x-watcher.h

#ifndef __X_WATCHER_H
#define __X_WATCHER_H

// necessary includes for the public stuff
#include <pthread.h>
#include <stdbool.h>
#if defined(__linux__)
	// noop
#elif defined(__WIN32__)
	#include <windows.h>
	#include <stdint.h>
#else
	#error "Unsupported"
#endif

// PUBLIC STUFF
typedef enum event {
	XWATCHER_FILE_UNSPECIFIED,
	XWATCHER_FILE_REMOVED,
	XWATCHER_FILE_CREATED,
	XWATCHER_FILE_MODIFIED,
	XWATCHER_FILE_OPENED,
	XWATCHER_FILE_ATTRIBUTES_CHANGED,
	XWATCHER_FILE_NONE,
	XWATCHER_FILE_RENAMED,
	// probs more but i couldn't care much
} XWATCHER_FILE_EVENT;

typedef struct xWatcher_reference {
	char *path;
	void (*callback_func)(
			XWATCHER_FILE_EVENT event,
			const char *path,
			int context,
			void *additional_data);
	int context;
	void *additional_data;
} xWatcher_reference;

struct file {
	// just the file name alone
	char *name;
	// used for adding (additional) context in the handler (if needed)
	int  context;
	// in case you'd like to avoid global variables
	void *additional_data;

	void (*callback_func)(
			XWATCHER_FILE_EVENT event,
			const char *path,
			int context,
			void *additional_data);
} file;

struct directory {
	// list of files
	struct file   *files;

	char          *path;
	// used for adding (additional) context in the handler (if needed)
	int           context;
	// in case you'd like to avoid global variables
	void          *additional_data;

	void (*callback_func)(
			XWATCHER_FILE_EVENT event,
			const char *path,
			int context,
			void *additional_data);

	#if defined(__linux__)
		// we need additional file descriptors (per directory basis)
		int inotify_watch_fd;
	#elif defined(__WIN32__)
		HANDLE     handle;
		OVERLAPPED overlapped;
		uint8_t    *event_buffer;
	#else
		#error "Unsupported"
	#endif
} directory;

typedef struct x_watcher {
	struct directory *directories;
	pthread_t  thread;
	int        thread_id;
	bool       alive;

	#if defined(__linux__)
		int inotify_fd; // fd == file descriptor (a common UNIX thing)
	#elif defined(__WIN32__)
		// literal noop
	#else
		#error "Unsupported"
	#endif
} x_watcher;

// PRIVATE STUFF
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "array.h"

#ifdef __linux__
	#include <sys/types.h>
	#include <sys/inotify.h>
	#include <errno.h>
	#include <unistd.h>
	#include <poll.h>  // for POLLIN
	#include <fcntl.h> // for O_NONBLOCK

	#define EVENT_SIZE  (sizeof(struct inotify_event))
	#define BUF_LEN     (1024 * (EVENT_SIZE + 16))
	#define DIRBRK      '/'

	static inline void *__internal_xWatcherProcess(void *argument) {
		x_watcher *watcher = (x_watcher*) argument;
		char buffer[BUF_LEN];
		ssize_t lenght;
		struct directory *directories = watcher->directories;

		while(watcher->alive) {
			// poll for events
			struct pollfd pfd = { watcher->inotify_fd, POLLIN, 0 };
			int ret = poll(&pfd, 1, 50);  // timeout of 50ms

			if (ret < 0) {
				// oops
				fprintf(stderr, "poll failed: %s\n", strerror(errno));
				break;
			} else if (ret == 0) {
				// Timeout with no events, move on.
				continue;
			}

			// wait for the kernel to do it's thing
			lenght = read(watcher->inotify_fd, buffer, BUF_LEN);
			if(lenght < 0) {
				// something messed up clearly
				perror("read");
				return NULL;
			}

			// pointer to the event structure
			ssize_t i = 0;
			while(i < lenght) {
				// the event list itself
				struct inotify_event *event = (struct inotify_event *)
					&buffer[i];

