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lib: ensure no holey array in fixed_queue #54537

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Merged
nodejs-github-bot merged 2 commits into from
Sep 2, 2024
Merged

lib: ensure no holey array in fixed_queue #54537

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5f3a09d
lib: ensure no holey array in fixed_queue
jazelly Aug 25, 2024
348536f
add a test
jazelly Aug 27, 2024
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29 changes: 15 additions & 14 deletions lib/internal/fixed_queue.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

const {
Array,
ArrayPrototypeFill,
} = primordials;

// Currently optimal queue size, tested on V8 6.0 - 6.6. Must be power of two.
Expand All @@ -17,18 +18,18 @@ const kMask = kSize - 1;
// +-----------+ <-----\ +-----------+ <------\ +-----------+
// | [null] | \----- | next | \------- | next |
// +-----------+ +-----------+ +-----------+
// | item | <-- bottom | item | <-- bottom | [empty] |
// | item | | item | | [empty] |
// | item | | item | | [empty] |
// | item | | item | | [empty] |
// | 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 |
// | [empty] | <-- top | item | | item |
// | [empty] | | item | | item |
// | [empty] | | [empty] | <-- top top --> | [empty] |
// | undefined | <-- top | item | | item |
// | undefined | | item | | item |
// | undefined | | undefined | <-- top top --> | undefined |
// +-----------+ +-----------+ +-----------+
//
// Or, if there is only one circular buffer, it looks something
Expand All @@ -40,12 +41,12 @@ const kMask = kSize - 1;
// +-----------+ +-----------+
// | [null] | | [null] |
// +-----------+ +-----------+
// | [empty] | | item |
// | [empty] | | item |
// | item | <-- bottom top --> | [empty] |
// | item | | [empty] |
// | [empty] | <-- top bottom --> | item |
// | [empty] | | item |
// | 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
Expand All @@ -60,7 +61,7 @@ class FixedCircularBuffer {
constructor() {
this.bottom = 0;
this.top = 0;
this.list = new Array(kSize);
this.list = ArrayPrototypeFill(new Array(kSize), undefined);
this.next = null;
}

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