diff --git a/examples/rustc.html b/examples/rustc.html
index b6cfe1f..3e46b63 100644
--- a/examples/rustc.html
+++ b/examples/rustc.html
@@ -47,15 +47,11 @@
             super();
             this.term = term;
         }
-        fd_write(view8/*: Uint8Array*/, iovs/*: [wasi.Iovec]*/)/*: {ret: number, nwritten: number}*/ {
+        fd_write(data/*: Uint8Array*/)/*: {ret: number, nwritten: number}*/ {
             let nwritten = 0;
-            for (let iovec of iovs) {
-                console.log(iovec.buf_len, iovec.buf_len, view8.slice(iovec.buf, iovec.buf + iovec.buf_len));
-                let buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-                this.term.writeUtf8(buffer);
-                nwritten += iovec.buf_len;
-            }
-            return { ret: 0, nwritten };
+            console.log(data);
+            this.term.writeUtf8(data);
+            return { ret: 0, nwritten: data.byteLength };
         }
     }
 
diff --git a/src/fd.ts b/src/fd.ts
index b192ce9..2227ab6 100644
--- a/src/fd.ts
+++ b/src/fd.ts
@@ -35,12 +35,8 @@ export abstract class Fd {
   fd_filestat_set_times(atim: bigint, mtim: bigint, fst_flags: number): number {
     return wasi.ERRNO_NOTSUP;
   }
-  fd_pread(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-    offset: bigint,
-  ): { ret: number; nread: number } {
-    return { ret: wasi.ERRNO_NOTSUP, nread: 0 };
+  fd_pread(size: number, offset: bigint): { ret: number; data: Uint8Array } {
+    return { ret: wasi.ERRNO_NOTSUP, data: new Uint8Array() };
   }
   fd_prestat_get(): { ret: number; prestat: wasi.Prestat | null } {
     return { ret: wasi.ERRNO_NOTSUP, prestat: null };
@@ -49,17 +45,13 @@ export abstract class Fd {
     return { ret: wasi.ERRNO_NOTSUP, prestat_dir_name: null };
   }
   fd_pwrite(
-    view8: Uint8Array,
-    iovs: Array<wasi.Ciovec>,
+    data: Uint8Array,
     offset: bigint,
   ): { ret: number; nwritten: number } {
     return { ret: wasi.ERRNO_NOTSUP, nwritten: 0 };
   }
-  fd_read(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-  ): { ret: number; nread: number } {
-    return { ret: wasi.ERRNO_NOTSUP, nread: 0 };
+  fd_read(size: number): { ret: number; data: Uint8Array } {
+    return { ret: wasi.ERRNO_NOTSUP, data: new Uint8Array() };
   }
   fd_readdir_single(cookie: bigint): {
     ret: number;
@@ -76,10 +68,7 @@ export abstract class Fd {
   fd_tell(): { ret: number; offset: bigint } {
     return { ret: wasi.ERRNO_NOTSUP, offset: 0n };
   }
-  fd_write(
-    view8: Uint8Array,
-    iovs: Array<wasi.Ciovec>,
-  ): { ret: number; nwritten: number } {
+  fd_write(data: Uint8Array): { ret: number; nwritten: number } {
     return { ret: wasi.ERRNO_NOTSUP, nwritten: 0 };
   }
   path_create_directory(path: string): number {
diff --git a/src/fs_mem.ts b/src/fs_mem.ts
index 4cea8f0..d089bb6 100644
--- a/src/fs_mem.ts
+++ b/src/fs_mem.ts
@@ -42,47 +42,21 @@ export class OpenFile extends Fd {
     return wasi.ERRNO_SUCCESS;
   }
 
-  fd_read(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-  ): { ret: number; nread: number } {
-    let nread = 0;
-    for (const iovec of iovs) {
-      if (this.file_pos < this.file.data.byteLength) {
-        const slice = this.file.data.slice(
-          Number(this.file_pos),
-          Number(this.file_pos + BigInt(iovec.buf_len)),
-        );
-        view8.set(slice, iovec.buf);
-        this.file_pos += BigInt(slice.length);
-        nread += slice.length;
-      } else {
-        break;
-      }
-    }
-    return { ret: 0, nread };
+  fd_read(size: number): { ret: number; data: Uint8Array } {
+    const slice = this.file.data.slice(
+      Number(this.file_pos),
+      Number(this.file_pos + BigInt(size)),
+    );
+    this.file_pos += BigInt(slice.length);
+    return { ret: 0, data: slice };
   }
 
