区块链的简单尝试

# -*- coding: utf-8 -*-

from __future__ import print_function

import time, random

from hashlib import sha256


class BlockChain(object):
    """ 区块.

    :param index: 当前区块的 `index`.
    :type index: int
    :param pre_hash: 前一个区块的 `hash`.
    :type pre_hash: str
    :param data: 当前区块要储存的信息.
    :type data: str
    """
    def __init__(self, index, pre_hash, data):
        self.index = index
        self.pre_hash = pre_hash
        self.time = time.ctime()
        self.data = data
        self.hash = None
        self.nonce = 0      # 计算 `hash` 的次数

    def calc_hash(self, difficulty):
        """ 计算 `hash`.

        :pparam difficulty: 计算难度.
        :type difficulty: int
        """
        def is_vaild_hash(hash, difficulty):
            """ 判断算的的 `hash` 是否有效.
            """
            for i in range(len(hash)):
                if not hash[i] == '0':
                    break
            return i >= difficulty

        input = str(self.index) + self.pre_hash + \
                self.time + self.data + str(self.nonce)
        self.hash = sha256(input).hexdigest()

        while not is_vaild_hash(self.hash, difficulty):
            self.nonce += 1
            input = str(self.index) + self.pre_hash + \
                    self.time + self.data + str(self.nonce)
            self.hash = sha256(input).hexdigest()


def genesis_block():
    """ 获取创世区块.
    """
    first_block = BlockChain(0, '0', 'My first block')
    first_block.calc_hash(random.randint(1, 4))
    return first_block


def print_block(block):
    """ 输出区块信息.
    """
    print('index: %s' % block.index)
    print('hash: %s' % block.hash)
    print('nonce: %s\n' % block.nonce)


if __name__ == '__main__':
    print('Genesis block:')
    first_block = genesis_block()
    print_block(first_block)

    pre_block = first_block

    while True:
        data = raw_input('Input data: ')
        if data:
            cur_block = BlockChain(pre_block.index + 1, pre_block.hash, data)

            difficulty = random.randint(1, 4)    # ..., 难度稍微大一点居然都要算半天...
            print('difficulty: %s' % difficulty)

            cur_block.calc_hash(difficulty)
            print_block(cur_block)

            pre_block = cur_block

        else:
            break

    print('over')