fs_mem: poor man's symlink via hardlink

Author: TerrorJack

src/fd.ts

@@ -105,6 +105,9 @@ export abstract class Fd {
   path_readlink(path: string): { ret: number; data: string | null } {
     return { ret: wasi.ERRNO_NOTSUP, data: null };
   }
+  path_symlink(old_path: string, new_path: string): number {
+    return wasi.ERRNO_NOTSUP;
+  }
   path_remove_directory(path: string): number {
     return wasi.ERRNO_NOTSUP;
   }

src/fs_mem.ts

@@ -398,6 +398,34 @@ export class OpenDirectory extends Fd {
     return wasi.ERRNO_SUCCESS;
   }
 
+  path_symlink(old_path_str: string, new_path_str: string): number {
+    const { ret: new_ret, path: new_path } = Path.from(new_path_str);
+    if (new_path == null) {
+      return new_ret;
+    }
+
+    const {
+      ret: parent_ret,
+      parent_entry,
+      filename,
+    } = this.dir.get_parent_dir_and_entry_for_path(new_path, true);
+    if (parent_entry == null || filename == null) {
+      return parent_ret;
+    }
+
+    const { ret: old_ret, path: old_path } = Path.from(old_path_str);
+    if (old_path == null) {
+      return old_ret;
+    }
+
+    const { ret: entry_ret, entry } = parent_entry.get_entry_for_path(old_path);
+    if (entry == null) {
+      return entry_ret;
+    }
+
+    return this.path_link(new_path_str, entry, true);
+  }
+
   path_unlink(path_str: string): { ret: number; inode_obj: InodeMem | null } {
     const { ret: path_ret, path } = Path.from(path_str);
     if (path == null) {

src/wasi.ts

@@ -813,15 +813,13 @@ export default class WASI {
       ): number {
         const buffer8 = new Uint8Array(self.inst.exports.memory.buffer);
         if (self.fds[fd] != undefined) {
-          // eslint-disable-next-line @typescript-eslint/no-unused-vars
           const old_path = new TextDecoder("utf-8").decode(
             buffer8.slice(old_path_ptr, old_path_ptr + old_path_len),
           );
-          // eslint-disable-next-line @typescript-eslint/no-unused-vars
           const new_path = new TextDecoder("utf-8").decode(
             buffer8.slice(new_path_ptr, new_path_ptr + new_path_len),
           );
-          return wasi.ERRNO_NOTSUP;
+          return self.fds[fd].path_symlink(old_path, new_path);
         } else {
           return wasi.ERRNO_BADF;
         }