.s. also I found that manually written assembly code 15% faster than code on C in spite of using “-O2” optimisation flag.

Yuriy Nazarov | Permalink | Comment (0)

programming

Suffering Oriented Programming

24.10.2012 – 20:12

Do you suffer greatly without some feature?
We will implement it!

We take into account only the great suffering

Yuriy Artamonov | Permalink | Comment (0)

backup programming svn vcs

Remote SVN backup with svnsync

07.09.2012 – 01:50

Create local svn repository with name “my_local_repo”

$ svnadmin create my_local_repo

1	$ svnadmin create my_local_repo

prepare local repo

$ echo "#!/bin/sh" > hooks/pre-revprop-change
$ chmod 755 hooks/pre-revprop-change

1 2	$ echo "#!/bin/sh" > hooks/pre-revprop-change $ chmod 755 hooks/pre-revprop-change

initialize local copy

$ svnsync init file:///path/to/my_local_repo http://from.server/from_repo

1	$ svnsync init file:///path/to/my_local_repo http://from.server/from_repo

first run must be interactive to input and save your login and password

svnsync sync file:///path/to/my_local_repo

1	svnsync sync file:///path/to/my_local_repo

write script to run it in cron
backup_svn_script.sh:

#!/bin/bash
svnsync --non-interactive sync file:///path/to/my_local_repo
tar -C /path/to/ -czf /path/to/backup/$(date +"svn_%Y_%m_%d_%H_%M_%S").tar.gz my_local_repo

#!/bin/bash

svnsync --non-interactive sync file:///path/to/my_local_repo

tar -C /path/to/ -czf /path/to/backup/$(date +"svn_%Y_%m_%d_%H_%M_%S").tar.gz my_local_repo

it produce files like “svn_2012_09_07_01_34_01.tar.gz” in your backup directory

Now you can add task to cron. Execute:

$ crontab -e

1	$ crontab -e

and add following line to run backup at 4:00 (4 a.m.) every day

0 4 * * * /path/to/backup_svn_script.sh

1	0 4 * * * /path/to/backup_svn_script.sh

This method is not disk space efficient, but very simple.

Sources:
using svnsync
installing subversion server in ubuntu

Yuriy Nazarov | Permalink | Comment (0)

From idea to profit

Category Archives: programming

Space efficient source code storage

Selfmade dyndns

1. Getting current ip address

2. Updating DNS record

3. Scheduling dns records updating

Buzz words collection

Principles

Some weekend’s madness

Link assembly and c

Precision of calculation with floating point numbers

Suffering Oriented Programming

Do you suffer greatly without some feature?
We will implement it!

Remote SVN backup with svnsync

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Category Archives: programming

1. Getting current ip address

2. Updating DNS record

3. Scheduling dns records updating

Principles

Do you suffer greatly without some feature? We will implement it!

Recent Posts

Meta

Categories

Archives

Do you suffer greatly without some feature?
We will implement it!