Fix getdents syscall to handle seekdir/telldir (#8540)

Directory seeking was broken, this change makes syscall220() respect
the current directory offset.

src/library_syscall.js

@@ -1081,11 +1081,17 @@ var SyscallsLibrary = {
     if (!stream.getdents) {
       stream.getdents = FS.readdir(stream.path);
     }
+
+    var struct_size = {{{ C_STRUCTS.dirent.__size__ }}};
     var pos = 0;
-    while (stream.getdents.length > 0 && pos + {{{ C_STRUCTS.dirent.__size__ }}} <= count) {
+    var off = FS.llseek(stream, 0, {{{ cDefine('SEEK_CUR') }}});
+
+    var idx = Math.floor(off / struct_size);
+
+    while (idx < stream.getdents.length && pos + struct_size <= count) {
       var id;
       var type;
-      var name = stream.getdents.pop();
+      var name = stream.getdents[idx];
       if (name[0] === '.') {
         id = 1;
         type = 4; // DT_DIR
@@ -1098,12 +1104,14 @@ var SyscallsLibrary = {
                8;                             // DT_REG, regular file.
       }
       {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_ino, 'id', 'i64') }}};
-      {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_off, 'stream.position', 'i64') }}};
+      {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_off, '(idx + 1) * struct_size', 'i64') }}};
       {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_reclen, C_STRUCTS.dirent.__size__, 'i16') }}};
       {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_type, 'type', 'i8') }}};
       stringToUTF8(name, dirp + pos + {{{ C_STRUCTS.dirent.d_name }}}, 256);
-      pos += {{{ C_STRUCTS.dirent.__size__ }}};
+      pos += struct_size;
+      idx += 1;
     }
+    FS.llseek(stream, idx * struct_size, {{{ cDefine('SEEK_SET') }}});
     return pos;
   },
   __syscall221__deps: ['__setErrNo'],

src/struct_info.json

@@ -868,6 +868,7 @@
         "defines": [
             "EOF", 
             "SEEK_END", 
+            "SEEK_CUR", 
             "SEEK_SET"
         ],
         "structs": {}

system/lib/fetch/asmfs.cpp

@@ -1910,7 +1910,7 @@ long __syscall220(int which, ...) // getdents64 (get directory entries 64-bit)
 	if (desc->file_pos <= file_pos)
 	{
 		de->d_ino = (ino_t)node; // TODO: Create inode numbers instead of using pointers
-		de->d_off = file_pos;
+		de->d_off = file_pos + sizeof(dirent);
 		de->d_reclen = sizeof(dirent);
 		de->d_type = DT_DIR;
 		strcpy(de->d_name, ".");
@@ -1923,7 +1923,7 @@ long __syscall220(int which, ...) // getdents64 (get directory entries 64-bit)
 	if (desc->file_pos <= file_pos)
 	{
 		de->d_ino = (ino_t)dotdot; // TODO: Create inode numbers instead of using pointers
-		de->d_off = file_pos;
+		de->d_off = file_pos + sizeof(dirent);
 		de->d_reclen = sizeof(dirent);
 		de->d_type = DT_DIR;
 		strcpy(de->d_name, "..");
@@ -1938,7 +1938,7 @@ long __syscall220(int which, ...) // getdents64 (get directory entries 64-bit)
 		if (desc->file_pos <= file_pos)
 		{
 			de->d_ino = (ino_t)node; // TODO: Create inode numbers instead of using pointers
-			de->d_off = file_pos;
+			de->d_off = file_pos + sizeof(dirent);
 			de->d_reclen = sizeof(dirent);
 			de->d_type = (node->type == INODE_DIR) ? DT_DIR : DT_REG /*Regular file*/;
 			de->d_name[255] = 0;

tests/dirent/test_readdir.c

@@ -43,7 +43,7 @@ void cleanup() {
 
 void test() {
   int err;
-  long loc;
+  long loc, loc2;
   DIR *dir;
   struct dirent *ent;
   struct dirent ent_r;
@@ -118,11 +118,9 @@ void test() {
   ent = readdir(dir);
   assert(!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, "..") || !strcmp(ent->d_name, "file.txt"));
   loc = telldir(dir);
-#ifndef __EMSCRIPTEN__
-  // TODO(https://github.com/emscripten-core/emscripten/issues/8526): Implement telldir/seekdir
-  assert(loc > 0);
+  assert(loc >= 0);
   //printf("loc=%d\n", loc);
-#endif
+  loc2 = ent->d_off;
   ent = readdir(dir);
   char name_at_loc[1024];
   strcpy(name_at_loc, ent->d_name);
@@ -133,11 +131,14 @@ void test() {
   seekdir(dir, loc);
   ent = readdir(dir);
   assert(ent);
-#ifndef __EMSCRIPTEN__
-  // TODO(https://github.com/emscripten-core/emscripten/issues/8526: Implement telldir/seekdir
   //printf("check: %s / %s\n", ent->d_name, name_at_loc);
   assert(!strcmp(ent->d_name, name_at_loc));
-#endif
+
+  seekdir(dir, loc2);
+  ent = readdir(dir);
+  assert(ent);
+  //printf("check: %s / %s\n", ent->d_name, name_at_loc);
+  assert(!strcmp(ent->d_name, name_at_loc));
 
   //
   // do a normal read with readdir_r

tests/test_other.py

@@ -4276,12 +4276,12 @@ int main(int argc, char **argv) {
 1:
   make /: -1
   open /: 1
-  proc, 4
-  dev, 4
-  home, 4
-  tmp, 4
-  .., 4
   ., 4
+  .., 4
+  tmp, 4
+  home, 4
+  dev, 4
+  proc, 4
 ''', run_js('a.out.js', args=['/']))
     # cannot create empty name, cannot open
     self.assertContained(r'''
@@ -4294,21 +4294,21 @@ int main(int argc, char **argv) {
 1:
   make /a//: 0
   open /a//: 1
-  .., 4
   ., 4
+  .., 4
 ''', run_js('a.out.js', args=['/a//']))
     # can create child unnormalized
     self.assertContained(r'''
 1:
   make /a: 0
   open /a: 1
-  .., 4
   ., 4
+  .., 4
 2:
   make /a//b//: 0
   open /a//b//: 1
-  .., 4
   ., 4
+  .., 4
 ''', run_js('a.out.js', args=['/a', '/a//b//']))
 
   def test_stat_silly(self):
@@ -4500,17 +4500,17 @@ int main()
     # cannot symlink nonexistents
     self.assertContained(r'''Before:
 dir
-  e
-  d
-  c
-  b
   a
+  b
+  c
+  d
+  e
 
-Unlinking e
-Unlinking d
-Unlinking c
-Unlinking b
 Unlinking a
+Unlinking b
+Unlinking c
+Unlinking d
+Unlinking e
 After:
 dir
 ''', run_js('a.out.js', args=['', 'abc']))