x.vweb: fix large payload (#20155)

vlib/x/vweb/vweb.v

@@ -11,7 +11,6 @@ import picoev
 
 // max read and write limits in bytes
 const max_read = 8096
-
 const max_write = 8096 * 2
 
 // A type which doesn't get filtered inside templates
@@ -307,8 +306,12 @@ fn ev_callback[A, X](mut pv picoev.Picoev, fd int, events int) {
 
 		if params.file_responses[fd].open {
 			handle_write_file(mut pv, mut params, fd)
-		} else {
+		} else if params.string_responses[fd].open {
 			handle_write_string(mut pv, mut params, fd)
+		} else {
+			// this should never happen
+			eprintln('[vweb] error: write event on connection should be closed')
+			pv.close_conn(fd)
 		}
 	} else {
 		$if trace_picoev_callback ? {
@@ -461,6 +464,7 @@ fn handle_read[A, X](mut pv picoev.Picoev, mut params RequestParams, fd int) {
 			eprintln('[vweb] error parsing request: ${err}')
 			pv.close_conn(fd)
 			params.incomplete_requests[fd] = http.Request{}
+			params.idx[fd] = 0
 			return
 		}
 
@@ -476,18 +480,21 @@ fn handle_read[A, X](mut pv picoev.Picoev, mut params RequestParams, fd int) {
 					value: 'text/plain'
 				).join(vweb.headers_close)
 			)) or {}
+
 			pv.close_conn(fd)
 			params.incomplete_requests[fd] = http.Request{}
+			params.idx[fd] = 0
 			return
 		} else if n < bytes_to_read || params.idx[fd] + n < content_length.int() {
 			// request is incomplete wait until the socket becomes ready to read again
 			params.idx[fd] += n
 			// TODO: change this to a memcpy function?
-			req.data += buf.bytestr()
+			req.data += buf[0..n].bytestr()
 			params.incomplete_requests[fd] = req
 			return
 		} else {
 			// request is complete: n = bytes_to_read
+			params.idx[fd] += n
 			req.data += buf[0..n].bytestr()
 		}
 	}
@@ -522,6 +529,7 @@ fn handle_read[A, X](mut pv picoev.Picoev, mut params RequestParams, fd int) {
 					fast_send_resp(mut conn, completed_context.res) or {}
 					pv.close_conn(fd)
 				} else {
+					params.string_responses[fd].open = true
 					params.string_responses[fd].str = completed_context.res.body
 					res := pv.add(fd, picoev.picoev_write, params.timeout_in_seconds,
 						picoev.raw_callback)
@@ -587,7 +595,7 @@ fn handle_request[A, X](mut conn net.TcpConn, req http.Request, params &RequestP
 
 	// parse the URL, query and form data
 	mut url := urllib.parse(req.url) or {
-		eprintln('[vweb] error parsing path: ${err}')
+		eprintln('[vweb] error parsing path "${req.url}": ${err}')
 		return none
 	}
 	query := parse_query_from_url(url)