Reorgnanize repos, examples and tests (denoland/deno_std#105)

Original: https://github.com/denoland/deno_std/commit/c5e6e015b5be19027f60c19ca86283d12f9258f3

6 files changed, 993 insertions, 0 deletions

diff --git a/io/bufio.ts b/io/bufio.ts
new file mode 100644
index 000000000..0dd2b94b4
--- /dev/null
+++ b/io/bufio.ts
@@ -0,0 +1,464 @@
+// Based on https://github.com/golang/go/blob/891682/src/bufio/bufio.go
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+import { Reader, ReadResult, Writer } from "deno";
+import { assert, charCode, copyBytes } from "./util.ts";
+
+const DEFAULT_BUF_SIZE = 4096;
+const MIN_BUF_SIZE = 16;
+const MAX_CONSECUTIVE_EMPTY_READS = 100;
+const CR = charCode("\r");
+const LF = charCode("\n");
+
+export type BufState =
+  | null
+  | "EOF"
+  | "BufferFull"
+  | "ShortWrite"
+  | "NoProgress"
+  | Error;
+
+/** BufReader implements buffering for a Reader object. */
+export class BufReader implements Reader {
+  private buf: Uint8Array;
+  private rd: Reader; // Reader provided by caller.
+  private r = 0; // buf read position.
+  private w = 0; // buf write position.
+  private lastByte: number;
+  private lastCharSize: number;
+  private err: BufState;
+
+  constructor(rd: Reader, size = DEFAULT_BUF_SIZE) {
+    if (size < MIN_BUF_SIZE) {
+      size = MIN_BUF_SIZE;
+    }
+    this._reset(new Uint8Array(size), rd);
+  }
+
+  /** Returns the size of the underlying buffer in bytes. */
+  size(): number {
+    return this.buf.byteLength;
+  }
+
+  buffered(): number {
+    return this.w - this.r;
+  }
+
+  private _readErr(): BufState {
+    const err = this.err;
+    this.err = null;
+    return err;
+  }
+
+  // Reads a new chunk into the buffer.
+  private async _fill(): Promise<void> {
+    // Slide existing data to beginning.
+    if (this.r > 0) {
+      this.buf.copyWithin(0, this.r, this.w);
+      this.w -= this.r;
+      this.r = 0;
+    }
+
+    if (this.w >= this.buf.byteLength) {
+      throw Error("bufio: tried to fill full buffer");
+    }
+
+    // Read new data: try a limited number of times.
+    for (let i = MAX_CONSECUTIVE_EMPTY_READS; i > 0; i--) {
+      let rr: ReadResult;
+      try {
+        rr = await this.rd.read(this.buf.subarray(this.w));
+      } catch (e) {
+        this.err = e;
+        return;
+      }
+      assert(rr.nread >= 0, "negative read");
+      this.w += rr.nread;
+      if (rr.eof) {
+        this.err = "EOF";
+        return;
+      }
+      if (rr.nread > 0) {
+        return;
+      }
+    }
+    this.err = "NoProgress";
+  }
+
+  /** Discards any buffered data, resets all state, and switches
+   * the buffered reader to read from r.
+   */
+  reset(r: Reader): void {
+    this._reset(this.buf, r);
+  }
+
+  private _reset(buf: Uint8Array, rd: Reader): void {
+    this.buf = buf;
+    this.rd = rd;
+    this.lastByte = -1;
+    // this.lastRuneSize = -1;
+  }
+
+  /** reads data into p.
+   * It returns the number of bytes read into p.
+   * The bytes are taken from at most one Read on the underlying Reader,
+   * hence n may be less than len(p).
+   * At EOF, the count will be zero and err will be io.EOF.
+   * To read exactly len(p) bytes, use io.ReadFull(b, p).
