Make recursive removal threaded.

erm.c

@@ -1,6 +1,7 @@
 #define _XOPEN_SOURCE 500 /* nftw */
 #include <errno.h>
 #include <ftw.h>
+#include <pthread.h>
 #include <stdbool.h>
 #include <stdnoreturn.h>
 #include <stdio.h>
@@ -11,20 +12,36 @@
 static int ftw_cb(const char *fpath, const struct stat *sb,
 		int typeflag, struct FTW *ftwbuf)
 {
+	if (typeflag == FTW_D || typeflag == FTW_DP) return rmdir(fpath);
+	else return unlink(fpath);
+}
+
+struct task {
+	pthread_t thread;
+	const char *path;
 	int rv;
-	if (typeflag == FTW_D || typeflag == FTW_DP) rv = rmdir(fpath);
-	else rv = unlink(fpath);
+} *task_list = NULL;
 
-	return rv;
+void *run_ftw(void *arg)
+{
+	struct task *t = arg;
+	t->rv = nftw(t->path, ftw_cb, 20, FTW_DEPTH|FTW_PHYS);
+	return NULL;
+}
+static int recurse_into(const char *path, int c)
+{
+	task_list[c].path = path;
+	return pthread_create(&task_list[c].thread, NULL, run_ftw, &task_list[c]);
+}
+static int join_thread(const char *path, int c)
+{
+	pthread_join(task_list[c].thread, NULL);
+	return task_list[c].rv;
 }
 
-static int recurse_into(const char *path)
-{
-	return nftw(path, ftw_cb, 40, FTW_DEPTH | FTW_PHYS);
-}
-
-static int single_file(const char *path)
+static int single_file(const char *path, int c)
 {
+	(void)c;
 	return remove(path);
 }
 
@@ -57,14 +74,22 @@ int main(int argc, char **argv)
 	argc -= optind;
 	argv += optind;
 
-	int (*action)(const char *) = recursive ? recurse_into : single_file;
+	if (recursive) {
+		task_list = calloc(sizeof(*task_list), argc);
+		if (!task_list) {
+			perror("malloc");
+			return 5;
+		}
+	}
+	int (*action)(const char *, int) = recursive ? recurse_into : single_file;
+	int (*callback)(const char *, int) = recursive ? join_thread : NULL;
 	const char *err_fmt = recursive ?
 		"failed to delve into '%s': %s\n" : "failed to remove '%s': %s\n";
 
 	int rv = 0;
 	for (int i = 0; i < argc; i++) {
 		const char *path = argv[i];
-		if (action(path)) {
+		if (action(path, i)) {
 			fprintf(stderr, err_fmt, path, strerror(errno));
 			if (stop_at_error) {
 				return 1;
@@ -73,6 +98,19 @@ int main(int argc, char **argv)
 			}
 		}
 	}
+	if (callback) {
+		for (int i = 0; i < argc; i++) {
+			const char *path = argv[i];
+			if (callback(path, i)) {
+				fprintf(stderr, err_fmt, path, strerror(errno));
+				if (stop_at_error) {
+					return 1;
+				} else {
+					rv = 1;
+				}
+			}
+		}
+	}
 
 	return rv;
 }