1 files changed, 135 insertions, 0 deletions
diff --git a/vanilla/node_modules/undici/lib/dispatcher/fixed-queue.js b/vanilla/node_modules/undici/lib/dispatcher/fixed-queue.js
new file mode 100644
index 0000000..f918849
--- /dev/null
+++ b/vanilla/node_modules/undici/lib/dispatcher/fixed-queue.js
@@ -0,0 +1,135 @@
+'use strict'
+
+// Extracted from node/lib/internal/fixed_queue.js
+
+// Currently optimal queue size, tested on V8 6.0 - 6.6. Must be power of two.
+const kSize = 2048
+const kMask = kSize - 1
+
+// The FixedQueue is implemented as a singly-linked list of fixed-size
+// circular buffers. It looks something like this:
+//
+//  head                                                       tail
+//    |                                                          |
+//    v                                                          v
+// +-----------+ <-----\       +-----------+ <------\         +-----------+
+// |  [null]   |        \----- |   next    |         \------- |   next    |
+// +-----------+               +-----------+                  +-----------+
+// |   item    | <-- bottom    |   item    | <-- bottom       | undefined |
+// |   item    |               |   item    |                  | undefined |
+// |   item    |               |   item    |                  | undefined |
+// |   item    |               |   item    |                  | undefined |
+// |   item    |               |   item    |       bottom --> |   item    |
+// |   item    |               |   item    |                  |   item    |
+// |    ...    |               |    ...    |                  |    ...    |
+// |   item    |               |   item    |                  |   item    |
+// |   item    |               |   item    |                  |   item    |
+// | undefined | <-- top       |   item    |                  |   item    |
+// | undefined |               |   item    |                  |   item    |
+// | undefined |               | undefined | <-- top  top --> | undefined |
+// +-----------+               +-----------+                  +-----------+
+//
+// Or, if there is only one circular buffer, it looks something
+// like either of these:
+//
+//  head   tail                                 head   tail
+//    |     |                                     |     |
+//    v     v                                     v     v
+// +-----------+                               +-----------+
+// |  [null]   |                               |  [null]   |
+// +-----------+                               +-----------+
+// | undefined |                               |   item    |
+// | undefined |                               |   item    |
+// |   item    | <-- bottom            top --> | undefined |
+// |   item    |                               | undefined |
+// | undefined | <-- top            bottom --> |   item    |
+// | undefined |                               |   item    |
+// +-----------+                               +-----------+
+//
+// Adding a value means moving `top` forward by one, removing means
+// moving `bottom` forward by one. After reaching the end, the queue
+// wraps around.
+//
+// When `top === bottom` the current queue is empty and when
+// `top + 1 === bottom` it's full. This wastes a single space of storage
+// but allows much quicker checks.
+
+/**
+ * @type {FixedCircularBuffer}
+ * @template T
+ */
+class FixedCircularBuffer {
+  /** @type {number} */
+  bottom = 0
+  /** @type {number} */
+  top = 0
+  /** @type {Array<T|undefined>} */
+  list = new Array(kSize).fill(undefined)
+  /** @type {T|null} */
+  next = null
+
+  /** @returns {boolean} */
+  isEmpty () {
+    return this.top === this.bottom
+  }
+
+  /** @returns {boolean} */
+  isFull () {
+    return ((this.top + 1) & kMask) === this.bottom
+  }
+
+  /**
+   * @param {T} data
+   * @returns {void}
+   */
+  push (data) {
+    this.list[this.top] = data
+    this.top = (this.top + 1) & kMask
+  }
+
+  /** @returns {T|null} */
+  shift () {
+    const nextItem = this.list[this.bottom]
+    if (nextItem === undefined) { return null }
+    this.list[this.bottom] = undefined
+    this.bottom = (this.bottom + 1) & kMask
+    return nextItem
+  }
+}
+
+/**
+ * @template T
+ */
+module.exports = class FixedQueue {
+  constructor () {
+    /** @type {FixedCircularBuffer<T>} */
+    this.head = this.tail = new FixedCircularBuffer()
+  }
+
+  /** @returns {boolean} */
+  isEmpty () {
+    return this.head.isEmpty()
+  }
+
+  /** @param {T} data */
+  push (data) {
+    if (this.head.isFull()) {
+      // Head is full: Creates a new queue, sets the old queue's `.next` to it,
+      // and sets it as the new main queue.
+      this.head = this.head.next = new FixedCircularBuffer()
+    }
+    this.head.push(data)
+  }
+
+  /** @returns {T|null} */
+  shift () {
+    const tail = this.tail
+    const next = tail.shift()
+    if (tail.isEmpty() && tail.next !== null) {
+      // If there is another queue, it forms the new tail.
+      this.tail = tail.next
+      tail.next = null
+    }
+    return next
+  }
+}