Merge branch 'std_modified' into merge_std3

1 files changed, 37 insertions, 0 deletions

diff --git a/std/io/writers.ts b/std/io/writers.ts
new file mode 100644
index 000000000..91d19a9d7
--- /dev/null
+++ b/std/io/writers.ts
@@ -0,0 +1,37 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+type Writer = Deno.Writer;
+import { decode, encode } from "../strings/mod.ts";
+
+/** Writer utility for buffering string chunks */
+export class StringWriter implements Writer {
+  private chunks: Uint8Array[] = [];
+  private byteLength = 0;
+  private cache: string | undefined;
+
+  constructor(private base: string = "") {
+    const c = encode(base);
+    this.chunks.push(c);
+    this.byteLength += c.byteLength;
+  }
+
+  async write(p: Uint8Array): Promise<number> {
+    this.chunks.push(p);
+    this.byteLength += p.byteLength;
+    this.cache = undefined;
+    return p.byteLength;
+  }
+
+  toString(): string {
+    if (this.cache) {
+      return this.cache;
+    }
+    const buf = new Uint8Array(this.byteLength);
+    let offs = 0;
+    for (const chunk of this.chunks) {
+      buf.set(chunk, offs);
+      offs += chunk.byteLength;
+    }
+    this.cache = decode(buf);
+    return this.cache!;
+  }
+}