+   */
+  async read(p: Uint8Array): Promise<ReadResult> {
+    let rr: ReadResult = { nread: p.byteLength, eof: false };
+    if (rr.nread === 0) {
+      if (this.err) {
+        throw this._readErr();
+      }
+      return rr;
+    }
+
+    if (this.r === this.w) {
+      if (this.err) {
+        throw this._readErr();
+      }
+      if (p.byteLength >= this.buf.byteLength) {
+        // Large read, empty buffer.
+        // Read directly into p to avoid copy.
+        rr = await this.rd.read(p);
+        assert(rr.nread >= 0, "negative read");
+        if (rr.nread > 0) {
+          this.lastByte = p[rr.nread - 1];
+          // this.lastRuneSize = -1;
+        }
+        if (this.err) {
+          throw this._readErr();
+        }
+        return rr;
+      }
+      // One read.
+      // Do not use this.fill, which will loop.
+      this.r = 0;
+      this.w = 0;
+      try {
+        rr = await this.rd.read(this.buf);
+      } catch (e) {
+        this.err = e;
+      }
+      assert(rr.nread >= 0, "negative read");
+      if (rr.nread === 0) {
+        if (this.err) {
+          throw this._readErr();
+        }
+        return rr;
+      }
+      this.w += rr.nread;
+    }
+
+    // copy as much as we can
+    rr.nread = copyBytes(p as Uint8Array, this.buf.subarray(this.r, this.w), 0);
+    this.r += rr.nread;
+    this.lastByte = this.buf[this.r - 1];
+    // this.lastRuneSize = -1;
+    return rr;
+  }
+
+  /** reads exactly len(p) bytes into p.
+   * Ported from https://golang.org/pkg/io/#ReadFull
+   * It returns the number of bytes copied and an error if fewer bytes were read.
+   * The error is EOF only if no bytes were read.
+   * If an EOF happens after reading some but not all the bytes,
+   * readFull returns ErrUnexpectedEOF. ("EOF" for current impl)
+   * On return, n == len(p) if and only if err == nil.
+   * If r returns an error having read at least len(buf) bytes,
+   * the error is dropped.
+   */
+  async readFull(p: Uint8Array): Promise<[number, BufState]> {
+    let rr = await this.read(p);
+    let nread = rr.nread;
+    if (rr.eof) {
+      return [nread, nread < p.length ? "EOF" : null];
+    }
+    while (!rr.eof && nread < p.length) {
+      rr = await this.read(p.subarray(nread));
+      nread += rr.nread;
+    }
+    return [nread, nread < p.length ? "EOF" : null];
+  }
+
+  /** Returns the next byte [0, 255] or -1 if EOF. */
+  async readByte(): Promise<number> {
+    while (this.r === this.w) {
+      await this._fill(); // buffer is empty.
+      if (this.err == "EOF") {
+        return -1;
+      }
+      if (this.err != null) {
+        throw this._readErr();
+      }
+    }
+    const c = this.buf[this.r];
+    this.r++;
+    this.lastByte = c;
+    return c;
+  }
+
+  /** readString() reads until the first occurrence of delim in the input,
+   * returning a string containing the data up to and including the delimiter.
+   * If ReadString encounters an error before finding a delimiter,
+   * it returns the data read before the error and the error itself (often io.EOF).
+   * ReadString returns err != nil if and only if the returned data does not end in
+   * delim.
+   * For simple uses, a Scanner may be more convenient.
+   */
+  async readString(delim: string): Promise<string> {
+    throw new Error("Not implemented");
+  }
+
+  /** readLine() is a low-level line-reading primitive. Most callers should use
+   * readBytes('\n') or readString('\n') instead or use a Scanner.
+   *
+   * readLine tries to return a single line, not including the end-of-line bytes.
+   * If the line was too long for the buffer then isPrefix is set and the
+   * beginning of the line is returned. The rest of the line will be returned
+   * from future calls. isPrefix will be false when returning the last fragment
+   * of the line. The returned buffer is only valid until the next call to
+   * ReadLine. ReadLine either returns a non-nil line or it returns an error,
+   * never both.
+   *
+   * The text returned from ReadLine does not include the line end ("\r\n" or "\n").
