WasmFS JS API: Implement truncate

emcc.py

@@ -2325,6 +2325,8 @@ def phase_linker_setup(options, state, newargs):
         '_wasmfs_pwrite',
         '_wasmfs_rename',
         '_wasmfs_mkdir',
+        '_wasmfs_truncate',
+        '_wasmfs_ftruncate',
         '_wasmfs_unlink',
         '_wasmfs_chdir',
         '_wasmfs_mknod',

src/library_wasmfs.js

@@ -276,8 +276,12 @@ FS.createPreloadedFile = FS_createPreloadedFile;
     // TDOO: chown
     // TODO: lchown
     // TODO: fchown
-    // TODO: truncate
-    // TODO: ftruncate
+    truncate: (path, len) => {
+      return FS.handleError(withStackSave(() => (__wasmfs_truncate(stringToUTF8OnStack(path), len))));
+    },
+    ftruncate: (fd, len) => {
+      return FS.handleError(__wasmfs_ftruncate(fd, len));
+    },
     // TODO: utime
     findObject: (path) => {
       var result = __wasmfs_identify(path);

system/lib/wasmfs/js_api.cpp

@@ -126,25 +126,25 @@ int _wasmfs_mkdir(char* path, int mode) {
 int _wasmfs_rmdir(char* path){ return __syscall_unlinkat(AT_FDCWD, (intptr_t)path, AT_REMOVEDIR); }
 
 int _wasmfs_open(char* path, int flags, mode_t mode) {
-  int err = __syscall_openat(AT_FDCWD, (intptr_t)path, flags, mode);
-  if (err == -1) {
-    return -errno;
-  }
-  return err;
+  return __syscall_openat(AT_FDCWD, (intptr_t)path, flags, mode);
 }
 
 int _wasmfs_mknod(char* path, mode_t mode, dev_t dev) {
-  int err = __syscall_mknodat(AT_FDCWD, (intptr_t)path, mode, dev);
-  if (err == -1) {
-    return errno;
-  }
-  return err;
+  return __syscall_mknodat(AT_FDCWD, (intptr_t)path, mode, dev);
 }
 
 int _wasmfs_unlink(char* path) {
   return __syscall_unlinkat(AT_FDCWD, (intptr_t)path, 0);
 }
 
+int _wasmfs_truncate(char *path, long size) {
+  return __syscall_truncate64((intptr_t)path, size);
+}
+
+int _wasmfs_ftruncate(int fd, long size) {
+  return __syscall_ftruncate64(fd, size);
+}
+
 int _wasmfs_chdir(char* path) { return __syscall_chdir((intptr_t)path); }
 
 int _wasmfs_symlink(char* old_path, char* new_path) {
@@ -190,11 +190,7 @@ int _wasmfs_lchmod(char* path, mode_t mode) {
 }
 
 int _wasmfs_rename(char* oldpath, char* newpath) {
-  int err = __syscall_renameat(AT_FDCWD, (intptr_t)oldpath, AT_FDCWD, (intptr_t)newpath);
-  if (err == -1) {
-    return errno;
-  }
-  return err;
+  return __syscall_renameat(AT_FDCWD, (intptr_t)oldpath, AT_FDCWD, (intptr_t)newpath);
 };
 
 int _wasmfs_read(int fd, void *buf, size_t count) {
@@ -228,19 +224,11 @@ int _wasmfs_close(int 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;
+  return __syscall_stat64((intptr_t)path, (intptr_t)statBuf);
 }
 
 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;
+  return __syscall_lstat64((intptr_t)path, (intptr_t)statBuf);
 }
 
 // Helper method that identifies what a path is:

test/fs/test_fs_js_api.c

@@ -31,6 +31,76 @@ int main() {
         assert(createFileNotHere && createFileNotHere.fd >= 0);
     );
 
+    /********** test FS.truncate() **********/
+    EM_ASM(
+        FS.writeFile('truncatetest', 'a=1\nb=2\n');
+    );
+
+    struct stat s;
+    stat("truncatetest", &s);
+    assert(s.st_size == 8);
+
+    EM_ASM(
+        FS.truncate('truncatetest', 2);
+    );
+    stat("truncatetest", &s);
+    assert(s.st_size == 2);
+
+    EM_ASM(
+        FS.truncate('truncatetest', 10);
+    );
+    stat("truncatetest", &s);
+    assert(s.st_size == 10);
+
+    EM_ASM(
+        var truncateStream = FS.open('truncatetest', 'w');
+        FS.ftruncate(truncateStream.fd, 4);
+    );
+    stat("truncatetest", &s);
+    assert(s.st_size == 4);
+
+    EM_ASM(
+        var ex;
+        try {
+            FS.truncate('truncatetest', -10);
+        } catch(err) {
+            ex = err;
+        }
+
+        assert(ex.name === "ErrnoError" && ex.errno === 28 /* EINVAL */);
+    );
+
+    EM_ASM(
+        var ex;
+        try {
+            var truncateStream = FS.open('truncatetest', 'w');
+            FS.ftruncate(truncateStream.fd, -10);
+        } catch(err) {
+            ex = err;
+        }
+
+        assert(ex.name === "ErrnoError" && ex.errno === 28 /* EINVAL */);
+    );
+
+    EM_ASM(
+        var ex;
+        try {
+            FS.truncate('nonexistent', 10);
+        } catch(err) {
+            ex = err;
+        }
+        assert(ex.name === "ErrnoError" && ex.errno === 44 /* ENOENT */);
+
+        var ex;
+        try {
+            FS.ftruncate(99, 10);
+        } catch(err) {
+            ex = err;
+        }
+
+        assert(ex.name === "ErrnoError" && ex.errno === 8 /* EBADF */);
+    );
+
     /********** test FS.rename() **********/
     EM_ASM(
         FS.mkdir('renamedir');
@@ -151,6 +221,7 @@ int main() {
 
     remove("mknodtest");
     remove("createtest");
+    remove("truncatetest");
     remove("testfile");
     remove("renametestfile");
     remove("readtestfile");