perf(encode): reduce alloc mem

benchmark.txt

@@ -2,15 +2,10 @@ goos: windows
 goarch: amd64
 pkg: github.com/nonzzz/bencode
 cpu: Intel(R) Core(TM) i5-10400F CPU @ 2.90GHz
-BenchmarkEncode-12    	   10000	     34307 ns/op	  145993 B/op	      80 allocs/op
-BenchmarkEncode-12    	   10000	     26206 ns/op	  145992 B/op	      80 allocs/op
-BenchmarkEncode-12    	   10000	     28097 ns/op	  145992 B/op	      80 allocs/op
-BenchmarkEncode-12    	   10000	     26583 ns/op	  145992 B/op	      80 allocs/op
-BenchmarkEncode-12    	   10000	     27728 ns/op	  145992 B/op	      80 allocs/op
-BenchmarkDecode-12    	   10000	     43816 ns/op	    1088 B/op	      29 allocs/op
-BenchmarkDecode-12    	   10000	     43490 ns/op	    1088 B/op	      29 allocs/op
-BenchmarkDecode-12    	   10000	     43359 ns/op	    1088 B/op	      29 allocs/op
-BenchmarkDecode-12    	   10000	     43092 ns/op	    1088 B/op	      29 allocs/op
-BenchmarkDecode-12    	   10000	     43342 ns/op	    1088 B/op	      29 allocs/op
+BenchmarkEncode-12    	   10000	     17554 ns/op	   88344 B/op	      70 allocs/op
+BenchmarkEncode-12    	   10000	     19004 ns/op	   88344 B/op	      70 allocs/op
+BenchmarkEncode-12    	   10000	     18961 ns/op	   88344 B/op	      70 allocs/op
+BenchmarkEncode-12    	   10000	     18592 ns/op	   88344 B/op	      70 allocs/op
+BenchmarkEncode-12    	   10000	     18454 ns/op	   88344 B/op	      70 allocs/op
 PASS
-ok  	github.com/nonzzz/bencode	3.863s
+ok  	github.com/nonzzz/bencode	1.199s

benchmark_result.txt

@@ -4,21 +4,15 @@ pkg: github.com/nonzzz/bencode
 cpu: Intel(R) Core(TM) i5-10400F CPU @ 2.90GHz
           │ benchmark.txt │
           │    sec/op     │
-Encode-12    27.73µ ± ∞ ¹
-Decode-12    43.36µ ± ∞ ¹
-geomean      34.67µ
+Encode-12    18.59µ ± ∞ ¹
 ¹ need >= 6 samples for confidence interval at level 0.95
 
           │ benchmark.txt │
           │     B/op      │
-Encode-12   142.6Ki ± ∞ ¹
-Decode-12   1.062Ki ± ∞ ¹
-geomean     12.31Ki
+Encode-12   86.27Ki ± ∞ ¹
 ¹ need >= 6 samples for confidence interval at level 0.95
 
           │ benchmark.txt │
           │   allocs/op   │
-Encode-12     80.00 ± ∞ ¹
-Decode-12     29.00 ± ∞ ¹
-geomean       48.17
+Encode-12     70.00 ± ∞ ¹
 ¹ need >= 6 samples for confidence interval at level 0.95

cmd/main.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/nonzzz/bencode"
+)
+
+var buf, _ = os.ReadFile("./test.torrent")
+
+func main() {
+	s, _ := bencode.Decode(buf)
+	fmt.Println(s)
+}

encode.go

@@ -59,16 +59,15 @@ func (encode *encode) next(input interface{}) {
 	}
 }
 
-// Someone need convert WTF string(non-standard ASCLL) if necessary.
+// Someone need convert WTF string(non-standard ASCII) if necessary.
 
 func (encode *encode) encodeString(s string) {
 	var sb strings.Builder
-	menu := []byte(s)
-	l := strconv.Itoa(len(menu))
+	l := strconv.Itoa(len(s))
 	sb.WriteString(l)
 	sb.WriteByte(StringDelim)
 	sb.WriteString(s)
-	encode.output = append(encode.output, []byte(sb.String())...)
+	encode.output = append(encode.output, sb.String()...)
 }
 
 // Should sort directory
@@ -95,9 +94,9 @@ func (encode *encode) encodeSlice(value reflect.Value) {
 }
 
 func (encode *encode) encodeNumeric(s string) {
-	var sb strings.Builder
-	sb.WriteByte(NumericStart)
-	sb.WriteString(s)
-	sb.WriteByte(EndOfType)
-	encode.output = append(encode.output, []byte(sb.String())...)
+	content := make([]byte, 0, 2+len(s))
+	content = append(content, NumericStart)
+	content = append(content, s...)
+	content = append(content, EndOfType)
+	encode.output = append(encode.output, content...)
 }