+   * No indication or error is given if the input ends without a final line end.
+   * Calling UnreadByte after ReadLine will always unread the last byte read
+   * (possibly a character belonging to the line end) even if that byte is not
+   * part of the line returned by ReadLine.
+   */
+  async readLine(): Promise<[Uint8Array, boolean, BufState]> {
+    let [line, err] = await this.readSlice(LF);
+
+    if (err === "BufferFull") {
+      // Handle the case where "\r\n" straddles the buffer.
+      if (line.byteLength > 0 && line[line.byteLength - 1] === CR) {
+        // Put the '\r' back on buf and drop it from line.
+        // Let the next call to ReadLine check for "\r\n".
+        assert(this.r > 0, "bufio: tried to rewind past start of buffer");
+        this.r--;
+        line = line.subarray(0, line.byteLength - 1);
+      }
+      return [line, true, null];
+    }
+
+    if (line.byteLength === 0) {
+      return [line, false, err];
+    }
+    err = null;
+
+    if (line[line.byteLength - 1] == LF) {
+      let drop = 1;
+      if (line.byteLength > 1 && line[line.byteLength - 2] === CR) {
+        drop = 2;
+      }
+      line = line.subarray(0, line.byteLength - drop);
+    }
+    return [line, false, err];
+  }
+
+  /** readSlice() reads until the first occurrence of delim in the input,
+   * returning a slice pointing at the bytes in the buffer. The bytes stop
+   * being valid at the next read. If readSlice() encounters an error before
+   * finding a delimiter, it returns all the data in the buffer and the error
+   * itself (often io.EOF).  readSlice() fails with error ErrBufferFull if the
+   * buffer fills without a delim. Because the data returned from readSlice()
+   * will be overwritten by the next I/O operation, most clients should use
+   * readBytes() or readString() instead. readSlice() returns err != nil if and
+   * only if line does not end in delim.
+   */
+  async readSlice(delim: number): Promise<[Uint8Array, BufState]> {
+    let s = 0; // search start index
+    let line: Uint8Array;
+    let err: BufState;
+    while (true) {
+      // Search buffer.
+      let i = this.buf.subarray(this.r + s, this.w).indexOf(delim);
+      if (i >= 0) {
+        i += s;
+        line = this.buf.subarray(this.r, this.r + i + 1);
+        this.r += i + 1;
+        break;
+      }
+
+      // Pending error?
+      if (this.err) {
+        line = this.buf.subarray(this.r, this.w);
+        this.r = this.w;
+        err = this._readErr();
+        break;
+      }
+
+      // Buffer full?
+      if (this.buffered() >= this.buf.byteLength) {
+        this.r = this.w;
+        line = this.buf;
+        err = "BufferFull";
+        break;
+      }
+
+      s = this.w - this.r; // do not rescan area we scanned before
+
+      await this._fill(); // buffer is not full
+    }
+
+    // Handle last byte, if any.
+    let i = line.byteLength - 1;
+    if (i >= 0) {
+      this.lastByte = line[i];
+      // this.lastRuneSize = -1
+    }
+
+    return [line, err];
+  }
+
+  /** Peek returns the next n bytes without advancing the reader. The bytes stop
+   * being valid at the next read call. If Peek returns fewer than n bytes, it
+   * also returns an error explaining why the read is short. The error is
+   * ErrBufferFull if n is larger than b's buffer size.
+   */
+  async peek(n: number): Promise<[Uint8Array, BufState]> {
+    if (n < 0) {
+      throw Error("negative count");
+    }
+
+    while (
+      this.w - this.r < n &&
+      this.w - this.r < this.buf.byteLength &&
+      this.err == null
+    ) {
+      await this._fill(); // this.w - this.r < len(this.buf) => buffer is not full
+    }
+
+    if (n > this.buf.byteLength) {
+      return [this.buf.subarray(this.r, this.w), "BufferFull"];
+    }
+
+    // 0 <= n <= len(this.buf)
+    let err: BufState;
+    let avail = this.w - this.r;
+    if (avail < n) {
+      // not enough data in buffer
+      n = avail;
+      err = this._readErr();
+      if (!err) {
+        err = "BufferFull";
+      }
+    }
+    return [this.buf.subarray(this.r, this.r + n), err];
+  }
+}
+
+/** BufWriter implements buffering for an deno.Writer object.
