Implement a simple C module to wait for keypresses

evdev/evdev.c

@@ -0,0 +1,33 @@
+#include "evdev.h"
+
+
+int block_until_keypress(const char* keyboardPath) {
+    int keyboardFd = open(keyboardPath, O_RDONLY);
+    if (keyboardFd < 0) {
+        return keyboardFd;
+    }
+
+    int eventSize = sizeof(struct input_event);
+    int bytesRead = 0;
+    struct input_event events[NUM_EVENTS];
+
+    int readEvents = 1;
+    while(readEvents) {
+        bytesRead = read(keyboardFd, events, eventSize * NUM_EVENTS);
+        if (bytesRead < 0) {
+            return bytesRead;
+        }
+
+        for(int i = 0; i < (bytesRead / eventSize); ++i) {
+            struct input_event event = events[i];
+            if(event.type == EV_KEY) {
+                if(event.value == 1) {
+                    readEvents = 0;
+                }
+            }
+        }
+    }
+
+    close(keyboardFd);
+    return 0;
+}

evdev/evdev.go

@@ -0,0 +1,24 @@
+package evdev
+
+// #cgo CFLAGS: -g -Wall
+// #include "evdev.h"
+// #include <stdlib.h>
+import "C"
+
+import (
+	"unsafe"
+	"syscall"
+)
+
+
+func BlockUntilKeypress(devicePath string) error {
+	path := C.CString(devicePath)
+	defer C.free(unsafe.Pointer(path))
+
+	ret := C.block_until_keypress(path)
+	if ret < 0 {
+		return syscall.Errno(ret)
+	}
+
+	return nil
+}

evdev/evdev.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <linux/input.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+
+#define NUM_EVENTS 128
+
+int block_until_keypress(const char* keyboardPath);

go.mod

@@ -0,0 +1,3 @@
+module after-lock
+
+go 1.15

main.go

@@ -0,0 +1,13 @@
+package main
+
+import(
+	"after-lock/evdev"
+	"log"
+)
+
+func main() {
+	err := evdev.BlockUntilKeypress("/dev/input/by-id/usb-Dell_Dell_USB_Entry_Keyboard-event-kbd")
+	if err != nil {
+		log.Fatal(err)
+	}
+}