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authorBartek IwaƄczuk <biwanczuk@gmail.com>2023-02-14 17:38:45 +0100
committerGitHub <noreply@github.com>2023-02-14 17:38:45 +0100
commitd47147fb6ad229b1c039aff9d0959b6e281f4df5 (patch)
tree6e9e790f2b9bc71b5f0c9c7e64b95cae31579d58 /ext/node/polyfills/internal/fixed_queue.ts
parent1d00bbe47e2ca14e2d2151518e02b2324461a065 (diff)
feat(ext/node): embed std/node into the snapshot (#17724)
This commit moves "deno_std/node" in "ext/node" crate. The code is transpiled and snapshotted during the build process. During the first pass a minimal amount of work was done to create the snapshot, a lot of code in "ext/node" depends on presence of "Deno" global. This code will be gradually fixed in the follow up PRs to migrate it to import relevant APIs from "internal:" modules. Currently the code from snapshot is not used in any way, and all Node/npm compatibility still uses code from "https://deno.land/std/node" (or from the location specified by "DENO_NODE_COMPAT_URL"). This will also be handled in a follow up PRs. --------- Co-authored-by: crowlkats <crowlkats@toaxl.com> Co-authored-by: Divy Srivastava <dj.srivastava23@gmail.com> Co-authored-by: Yoshiya Hinosawa <stibium121@gmail.com>
Diffstat (limited to 'ext/node/polyfills/internal/fixed_queue.ts')
-rw-r--r--ext/node/polyfills/internal/fixed_queue.ts123
1 files changed, 123 insertions, 0 deletions
diff --git a/ext/node/polyfills/internal/fixed_queue.ts b/ext/node/polyfills/internal/fixed_queue.ts
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+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+// Copyright Joyent, Inc. and other Node contributors.
+
+// 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 | [empty] |
+// | item | | item | | [empty] |
+// | item | | item | | [empty] |
+// | item | | item | | [empty] |
+// | item | | item | bottom --> | item |
+// | item | | item | | item |
+// | ... | | ... | | ... |
+// | item | | item | | item |
+// | item | | item | | item |
+// | [empty] | <-- top | item | | item |
+// | [empty] | | item | | item |
+// | [empty] | | [empty] | <-- top top --> | [empty] |
+// +-----------+ +-----------+ +-----------+
+//
+// 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] |
+// +-----------+ +-----------+
+// | [empty] | | item |
+// | [empty] | | item |
+// | item | <-- bottom top --> | [empty] |
+// | item | | [empty] |
+// | [empty] | <-- top bottom --> | item |
+// | [empty] | | 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.
+
+class FixedCircularBuffer {
+ bottom: number;
+ top: number;
+ list: undefined | Array<unknown>;
+ next: FixedCircularBuffer | null;
+
+ constructor() {
+ this.bottom = 0;
+ this.top = 0;
+ this.list = new Array(kSize);
+ this.next = null;
+ }
+
+ isEmpty() {
+ return this.top === this.bottom;
+ }
+
+ isFull() {
+ return ((this.top + 1) & kMask) === this.bottom;
+ }
+
+ push(data: unknown) {
+ this.list![this.top] = data;
+ this.top = (this.top + 1) & kMask;
+ }
+
+ 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;
+ }
+}
+
+export class FixedQueue {
+ head: FixedCircularBuffer;
+ tail: FixedCircularBuffer;
+
+ constructor() {
+ this.head = this.tail = new FixedCircularBuffer();
+ }
+
+ isEmpty() {
+ return this.head.isEmpty();
+ }
+
+ push(data: unknown) {
+ 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);
+ }
+
+ 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;
+ }
+ return next;
+ }
+}