+ * If an error occurs writing to a Writer, no more data will be
+ * accepted and all subsequent writes, and flush(), will return the error.
+ * After all data has been written, the client should call the
+ * flush() method to guarantee all data has been forwarded to
+ * the underlying deno.Writer.
+ */
+export class BufWriter implements Writer {
+  buf: Uint8Array;
+  n: number = 0;
+  err: null | BufState = 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<BufState> {
+    if (this.err != null) {
+      return this.err;
+    }
+    if (this.n == 0) {
+      return null;
+    }
+
+    let n: number;
+    let err: BufState = null;
+    try {
+      n = await this.wr.write(this.buf.subarray(0, this.n));
+    } catch (e) {
+      err = e;
+    }
+
+    if (n < this.n && err == null) {
+      err = "ShortWrite";
+    }
+
+    if (err != null) {
+      if (n > 0 && n < this.n) {
+        this.buf.copyWithin(0, n, this.n);
+      }
+      this.n -= n;
+      this.err = err;
+      return err;
+    }
+    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;
+        await 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/io/bufio_test.ts b/io/bufio_test.ts
new file mode 100644
index 000000000..fa8f4b73b
--- /dev/null
+++ b/io/bufio_test.ts
@@ -0,0 +1,341 @@
+// Based on https://github.com/golang/go/blob/891682/src/bufio/bufio_test.go
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+import { Buffer, Reader, ReadResult } from "deno";
+import { test, assert, assertEqual } from "../testing/mod.ts";
+import { BufReader, BufState, BufWriter } from "./bufio.ts";
+import * as iotest from "./iotest.ts";
+import { charCode, copyBytes, stringsReader } from "./util.ts";
+
+const encoder = new TextEncoder();
+
+async function readBytes(buf: BufReader): Promise<string> {
+  const b = new Uint8Array(1000);
+  let nb = 0;
+  while (true) {
+    let c = await buf.readByte();
+    if (c < 0) {
+      break; // EOF
+    }
+    b[nb] = c;
+    nb++;
+  }
+  const decoder = new TextDecoder();
+  return decoder.decode(b.subarray(0, nb));
+}
+
+test(async function bufioReaderSimple() {
+  const data = "hello world";
+  const b = new BufReader(stringsReader(data));
+  const s = await readBytes(b);
+  assertEqual(s, data);
+});
+
+type ReadMaker = { name: string; fn: (r: Reader) => Reader };
+
+const readMakers: ReadMaker[] = [
+  { name: "full", fn: r => r },
+  { name: "byte", fn: r => new iotest.OneByteReader(r) },
+  { name: "half", fn: r => new iotest.HalfReader(r) }
+  // TODO { name: "data+err", r => new iotest.DataErrReader(r) },
+  // { name: "timeout", fn: r => new iotest.TimeoutReader(r) },
+];
+
+function readLines(b: BufReader): string {
+  let s = "";
+  while (true) {
+    let s1 = b.readString("\n");
+    if (s1 == null) {
+      break; // EOF
+    }
+    s += s1;
+  }
+  return s;
+}
+
+// Call read to accumulate the text of a file
