perf(json-pack): ⚡️ speed up length encoding

Author: streamich

src/json-pack/resp/RespEncoder.ts

@@ -52,31 +52,23 @@ export class RespEncoder<W extends IWriter & IWriterGrowable = IWriter & IWriter
   }
 
   protected writeLength(length: number): void {
-    let digits = 1;
-    if (length < 10000) {
-      if (length < 100) {
-        if (length < 10) digits = 1;
-        else digits = 2;
-      } else {
-        if (length < 1000) digits = 3;
-        else digits = 4;
-      }
-    } else if (length < 100000000) {
-      if (length < 1000000) {
-        if (length < 100000) digits = 5;
-        else digits = 6;
-      } else {
-        if (length < 10000000) digits = 7;
-        else digits = 8;
-      }
-    } else {
-      let pow = 10;
-      while (length >= pow) {
-        digits++;
-        pow *= 10;
+    const writer = this.writer;
+    if (length < 100) {
+      if (length < 10) {
+        writer.u8(length + 48);
+        return;
       }
+      const octet1 = length % 10;
+      const octet2 = (length - octet1) / 10;
+      writer.u16(((octet2 + 48) << 8) + octet1 + 48);
+      return;
+    }
+    let digits = 1;
+    let pow = 10;
+    while (length >= pow) {
+      digits++;
+      pow *= 10;
     }
-    const writer = this.writer;
     writer.ensureCapacity(digits);
     const uint8 = writer.uint8;
     const x = writer.x;