check writer level when use NewWriterLevel

Signed-off-by: luke <chenjinguang@huawei.com>

brotli_test.go

@@ -484,7 +484,7 @@ func BenchmarkEncodeLevels(b *testing.B) {
 			b.ReportAllocs()
 			b.SetBytes(int64(len(opticks)))
 			for i := 0; i < b.N; i++ {
-				w := NewWriterLevel(ioutil.Discard, level)
+				w, _ := NewWriterLevel(ioutil.Discard, level)
 				w.Write(opticks)
 				w.Close()
 			}
@@ -500,7 +500,7 @@ func BenchmarkEncodeLevelsReset(b *testing.B) {
 
 	for level := BestSpeed; level <= BestCompression; level++ {
 		buf := new(bytes.Buffer)
-		w := NewWriterLevel(buf, level)
+		w, _ := NewWriterLevel(buf, level)
 		w.Write(opticks)
 		w.Close()
 		b.Run(fmt.Sprintf("%d", level), func(b *testing.B) {
@@ -524,7 +524,7 @@ func BenchmarkDecodeLevels(b *testing.B) {
 
 	for level := BestSpeed; level <= BestCompression; level++ {
 		buf := new(bytes.Buffer)
-		w := NewWriterLevel(buf, level)
+		w, _ := NewWriterLevel(buf, level)
 		w.Write(opticks)
 		w.Close()
 		compressed := buf.Bytes()

writer.go

@@ -2,6 +2,7 @@ package brotli
 
 import (
 	"errors"
+	"fmt"
 	"io"
 )
 
@@ -30,17 +31,21 @@ var (
 // It is the caller's responsibility to call Close on the Writer when done.
 // Writes may be buffered and not flushed until Close.
 func NewWriter(dst io.Writer) *Writer {
-	return NewWriterLevel(dst, DefaultCompression)
+	b, _ := NewWriterLevel(dst, DefaultCompression)
+	return b
 }
 
 // NewWriterLevel is like NewWriter but specifies the compression level instead
 // of assuming DefaultCompression.
 // The compression level can be DefaultCompression or any integer value between
 // BestSpeed and BestCompression inclusive.
-func NewWriterLevel(dst io.Writer, level int) *Writer {
+func NewWriterLevel(dst io.Writer, level int) (*Writer, error) {
+	if level < BestSpeed || level > BestCompression {
+		return nil, fmt.Errorf("brotli: invalid compression level: %d", level)
+	}
 	return NewWriterOptions(dst, WriterOptions{
 		Quality: level,
-	})
+	}), nil
 }
 
 // NewWriterOptions is like NewWriter but specifies WriterOptions