Month: March 2024

[c++] #define __atribute__

– The __attribute__ directive is used to decorate a code declaration in C, C++ and Objective-C programming languages. This gives the declared code additional attributes that would help the compiler incorporate optimizations or elicit useful warnings to the consumer of that code.

–
__attribute__((constructor)) is a GCC compiler extension in C++ that allows you to specify a function that should be executed automatically before the main function of your program.

[c++] ifdefディレクティブ

条件付きコンパイラ
#ifdef および #ifndef のディレクティブは、#if を使用できるところならどこでも使用できる。

#defineはプリプロセッサ(コンパイル前の処理)を行う

[c++] mutex

mutexはスレッド間で使用する共有リソースを排他制御するためのクラス
lock()メンバ関数によってロックを取得し、unlock()メンバ関数でリソースのロックを手放す

#include <iostream>
#include <thread>
#include <mutex>
#include <vector>

class X {
    std::mutex mtx_;
    std::vector<int> data_;

    public:
        void add_value(int value){
            std::lock_guard<std::mutex> lock(mtx_);
            data_.push_back(value);
        }

        void print(){
            for(int x: data_){
                std::cout << x << std::endl;
            }
        };
}

int main() {
    X x;

    std::thread t1([&x]{x.add_value(1);})
    std::thread t2([&x]{x.add_value(2);})

    t1.join();
    t2.join();

    x.print();
}

[c++] explicitとは？

構造体やclassのコンストラクタにつけることで暗黙的な型変換を防止する機能

struct A {
    explicit A(int);
};
struct B {
    B(A) {}
};

int main(){
    // B b(1);
    return 0;
}

型変換できない

[c++] int64_t

64ビットの符号付き整数型
64ビット固定の場合はlong longよりも推奨される

int64_t x = 0LL;

[C++] constexpr

constexprを使わないケース
### 変数
– constでない変数
– クラスのメンバ変数
– 標準入力などの非constexpr関数を用いて計算する値
– 引数などのconstexprでない可能性がある値を用いて計算する値
### 関数
– inline化できない関数
– 引数でもthisでもない非constexprな外側の変数を参照する操作を含む関数
– 引数でもthisでもない外側に副作用を及ぼすような操作を含む関数


#include

auto answer() {return 42;}

constexpr auto auto_constexpr() {return 42;}

constexpr auto answer_print(){
return 42;
}

int main(){
const expr auto b = answer_constexpr();

std::cout << /* a << ", " << */ b << /* ", " << c << */ std::endl; return 0; } [code]

C++ mapの使い方

key, valueの連想配列class

struct Person {
    public:
        Person(const string &name, int height)
            : m_name(name)
            , m_height(height)
            {}
    public:
        string m_name;
        int m_height;
}

    ...
    map<Person, int> mp;
    Person p("aaa", 180);
    mp[p] = 123;

c++ cstdint

符号付き、符号なしで型の指定ができる

int8_t、int16_t、int32_t、int64_t、uint8_t、uint16_t、uint32_t、uint64_t、int_fast8_t、int_fast16_t、int_fast32_t、int_fast64_t、uint_fast8_t、uint_fast16_t、uint_fast32_t、uint_fast64_t、int_least8_t、int_least16_t、int_least32_t、int_least64_t、uint_least8_t、uint_least16_t、uint_least32_t、uint_least64_t、intmax_t、uintmax_t、intptr_t、uintptr_t

それにしても多いですね

[bitcoin]Signetとは？

Signetは、Bitcoinのテストネットとは異なり、特定のプロジェクトや開発者が制御できる独自のテストネットワーク
cmd, faucet, addr, passwordなどのオプションがある

getcoins.py

import argparse
import io
import requests
import subprocess
import sys
import xml.etree.ElementTree

DEFAULT_GLOBAL_FAUCET = 'https://signetfaucet.com/claim'
DEFAULT_GLOBAL_CAPTCHA = 'https://signetfaucet.com/captcha'
GLOBAL_FIRST_BLOCK_HASH = '00000086d6b2636cb2a392d45edc4ec544a10024d30141c9adf4bfd9de533b53'

# braille unicode block
BASE = 0x2800
BIT_PER_PIXEL = [
    [0x01, 0x08],
    [0x02, 0x10],
    [0x04, 0x20],
    [0x40, 0x80],
]
BW = 2
BH = 4

# imagemagick or compatible fork (used for converting SVG)
CONVERT = 'convert'

class PPMImage:
    '''
    Load a PPM image (Pillow-ish API).
    '''
    def __init__(self, f):
        if f.readline() != b'P6\n':
            raise ValueError('Invalid ppm format: header')
        line = f.readline()
        (width, height) = (int(x) for x in line.rstrip().split(b' '))
        if f.readline() != b'255\n':
            raise ValueError('Invalid ppm format: color depth')
        data = f.read(width * height * 3)
        stride = width * 3
        self.size = (width, height)
        self._grid = [[tuple(data[stride * y + 3 * x:stride * y + 3 * (x + 1)]) for x in range(width)] for y in range(height)]

    def getpixel(self, pos):
        return self._grid[pos[1]][pos[0]]