				// find directory for which this even matches via the descriptor
				struct directory *directory = NULL;
				for(size_t j = 0; j < arr_count(directories); j++) {
					if(directories[j].inotify_watch_fd == event->wd) {
						directory = &directories[j];
					}
				}
				if(directory == NULL) {
					fprintf(stderr,
							"MATCHING FILE DESCRIPTOR NOT FOUND! ERROR!\n");
					// BAIL????
				}

				// find matching file (if any)
				struct file *file = NULL;
				for(size_t j = 0; j < arr_count(directory->files); j++) {
					if(strcmp(directory->files[j].name, event->name) == 0) {
						file = &directory->files[j];
					}
				}

				XWATCHER_FILE_EVENT send_event = XWATCHER_FILE_NONE;

				if(event->mask & IN_CREATE)
					send_event = XWATCHER_FILE_CREATED;
				if(event->mask & IN_MODIFY)
					send_event = XWATCHER_FILE_MODIFIED;
				if(event->mask & IN_DELETE)
					send_event = XWATCHER_FILE_REMOVED;
				if(event->mask & IN_CLOSE_WRITE ||
						event->mask & IN_CLOSE_NOWRITE)
					send_event = XWATCHER_FILE_REMOVED;
				if(event->mask & IN_ATTRIB)
					send_event = XWATCHER_FILE_ATTRIBUTES_CHANGED;
				if(event->mask & IN_OPEN)
					send_event = XWATCHER_FILE_OPENED;

				// file found(?)
				if(file != NULL) {
					if(send_event != XWATCHER_FILE_NONE) {
						// figure out the file path size
						size_t filepath_size = strlen(directory->path);
						filepath_size += strlen(file->name);
						filepath_size += 2;

						// create file path string
						char *filepath = (char*)malloc(filepath_size);
						snprintf(filepath, filepath_size, "%s/%s",
								directory->path, file->name);

						// callback
						file->callback_func(send_event,
											filepath,
											file->context,
											file->additional_data);

						// free that garbage
						free(filepath);
					}
				} else {
					// Cannot find file, lets try directory
					if(directory->callback_func != NULL &&
							send_event != XWATCHER_FILE_NONE) {
						directory->callback_func(send_event,
								directory->path,
								directory->context,
								directory->additional_data);
					}
				}

				i += EVENT_SIZE + event->len;
			}
		}

		// cleanup time
		for(size_t i = 0; i < arr_count(watcher->directories); i++) {
			struct directory *directory = &watcher->directories[i];
			for(size_t j = 0; j < arr_count(directory->files); j++) {
				struct file *file = &directory->files[j];
				free(file->name);
			}
			arr_free(directory->files);
			free(directory->path);
			inotify_rm_watch(watcher->inotify_fd, directory->inotify_watch_fd);
		}
		close(watcher->inotify_fd);
		arr_free(watcher->directories);
		// should we signify that the thread is dead?
		return NULL;
	}
#elif defined(__WIN32__)
	#include <tchar.h>

	#define BUF_LEN 1024
	#define DIRBRK  '\\'

	static inline void *__internal_xWatcherProcess(void *argument) {
		x_watcher *watcher = (x_watcher*) argument;
		struct directory *directories = watcher->directories;

		// create an event list so we can still make use of the Windows API
		HANDLE events[arr_count(directories)];
		for(int i = 0; i < arr_count(directories); i++) {
			events[i] = directories[i].overlapped.hEvent;
		}

		// obv first check if we need to stay alive
		while(watcher->alive) {
			// wait for any of the objects to respond
			DWORD result = WaitForMultipleObjects(arr_count(directories),
					events, FALSE, 50 /** timeout of 50ms **/);

			// test which object was it
			int object_index = -1;
			for(int i = 0; i < arr_count(directories); i++) {
				if(result == (WAIT_OBJECT_0 + i)) {
					object_index = i;
					break;
				}
			}

			if(object_index == -1) {
				if(result == WAIT_TIMEOUT) {
					// it just timed out, let's continue
					continue;
				} else {
					// RUNTIME ERROR! Let's bail
					ExitProcess(GetLastError());
				}
			}

