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perf: make arena 10% smaller; store 1 offset + some deltas #31

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Merged
bartveneman merged 1 commit into from
Dec 9, 2025
Merged

perf: make arena 10% smaller; store 1 offset + some deltas #31

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52 changes: 30 additions & 22 deletions src/arena.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
// CSS Data Arena - Single contiguous ArrayBuffer for all AST nodes
//
// Each node occupies 44 bytes with the following layout:
// Each node occupies 40 bytes with the following layout:
// Offset | Size | Field
// -------|------|-------------
// 0 | 1 | type
Expand All @@ -9,18 +9,18 @@
// 4 | 4 | startOffset
// 8 | 2 | length
// 10 | 2 | (padding)
// 12 | 4 | contentStart (property name / at-rule name)
// 16 | 2 | contentLength
// 18 | 2 | (padding)
// 12 | 2 | contentStartDelta (offset from startOffset, property name / at-rule name)
// 14 | 2 | contentLength
// 16 | 2 | valueStartDelta (offset from startOffset, declaration value / at-rule prelude)
// 18 | 2 | valueLength
// 20 | 4 | firstChild
// 24 | 4 | lastChild
// 28 | 4 | nextSibling
// 32 | 4 | startLine
// 36 | 4 | valueStart (declaration value / at-rule prelude)
// 40 | 2 | valueLength
// 42 | 2 | startColumn
// 36 | 2 | startColumn
// 38 | 2 | (padding)

let BYTES_PER_NODE = 44
let BYTES_PER_NODE = 40

// Node type constants
export const NODE_STYLESHEET = 1
Expand Down Expand Up @@ -160,14 +160,16 @@ export class CSSDataArena {
return this.view.getUint16(this.node_offset(node_index) + 8, true)
}

// Read content start offset
// Read content start offset (stored as delta from startOffset)
get_content_start(node_index: number): number {
return this.view.getUint32(this.node_offset(node_index) + 12, true)
const startOffset = this.get_start_offset(node_index)
const delta = this.view.getUint16(this.node_offset(node_index) + 12, true)
return startOffset + delta
}

// Read content length
get_content_length(node_index: number): number {
return this.view.getUint16(this.node_offset(node_index) + 16, true)
return this.view.getUint16(this.node_offset(node_index) + 14, true)
}

// Read attribute operator (for NODE_SELECTOR_ATTRIBUTE)
Expand Down Expand Up @@ -202,17 +204,19 @@ export class CSSDataArena {

// Read start column
get_start_column(node_index: number): number {
return this.view.getUint16(this.node_offset(node_index) + 42, true)
return this.view.getUint16(this.node_offset(node_index) + 36, true)
}

// Read value start offset (declaration value / at-rule prelude)
// Read value start offset (stored as delta from startOffset, declaration value / at-rule prelude)
get_value_start(node_index: number): number {
return this.view.getUint32(this.node_offset(node_index) + 36, true)
const startOffset = this.get_start_offset(node_index)
const delta = this.view.getUint16(this.node_offset(node_index) + 16, true)
return startOffset + delta
}

// Read value length
get_value_length(node_index: number): number {
return this.view.getUint16(this.node_offset(node_index) + 40, true)
return this.view.getUint16(this.node_offset(node_index) + 18, true)
}

// --- Write Methods ---
Expand All @@ -237,14 +241,16 @@ export class CSSDataArena {
this.view.setUint16(this.node_offset(node_index) + 8, length, true)
}

// Write content start offset
// Write content start offset (stored as delta from startOffset)
set_content_start(node_index: number, offset: number): void {
this.view.setUint32(this.node_offset(node_index) + 12, offset, true)
const startOffset = this.get_start_offset(node_index)
const delta = offset - startOffset
this.view.setUint16(this.node_offset(node_index) + 12, delta, true)
}

// Write content length
set_content_length(node_index: number, length: number): void {
this.view.setUint16(this.node_offset(node_index) + 16, length, true)
this.view.setUint16(this.node_offset(node_index) + 14, length, true)
}

// Write attribute operator (for NODE_SELECTOR_ATTRIBUTE)
Expand Down Expand Up @@ -279,17 +285,19 @@ export class CSSDataArena {

// Write start column
set_start_column(node_index: number, column: number): void {
this.view.setUint16(this.node_offset(node_index) + 42, column, true)
this.view.setUint16(this.node_offset(node_index) + 36, column, true)
}

// Write value start offset (declaration value / at-rule prelude)
// Write value start offset (stored as delta from startOffset, declaration value / at-rule prelude)
set_value_start(node_index: number, offset: number): void {
this.view.setUint32(this.node_offset(node_index) + 36, offset, true)
const startOffset = this.get_start_offset(node_index)
const delta = offset - startOffset
this.view.setUint16(this.node_offset(node_index) + 16, delta, true)
}

// Write value length
set_value_length(node_index: number, length: number): void {
this.view.setUint16(this.node_offset(node_index) + 40, length, true)
this.view.setUint16(this.node_offset(node_index) + 18, length, true)
}

// --- Node Creation ---
Expand Down
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