def print_image(img, threshold=128):
    '''Print black-and-white image to terminal in braille unicode characters.'''
    x_blocks = (img.size[0] + BW - 1) // BW
    y_blocks = (img.size[1] + BH - 1) // BH

    for yb in range(y_blocks):
        line = []
        for xb in range(x_blocks):
            ch = BASE
            for y in range(BH):
                for x in range(BW):
                    try:
                        val = img.getpixel((xb * BW + x, yb * BH + y))
                    except IndexError:
                        pass
                    else:
                        if val[0] < threshold:
                            ch |= BIT_PER_PIXEL[y][x]
            line.append(chr(ch))
        print(''.join(line))

parser = argparse.ArgumentParser(description='Script to get coins from a faucet.', epilog='You may need to start with double-dash (--) when providing bitcoin-cli arguments.')
parser.add_argument('-c', '--cmd', dest='cmd', default='bitcoin-cli', help='bitcoin-cli command to use')
parser.add_argument('-f', '--faucet', dest='faucet', default=DEFAULT_GLOBAL_FAUCET, help='URL of the faucet')
parser.add_argument('-g', '--captcha', dest='captcha', default=DEFAULT_GLOBAL_CAPTCHA, help='URL of the faucet captcha, or empty if no captcha is needed')
parser.add_argument('-a', '--addr', dest='addr', default='', help='Bitcoin address to which the faucet should send')
parser.add_argument('-p', '--password', dest='password', default='', help='Faucet password, if any')
parser.add_argument('-n', '--amount', dest='amount', default='0.001', help='Amount to request (0.001-0.1, default is 0.001)')
parser.add_argument('-i', '--imagemagick', dest='imagemagick', default=CONVERT, help='Path to imagemagick convert utility')
parser.add_argument('bitcoin_cli_args', nargs='*', help='Arguments to pass on to bitcoin-cli (default: -signet)')

args = parser.parse_args()

if args.bitcoin_cli_args == []:
    args.bitcoin_cli_args = ['-signet']


def bitcoin_cli(rpc_command_and_params):
    argv = [args.cmd] + args.bitcoin_cli_args + rpc_command_and_params
    try:
        return subprocess.check_output(argv).strip().decode()
    except FileNotFoundError:
        raise SystemExit(f"The binary {args.cmd} could not be found")
    except subprocess.CalledProcessError:
        cmdline = ' '.join(argv)
        raise SystemExit(f"-----\nError while calling {cmdline} (see output above).")


if args.faucet.lower() == DEFAULT_GLOBAL_FAUCET:
    # Get the hash of the block at height 1 of the currently active signet chain
    curr_signet_hash = bitcoin_cli(['getblockhash', '1'])
    if curr_signet_hash != GLOBAL_FIRST_BLOCK_HASH:
        raise SystemExit('The global faucet cannot be used with a custom Signet network. Please use the global signet or setup your custom faucet to use this functionality.\n')
else:
    # For custom faucets, don't request captcha by default.
    if args.captcha == DEFAULT_GLOBAL_CAPTCHA:
        args.captcha = ''

if args.addr == '':
    # get address for receiving coins
    args.addr = bitcoin_cli(['getnewaddress', 'faucet', 'bech32'])

data = {'address': args.addr, 'password': args.password, 'amount': args.amount}

# Store cookies
# for debugging: print(session.cookies.get_dict())
session = requests.Session()

if args.captcha != '': # Retrieve a captcha
    try:
        res = session.get(args.captcha)
        res.raise_for_status()
    except requests.exceptions.RequestException as e:
        raise SystemExit(f"Unexpected error when contacting faucet: {e}")

    # Size limitation
    svg = xml.etree.ElementTree.fromstring(res.content)
    if svg.attrib.get('width') != '150' or svg.attrib.get('height') != '50':
        raise SystemExit("Captcha size doesn't match expected dimensions 150x50")

    # Convert SVG image to PPM, and load it
    try:
        rv = subprocess.run([args.imagemagick, 'svg:-', '-depth', '8', 'ppm:-'], input=res.content, check=True, capture_output=True)
    except FileNotFoundError:
        raise SystemExit(f"The binary {args.imagemagick} could not be found. Please make sure ImageMagick (or a compatible fork) is installed and that the correct path is specified.")

    img = PPMImage(io.BytesIO(rv.stdout))

    # Terminal interaction
    print_image(img)
    print(f"Captcha from URL {args.captcha}")
    data['captcha'] = input('Enter captcha: ')

try:
    res = session.post(args.faucet, data=data)
except Exception:
    raise SystemExit(f"Unexpected error when contacting faucet: {sys.exc_info()[0]}")

# Display the output as per the returned status code
if res:
    # When the return code is in between 200 and 400 i.e. successful
    print(res.text)
elif res.status_code == 404:
    print('The specified faucet URL does not exist. Please check for any server issues/typo.')
elif res.status_code == 429:
    print('The script does not allow for repeated transactions as the global faucet is rate-limitied to 1 request/IP/day. You can access the faucet website to get more coins manually')
else:
    print(f'Returned Error Code {res.status_code}\n{res.text}\n')
    print('Please check the provided arguments for their validity and/or any possible typo.')