3 files changed, 136 insertions, 4 deletions

diff --git a/bufio.ts b/bufio.ts
index dccd3afc0..2ad9bdd09 100644
--- a/bufio.ts
+++ b/bufio.ts
@@ -3,7 +3,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-import { Reader, ReadResult } from "deno";
+import { Reader, ReadResult, Writer } from "deno";
 import { assert, charCode, copyBytes } from "./util.ts";
 
 const DEFAULT_BUF_SIZE = 4096;
@@ -32,7 +32,7 @@ export class BufReader implements Reader {
   }
 
   /** Returns the size of the underlying buffer in bytes. */
-  get byteLength(): number {
+  size(): number {
     return this.buf.byteLength;
   }
 
@@ -332,4 +332,104 @@ export class BufReader implements Reader {
  * the underlying deno.Writer.
  */
 export class BufWriter implements Writer {
+  buf: Uint8Array;
+  n: number = 0;
+  err: null | Error = null;
+
+  constructor(private wr: Writer, size = DEFAULT_BUF_SIZE) {
+    if (size <= 0) {
+      size = DEFAULT_BUF_SIZE;
+    }
+    this.buf = new Uint8Array(size);
+  }
+
+  /** Size returns the size of the underlying buffer in bytes. */
+  size(): number {
+    return this.buf.byteLength;
+  }
+
+  /** Discards any unflushed buffered data, clears any error, and
+   * resets b to write its output to w.
+   */
+  reset(w: Writer): void {
+    this.err = null;
+    this.n = 0;
+    this.wr = w;
+  }
+
+  /** Flush writes any buffered data to the underlying io.Writer. */
+  async flush(): Promise<void> {
+    if (this.err != null) {
+      throw this.err;
+    }
+    if (this.n == 0) {
+      return;
+    }
+
+    let n: number;
+    let err: Error = null;
+    try {
+      n = await this.wr.write(this.buf.subarray(0, this.n));
+    } catch (e) {
+      err = e;
+    }
+
+    if (n < this.n && err == null) {
+      err = new Error("ShortWrite");
+    }
+
+    if (err != null) {
+      if (n > 0 && n < this.n) {
+        this.buf.copyWithin(0, n, this.n);
+      }
+      this.n -= n;
+      this.err = err;
+      return;
+    }
+    this.n = 0;
+  }
+
+  /** Returns how many bytes are unused in the buffer. */
+  available(): number {
+    return this.buf.byteLength - this.n;
+  }
+
+  /** buffered returns the number of bytes that have been written into the
+   * current buffer.
+   */
+  buffered(): number {
+    return this.n;
+  }
+
+  /** Writes the contents of p into the buffer.
+   * Returns the number of bytes written.
+   */
+  async write(p: Uint8Array): Promise<number> {
+    let nn = 0;
+    let n: number;
+    while (p.byteLength > this.available() && !this.err) {
+      if (this.buffered() == 0) {
+        // Large write, empty buffer.
+        // Write directly from p to avoid copy.
+        try {
+          n = await this.wr.write(p);
+        } catch (e) {
+          this.err = e;
+        }
+      } else {
+        n = copyBytes(this.buf, p, this.n);
+        this.n += n;
+        this.flush();
+      }
+      nn += n;
+      p = p.subarray(n);
+    }
+    if (this.err) {
+      throw this.err;
+    }
+    n = copyBytes(this.buf, p, this.n);
+    this.n += n;
+    nn += n;
+    return nn;
+  }
 }
diff --git a/bufio_test.ts b/bufio_test.ts
index 9c89f0216..f3430a755 100644
--- a/bufio_test.ts
+++ b/bufio_test.ts
@@ -9,7 +9,7 @@ import {
   assert,
   assertEqual
 } from "https://deno.land/x/testing/testing.ts";
-import { BufReader, BufState } from "./bufio.ts";
+import { BufReader, BufState, BufWriter } from "./bufio.ts";
 import { Buffer, stringsReader } from "./buffer.ts";
 import * as iotest from "./iotest.ts";
 import { charCode, copyBytes } from "./util.ts";
@@ -289,3 +289,36 @@ test(async function bufioPeek() {
 	}
   */
 });
+
+test(async function bufioWriter() {
+  const data = new Uint8Array(8192);
+
+  for (let i = 0; i < data.byteLength; i++) {
+    data[i] = charCode(" ") + i % (charCode("~") - charCode(" "));
+  }
+
+  const w = new Buffer();
+  for (let nwrite of bufsizes) {
+    for (let bs of bufsizes) {
+      // Write nwrite bytes using buffer size bs.
+      // Check that the right amount makes it out
+      // and that the data is correct.
+
+      w.reset();
+      const buf = new BufWriter(w, bs);
+
+      const context = `nwrite=${nwrite} bufsize=${bs}`;
+      const n = await buf.write(data.subarray(0, nwrite));
+      assertEqual(n, nwrite, context);
+
+      await buf.flush();
+
+      const written = w.bytes();
+      assertEqual(written.byteLength, nwrite);
+
+      for (let l = 0; l < written.byteLength; l++) {
+        assertEqual(written[l], data[l]);
+      }
+    }
+  }
+});
diff --git a/http.ts b/http.ts
index c33bc97a2..0266501ae 100644
--- a/http.ts
+++ b/http.ts
@@ -55,4 +55,3 @@ async function readRequest(b: BufReader): Promise<ServerRequest> {
 
   return req;
 }
-