+async function reads(buf: BufReader, m: number): Promise<string> {
+  const b = new Uint8Array(1000);
+  let nb = 0;
+  while (true) {
+    const { nread, eof } = await buf.read(b.subarray(nb, nb + m));
+    nb += nread;
+    if (eof) {
+      break;
+    }
+  }
+  const decoder = new TextDecoder();
+  return decoder.decode(b.subarray(0, nb));
+}
+
+type NamedBufReader = { name: string; fn: (r: BufReader) => Promise<string> };
+
+const bufreaders: NamedBufReader[] = [
+  { name: "1", fn: (b: BufReader) => reads(b, 1) },
+  { name: "2", fn: (b: BufReader) => reads(b, 2) },
+  { name: "3", fn: (b: BufReader) => reads(b, 3) },
+  { name: "4", fn: (b: BufReader) => reads(b, 4) },
+  { name: "5", fn: (b: BufReader) => reads(b, 5) },
+  { name: "7", fn: (b: BufReader) => reads(b, 7) },
+  { name: "bytes", fn: readBytes }
+  // { name: "lines", fn: readLines },
+];
+
+const MIN_READ_BUFFER_SIZE = 16;
+const bufsizes: number[] = [
+  0,
+  MIN_READ_BUFFER_SIZE,
+  23,
+  32,
+  46,
+  64,
+  93,
+  128,
+  1024,
+  4096
+];
+
+test(async function bufioBufReader() {
+  const texts = new Array<string>(31);
+  let str = "";
+  let all = "";
+  for (let i = 0; i < texts.length - 1; i++) {
+    texts[i] = str + "\n";
+    all += texts[i];
+    str += String.fromCharCode((i % 26) + 97);
+  }
+  texts[texts.length - 1] = all;
+
+  for (let text of texts) {
+    for (let readmaker of readMakers) {
+      for (let bufreader of bufreaders) {
+        for (let bufsize of bufsizes) {
+          const read = readmaker.fn(stringsReader(text));
+          const buf = new BufReader(read, bufsize);
+          const s = await bufreader.fn(buf);
+          const debugStr =
+            `reader=${readmaker.name} ` +
+            `fn=${bufreader.name} bufsize=${bufsize} want=${text} got=${s}`;
+          assertEqual(s, text, debugStr);
+        }
+      }
+    }
+  }
+});
+
+test(async function bufioBufferFull() {
+  const longString =
+    "And now, hello, world! It is the time for all good men to come to the aid of their party";
+  const buf = new BufReader(stringsReader(longString), MIN_READ_BUFFER_SIZE);
+  let [line, err] = await buf.readSlice(charCode("!"));
+
+  const decoder = new TextDecoder();
+  let actual = decoder.decode(line);
+  assertEqual(err, "BufferFull");
+  assertEqual(actual, "And now, hello, ");
+
+  [line, err] = await buf.readSlice(charCode("!"));
+  actual = decoder.decode(line);
+  assertEqual(actual, "world!");
+  assert(err == null);
+});
+
+const testInput = encoder.encode(
+  "012\n345\n678\n9ab\ncde\nfgh\nijk\nlmn\nopq\nrst\nuvw\nxy"
+);
+const testInputrn = encoder.encode(
+  "012\r\n345\r\n678\r\n9ab\r\ncde\r\nfgh\r\nijk\r\nlmn\r\nopq\r\nrst\r\nuvw\r\nxy\r\n\n\r\n"
+);
+const testOutput = encoder.encode("0123456789abcdefghijklmnopqrstuvwxy");
+
+// TestReader wraps a Uint8Array and returns reads of a specific length.
