Adding zero-allocation uint64 to byte slice conversion and fixing the…

… ResponseHeader.SetStatusLine function call signature

bytesconv.go

@@ -350,6 +350,75 @@ func s2b(s string) (b []byte) {
 	return b
 }
 
+const host32bit = ^uint(0)>>32 == 0
+
+const smallsString = "00010203040506070809" +
+	"10111213141516171819" +
+	"20212223242526272829" +
+	"30313233343536373839" +
+	"40414243444546474849" +
+	"50515253545556575859" +
+	"60616263646566676869" +
+	"70717273747576777879" +
+	"80818283848586878889" +
+	"90919293949596979899"
+
+// i2b converts a uint64 to a byte slice without memory allocation.
+//
+// Note that this is a slightly modified version of strconv.formatBits
+func i2b(dst []byte, i uint64) []byte {
+	var a [64 + 1]byte
+	ignore := len(a)
+
+	// convert bits
+	// We use uint values where we can because those will
+	// fit into a single register even on a 32bit machine.
+	if host32bit {
+		// convert the lower digits using 32bit operations
+		for i >= 1e9 {
+			// Avoid using r = a%b in addition to q = a/b
+			// since 64bit division and modulo operations
+			// are calculated by runtime functions on 32bit machines.
+			q := i / 1e9
+			is := uint(i - q*1e9) // i % 1e9 fits into a uint
+			for j := 4; j > 0; j-- {
+				is := is % 100 * 2
+				is /= 100
+				ignore -= 2
+				a[ignore+1] = smallsString[is+1]
+				a[ignore+0] = smallsString[is+0]
+			}
+
+			// is < 10, since it contains the last digit
+			// from the initial 9-digit is.
+			ignore--
+			a[ignore] = smallsString[is*2+1]
+
+			i = q
+		}
+		// i < 1e9
+	}
+	// i guaranteed to fit into a uint
+	us := uint(i)
+	for us >= 100 {
+		is := us % 100 * 2
+		us /= 100
+		ignore -= 2
+		a[ignore+1] = smallsString[is+1]
+		a[ignore+0] = smallsString[is+0]
+	}
+
+	// us < 100
+	is := us * 2
+	ignore--
+	a[ignore] = smallsString[is+1]
+	if us >= 10 {
+		ignore--
+		a[ignore] = smallsString[is]
+	}
+	return append(dst, a[ignore:]...)
+}
+
 // AppendUnquotedArg appends url-decoded src to dst and returns appended dst.
 //
 // dst may point to src. In this case src will be overwritten.

header.go

@@ -146,8 +146,8 @@ func (h *ResponseHeader) StatusLine() []byte {
 }
 
 // SetStatusLine sets response status line bytes.
-func (h *ResponseHeader) SetStatusLine(statusLine []byte) {
-	h.statusLine = append(h.statusLine[:0], statusLine...)
+func (h *ResponseHeader) SetStatusLine(statusCode int, statusLine []byte) {
+	h.statusLine = formatStatusLine(h.statusLine, statusCode, statusLine)
 }
 
 // SetLastModified sets 'Last-Modified' header to the given value.
@@ -1880,8 +1880,8 @@ func (h *ResponseHeader) parseFirstLine(buf []byte) (int, error) {
 		}
 		return 0, fmt.Errorf("unexpected char at the end of status code. Response %q", buf)
 	}
-	if len(b) > n+1 && !bytes.Equal(b[n+1:], statusLine(h.statusCode)) {
-		h.SetStatusLine(b[n+1:])
+	if len(b) > n+1 && !bytes.Equal(b[n+1:], statusLines[h.statusCode]) {
+		h.SetStatusLine(h.statusCode, b[n+1:])
 	}
 
 	return len(buf) - len(bNext), nil

header_test.go

@@ -52,8 +52,8 @@ func TestResponseHeaderMultiLineValue(t *testing.T) {
 		t.Fatalf("parse response using net/http failed, %s", err)
 	}
 
-	if !bytes.Equal(header.StatusLine(), []byte("SuperOK")) {
-		t.Errorf("parse status line with non-default value failed, got: %s want: SuperOK", header.StatusLine())
+	if !bytes.Equal(header.StatusLine(), []byte("HTTP/1.1 200 SuperOK\r\n")) {
+		t.Errorf("parse status line with non-default value failed, got: %s want: HTTP/1.1 200 SuperOK", header.StatusLine())
 	}
 
 	for name, vals := range response.Header {
@@ -83,7 +83,7 @@ func TestResponseHeaderMultiLineName(t *testing.T) {
 		t.Errorf("expected error, got %q (%v)", m, err)
 	}
 
-	if !bytes.Equal(header.StatusLine(), []byte("OK")) {
+	if !bytes.Equal(header.StatusLine(), []byte("HTTP/1.1 200 OK\r\n")) {
 		t.Errorf("expected default status line, got: %s", header.StatusLine())
 	}
 }

http_test.go

@@ -839,7 +839,7 @@ func TestResponseSkipBody(t *testing.T) {
 
 	// set StatusNoContent with statusLine
 	r.Header.SetStatusCode(StatusNoContent)
-	r.Header.SetStatusLine([]byte("HTTP/1.1 204 NC\r\n"))
+	r.Header.SetStatusLine(204, []byte("NC"))
 	r.SetBodyString("foobar")
 	s = r.String()
 	if strings.Contains(s, "\r\n\r\nfoobar") {

status.go

@@ -1,7 +1,6 @@
 package fasthttp
 
 import (
-	"fmt"
 	"strconv"
 )
 
@@ -81,6 +80,8 @@ const (
 )
 
 var (
+	httpHeader = []byte("HTTP/1.1")
+
 	statusLines = make([][]byte, statusMessageMax+1)
 
 	statusMessages = []string{
@@ -168,10 +169,20 @@ func StatusMessage(statusCode int) string {
 func init() {
 	// Fill all valid status lines
 	for i := 0; i < len(statusLines); i++ {
-		statusLines[i] = []byte(fmt.Sprintf("HTTP/1.1 %d %s\r\n", i, StatusMessage(i)))
+		statusLines[i] = formatStatusLine([]byte{}, i, []byte(StatusMessage(i)))
 	}
 }
 
+func formatStatusLine(dst []byte, statusCode int, statusMessage []byte) []byte {
+	dst = append(dst[:0], httpHeader...)
+	dst = append(dst, ' ')
+	dst = i2b(dst, uint64(statusCode))
+	dst = append(dst, ' ')
+	dst = append(dst, statusMessage...)
+	dst = append(dst, strCRLF...)
+	return dst
+}
+
 func statusLine(statusCode int) []byte {
 	if statusCode < 0 || statusCode > statusMessageMax {
 		return invalidStatusLine(statusCode)