readdir_r(): uses the logic of readdir()...

to retrieve more than one entry.
* readdir_r() is now affected by rewinddir(), thus fixing #12755.
* extends dirent_test with readdir_r().

src/system/libroot/posix/dirent.c

@@ -243,7 +243,26 @@ readdir(DIR* dir)
 int
 readdir_r(DIR* dir, struct dirent* entry, struct dirent** _result)
 {
-	ssize_t count = _kern_read_dir(dir->fd, entry, sizeof(struct dirent)
+	ssize_t count;
+
+	if (dir->seek_position != dir->current_position) {
+		if (do_seek_dir(dir) != 0)
+			return -1;
+	}
+
+	if (dir->entries_left > 0) {
+		*_result
+			= (struct dirent *)((uint8 *)&dir->first_entry + dir->next_entry);
+
+		dir->entries_left--;
+		dir->next_entry += (*_result)->d_reclen;
+		dir->seek_position++;
+		dir->current_position++;
+
+		return 0;
+	}
+
+	count = _kern_read_dir(dir->fd, entry, sizeof(struct dirent)
 		+ B_FILE_NAME_LENGTH, 1);
 	if (count < B_OK)
 		return count;
@@ -251,8 +270,13 @@ readdir_r(DIR* dir, struct dirent* entry, struct dirent** _result)
 	if (count == 0) {
 		// end of directory
 		*_result = NULL;
-	} else
+	} else {
 		*_result = entry;
+		dir->entries_left = count - 1;
+		dir->next_entry = dir->first_entry.d_reclen;
+		dir->seek_position++;
+		dir->current_position++;
+	}
 
 	return 0;
 }

src/tests/system/libroot/posix/dirent_test.cpp

@@ -6,15 +6,18 @@
 
 #include <dirent.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 
 int
 main(int argc, char** argv)
 {
+	dirent *buf, *dirent;
 	DIR* dir = opendir(".");
 
+	printf("first pass:\n");
 	while (true) {
-		dirent* dirent = readdir(dir);
+		dirent = readdir(dir);
 		if (dirent == NULL)
 			break;
 
@@ -23,6 +26,48 @@ main(int argc, char** argv)
 		//printf("  left: %u, next: %d\n", dir->entries_left, dir->next_entry);
 	}
 
+	rewinddir(dir);
+	printf("second pass:\n");
+	while (true) {
+		dirent = readdir(dir);
+		if (dirent == NULL)
+			break;
+
+		printf("Entry: dev %ld, ino %Ld, name \"%s\"\n", dirent->d_dev,
+			dirent->d_ino, dirent->d_name);
+		//printf("  left: %u, next: %d\n", dir->entries_left, dir->next_entry);
+	}
+
+
 	closedir(dir);
+
+	dirent = NULL;
+	buf = (struct dirent*)malloc(sizeof(struct dirent) + NAME_MAX);
+
+	dir = opendir(".");
+
+	printf("first pass:\n");
+	while (true) {
+		if (readdir_r(dir, buf, &dirent) != 0 || dirent == NULL)
+			break;
+
+		printf("Entry: dev %ld, ino %Ld, name \"%s\"\n", dirent->d_dev,
+			dirent->d_ino, dirent->d_name);
+		//printf("  left: %u, next: %d\n", dir->entries_left, dir->next_entry);
+	}
+
+	rewinddir(dir);
+	printf("second pass:\n");
+	while (true) {
+		if (readdir_r(dir, buf, &dirent) != 0 || dirent == NULL)
+			break;
+
+		printf("Entry: dev %ld, ino %Ld, name \"%s\"\n", dirent->d_dev,
+			dirent->d_ino, dirent->d_name);
+		//printf("  left: %u, next: %d\n", dir->entries_left, dir->next_entry);
+	}
+
+	closedir(dir);
+
 	return 0;
 }