From 8f9320eb45543809ef5c21a4747a0ce6a006040a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?XC=E3=81=A1=E3=82=83=E3=82=93?=
 <60663465+XC-Qan@users.noreply.github.com>
Date: Tue, 13 Sep 2022 20:03:41 +0800
Subject: [PATCH] Update bvid_desc.md (#479)

---
 other/bvid_desc.md | 71 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 69 insertions(+), 2 deletions(-)

diff --git a/other/bvid_desc.md b/other/bvid_desc.md
index c455d3f..b5ffa09 100644
--- a/other/bvid_desc.md
+++ b/other/bvid_desc.md
@@ -59,7 +59,7 @@
 
 ## 转换程序
 
-使用Python、C、TypeScript以及Java作为示例，欢迎社区提交更多例程
+使用Python、C、TypeScript、Java以及Kotlin作为示例，欢迎社区提交更多例程
 
 ### Python
 
@@ -237,4 +237,71 @@ public class Util {
         return (int) ((r - ADD) ^ XOR);
     }
 }
-```
\ No newline at end of file
+```
+
+### Kotlin
+```kotlin
+/**
+ * 此程序非完全原创，改编自GH站内某大佬的Java程序，修改了部分代码，且转换为Kotlin
+ * 算法来源同上
+ */
+object VideoUtils {
+    //这里是由知乎大佬不知道用什么方法得出的转换用数字
+    var ss = intArrayOf(11, 10, 3, 8, 4, 6, 2, 9, 5, 7)
+    var xor: Long = 177451812 //二进制时加减数1
+
+    var add = 8728348608L //十进制时加减数2
+
+    //变量初始化工作，加载哈希表
+    private const val table = "fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF"
+    private val mp = HashMap<String, Int>()
+    private val mp2 = HashMap<Int, String>()
+
+    //现在，定义av号和bv号互转的方法
+//定义一个power乘方方法，这是转换进制必要的
+    fun power(a: Int, b: Int): Long {
+        var power: Long = 1
+        for (c in 0 until b) power *= a.toLong()
+        return power
+    }
+
+    //bv转av方法
+    fun bv2av(s: String): String {
+        var r: Long = 0
+        //58进制转换
+        for (i in 0..57) {
+            val s1 = table.substring(i, i + 1)
+            mp[s1] = i
+        }
+        for (i in 0..5) {
+            r += mp[s.substring(ss[i], ss[i] + 1)]!! * power(58, i)
+        }
+        //转换完成后，需要处理，带上两个随机数
+        return (r - add xor xor).toString()
+    }
+
+    //av转bv方法
+    fun av2bv(st: String): String {
+        try {
+            var s = java.lang.Long.valueOf(st.split("av".toRegex()).dropLastWhile { it.isEmpty() }
+                .toTypedArray()[1])
+            val sb = StringBuffer("BV1  4 1 7  ")
+            //逆向思路，先将随机数还原
+            s = (s xor xor) + add
+            //58进制转回
+            for (i in 0..57) {
+                val s1 = table.substring(i, i + 1)
+                mp2[i] = s1
+            }
+            for (i in 0..5) {
+                val r = mp2[(s / power(58, i) % 58).toInt()]
+                sb.replace(ss[i], ss[i] + 1, r!!)
+            }
+            return sb.toString()
+        } catch (e: ArrayIndexOutOfBoundsException) {
+            return ""
+        }
+    }
+
+}
+```