initial commit

Author: ProgramRipper

README.md

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+# crc32Cracker 
+> 反查B站弹幕发送者
+
+## 使用
+```shell
+python main.py [crc32hash] 
+```
+
+### 示例
+```shell
+python main.py 76B81C71
+```
+#### 结果
+```
+160148624 0.7555286884307861
+```
+第一个数为发送者mid，第二个数为用时。
+
+
+## 鸣谢
+算法作者：[MoePus](https://github.com/MoePus)
+文章：https://moepus.oicp.net/2016/11/27/crccrack/

main.py

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+POLY = 0xEDB88320
+
+
+class crc32Cracker:
+    def __init__(self):
+        self.table = self.table()
+
+    def crc32(self, string: str) -> (int, int):
+        INIT = 0xFFFFFFFF
+        index = None
+        for i in string:
+            index = (INIT ^ ord(i)) & 0xFF
+            INIT = INIT >> 8 ^ self.table[index]
+        return INIT, index
+
+    def lastIndex(self, crc: int) -> int:
+        for i in range(256):
+            if crc == self.table[i] >> 24:
+                return i
+
+    def check(self, high: int, indexes: list) -> (bool, str):
+        crc, index = self.crc32(str(high))
+        if index != indexes[3]:
+            return False
+        low = ''
+        for i in range(2, -1, -1):
+            num = crc & 0xFF ^ indexes[i]
+            if num not in range(48, 58):
+                return False
+            low += str(num - 48)
+            crc = self.table[indexes[i]] ^ crc >> 8
+        return low
+
+    @staticmethod
+    def table():
+        table = []
+        for i in range(256):
+            value = i
+            for _ in range(8):
+                if value & 1:
+                    value = value >> 1 ^ POLY
+                else:
+                    value >>= 1
+            table.append(value)
+        return table
+
+    def main(self, crc):
+        indexes = [0 for _ in range(4)]
+        crc = int(crc, 16) ^ 0xFFFFFFFF
+        for i in range(1, 1000):
+            if crc == self.crc32(str(i))[0]:
+                return i
+        for i in range(3, -1, -1):
+            index = indexes[3 - i] = self.lastIndex(crc >> (i << 3))
+            value = self.table[index]
+            crc ^= value >> ((3 - i) << 3)
+        i = 0
+        while True:
+            i += 1
+            low = self.check(i, indexes)
+            if low:
+                return int(str(i) + low)
+
+    def __call__(self, crc):
+        return self.main(crc)
+
+
+if __name__ == '__main__':
+    from time import time
+    from sys import argv
+
+    cracker = crc32Cracker()
+    t = time()
+    print(cracker(argv[1]), time() - t)