feat(resp):优化BulkStrings解析逻辑与SET命令性能

- 在BulkStrings解析完成时增加对空输出流的判断，避免不必要的toString调用
- 将SetCommand中的固定HEADER替换为预构建的FAST_HEADER数组，提升写入效率- 根据键长度动态选择FAST_HEADER模板，减少运行时字节拼接操作
- 当键长度超出预设范围时，回退到通用写入方式并保留原有兼容性处理

Author: smthing

src/main/java/tech/smartboot/redisun/cmd/SetCommand.java

@@ -45,7 +45,19 @@ public class SetCommand extends Command {
     private static final BulkStrings CONSTANTS_EX = BulkStrings.of("EX");
     private static final BulkStrings CONSTANTS_PX = BulkStrings.of("PX");
     private static final BulkStrings CONSTANTS_PXAT = BulkStrings.of("PXAT");
-    private static final byte[] HEADER = new byte[]{RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK};
+    //    private static final byte[] HEADER = new byte[]{RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK};
+    private static final byte[][] FAST_HEADER = new byte[][]{
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '0', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '1', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '2', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '4', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '5', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '6', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '7', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '8', '\r', '\n'},
+            {RESP.RESP_DATA_TYPE_ARRAY, '3', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '3', '\r', '\n', 'S', 'E', 'T', '\r', '\n', RESP.RESP_DATA_TYPE_BULK, '9', '\r', '\n'},
+    };
     private static final byte[] PART = new byte[]{'\r', '\n', RESP.RESP_DATA_TYPE_BULK};
     // 要设置的键
     private final String key;
@@ -102,8 +114,15 @@ public void writeTo(WriteBuffer writeBuffer) throws IOException {
         }
         byte[] keyBytes = key.getBytes();
         byte[] valBytes = value.getBytes();
-        writeBuffer.write(HEADER);
-        RESP.writeInt(writeBuffer, keyBytes.length);
+        if (keyBytes.length < FAST_HEADER.length) {
+            writeBuffer.write(FAST_HEADER[keyBytes.length]);
+        } else {
+            byte[] header = FAST_HEADER[0];
+            writeBuffer.write(header, 0, header.length - 3);
+            RESP.writeInt(writeBuffer, keyBytes.length);
+        }
+//        writeBuffer.write(HEADER);
+//        RESP.writeInt(writeBuffer, keyBytes.length);
         writeBuffer.write(keyBytes);
         writeBuffer.write(PART);
         RESP.writeInt(writeBuffer, valBytes.length);

src/main/java/tech/smartboot/redisun/resp/BulkStrings.java

@@ -121,7 +121,9 @@ public boolean decode(ByteBuffer readBuffer) {
                     if (readBuffer.remaining() >= 2) {
                         if (readBuffer.get() == CR && readBuffer.get() == LF) {
                             // 解析完成，设置字符串值
-                            value = out.toString();
+                            if (out != EMPTY_OUTPUT_STREAM) {
+                                value = out.toString();
+                            }
                             return true;
                         }
                         throw new RedisunException("数据格式错误");