实现一个CRDT工具库——PNCounter

PNCounter

这段代码实现了一个PNCounter，即正负计数器。PNCounter是基于GCounter实现的，GCounter是一个只增不减的计数器，而PNCounter则是在GCounter的基础上增加了减操作。PNCounter由两个GCounter组成，一个用于记录增加操作，一个用于记录减少操作。value函数用于计算PNCounter的值，即增加操作的值减去减少操作的值。inc和dec函数分别用于增加和减少操作。merge函数用于合并两个PNCounter。

import GCounter

def PNCounter():
    return (GCounter.GCounter(), GCounter.GCounter())

def zero():
    return GCounter.zero(), GCounter.zero()

def value(pn: PNCounter):
    inc, dec = pn
    return {key: inc.get(key, 0) - dec.get(key, 0) for key in set(inc.keys()) | set(dec.keys())}

def inc(pn: PNCounter, key):
    inc, dec = pn
    return GCounter.inc(inc, key)

def dec(pn: PNCounter, key):
    inc, dec = pn
    return GCounter.inc(dec, key)

def merge(a: PNCounter, b: PNCounter):
    inc_a, dec_a = a
    inc_b, dec_b = b
    return (GCounter.merge(inc_a, inc_b), GCounter.merge(dec_a, dec_b))

import java.util.HashMap;
import java.util.Map;

public class PNCounter {
    private GCounter inc;
    private GCounter dec;

    public PNCounter() {
        this.inc = new GCounter();
        this.dec = new GCounter();
    }

    public static PNCounter zero() {
        return new PNCounter();
    }

    public Map<String, Integer> value() {
        Map<String, Integer> result = new HashMap<>();
        Map<String, Integer> incMap = inc.value();
        Map<String, Integer> decMap = dec.value();
        for (String key : incMap.keySet()) {
            result.put(key, incMap.get(key) - decMap.getOrDefault(key, 0));
        }
        for (String key : decMap.keySet()) {
            if (!result.containsKey(key)) {
                result.put(key, -decMap.get(key));
            }
        }
        return result;
    }

    public void inc(String key) {
        inc.inc(key);
    }

    public void dec(String key) {
        dec.inc(key);
    }

    public void merge(PNCounter other) {
        inc.merge(other.inc);
        dec.merge(other.dec);
    }
}