picoev, picohttparser: reimplement in V (#18506)

vlib/picoev/loop_default.c.v

@@ -0,0 +1,95 @@
+module picoev
+
+$if windows {
+	#include <winsock2.h>
+	#include <ws2tcpip.h>
+} $else {
+	#include <sys/select.h>
+}
+
+pub struct SelectLoop {
+mut:
+	id  int
+	now i64
+}
+
+type LoopType = SelectLoop
+
+// create_select_loop creates a `SelectLoop` struct with `id`
+pub fn create_select_loop(id int) !&SelectLoop {
+	return &SelectLoop{
+		id: id
+	}
+}
+
+[direct_array_access]
+fn (mut pv Picoev) update_events(fd int, events int) int {
+	// check if fd is in range
+	assert fd < max_fds
+
+	pv.file_descriptors[fd].events = u32(events & picoev_readwrite)
+	return 0
+}
+
+[direct_array_access]
+fn (mut pv Picoev) poll_once(max_wait int) int {
+	readfds, writefds, errorfds := C.fd_set{}, C.fd_set{}, C.fd_set{}
+
+	// setup
+	C.FD_ZERO(&readfds)
+	C.FD_ZERO(&writefds)
+	C.FD_ZERO(&errorfds)
+
+	mut maxfd := 0
+
+	// find the maximum socket for `select` and add sockets to the fd_sets
+	for target in pv.file_descriptors {
+		if target.loop_id == pv.loop.id {
+			if target.events & picoev_read != 0 {
+				C.FD_SET(target.fd, &readfds)
+				if maxfd < target.fd {
+					maxfd = target.fd
+				}
+			}
+			if target.events & picoev_write != 0 {
+				C.FD_SET(target.fd, &writefds)
+				if maxfd < target.fd {
+					maxfd = target.fd
+				}
+			}
+		}
+	}
+
+	// select and handle sockets if any
+	tv := C.timeval{
+		tv_sec: u64(max_wait)
+		tv_usec: 0
+	}
+	r := C.@select(maxfd + 1, &readfds, &writefds, &errorfds, &tv)
+	if r == -1 {
+		// timeout
+		return -1
+	} else if r > 0 {
+		for target in pv.file_descriptors {
+			if target.loop_id == pv.loop.id {
+				// vfmt off
+				read_events := (
+					(if C.FD_ISSET(target.fd, &readfds) { picoev_read } else { 0 })
+						|
+					(if C.FD_ISSET(target.fd, &writefds) { picoev_write } else { 0 })
+				)
+				// vfmt on
+				if read_events != 0 {
+					$if trace_fd ? {
+						eprintln('do callback ${target.fd}')
+					}
+
+					// do callback!
+					unsafe { target.cb(target.fd, read_events, &pv) }
+				}
+			}
+		}
+	}
+
+	return 0
+}