			// shorhand for convenience
			struct directory *dir = &directories[object_index];

			// retrieve event data
			DWORD bytes_transferred;
			GetOverlappedResult(dir->handle,
					&dir->overlapped,
					&bytes_transferred, FALSE);

			// assign the data's pointer to a proper format for convenience
			FILE_NOTIFY_INFORMATION *event = (FILE_NOTIFY_INFORMATION*)
					dir->event_buffer;

			// loop through the data
			for (;;) {
				// figure out the wchar string size and allocate as needed
				DWORD name_len = event->FileNameLength / sizeof(wchar_t);
				char *name_char = malloc(sizeof(char)*(name_len+1));
				size_t converted_chars;

				// convert wchar* filename to char*
				wcstombs_s(&converted_chars, name_char,
						name_len+1, event->FileName, name_len);

				// convert to proper event type
				XWATCHER_FILE_EVENT send_event = XWATCHER_FILE_NONE;
				switch (event->Action) {
					case FILE_ACTION_ADDED:
						send_event = XWATCHER_FILE_CREATED;
						break;
					case FILE_ACTION_REMOVED:
						send_event = XWATCHER_FILE_REMOVED;
						break;
					case FILE_ACTION_MODIFIED:
						send_event = XWATCHER_FILE_MODIFIED;
						break;
					case FILE_ACTION_RENAMED_OLD_NAME:
					case FILE_ACTION_RENAMED_NEW_NAME:
						send_event = XWATCHER_FILE_RENAMED;
						break;
					default:
						send_event = XWATCHER_FILE_UNSPECIFIED;
						break;
				}

				// find matching file (if any)
				struct file *file = NULL;
				for(size_t j = 0; j < arr_count(dir->files); j++) {
					if(strcmp(dir->files[j].name, name_char) == 0) {
						file = &dir->files[j];
					}
				}

				// file found(?)
				if(file != NULL) {
					if(send_event != XWATCHER_FILE_NONE) {
						// figure out the file path size
						size_t filepath_size = strlen(dir->path);
						filepath_size += strlen(file->name);
						filepath_size += 2;

						// create file path string
						char *filepath = (char*)malloc(filepath_size);
						snprintf(filepath, filepath_size, "%s%c%s",
								dir->path, DIRBRK, file->name);

						// callback
						file->callback_func(send_event,
											filepath,
											file->context,
											file->additional_data);

						// free that garbage
						free(filepath);
					}
				} else {
					// Cannot find file, lets try directory
					if(dir->callback_func != NULL &&
							send_event != XWATCHER_FILE_NONE) {
						dir->callback_func(send_event,
								dir->path,
								dir->context,
								dir->additional_data);
					}
				}

				// free up the converted string
				free(name_char);

				// Are there more events to handle?
				if (event->NextEntryOffset) {
					*((uint8_t**)&event) += event->NextEntryOffset;
				} else {
					break;
				}
			}

			DWORD dwNotifyFilter =
					FILE_NOTIFY_CHANGE_FILE_NAME |
					FILE_NOTIFY_CHANGE_DIR_NAME |
					FILE_NOTIFY_CHANGE_ATTRIBUTES |
					FILE_NOTIFY_CHANGE_SIZE |
					FILE_NOTIFY_CHANGE_LAST_WRITE |
					FILE_NOTIFY_CHANGE_LAST_ACCESS |
					FILE_NOTIFY_CHANGE_CREATION |
					FILE_NOTIFY_CHANGE_SECURITY;
			BOOL recursive = FALSE;

			// Queue the next event
			BOOL success = ReadDirectoryChangesW(
					dir->handle,
					dir->event_buffer,
					BUF_LEN,
					recursive,
					dwNotifyFilter,
					NULL,
					&dir->overlapped,
					NULL);

			if(!success) {
				// get error code
				DWORD error = GetLastError();
				char *message;

