vweb: Implement chunked encoding transfer (#8179)

examples/vweb/vweb_example.v

@@ -31,6 +31,7 @@ pub fn (mut app App) index() vweb.Result {
 	// app.text('Hello world from vweb')
 	hello := 'Hello world from vweb'
 	numbers := [1, 2, 3]
+	app.enable_chunked_transfer(40)
 	return $vweb.html()
 }
 

vlib/vweb/tests/vweb_test.v

@@ -106,6 +106,13 @@ fn test_http_client_index() {
 	assert x.text == 'Welcome to VWeb'
 }
 
+fn test_http_client_chunk_transfer() {
+	x := http.get('http://127.0.0.1:$sport/chunk') or { panic(err) }
+	assert_common_http_headers(x)
+	assert x.headers['Transfer-Encoding'] == 'chunked'
+	assert x.text == 'Lorem ipsum dolor sit amet, consetetur sadipscing'
+}
+
 fn test_http_client_404() {
 	url_404_list := [
 		'http://127.0.0.1:$sport/zxcnbnm',

vlib/vweb/tests/vweb_test_server.v

@@ -56,6 +56,11 @@ pub fn (mut app App) html_page() vweb.Result {
 	return app.html('<h1>ok</h1>')
 }
 
+pub fn (mut app App) chunk() vweb.Result {
+	app.enable_chunked_transfer(20)
+	return app.html('Lorem ipsum dolor sit amet, consetetur sadipscing')
+}
+
 // the following serve custom routes
 ['/:user/settings']
 pub fn (mut app App) settings(username string) vweb.Result {

vlib/vweb/vweb.v

@@ -56,6 +56,8 @@ pub mut:
 	done              bool
 	page_gen_start    i64
 	form_error        string
+	chunked_transfer  bool
+	max_chunk_len     int = 20
 }
 
 // declaring init_once in your App struct is optional
@@ -88,10 +90,35 @@ pub fn (mut ctx Context) send_response_to_client(mimetype string, res string) bo
 	sb.write('HTTP/1.1 $ctx.status')
 	sb.write('\r\nContent-Type: $mimetype')
 	sb.write('\r\nContent-Length: $res.len')
+	if ctx.chunked_transfer {
+		sb.write('\r\nTransfer-Encoding: chunked')
+	}
 	sb.write(ctx.headers)
 	sb.write('\r\n')
 	sb.write(headers_close)
+	if ctx.chunked_transfer {
+		mut i := 0
+		mut len := res.len
+		for {
+			if len <= 0 {
+				break
+			}
+			mut chunk := ''
+			if len > ctx.max_chunk_len {
+				chunk = res[i..i + ctx.max_chunk_len]
+				i += ctx.max_chunk_len
+				len -= ctx.max_chunk_len
+			} else {
+				chunk = res[i..]
+				len = 0
+			}
+			sb.write(chunk.len.hex())
+			sb.write('\r\n$chunk\r\n')
+		}
+		sb.write('0\r\n\r\n') // End of chunks
+	} else {
 		sb.write(res)
+	}
 	s := sb.str()
 	defer {
 		s.free()
@@ -140,6 +167,11 @@ pub fn (mut ctx Context) not_found() Result {
 	return Result{}
 }
 
+pub fn (mut ctx Context) enable_chunked_transfer(max_chunk_len int) {
+	ctx.chunked_transfer = true
+	ctx.max_chunk_len = max_chunk_len
+}
+
 pub fn (mut ctx Context) set_cookie(cookie Cookie) {
 	mut cookie_data := []string{}
 	mut secure := if cookie.secure { 'Secure;' } else { '' }