-  fd_pread(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-    offset: bigint,
-  ): { ret: number; nread: number } {
-    let nread = 0;
-    for (const iovec of iovs) {
-      if (offset < this.file.data.byteLength) {
-        const slice = this.file.data.slice(
-          Number(offset),
-          Number(offset + BigInt(iovec.buf_len)),
-        );
-        view8.set(slice, iovec.buf);
-        offset += BigInt(slice.length);
-        nread += slice.length;
-      } else {
-        break;
-      }
-    }
-    return { ret: 0, nread };
+  fd_pread(size: number, offset: bigint): { ret: number; data: Uint8Array } {
+    const slice = this.file.data.slice(
+      Number(offset),
+      Number(offset + BigInt(size)),
+    );
+    return { ret: 0, data: slice };
   }
 
   fd_seek(offset: bigint, whence: number): { ret: number; offset: bigint } {
@@ -113,51 +87,33 @@ export class OpenFile extends Fd {
     return { ret: 0, offset: this.file_pos };
   }
 
-  fd_write(
-    view8: Uint8Array,
-    iovs: Array<wasi.Ciovec>,
-  ): { ret: number; nwritten: number } {
-    let nwritten = 0;
-    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten };
-    for (const iovec of iovs) {
-      const buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-      if (this.file_pos + BigInt(buffer.byteLength) > this.file.size) {
-        const old = this.file.data;
-        this.file.data = new Uint8Array(
-          Number(this.file_pos + BigInt(buffer.byteLength)),
-        );
-        this.file.data.set(old);
-      }
-      this.file.data.set(
-        buffer.slice(0, Number(this.file.size - this.file_pos)),
-        Number(this.file_pos),
+  fd_write(data: Uint8Array): { ret: number; nwritten: number } {
+    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten: 0 };
+
+    if (this.file_pos + BigInt(data.byteLength) > this.file.size) {
+      const old = this.file.data;
+      this.file.data = new Uint8Array(
+        Number(this.file_pos + BigInt(data.byteLength)),
       );
-      this.file_pos += BigInt(buffer.byteLength);
-      nwritten += iovec.buf_len;
+      this.file.data.set(old);
     }
-    return { ret: 0, nwritten };
+
+    this.file.data.set(data, Number(this.file_pos));
+    this.file_pos += BigInt(data.byteLength);
+    return { ret: 0, nwritten: data.byteLength };
   }
 
-  fd_pwrite(view8: Uint8Array, iovs: Array<wasi.Ciovec>, offset: bigint) {
-    let nwritten = 0;
-    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten };
-    for (const iovec of iovs) {
-      const buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-      if (offset + BigInt(buffer.byteLength) > this.file.size) {
-        const old = this.file.data;
-        this.file.data = new Uint8Array(
-          Number(offset + BigInt(buffer.byteLength)),
-        );
-        this.file.data.set(old);
-      }
-      this.file.data.set(
-        buffer.slice(0, Number(this.file.size - offset)),
-        Number(offset),
-      );
-      offset += BigInt(buffer.byteLength);
-      nwritten += iovec.buf_len;
+  fd_pwrite(data: Uint8Array, offset: bigint) {
+    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten: 0 };
+
+    if (offset + BigInt(data.byteLength) > this.file.size) {
+      const old = this.file.data;
+      this.file.data = new Uint8Array(Number(offset + BigInt(data.byteLength)));
+      this.file.data.set(old);
     }
-    return { ret: 0, nwritten };
+
+    this.file.data.set(data, Number(offset));
+    return { ret: 0, nwritten: data.byteLength };
   }
 
   fd_filestat_get(): { ret: number; filestat: wasi.Filestat } {
@@ -464,40 +420,24 @@ export class OpenDirectory extends Fd {
     return wasi.ERRNO_BADF;
   }
 
-  fd_read(
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    view8: Uint8Array,
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    iovs: wasi.Iovec[],
-  ): { ret: number; nread: number } {
-    return { ret: wasi.ERRNO_BADF, nread: 0 };
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  fd_read(size: number): { ret: number; data: Uint8Array } {
+    return { ret: wasi.ERRNO_BADF, data: new Uint8Array() };
   }
 
