fix: implement fd_fdstat_get WASIp1 function (#55)

Author: uhyo

packages/wasi-preview1/src/dataStructure.ts

@@ -35,6 +35,21 @@ export function writeFilestat(
   view.setBigUint64(56, ctim, true);
 }
 
+export function writeFdstat(
+  memory: ArrayBuffer,
+  ptr: number,
+  filetype: number,
+  fs_flags: number,
+  fs_rights_base: bigint,
+  fs_rights_inheriting: bigint
+) {
+  const view = new DataView(memory, ptr, 24);
+  view.setUint8(0, filetype);
+  view.setUint16(2, fs_flags, true);
+  view.setBigUint64(8, fs_rights_base, true);
+  view.setBigUint64(16, fs_rights_inheriting, true);
+}
+
 export function generateOneReaddirEntry(
   ent: DirEntry,
   index: number

packages/wasi-preview1/src/wasi.ts

@@ -5,6 +5,7 @@ import * as error from "./error.js";
 import {
   generateOneReaddirEntry,
   getFiletypeOfStat,
+  writeFdstat,
   writeFilestat,
   writePrestatDir,
 } from "./dataStructure.js";
@@ -304,7 +305,26 @@ export function initWASI(config: WASIConfig): WASIAPI & WASIMeta {
       }
     },
     fd_fdstat_get: (fd, ret_buf) => {
-      throw new Error("Function not implemented.");
+      const fdObj = fs.get(fd);
+      if (fdObj === undefined) {
+        return error.badf;
+      }
+      try {
+        const stat = fs.stat(fdObj);
+        // fd_write | path_create_directory | path_open | fd_readdir | path_filestat_get | fd_filestat_get
+        const fs_flags = 0b0001_0010_0011_0001_0010_0000n;
+        writeFdstat(
+          memory(),
+          ret_buf,
+          getFiletypeOfStat(stat),
+          0,
+          fs_flags,
+          fs_flags
+        );
+        return 0;
+      } catch (e) {
+        return handleFsError(e, debug);
+      }
     },
     random_get: (buf, buf_len): number => {
       crypto.randomFillSync(new Uint8Array(memory(), buf, buf_len));