1 files changed, 135 insertions, 0 deletions
diff --git a/runtime/rt/12_io.js b/runtime/rt/12_io.js
new file mode 100644
index 000000000..006d51cdd
--- /dev/null
+++ b/runtime/rt/12_io.js
@@ -0,0 +1,135 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+// Interfaces 100% copied from Go.
+// Documentation liberally lifted from them too.
+// Thank you! We love Go! <3
+
+((window) => {
+  const DEFAULT_BUFFER_SIZE = 32 * 1024;
+  const { sendSync, sendAsync } = window.__bootstrap.dispatchMinimal;
+  // Seek whence values.
+  // https://golang.org/pkg/io/#pkg-constants
+  const SeekMode = {
+    0: "Start",
+    1: "Current",
+    2: "End",
+
+    Start: 0,
+    Current: 1,
+    End: 2,
+  };
+
+  async function copy(
+    src,
+    dst,
+    options,
+  ) {
+    let n = 0;
+    const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;
+    const b = new Uint8Array(bufSize);
+    let gotEOF = false;
+    while (gotEOF === false) {
+      const result = await src.read(b);
+      if (result === null) {
+        gotEOF = true;
+      } else {
+        let nwritten = 0;
+        while (nwritten < result) {
+          nwritten += await dst.write(b.subarray(nwritten, result));
+        }
+        n += nwritten;
+      }
+    }
+    return n;
+  }
+
+  async function* iter(
+    r,
+    options,
+  ) {
+    const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;
+    const b = new Uint8Array(bufSize);
+    while (true) {
+      const result = await r.read(b);
+      if (result === null) {
+        break;
+      }
+
+      yield b.subarray(0, result);
+    }
+  }
+
+  function* iterSync(
+    r,
+    options,
+  ) {
+    const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;
+    const b = new Uint8Array(bufSize);
+    while (true) {
+      const result = r.readSync(b);
+      if (result === null) {
+        break;
+      }
+
+      yield b.subarray(0, result);
+    }
+  }
+
+  function readSync(rid, buffer) {
+    if (buffer.length === 0) {
+      return 0;
+    }
+
+    const nread = sendSync("op_read", rid, buffer);
+    if (nread < 0) {
+      throw new Error("read error");
+    }
+
+    return nread === 0 ? null : nread;
+  }
+
+  async function read(
+    rid,
+    buffer,
+  ) {
+    if (buffer.length === 0) {
+      return 0;
+    }
+
+    const nread = await sendAsync("op_read", rid, buffer);
+    if (nread < 0) {
+      throw new Error("read error");
+    }
+
+    return nread === 0 ? null : nread;
+  }
+
+  function writeSync(rid, data) {
+    const result = sendSync("op_write", rid, data);
+    if (result < 0) {
+      throw new Error("write error");
+    }
+
+    return result;
+  }
+
+  async function write(rid, data) {
+    const result = await sendAsync("op_write", rid, data);
+    if (result < 0) {
+      throw new Error("write error");
+    }
+
+    return result;
+  }
+
+  window.__bootstrap.io = {
+    iterSync,
+    iter,
+    copy,
+    SeekMode,
+    read,
+    readSync,
+    write,
+    writeSync,
+  };
+})(this);