From 52b7b6a9d7058d086166d67bde66002da18ea19f Mon Sep 17 00:00:00 2001
From: heavyrain2012 <heavyrain.lee@gmail.com>
Date: Tue, 14 Dec 2021 12:18:14 +0800
Subject: [PATCH] =?UTF-8?q?=E6=9B=BF=E6=8D=A2=E6=96=B0=E7=9A=84id=E7=94=9F?=
 =?UTF-8?q?=E6=88=90=E6=96=B9=E6=B3=95=EF=BC=8C=E7=94=9F=E6=88=909?=
 =?UTF-8?q?=E4=BD=8Did?=
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../src/main/java/win/liyufan/im/IDUtils.java | 113 ++++--------------
 1 file changed, 23 insertions(+), 90 deletions(-)

diff --git a/broker/src/main/java/win/liyufan/im/IDUtils.java b/broker/src/main/java/win/liyufan/im/IDUtils.java
index 3c8b3a3a..7e414c0d 100644
--- a/broker/src/main/java/win/liyufan/im/IDUtils.java
+++ b/broker/src/main/java/win/liyufan/im/IDUtils.java
@@ -8,107 +8,40 @@
 
 package win.liyufan.im;
 
+import java.util.HashMap;
+import java.util.HashSet;
+
 public class IDUtils {
-    private static char getChar(int number) {
-        if (number < 0 || number >= 64) {
-            number = number % 64;
-        }
+    private static final int RADIX = 36;
+    private static final int IDLEN = 9;
+    private static final int[] FACTOR = {29,19,1,11,7,17,13,23,5};
+
+    private static char getChar(long number) {
         if (number < 26) {
-            return (char)('A' + number);
-        } else if(number < 52) {
-            return (char)('a' + number - 26);
-        } else if(number < 62) {
-            return (char)('0' + number - 52);
-        } else if(number == 62) {
-            return '_';
+            return (char)('a' + number);
+        } else {
+            return (char)('0' + number - 26);
         }
-        return '-';
     }
 
-    private static int getNumber(char ch) {
-
-        if (ch >= 'A' && ch <= 'Z') {
-            return ch - 'A';
-        } else if(ch >= 'a' && ch <= 'z') {
-            return ch - 'a' + 26;
-        } else if(ch >= '0' && ch <= '9') {
-            return ch - '0' + 52;
-        } else if(ch == '+') {
-            return 62;
-        }
-        return 63;
-    }
-
-    public static String toUid(int id) {
+    public static String toUid(long id) {
         StringBuilder sb = new StringBuilder();
-        int rand0 = 0;
-        int rand3 = 0;
-        int rand6 = 0;
-        for (int i = 0; i < 8; i++) {
-            if (i == 0 || i == 3 || i == 6) {
-                int rand = (int)(Math.random()*64+0.5);
-                sb.append(getChar(rand));
-                if (i == 0) {
-                    rand0 = rand;
-                } else if (i == 3) {
-                    rand3 = rand;
-                } else {
-                    rand6 = rand;
-                }
-            } else {
-                if (i < 5) {
-                    sb.append(getChar((id + rand0) % 64));
-                } else if(i == 5) {
-                    sb.append(getChar((id + rand3) % 64));
-                } else {
-                    sb.append(getChar((id + rand6) % 64));
-                }
-                id = id / 64;
-            }
+        for (int i = 0; i < IDLEN; i++) {
+            long bit = ((id % RADIX) * FACTOR[i] + FACTOR[i] + 5)%RADIX;
+            sb.append(getChar(bit));
+            id = id / RADIX;
         }
         return sb.toString();
     }
-
-    public static int fromUid(String uid) {
-        int id = 0;
-        int rand0 = 0;
-        int rand3 = 0;
-        int rand6 = 0;
-        for (int i = 0; i < 8; i++) {
-            if (i == 0 || i == 3 || i == 6) {
-                int rand = getNumber(uid.charAt(i));
-                if (i == 0) {
-                    rand0 = rand;
-                } else if (i == 3) {
-                    rand3 = rand;
-                } else {
-                    rand6 = rand;
-                }
-            } else {
-                int c = getNumber(uid.charAt(i));
-
-                if (i < 5) {
-                    c = (c+64-rand0)%64;
-                } else if(i == 5) {
-                    c = (c+64-rand3)%64;
-                } else {
-                    c = (c+64-rand6)%64;
-                }
-                if (i < 3)
-                    id = id + (c << (i-1)*6);
-                else if(i < 6)
-                    id = id + (c << (i-2)*6);
-                else
-                    id = id + (c << (i-3)*6);
-            }
-        }
-        return id;
-    }
-
+    
     public static void main(String[] args) {
-        for (int i = 0; i < 100000000; i++) {
+        HashSet<String> idset = new HashSet<>();
+        for (long i = 0; i < 1000000000000L; i++) {
             String uid = toUid(i);
-            System.out.println(i + ", " + uid + ", " + fromUid(uid));
+            if(!idset.add(uid)) {
+                System.out.println("error, dupliate id");
+                System.exit(-1);
+            }
         }
     }
 }