Fixed the position of MID of UUID in Snowflake-SI-vA.

Author: fenying

CHANGES.md

@@ -1,13 +1,5 @@
 # Changes Logs
 
-## v0.2.2
+## v0.1.1
 
-- Fixed: Error when creating text logger lacking `$trace` definition.
-
-## v0.2.1
-
-- Fixed: Only one level was operated in global operation.
-
-## v0.2.0
-
-- A full new simpler logger.
+- Fixed the position of MID of UUID in Snowflake-SI-vA.

docs/en-US/Snowflake-SI-vA.md

@@ -9,12 +9,12 @@ brought into being.
 The Snowflake-SI-vA algorithm uses 53-bits integer as the output of UUID
 generation, its bits-mapping shows like following:
 
-| H |                    52 ~ 10                  |    9 ~ 0   | L |
-|:-:|:-------------------------------------------:|:----------:|:-:|
-|   | 1111111111111111111111111111111111111111111 | 1111111111 |   |
-|   |                      UIN                    |    MID     |   |
+| H |   52 ~ 43  |                     42 ~ 0                  | L |
+|:-:|:----------:|:-------------------------------------------:|:-:|
+|   | 1111111111 | 1111111111111111111111111111111111111111111 |   |
+|   |    MID     |                      UIN                    |   |
 
-As above graph shows, the high 43 bits are the UIN(UUID Index Number). It's the
+As above graph shows, the low 43 bits are the UIN(UUID Index Number). It's the
 sum of the cursor of an incremental sequence and the current Unix timestamp in
 milliseconds. It means the genrated UUID is still an incremental sequence.
 
@@ -23,7 +23,7 @@ milliseconds. It means the genrated UUID is still an incremental sequence.
 > incremental sequence and timestamp, there is 2-bits as the extra reserved
 > zone.
 
-The low 10-bits is the ID of machine, for distributed services. So that it
+The high 10-bits is the ID of machine, for distributed services. So that it
 will not generate duplicated UUID between multi-instances. Different to the
 Snowflake-SI, Snowflake-SI-vA use a fixed 10-bits for MID, and then there could
 always be 1024 instances at most.

docs/zh-CN/Snowflake-SI-vA.md

@@ -7,18 +7,18 @@ Snowflake-SI-vA 算法是 Snowflake-SI 算法的变种。Snowflake-SI 算法使
 Snowflake-SI-vA 算法为了确保生成的 UUID 的精度，于是使用了 53 位整数作为 UUID 的生成
 结果，其位分部如下：
 
-| H |                    52 ~ 10                  |    9 ~ 0   | L |
-|:-:|:-------------------------------------------:|:----------:|:-:|
-|   | 1111111111111111111111111111111111111111111 | 1111111111 |   |
-|   |                      UIN                    |    MID     |   |
+| H |   52 ~ 43  |                     42 ~ 0                  | L |
+|:-:|:----------:|:-------------------------------------------:|:-:|
+|   | 1111111111 | 1111111111111111111111111111111111111111111 |   |
+|   |    MID     |                      UIN                    |   |
 
-如上表，高 43 位是 UUID 序号（UIN，UUID Index Number），它是一个递增序列当前指针和
+如上表，低 43 位是 UUID 序号（UIN，UUID Index Number），它是一个递增序列当前指针和
 当前 UNIX 毫秒时间戳的加法和。因此生成的 UUID 仍然是按时间递增的序列。
 
 > 到 2038 年， Unix 毫秒时间戳总共用了 41 个二进制位，但是考虑到递增序列的加和影响，
 > 因此额外增加了两位作为额外保留区（Extra Reserved Zone），防止溢出。
 
-低 10 位是机器序号（Machine ID），用于确保在分布式服务中，多个实例同时工作，也不会
+高 10 位是机器序号（Machine ID），用于确保在分布式服务中，多个实例同时工作，也不会
 生成重复的 UUID。此处固定为 10 位，因此最多允许 1024 个实例同时工作。
 
 ## 特点

src/algorithms/snowflake-si-va.ts

@@ -27,6 +27,11 @@ export namespace SnowflakeSIvA {
      */
     const MID_LENGTH = 10;
 
+    /**
+     * UUID Index Number
+     */
+    const UIN_LENGTH = 43;
+
     export function calculateCursor(lastUUID: number): number {
 
         const result = Math.floor(
@@ -41,6 +46,30 @@ export namespace SnowflakeSIvA {
         return 0;
     }
 
+    export interface UUIDRange {
+
+        max: number;
+
+        min: number;
+    }
+
+    export function getUUIDRangeByMID(mid: number): UUIDRange {
+
+        const MAX_MID = Math.pow(2, MID_LENGTH);
+
+        if (mid >= MAX_MID || mid < 0) {
+
+            throw new RangeError(`mid must be between 0 and ${MAX_MID - 1}.`);
+        }
+
+        const BASE = Math.pow(2, UIN_LENGTH);
+
+        return {
+            max: mid * BASE + BASE - 1,
+            min: mid * BASE
+        };
+    }
+
     export function createGenerateor(opts: {
 
         /**
@@ -68,13 +97,11 @@ export namespace SnowflakeSIvA {
 
         let ret: any;
 
-        const MID_FIELD = opts.mid;
-
-        const UIN_BASE = Math.pow(2, MID_LENGTH);
+        const MID_FIELD = opts.mid * Math.pow(2, UIN_LENGTH);
 
         ret = function(): number {
 
-            return MID_FIELD + (Date.now() + cursor++) * UIN_BASE;
+            return MID_FIELD + Date.now() + cursor++;
         };
 
         Object.defineProperty(ret, "MACHINE_ID", {

src/tests/snowflake-si-va.ts

@@ -27,6 +27,7 @@ const nextUUID = libuuid.SnowflakeSIvA.createGenerateor({
     "cursor": libuuid.SnowflakeSIvA.calculateCursor(1562244321456127)
 });
 
+console.log(libuuid.SnowflakeSIvA.getUUIDRangeByMID(10));
 console.log(nextUUID());
 console.log(nextUUID());
 console.log(nextUUID.MACHINE_ID);