-  fd_pread(
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    view8: Uint8Array,
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    iovs: wasi.Iovec[],
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    offset: bigint,
-  ): { ret: number; nread: number } {
-    return { ret: wasi.ERRNO_BADF, nread: 0 };
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  fd_pread(size: number, offset: bigint): { ret: number; data: Uint8Array } {
+    return { ret: wasi.ERRNO_BADF, data: new Uint8Array() };
   }
 
-  fd_write(
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    view8: Uint8Array,
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    iovs: wasi.Ciovec[],
-  ): { ret: number; nwritten: number } {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  fd_write(data: Uint8Array): { ret: number; nwritten: number } {
     return { ret: wasi.ERRNO_BADF, nwritten: 0 };
   }
 
   fd_pwrite(
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    view8: Uint8Array,
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    iovs: wasi.Ciovec[],
+    data: Uint8Array,
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
     offset: bigint,
   ): { ret: number; nwritten: number } {
@@ -785,17 +725,9 @@ export class ConsoleStdout extends Fd {
     return { ret: 0, fdstat };
   }
 
-  fd_write(
-    view8: Uint8Array,
-    iovs: Array<wasi.Ciovec>,
-  ): { ret: number; nwritten: number } {
-    let nwritten = 0;
-    for (const iovec of iovs) {
-      const buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-      this.write(buffer);
-      nwritten += iovec.buf_len;
-    }
-    return { ret: 0, nwritten };
+  fd_write(data: Uint8Array): { ret: number; nwritten: number } {
+    this.write(data);
+    return { ret: 0, nwritten: data.byteLength };
   }
 
   static lineBuffered(write: (line: string) => void): ConsoleStdout {
diff --git a/src/fs_opfs.ts b/src/fs_opfs.ts
index df43876..d1fe42a 100644
--- a/src/fs_opfs.ts
+++ b/src/fs_opfs.ts
@@ -101,22 +101,11 @@ export class OpenSyncOPFSFile extends Fd {
     return wasi.ERRNO_SUCCESS;
   }
 
-  fd_read(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-  ): { ret: number; nread: number } {
-    let nread = 0;
-    for (const iovec of iovs) {
-      if (this.position < this.file.handle.getSize()) {
-        const buf = new Uint8Array(view8.buffer, iovec.buf, iovec.buf_len);
-        const n = this.file.handle.read(buf, { at: Number(this.position) });
-        this.position += BigInt(n);
-        nread += n;
-      } else {
-        break;
-      }
-    }
-    return { ret: 0, nread };
+  fd_read(size: number): { ret: number; data: Uint8Array } {
+    const buf = new Uint8Array(size);
+    const n = this.file.handle.read(buf, { at: Number(this.position) });
+    this.position += BigInt(n);
+    return { ret: 0, data: buf.slice(0, n) };
   }
 
   fd_seek(
@@ -144,20 +133,13 @@ export class OpenSyncOPFSFile extends Fd {
     return { ret: wasi.ERRNO_SUCCESS, offset: this.position };
   }
 
-  fd_write(
-    view8: Uint8Array,
-    iovs: Array<wasi.Iovec>,
-  ): { ret: number; nwritten: number } {
-    let nwritten = 0;
-    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten };
-    for (const iovec of iovs) {
-      const buf = new Uint8Array(view8.buffer, iovec.buf, iovec.buf_len);
-      // don't need to extend file manually, just write
-      const n = this.file.handle.write(buf, { at: Number(this.position) });
-      this.position += BigInt(n);
-      nwritten += n;
-    }
-    return { ret: wasi.ERRNO_SUCCESS, nwritten };
+  fd_write(data: Uint8Array): { ret: number; nwritten: number } {
+    if (this.file.readonly) return { ret: wasi.ERRNO_BADF, nwritten: 0 };
+
+    // don't need to extend file manually, just write
+    const n = this.file.handle.write(data, { at: Number(this.position) });
+    this.position += BigInt(n);
+    return { ret: wasi.ERRNO_SUCCESS, nwritten: n };
   }
 
