From 127ace39b94fabe8d0e26e27b736869597b0fd93 Mon Sep 17 00:00:00 2001
From: Casper Beyer <caspervonb@pm.me>
Date: Tue, 30 Jun 2020 02:36:22 +0800
Subject: [PATCH] feat(wasi) implement fd_filestat_set_size
 (denoland/deno#6558)

---
 wasi/README.md                       |  2 +-
 wasi/snapshot_preview1.ts            | 13 ++++++++++++-
 wasi/testdata/std_fs_file_set_len.rs | 17 +++++++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 wasi/testdata/std_fs_file_set_len.rs

diff --git a/wasi/README.md b/wasi/README.md
index 6b89db1de484..530a9d8276af 100644
--- a/wasi/README.md
+++ b/wasi/README.md
@@ -20,7 +20,7 @@ This module provides an implementation of the WebAssembly System Interface
 - [ ] fd_fdstat_set_flags
 - [ ] fd_fdstat_set_rights
 - [x] fd_filestat_get
-- [ ] fd_filestat_set_size
+- [x] fd_filestat_set_size
 - [x] fd_filestat_set_times
 - [x] fd_pread
 - [x] fd_prestat_get
diff --git a/wasi/snapshot_preview1.ts b/wasi/snapshot_preview1.ts
index d52b81635ef8..4fe4e02b46f0 100644
--- a/wasi/snapshot_preview1.ts
+++ b/wasi/snapshot_preview1.ts
@@ -607,7 +607,18 @@ export default class Module {
       },
 
       fd_filestat_set_size: (fd: number, size: bigint): number => {
-        return ERRNO_NOSYS;
+        const entry = this.fds[fd];
+        if (!entry) {
+          return ERRNO_BADF;
+        }
+
+        try {
+          Deno.ftruncateSync(entry.handle.rid, Number(size));
+        } catch (err) {
+          return errno(err);
+        }
+
+        return ERRNO_SUCCESS;
       },
 
       fd_filestat_set_times: (
diff --git a/wasi/testdata/std_fs_file_set_len.rs b/wasi/testdata/std_fs_file_set_len.rs
new file mode 100644
index 000000000000..27f1054c7025
--- /dev/null
+++ b/wasi/testdata/std_fs_file_set_len.rs
@@ -0,0 +1,17 @@
+// { "preopens": { "/scratch": "scratch" } }
+
+fn main() {
+  let file = std::fs::File::create("/scratch/file").unwrap();
+
+  assert!(file.set_len(0).is_ok());
+  assert_eq!(file.metadata().unwrap().len(), 0);
+
+  assert!(file.set_len(5).is_ok());
+  assert_eq!(file.metadata().unwrap().len(), 5);
+
+  assert!(file.set_len(25).is_ok());
+  assert_eq!(file.metadata().unwrap().len(), 25);
+
+  assert!(file.set_len(0).is_ok());
+  assert_eq!(file.metadata().unwrap().len(), 0);
+}