				// get error message
				FormatMessage(
					FORMAT_MESSAGE_ALLOCATE_BUFFER |
					FORMAT_MESSAGE_FROM_SYSTEM |
					FORMAT_MESSAGE_IGNORE_INSERTS,
					NULL,
					error,
					MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
					(LPTSTR) &message,
					0, NULL);

				fprintf(stderr, "ReadDirectoryChangesW failed: %s\n",
						message);

				ExitProcess(error);
			}
		}
		// cleanup time
		for(size_t i = 0; i < arr_count(watcher->directories); i++) {
			struct directory *directory = &watcher->directories[i];
			for(size_t j = 0; j < arr_count(directory->files); j++) {
				struct file *file = &directory->files[j];
				free(file->name);
			}
			arr_free(directory->files);
			free(directory->path);
			free(directory->event_buffer);
			CloseHandle(directory->handle);
		}
		arr_free(watcher->directories);

		return NULL;
	}
#else
	#error "Unsupported"
#endif


static inline x_watcher *xWatcher_create(void) {
	x_watcher *watcher = (x_watcher*)malloc(sizeof(x_watcher));

	arr_init(watcher->directories);

	#if defined(__WIN32__)
		// literally noop
	#elif defined(__linux__)
		watcher->inotify_fd = inotify_init1(O_NONBLOCK);
		if(watcher->inotify_fd < 0) {
			perror("inotify_init");
			return NULL;
		}
	#else
		#error "Unsupported"
	#endif

	return watcher;
}

static inline bool xWatcher_appendFile(
		x_watcher *watcher,
		xWatcher_reference *reference) {
	char *path = strdup(reference->path);

	// the file MUST NOT contain slashed at the end
	if(path[strlen(path)-1] == DIRBRK)
		return false;

	char *filename = NULL;

	// we need to split the filename and path
	for(size_t i = strlen(path)-1; i > 0; i--) {
		if(path[i] == DIRBRK) {
			path[i]  = '\0'; // break the string, so it splits into two
			filename = &path[i+1]; // set the rest of it as the filename
			break;
		}
	}

	// If the directory is specifically local, treat it as such.
	if(filename == NULL) {
		filename = path;
	}

	struct directory *dir = NULL;

	// check against the database of (pre-existing) directories
	for(size_t i = 0; i < arr_count(watcher->directories); i++) {
		// paths match
		if(strcmp(watcher->directories[i].path, path) == 0) {
			dir = &watcher->directories[i];
		}
	}

	// directory exists, check if an callback has been already added
	if(dir == NULL) {
		struct directory new_dir;

		new_dir.callback_func    = NULL; // DO NOT add callbacks if it's a file
		new_dir.context          = 0;    // context should be invalid as well
		new_dir.additional_data  = NULL; // so should the data
		new_dir.path             = path; // add a path to the directory
		#if defined(__linux__)
			new_dir.inotify_watch_fd = -1;   // invalidate inotify
		#elif defined(__WIN32__)
			new_dir.handle       = NULL;
		#else
			#error "Unsupported"
		#endif

		// initialize file arrays
		arr_init(new_dir.files);

		// add the directory to the masses
		arr_add(watcher->directories, new_dir);

		// move the pointer to the newly added element
		dir = &watcher->directories[arr_count(watcher->directories)-1];
	}

	// search for the file
	struct file *file = NULL;
	for(size_t i = 0; i < arr_count(dir->files); i++) {
		if(strcmp(dir->files[i].name, filename) == 0) {
			file = &dir->files[i];
		}
	}

	if(file != NULL) {
		return false; // file already exists, that's an ERROR
	}

	struct file new_file;
	// avoid an invalid free because this shares the memory space
	// of the full path string
	new_file.name            = strdup(filename);
	new_file.context         = reference->context;
	new_file.additional_data = reference->additional_data;
	new_file.callback_func   = reference->callback_func;

	// the the element
	arr_add(dir->files, new_file);

	// and move the pointer to the newly added element
	file = &dir->files[arr_count(watcher->directories)-1];

