Refactor: use TransformStream

Build/lib/text-line-transform-stream.ts

@@ -0,0 +1,75 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+// This module is browser compatible.
+// Modified by Sukka (https://skk.moe) to increase compatibility and performance with Bun.
+
+interface TextLineStreamOptions {
+  /** Allow splitting by solo \r */
+  allowCR: boolean;
+}
+
+/** Transform a stream into a stream where each chunk is divided by a newline,
+ * be it `\n` or `\r\n`. `\r` can be enabled via the `allowCR` option.
+ *
+ * ```ts
+ * import { TextLineStream } from 'https://deno.land/std@$STD_VERSION/streams/text_line_stream.ts';
+ * const res = await fetch('https://example.com');
+ * const lines = res.body!
+ *   .pipeThrough(new TextDecoderStream())
+ *   .pipeThrough(new TextLineStream());
+ * ```
+ */
+export class TextLineStream extends TransformStream<string, string> {
+  private __allowCR: boolean;
+  private __buf = '';
+
+  constructor(options?: TextLineStreamOptions) {
+    super({
+      transform: (chunk, controller) => this.handle(chunk, controller),
+      flush: (controller) => {
+        if (this.__buf.length > 0) {
+          if (
+            this.__allowCR &&
+            this.__buf[this.__buf.length - 1] === '\r'
+          ) controller.enqueue(this.__buf.slice(0, -1));
+          else controller.enqueue(this.__buf);
+        }
+      },
+    });
+    this.__allowCR = options?.allowCR ?? false;
+  }
+
+  private handle(chunk: string, controller: TransformStreamDefaultController<string>) {
+    chunk = this.__buf + chunk;
+
+    for (;;) {
+      const lfIndex = chunk.indexOf('\n');
+
+      if (this.__allowCR) {
+        const crIndex = chunk.indexOf('\r');
+
+        if (
+          crIndex !== -1 && crIndex !== (chunk.length - 1) &&
+          (lfIndex === -1 || (lfIndex - 1) > crIndex)
+        ) {
+          controller.enqueue(chunk.slice(0, crIndex));
+          chunk = chunk.slice(crIndex + 1);
+          continue;
+        }
+      }
+
+      if (lfIndex !== -1) {
+        let crOrLfIndex = lfIndex;
+        if (chunk[lfIndex - 1] === '\r') {
+          crOrLfIndex--;
+        }
+        controller.enqueue(chunk.slice(0, crOrLfIndex));
+        chunk = chunk.slice(lfIndex + 1);
+        continue;
+      }
+
+      break;
+    }
+
+    this.__buf = chunk;
+  }
+}