   fd_datasync(): number {
diff --git a/src/wasi.ts b/src/wasi.ts
index 9da80f9..9c906b0 100644
--- a/src/wasi.ts
+++ b/src/wasi.ts
@@ -300,9 +300,22 @@ export default class WASI {
             iovs_ptr,
             iovs_len,
           );
-          const { ret, nread } = self.fds[fd].fd_pread(buffer8, iovecs, offset);
+          let nread = 0;
+          for (const iovec of iovecs) {
+            const { ret, data } = self.fds[fd].fd_pread(iovec.buf_len, offset);
+            if (ret != wasi.ERRNO_SUCCESS) {
+              buffer.setUint32(nread_ptr, nread, true);
+              return ret;
+            }
+            buffer8.set(data, iovec.buf);
+            nread += data.length;
+            offset += BigInt(data.length);
+            if (data.length != iovec.buf_len) {
+              break;
+            }
+          }
           buffer.setUint32(nread_ptr, nread, true);
-          return ret;
+          return wasi.ERRNO_SUCCESS;
         } else {
           return wasi.ERRNO_BADF;
         }
@@ -358,13 +371,25 @@ export default class WASI {
             iovs_ptr,
             iovs_len,
           );
-          const { ret, nwritten } = self.fds[fd].fd_pwrite(
-            buffer8,
-            iovecs,
-            offset,
-          );
+          let nwritten = 0;
+          for (const iovec of iovecs) {
+            const data = buffer8.slice(iovec.buf, iovec.buf + iovec.buf_len);
+            const { ret, nwritten: nwritten_part } = self.fds[fd].fd_pwrite(
+              data,
+              offset,
+            );
+            if (ret != wasi.ERRNO_SUCCESS) {
+              buffer.setUint32(nwritten_ptr, nwritten, true);
+              return ret;
+            }
+            nwritten += nwritten_part;
+            offset += BigInt(nwritten_part);
+            if (nwritten_part != data.byteLength) {
+              break;
+            }
+          }
           buffer.setUint32(nwritten_ptr, nwritten, true);
-          return ret;
+          return wasi.ERRNO_SUCCESS;
         } else {
           return wasi.ERRNO_BADF;
         }
@@ -383,9 +408,21 @@ export default class WASI {
             iovs_ptr,
             iovs_len,
           );
-          const { ret, nread } = self.fds[fd].fd_read(buffer8, iovecs);
+          let nread = 0;
+          for (const iovec of iovecs) {
+            const { ret, data } = self.fds[fd].fd_read(iovec.buf_len);
+            if (ret != wasi.ERRNO_SUCCESS) {
+              buffer.setUint32(nread_ptr, nread, true);
+              return ret;
+            }
+            buffer8.set(data, iovec.buf);
+            nread += data.length;
+            if (data.length != iovec.buf_len) {
+              break;
+            }
+          }
           buffer.setUint32(nread_ptr, nread, true);
-          return ret;
+          return wasi.ERRNO_SUCCESS;
         } else {
           return wasi.ERRNO_BADF;
         }
@@ -510,9 +547,22 @@ export default class WASI {
             iovs_ptr,
             iovs_len,
           );
-          const { ret, nwritten } = self.fds[fd].fd_write(buffer8, iovecs);
+          let nwritten = 0;
+          for (const iovec of iovecs) {
+            const data = buffer8.slice(iovec.buf, iovec.buf + iovec.buf_len);
+            const { ret, nwritten: nwritten_part } =
+              self.fds[fd].fd_write(data);
+            if (ret != wasi.ERRNO_SUCCESS) {
+              buffer.setUint32(nwritten_ptr, nwritten, true);
+              return ret;
+            }
+            nwritten += nwritten_part;
+            if (nwritten_part != data.byteLength) {
+              break;
+            }
+          }
           buffer.setUint32(nwritten_ptr, nwritten, true);
-          return ret;
+          return wasi.ERRNO_SUCCESS;
         } else {
           return wasi.ERRNO_BADF;
         }
diff --git a/test/adapters/node/run-wasi.mjs b/test/adapters/node/run-wasi.mjs
index ac31367..4a82d0d 100644
--- a/test/adapters/node/run-wasi.mjs
+++ b/test/adapters/node/run-wasi.mjs
@@ -25,14 +25,9 @@ class NodeStdout extends Fd {
     return { ret: 0, fdstat };
   }
 
-  fd_write(view8, iovs) {
-    let nwritten = 0;
-    for (let iovec of iovs) {
-      let buffer = view8.slice(iovec.buf, iovec.buf + iovec.buf_len);
-      this.out.write(buffer);
-      nwritten += iovec.buf_len;
-    }
-    return { ret: 0, nwritten };
+  fd_write(data) {
+    this.out.write(data);
+    return { ret: 0, nwritten: data.byteLength };
   }
 }