	// add the file watcher
	#if defined(__linux__)
		if(dir->inotify_watch_fd == -1) {
			dir->inotify_watch_fd = inotify_add_watch(
					watcher->inotify_fd,
					path,
					IN_ALL_EVENTS);
			if(dir->inotify_watch_fd == -1) {
				perror("inotify_watch_fd");
				return false;
			}
		}
	#elif defined(__WIN32__)
		// add directory path
		dir->handle = CreateFile(dir->path,
				FILE_LIST_DIRECTORY,
				FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_SHARE_DELETE,
				NULL,
				OPEN_EXISTING,
				FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
				NULL);
		if(dir->handle == INVALID_HANDLE_VALUE) {
			// get error code
			DWORD error = GetLastError();
			char *message;

			// get error message
			FormatMessage(
				FORMAT_MESSAGE_ALLOCATE_BUFFER |
				FORMAT_MESSAGE_FROM_SYSTEM |
				FORMAT_MESSAGE_IGNORE_INSERTS,
				NULL,
				error,
				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
				(LPTSTR) &message,
				0, NULL);

			fprintf(stderr, "CreateFile failed: %s\n",
					message);

			return false;
		}

		// create event structure
		dir->overlapped.hEvent = CreateEvent(NULL, FALSE, 0, NULL);
		if(dir->overlapped.hEvent == NULL) {
			// get error code
			DWORD error = GetLastError();
			char *message;

			// get error message
			FormatMessage(
				FORMAT_MESSAGE_ALLOCATE_BUFFER |
				FORMAT_MESSAGE_FROM_SYSTEM |
				FORMAT_MESSAGE_IGNORE_INSERTS,
				NULL,
				error,
				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
				(LPTSTR) &message,
				0, NULL);

			fprintf(stderr, "CreateEvent failed: %s\n",
					message);

			return false;
		}

		// allocate the event buffer
		dir->event_buffer = malloc(BUF_LEN);
		if(dir->event_buffer == NULL) {
			fprintf(stderr, "malloc failed at __FILE__:__LINE__!\n");
			return false;
		}

		// set reading params
		BOOL success = ReadDirectoryChangesW(
				dir->handle, dir->event_buffer, BUF_LEN, TRUE,
				FILE_NOTIFY_CHANGE_FILE_NAME  |
				FILE_NOTIFY_CHANGE_DIR_NAME   |
				FILE_NOTIFY_CHANGE_LAST_WRITE,
				NULL, &dir->overlapped, NULL);
		if(!success) {
			// get error code
			DWORD error = GetLastError();
			char *message;

			// get error message
			FormatMessage(
				FORMAT_MESSAGE_ALLOCATE_BUFFER |
				FORMAT_MESSAGE_FROM_SYSTEM |
				FORMAT_MESSAGE_IGNORE_INSERTS,
				NULL,
				error,
				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
				(LPTSTR) &message,
				0, NULL);

			fprintf(stderr, "ReadDirectoryChangesW failed: %s\n",
					message);

			return false;
		}
	#else
		#error "Unsupported"
	#endif
	return true;
}

static inline bool xWatcher_appendDir(
		x_watcher *watcher,
		xWatcher_reference *reference) {
	char *path = strdup(reference->path);

	// inotify only works with directories that do NOT have a front-slash
	// at the end, so we have to make sure to cut that out
	if(path[strlen(path)-1] == DIRBRK)
		path[strlen(path)-1] = '\0';

	struct directory *dir = NULL;

	// check against the database of (pre-existing) directories
	for(size_t i=0; i < arr_count(watcher->directories); i++) {
		// paths match
		if(strcmp(watcher->directories[i].path, path) == 0) {
			dir = &watcher->directories[i];
		}
	}

