feat: enhance read all function for less malloc

elton.go

@@ -696,3 +696,29 @@ func Compose(handlerList ...Handler) Handler {
 		return c.Next()
 	}
 }
+
+// copy from io.ReadAll
+// ReadAll reads from r until an error or EOF and returns the data it read.
+// A successful call returns err == nil, not err == EOF. Because ReadAll is
+// defined to read from src until EOF, it does not treat an EOF from Read
+// as an error to be reported.
+func ReadAllInitCap(r io.Reader, initCap int) ([]byte, error) {
+	if initCap <= 0 {
+		initCap = 512
+	}
+	b := make([]byte, 0, initCap)
+	for {
+		if len(b) == cap(b) {
+			// Add more capacity (let append pick how much).
+			b = append(b, 0)[:len(b)]
+		}
+		n, err := r.Read(b[len(b):cap(b)])
+		b = b[:len(b)+n]
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+			}
+			return b, err
+		}
+	}
+}

elton_test.go

@@ -565,6 +565,42 @@ func TestGracefulClose(t *testing.T) {
 	})
 }
 
+func TestReadAllInitCap(t *testing.T) {
+	assert := assert.New(t)
+
+	buf := &bytes.Buffer{}
+	for i := 0; i < 1024*1024; i++ {
+		buf.Write([]byte("hello world!"))
+	}
+	result := buf.Bytes()
+
+	data, err := ReadAllInitCap(buf, 1024*100)
+	assert.Nil(err)
+	assert.Equal(result, data)
+
+	data, err = ReadAllInitCap(bytes.NewBufferString("hello world!"), 1024*100)
+	assert.Nil(err)
+	assert.Equal([]byte("hello world!"), data)
+}
+
+func BenchmarkReadAllInitCap(b *testing.B) {
+	buf := &bytes.Buffer{}
+	for i := 0; i < 1024*1024; i++ {
+		buf.Write([]byte("hello world!"))
+	}
+	result := buf.Bytes()
+	size := buf.Len()
+	for i := 0; i < b.N; i++ {
+		data, err := ReadAllInitCap(bytes.NewBuffer(result), 1024*1024)
+		if err != nil {
+			panic(err)
+		}
+		if len(data) != size {
+			panic(errors.New("data is invalid"))
+		}
+	}
+}
+
 // https://stackoverflow.com/questions/50120427/fail-unit-tests-if-coverage-is-below-certain-percentage
 func TestMain(m *testing.M) {
 	// call flag.Parse() here if TestMain uses flags

middleware/body_parser.go

@@ -30,6 +30,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 
 	"github.com/vicanso/elton"
@@ -301,7 +302,13 @@ func NewBodyParser(config BodyParserConfig) elton.Handler {
 		}
 		defer r.Close()
 		var body []byte
-		body, err := ioutil.ReadAll(r)
+		initCapSize := 0
+		contentLength := c.GetRequestHeader(elton.HeaderContentLength)
+		// 如果请求头有指定了content length，则根据content length来分配[]byte大小
+		if contentLength != "" {
+			initCapSize, _ = strconv.Atoi(contentLength)
+		}
+		body, err := elton.ReadAllInitCap(r, initCapSize)
 		if err != nil {
 			if hes.IsError(err) {
 				return err

middleware/body_parser_test.go

@@ -31,6 +31,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -355,6 +356,7 @@ func TestBodyParserMiddleware(t *testing.T) {
 				body := `{"name": "tree.xie"}`
 				req := httptest.NewRequest("POST", "https://aslant.site/", strings.NewReader(body))
 				req.Header.Set(elton.HeaderContentType, "application/json")
+				req.Header.Set(elton.HeaderContentLength, strconv.Itoa(len(body)))
 				c := elton.NewContext(nil, req)
 				c.Next = next
 				return c