+class TestReader implements Reader {
+  constructor(private data: Uint8Array, private stride: number) {}
+
+  async read(buf: Uint8Array): Promise<ReadResult> {
+    let nread = this.stride;
+    if (nread > this.data.byteLength) {
+      nread = this.data.byteLength;
+    }
+    if (nread > buf.byteLength) {
+      nread = buf.byteLength;
+    }
+    copyBytes(buf as Uint8Array, this.data);
+    this.data = this.data.subarray(nread);
+    let eof = false;
+    if (this.data.byteLength == 0) {
+      eof = true;
+    }
+    return { nread, eof };
+  }
+}
+
+async function testReadLine(input: Uint8Array): Promise<void> {
+  for (let stride = 1; stride < 2; stride++) {
+    let done = 0;
+    let reader = new TestReader(input, stride);
+    let l = new BufReader(reader, input.byteLength + 1);
+    while (true) {
+      let [line, isPrefix, err] = await l.readLine();
+      if (line.byteLength > 0 && err != null) {
+        throw Error("readLine returned both data and error");
+      }
+      assertEqual(isPrefix, false);
+      if (err == "EOF") {
+        break;
+      }
+      let want = testOutput.subarray(done, done + line.byteLength);
+      assertEqual(
+        line,
+        want,
+        `Bad line at stride ${stride}: want: ${want} got: ${line}`
+      );
+      done += line.byteLength;
+    }
+    assertEqual(
+      done,
+      testOutput.byteLength,
+      `readLine didn't return everything: got: ${done}, ` +
+        `want: ${testOutput} (stride: ${stride})`
+    );
+  }
+}
+
+test(async function bufioReadLine() {
+  await testReadLine(testInput);
+  await testReadLine(testInputrn);
+});
+
+test(async function bufioPeek() {
+  const decoder = new TextDecoder();
+  let p = new Uint8Array(10);
+  // string is 16 (minReadBufferSize) long.
+  let buf = new BufReader(
+    stringsReader("abcdefghijklmnop"),
+    MIN_READ_BUFFER_SIZE
+  );
+
+  let [actual, err] = await buf.peek(1);
+  assertEqual(decoder.decode(actual), "a");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(4);
+  assertEqual(decoder.decode(actual), "abcd");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(32);
+  assertEqual(decoder.decode(actual), "abcdefghijklmnop");
+  assertEqual(err, "BufferFull");
+
+  await buf.read(p.subarray(0, 3));
+  assertEqual(decoder.decode(p.subarray(0, 3)), "abc");
+
+  [actual, err] = await buf.peek(1);
+  assertEqual(decoder.decode(actual), "d");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(1);
+  assertEqual(decoder.decode(actual), "d");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(1);
+  assertEqual(decoder.decode(actual), "d");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(2);
+  assertEqual(decoder.decode(actual), "de");
+  assert(err == null);
+
+  let { eof } = await buf.read(p.subarray(0, 3));
+  assertEqual(decoder.decode(p.subarray(0, 3)), "def");
+  assert(!eof);
+  assert(err == null);
+
+  [actual, err] = await buf.peek(4);
+  assertEqual(decoder.decode(actual), "ghij");
+  assert(err == null);
+
+  await buf.read(p);
+  assertEqual(decoder.decode(p), "ghijklmnop");
+
+  [actual, err] = await buf.peek(0);
+  assertEqual(decoder.decode(actual), "");
+  assert(err == null);
+
+  [actual, err] = await buf.peek(1);
+  assertEqual(decoder.decode(actual), "");
+  assert(err == "EOF");
+  /* TODO
+	// Test for issue 3022, not exposing a reader's error on a successful Peek.
+	buf = NewReaderSize(dataAndEOFReader("abcd"), 32)
+	if s, err := buf.Peek(2); string(s) != "ab" || err != nil {
+		t.Errorf(`Peek(2) on "abcd", EOF = %q, %v; want "ab", nil`, string(s), err)
+	}
+	if s, err := buf.Peek(4); string(s) != "abcd" || err != nil {
+		t.Errorf(`Peek(4) on "abcd", EOF = %q, %v; want "abcd", nil`, string(s), err)
+	}
+	if n, err := buf.Read(p[0:5]); string(p[0:n]) != "abcd" || err != nil {
+		t.Fatalf("Read after peek = %q, %v; want abcd, EOF", p[0:n], err)
+	}
+	if n, err := buf.Read(p[0:1]); string(p[0:n]) != "" || err != io.EOF {
+		t.Fatalf(`second Read after peek = %q, %v; want "", EOF`, p[0:n], err)
+	}
+  */
+});
+
+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]);
+      }
+    }
+  }
+});
+
+test(async function bufReaderReadFull() {
+  const enc = new TextEncoder();
+  const dec = new TextDecoder();
+  const text = "Hello World";
+  const data = new Buffer(enc.encode(text));
+  const bufr = new BufReader(data, 3);
+  {
+    const buf = new Uint8Array(6);
+    const [nread, err] = await bufr.readFull(buf);
+    assertEqual(nread, 6);
+    assert(!err);
+    assertEqual(dec.decode(buf), "Hello ");
+  }
+  {
+    const buf = new Uint8Array(6);
+    const [nread, err] = await bufr.readFull(buf);
+    assertEqual(nread, 5);
+    assertEqual(err, "EOF");
+    assertEqual(dec.decode(buf.subarray(0, 5)), "World");
+  }
+});
diff --git a/io/iotest.ts b/io/iotest.ts
new file mode 100644
index 000000000..e3a42f58a
--- /dev/null
+++ b/io/iotest.ts
@@ -0,0 +1,61 @@
+// Ported to Deno from
+// Copyright 2009 The Go Authors. All rights reserved.