	// directory exists, check if an callback has been already added
	if(dir) {
		// ERROR, CALLBACK EXISTS
		if(dir->callback_func) {
			return false;
		}

		dir->callback_func   = reference->callback_func;
		dir->context         = reference->context;
		dir->additional_data = reference->additional_data;
	} else {
		// keep an eye for this one as it's on the stack
		struct directory dir;

		dir.path = path;
		dir.callback_func   = reference->callback_func;
		dir.context         = reference->context;
		dir.additional_data = reference->additional_data;

		// initialize file arrays
		arr_init(dir.files);

		#if defined(__linux__)
			dir.inotify_watch_fd = inotify_add_watch(
					watcher->inotify_fd,
					dir.path,
					IN_ALL_EVENTS);
			if(dir.inotify_watch_fd == -1) {
				perror("inotify_watch_fd");
				return false;
			}
		#elif defined(__WIN32__)
			// add directory path
			dir.handle = CreateFile(dir.path,
					FILE_LIST_DIRECTORY,
					FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_SHARE_DELETE,
					NULL,
					OPEN_EXISTING,
					FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
					NULL);
			if(dir.handle == INVALID_HANDLE_VALUE) {
				// get error code
				DWORD error = GetLastError();
				char *message;

				// get error message
				FormatMessage(
					FORMAT_MESSAGE_ALLOCATE_BUFFER |
					FORMAT_MESSAGE_FROM_SYSTEM |
					FORMAT_MESSAGE_IGNORE_INSERTS,
					NULL,
					error,
					MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
					(LPTSTR) &message,
					0, NULL);

				fprintf(stderr, "CreateFile failed: %s\n",
						message);

				return false;
			}

			// create event structure
			dir.overlapped.hEvent = CreateEvent(NULL, FALSE, 0, NULL);
			if(dir.overlapped.hEvent == NULL) {
				// get error code
				DWORD error = GetLastError();
				char *message;

				// get error message
				FormatMessage(
					FORMAT_MESSAGE_ALLOCATE_BUFFER |
					FORMAT_MESSAGE_FROM_SYSTEM |
					FORMAT_MESSAGE_IGNORE_INSERTS,
					NULL,
					error,
					MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
					(LPTSTR) &message,
					0, NULL);

				fprintf(stderr, "CreateEvent failed: %s\n",
						message);

				return false;
			}

			// allocate the event buffer
			dir.event_buffer = malloc(BUF_LEN);
			if(dir.event_buffer == NULL) {
				fprintf(stderr, "malloc failed at __FILE__:__LINE__!\n");
				return false;
			}

			// set reading params
			BOOL success = ReadDirectoryChangesW(
					dir.handle, dir.event_buffer, BUF_LEN, TRUE,
					FILE_NOTIFY_CHANGE_FILE_NAME  |
					FILE_NOTIFY_CHANGE_DIR_NAME   |
					FILE_NOTIFY_CHANGE_LAST_WRITE,
					NULL, &dir.overlapped, NULL);
			if(!success) {
				// get error code
				DWORD error = GetLastError();
				char *message;

				// get error message
				FormatMessage(
					FORMAT_MESSAGE_ALLOCATE_BUFFER |
					FORMAT_MESSAGE_FROM_SYSTEM |
					FORMAT_MESSAGE_IGNORE_INSERTS,
					NULL,
					error,
					MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
					(LPTSTR) &message,
					0, NULL);

				fprintf(stderr, "ReadDirectoryChangesW failed: %s\n",
						message);

				return false;
			}
		#else
			#error "Unsupported"
		#endif

		arr_add(watcher->directories, dir);
	}

	return true;
}

static inline bool xWatcher_start(x_watcher *watcher) {
	watcher->alive = true;

	// create watcher thread
	watcher->thread_id = pthread_create(
			&watcher->thread,
			NULL,
			__internal_xWatcherProcess,
			watcher);

	if(watcher->thread_id != 0) {
		perror("pthread_create");
		watcher->alive = false;
		return false;
	}

	return true;
}

static inline void xWatcher_destroy(x_watcher *watcher) {
	void *ret;
	watcher->alive = false;
	pthread_join(watcher->thread, &ret);
	free(watcher);
}

#endif