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perf: use a Map for tracking chunks #313

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Merged
antfu merged 1 commit into from
Jul 23, 2026
+31 −31
Merged

perf: use a Map for tracking chunks #313

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62 changes: 31 additions & 31 deletions src/MagicString.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -66,9 +66,9 @@ export default class MagicString {
/** @internal */
declare lastSearchedChunk: Chunk
/** @internal */
declare byStart: Record<number, Chunk>
declare byStart: Map<number, Chunk>
/** @internal */
declare byEnd: Record<number, Chunk>
declare byEnd: Map<number, Chunk>
/** @internal */
declare sourcemapLocations: BitSet
/** @internal */
Expand Down Expand Up @@ -103,8 +103,8 @@ export default class MagicString {
Object.defineProperty(this, 'stats', { value: new Stats() })
}

this.byStart[0] = chunk
this.byEnd[string.length] = chunk
this.byStart = new Map<number, Chunk>([[0, chunk]])
this.byEnd = new Map<number, Chunk>([[string.length, chunk]])
}

/**
Expand Down Expand Up @@ -141,7 +141,7 @@ export default class MagicString {

this._split(index)

const chunk = this.byEnd[index]
const chunk = this.byEnd.get(index)

if (chunk) {
chunk.appendLeft(content)
Expand Down Expand Up @@ -171,7 +171,7 @@ export default class MagicString {

this._split(index)

const chunk = this.byStart[index]
const chunk = this.byStart.get(index)

if (chunk) {
chunk.appendRight(content)
Expand All @@ -195,8 +195,8 @@ export default class MagicString {
let clonedChunk = (cloned.firstChunk = cloned.lastSearchedChunk = originalChunk.clone())

while (originalChunk) {
cloned.byStart[clonedChunk.start] = clonedChunk
cloned.byEnd[clonedChunk.end] = clonedChunk
cloned.byStart.set(clonedChunk.start, clonedChunk)
cloned.byEnd.set(clonedChunk.end, clonedChunk)

const nextOriginalChunk = originalChunk.next
const nextClonedChunk = nextOriginalChunk && nextOriginalChunk.clone()
Expand Down Expand Up @@ -497,13 +497,13 @@ export default class MagicString {
this._split(end)
this._split(index)

const first = this.byStart[start]
const last = this.byEnd[end]
const first = this.byStart.get(start)
const last = this.byEnd.get(end)

const oldLeft = first.previous
const oldRight = last.next

const newRight = this.byStart[index]
const newRight = this.byStart.get(index)
if (!newRight && last === this.lastChunk)
return this
const newLeft = newRight ? newRight.previous : this.lastChunk
Expand Down Expand Up @@ -617,13 +617,13 @@ export default class MagicString {
})
}

const first = this.byStart[start]
const last = this.byEnd[end]
const first = this.byStart.get(start)
const last = this.byEnd.get(end)

if (first) {
let chunk = first
while (chunk !== last) {
if (chunk.next !== this.byStart[chunk.end]) {
if (chunk.next !== this.byStart.get(chunk.end)) {
throw new Error('Cannot overwrite across a split point')
}
chunk = chunk.next
Expand Down Expand Up @@ -671,7 +671,7 @@ export default class MagicString {

this._split(index)

const chunk = this.byEnd[index]
const chunk = this.byEnd.get(index)

if (chunk) {
chunk.prependLeft(content)
Expand Down Expand Up @@ -699,7 +699,7 @@ export default class MagicString {

this._split(index)

const chunk = this.byStart[index]
const chunk = this.byStart.get(index)

if (chunk) {
chunk.prependRight(content)
Expand Down Expand Up @@ -740,14 +740,14 @@ export default class MagicString {
this._split(start)
this._split(end)

let chunk = this.byStart[start]
let chunk = this.byStart.get(start)

while (chunk) {
chunk.intro = ''
chunk.outro = ''
chunk.edit('')

chunk = end > chunk.end ? this.byStart[chunk.end] : null
chunk = end > chunk.end ? this.byStart.get(chunk.end) : null
}

if (DEBUG)
Expand Down Expand Up @@ -781,12 +781,12 @@ export default class MagicString {
this._split(start)
this._split(end)

let chunk = this.byStart[start]
let chunk = this.byStart.get(start)

while (chunk) {
chunk.reset()

chunk = end > chunk.end ? this.byStart[chunk.end] : null
chunk = end > chunk.end ? this.byStart.get(chunk.end) : null
}

if (DEBUG)
Expand Down Expand Up @@ -919,7 +919,7 @@ export default class MagicString {

/** @internal */
_split(index: number): boolean | void {
if (this.byStart[index] || this.byEnd[index])
if (this.byStart.get(index) || this.byEnd.get(index))
return

if (DEBUG)
Expand All @@ -933,7 +933,7 @@ export default class MagicString {
if (chunk.contains(index))
return this._splitChunk(chunk, index)

chunk = searchForward ? this.byStart[chunk.end] : this.byEnd[chunk.start]
chunk = searchForward ? this.byStart.get(chunk.end) : this.byEnd.get(chunk.start)

// Prevent infinite loop (e.g. via empty chunks, where start === end)
if (chunk === previousChunk)
Expand All @@ -955,9 +955,9 @@ export default class MagicString {

const newChunk = chunk.split(index)

this.byEnd[index] = chunk
this.byStart[index] = newChunk
this.byEnd[newChunk.end] = newChunk
this.byEnd.set(index, chunk)
this.byStart.set(index, newChunk)
this.byEnd.set(newChunk.end, newChunk)

if (chunk === this.lastChunk)
this.lastChunk = newChunk
Expand Down Expand Up @@ -1045,9 +1045,9 @@ export default class MagicString {
this.lastChunk = chunk.next
}

this.byEnd[chunk.end] = chunk
this.byStart[chunk.next.start] = chunk.next
this.byEnd[chunk.next.end] = chunk.next
this.byEnd.set(chunk.end, chunk)
this.byStart.set(chunk.next.start, chunk.next)
this.byEnd.set(chunk.next.end, chunk.next)
}

if (aborted)
Expand Down Expand Up @@ -1085,9 +1085,9 @@ export default class MagicString {
if (chunk === this.lastChunk)
this.lastChunk = chunk.next

this.byEnd[chunk.end] = chunk
this.byStart[chunk.next.start] = chunk.next
this.byEnd[chunk.next.end] = chunk.next
this.byEnd.set(chunk.end, chunk)
this.byStart.set(chunk.next.start, chunk.next)
this.byEnd.set(chunk.next.end, chunk.next)
}

if (aborted)
Expand Down
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