+// 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";
+
+/** OneByteReader returns a Reader that implements
+ * each non-empty Read by reading one byte from r.
+ */
+export class OneByteReader implements Reader {
+  constructor(readonly r: Reader) {}
+
+  async read(p: Uint8Array): Promise<ReadResult> {
+    if (p.byteLength === 0) {
+      return { nread: 0, eof: false };
+    }
+    if (!(p instanceof Uint8Array)) {
+      throw Error("expected Uint8Array");
+    }
+    return this.r.read(p.subarray(0, 1));
+  }
+}
+
+/** HalfReader returns a Reader that implements Read
+ * by reading half as many requested bytes from r.
+ */
+export class HalfReader implements Reader {
+  constructor(readonly r: Reader) {}
+
+  async read(p: Uint8Array): Promise<ReadResult> {
+    if (!(p instanceof Uint8Array)) {
+      throw Error("expected Uint8Array");
+    }
+    const half = Math.floor((p.byteLength + 1) / 2);
+    return this.r.read(p.subarray(0, half));
+  }
+}
+
+export class ErrTimeout extends Error {
+  constructor() {
+    super("timeout");
+    this.name = "ErrTimeout";
+  }
+}
+
+/** TimeoutReader returns ErrTimeout on the second read
+ * with no data. Subsequent calls to read succeed.
+ */
+export class TimeoutReader implements Reader {
+  count = 0;
+  constructor(readonly r: Reader) {}
+
+  async read(p: Uint8Array): Promise<ReadResult> {
+    this.count++;
+    if (this.count === 2) {
+      throw new ErrTimeout();
+    }
+    return this.r.read(p);
+  }
+}
diff --git a/io/ioutil.ts b/io/ioutil.ts
new file mode 100644
index 000000000..68d6e5190
--- /dev/null
+++ b/io/ioutil.ts
@@ -0,0 +1,36 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { BufReader } from "./bufio.ts";
+
+/* Read big endian 16bit short from BufReader */
+export async function readShort(buf: BufReader): Promise<number> {
+  const [high, low] = [await buf.readByte(), await buf.readByte()];
+  return (high << 8) | low;
+}
+
+/* Read big endian 32bit integer from BufReader */
+export async function readInt(buf: BufReader): Promise<number> {
+  const [high, low] = [await readShort(buf), await readShort(buf)];
+  return (high << 16) | low;
+}
+
+const BIT32 = 0xffffffff;
+/* Read big endian 64bit long from BufReader */
+export async function readLong(buf: BufReader): Promise<number> {
+  const [high, low] = [await readInt(buf), await readInt(buf)];
+  // ECMAScript doesn't support 64bit bit ops.
