WasmFS JS API: Implement stat, lstat (#19458)

Author: jameshu15869

emcc.py

@@ -2325,6 +2325,8 @@ def phase_linker_setup(options, state, newargs):
         '_wasmfs_read',
         '_wasmfs_pread',
         '_wasmfs_symlink',
+        '_wasmfs_stat',
+        '_wasmfs_lstat',
         '_wasmfs_chmod',
         '_wasmfs_fchmod',
         '_wasmfs_lchmod',

src/library_wasmfs.js

@@ -18,6 +18,7 @@ FS.createPreloadedFile = FS_createPreloadedFile;
     '$stringToUTF8OnStack',
     '$withStackSave',
     '$readI53FromI64',
+    '$readI53FromU64',
     '$FS_createPreloadedFile',
     '$FS_getMode',
     // For FS.readFile
@@ -196,8 +197,46 @@ FS.createPreloadedFile = FS_createPreloadedFile;
       });
     },
     // TODO: readlink
+    statBufToObject : (statBuf) => {
+      // i53/u53 are enough for times and ino in practice.
+      return {
+          dev: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_dev, "u32") }}},
+          mode: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_mode, "u32") }}},
+          nlink: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_nlink, "u32") }}},
+          uid: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_uid, "u32") }}},
+          gid: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_gid, "u32") }}},
+          rdev: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_rdev, "u32") }}},
+          size: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_size, "i53") }}},
+          blksize: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_blksize, "u32") }}},
+          blocks: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_blocks, "u32") }}},
+          atime: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_atim.tv_sec, "i53") }}},
+          mtime: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_mtim.tv_sec, "i53") }}},
+          ctime: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_ctim.tv_sec, "i53") }}},
+          ino: {{{ makeGetValue('statBuf', C_STRUCTS.stat.st_ino, "u53") }}}
+      }
+    },
     // TODO: stat
+    stat: (path) => {
+      var statBuf = _malloc({{{ C_STRUCTS.stat.__size__ }}});
+      FS.handleError(withStackSave(() => {
+        return __wasmfs_stat(stringToUTF8OnStack(path), statBuf);
+      }));
+      var stats = FS.statBufToObject(statBuf);
+      _free(statBuf);
+
+      return stats;
+    },
     // TODO: lstat
+    lstat: (path) => {
+      var statBuf = _malloc({{{ C_STRUCTS.stat.__size__ }}});
+      FS.handleError(withStackSave(() => {
+        return __wasmfs_lstat(stringToUTF8OnStack(path), statBuf);
+      }));
+      var stats = FS.statBufToObject(statBuf);
+      _free(statBuf);
+
+      return stats;
+    },
     chmod: (path, mode) => {
       return FS.handleError(withStackSave(() => {
         var buffer = stringToUTF8OnStack(path);

system/lib/wasmfs/js_api.cpp

@@ -175,6 +175,22 @@ int _wasmfs_close(int fd) {
   return __wasi_fd_close(fd);
 }
 
+int _wasmfs_stat(char* path, struct stat* statBuf) {
+  int err = __syscall_stat64((intptr_t)path, (intptr_t)statBuf);
+  if (err == -1) {
+    return errno;
+  }
+  return err;
+}
+
+int _wasmfs_lstat(char* path, struct stat* statBuf) {
+  int err = __syscall_lstat64((intptr_t)path, (intptr_t)statBuf);
+  if (err == -1) {
+    return errno;
+  }
+  return err;
+}
+
 // Helper method that identifies what a path is:
 //   ENOENT - if nothing exists there
 //   EISDIR - if it is a directory

test/stat/test_stat.c

@@ -19,6 +19,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/sysmacros.h>
+#include <emscripten/emscripten.h>
 
 void create_file(const char *path, const char *buffer, int mode) {
   int fd = open(path, O_WRONLY | O_CREAT | O_EXCL, mode);
@@ -85,7 +86,6 @@ void test() {
   assert(s.st_blocks == 1);
 #endif
 #endif
-
   // stat a file
   memset(&s, 0, sizeof(s));
   err = stat("folder/file", &s);
@@ -193,6 +193,55 @@ void test() {
   err = stat("folder/subdir", &s);
   assert(s.st_mtime != TEST_TIME);
 
+  chmod("folder/file", 0666);
+  EM_ASM(
+    var stats = FS.stat("folder/file");
+    assert(stats.dev == 1);
+    assert(stats.ino);
+    assert(stats.mode == 0o100666);
+    assert(stats.nlink);
+    assert(stats.rdev == 0);
+    assert(stats.size == 6);
+    assert(stats.atime);
+    assert(stats.mtime);
+    assert(stats.ctime);
+  );
+
+  symlink("folder/file", "folder/symlinkfile");
+  
+  EM_ASM(
+    var linkStats = FS.lstat("folder/symlinkfile");
+    assert(linkStats.dev == 1);
+    assert(linkStats.ino);
+#if WASMFS
+    assert(linkStats.mode == 0o120000);
+#else
+    assert(linkStats.mode == 0o120777);
+#endif
+    assert(linkStats.nlink);
+    assert(linkStats.rdev == 0);
+    assert(linkStats.size == 11);
+    assert(linkStats.atime);
+    assert(linkStats.mtime);
+    assert(linkStats.ctime);
+    
+    var ex;
+    try {
+      FS.stat("nonexistent");
+    } catch (err) {
+      ex = err;
+    }
+    assert(ex.name === "ErrnoError" && ex.errno === 44 /* ENOENT */);
+
+    try {
+      FS.lstat("nonexistent");
+    } catch (err) {
+      ex = err;
+    }
+    assert(ex.name === "ErrnoError" && ex.errno === 44 /* ENOENT */);
+  );
+  chmod("folder/file", 0777);
+
   puts("success");
 }
 

test/test_core.py

@@ -5814,6 +5814,7 @@ def test_readdir_empty(self):
     self.do_run_in_out_file_test('dirent/test_readdir_empty.c')
 
   def test_stat(self):
+    self.set_setting("FORCE_FILESYSTEM")
     self.do_runf(test_file('stat/test_stat.c'), 'success')
     self.verify_in_strict_mode('test_stat.js')