+  return high ? high * (BIT32 + 1) + low : low;
+}
+
+/* Slice number into 64bit big endian byte array */
+export function sliceLongToBytes(d: number, dest = new Array(8)): number[] {
+  let mask = 0xff;
+  let low = (d << 32) >>> 32;
+  let high = (d - low) / (BIT32 + 1);
+  let shift = 24;
+  for (let i = 0; i < 4; i++) {
+    dest[i] = (high >>> shift) & mask;
+    dest[i + 4] = (low >>> shift) & mask;
+    shift -= 8;
+  }
+  return dest;
+}
diff --git a/io/ioutil_test.ts b/io/ioutil_test.ts
new file mode 100644
index 000000000..422901e4a
--- /dev/null
+++ b/io/ioutil_test.ts
@@ -0,0 +1,62 @@
+import { Reader, ReadResult } from "deno";
+import { assertEqual, test } from "../testing/mod.ts";
+import { readInt, readLong, readShort, sliceLongToBytes } from "./ioutil.ts";
+import { BufReader } from "./bufio.ts";
+
+class BinaryReader implements Reader {
+  index = 0;
+
+  constructor(private bytes: Uint8Array = new Uint8Array(0)) {}
+
+  async read(p: Uint8Array): Promise<ReadResult> {
+    p.set(this.bytes.subarray(this.index, p.byteLength));
+    this.index += p.byteLength;
+    return { nread: p.byteLength, eof: false };
+  }
+}
+
+test(async function testReadShort() {
+  const r = new BinaryReader(new Uint8Array([0x12, 0x34]));
+  const short = await readShort(new BufReader(r));
+  assertEqual(short, 0x1234);
+});
+
+test(async function testReadInt() {
+  const r = new BinaryReader(new Uint8Array([0x12, 0x34, 0x56, 0x78]));
+  const int = await readInt(new BufReader(r));
+  assertEqual(int, 0x12345678);
+});
+
+test(async function testReadLong() {
+  const r = new BinaryReader(
+    new Uint8Array([0x12, 0x34, 0x56, 0x78, 0x12, 0x34, 0x56, 0x78])
+  );
+  const long = await readLong(new BufReader(r));
+  assertEqual(long, 0x1234567812345678);
+});
+
+test(async function testReadLong2() {
+  const r = new BinaryReader(
+    new Uint8Array([0, 0, 0, 0, 0x12, 0x34, 0x56, 0x78])
+  );
+  const long = await readLong(new BufReader(r));
+  assertEqual(long, 0x12345678);
+});
+
+test(async function testSliceLongToBytes() {
+  const arr = sliceLongToBytes(0x1234567890abcdef);
+  const actual = readLong(new BufReader(new BinaryReader(new Uint8Array(arr))));
+  const expected = readLong(
+    new BufReader(
+      new BinaryReader(
+        new Uint8Array([0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef])
+      )
+    )
+  );
+  assertEqual(actual, expected);
+});
+
+test(async function testSliceLongToBytes2() {
+  const arr = sliceLongToBytes(0x12345678);
+  assertEqual(arr, [0, 0, 0, 0, 0x12, 0x34, 0x56, 0x78]);
+});
diff --git a/io/util.ts b/io/util.ts
new file mode 100644
index 000000000..811940b4d
--- /dev/null
+++ b/io/util.ts
@@ -0,0 +1,29 @@
+import { Buffer, Reader } from "deno";
+
+export function assert(cond: boolean, msg = "assert") {
+  if (!cond) {
+    throw Error(msg);
+  }
+}
+
+// `off` is the offset into `dst` where it will at which to begin writing values
+// from `src`.
+// Returns the number of bytes copied.
+export function copyBytes(dst: Uint8Array, src: Uint8Array, off = 0): number {
+  const r = dst.byteLength - off;
+  if (src.byteLength > r) {
+    src = src.subarray(0, r);
+  }
+  dst.set(src, off);
+  return src.byteLength;
+}
+
+export function charCode(s: string): number {
+  return s.charCodeAt(0);
+}
+
+const encoder = new TextEncoder();
+export function stringsReader(s: string): Reader {
+  const ui8 = encoder.encode(s);
+  return new Buffer(ui8.buffer as ArrayBuffer);
+}