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Merged
bartveneman merged 3 commits into from
Dec 17, 2025
Merged

perf: reduce arena function calls #43

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c4b62cf
perf: reduce arena function calls
bartveneman Dec 17, 2025
7e546ce
fix type error
bartveneman Dec 17, 2025
dba4dc1
fix codecov slug
bartveneman Dec 17, 2025
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1 change: 1 addition & 0 deletions .github/workflows/test.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ jobs:
uses: codecov/codecov-action@v5
with:
token: ${{ secrets.CODECOV_TOKEN }}
slug: projectwallace/css-parser

check-ts:
name: Check types
Expand Down
94 changes: 37 additions & 57 deletions src/arena.test.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import { describe, test, expect } from 'vitest'
import { CSSDataArena, STYLESHEET, DECLARATION, FLAG_IMPORTANT, FLAG_HAS_ERROR } from './arena'
import { CSSDataArena, STYLESHEET, STYLE_RULE, DECLARATION, FLAG_IMPORTANT, FLAG_HAS_ERROR } from './arena'

describe('CSSDataArena', () => {
describe('initialization', () => {
Expand All @@ -20,24 +20,24 @@ describe('CSSDataArena', () => {
test('should create nodes and increment count', () => {
const arena = new CSSDataArena(10)

const node1 = arena.create_node()
const node1 = arena.create_node(STYLESHEET, 0, 0, 1, 1)
expect(node1).toBe(1) // First node index is 1 (0 is reserved for "no node")
expect(arena.get_count()).toBe(2)

const node2 = arena.create_node()
const node2 = arena.create_node(STYLESHEET, 0, 0, 1, 1)
expect(node2).toBe(2)
expect(arena.get_count()).toBe(3)
})

test('should automatically grow when capacity is exceeded', () => {
const arena = new CSSDataArena(3)

arena.create_node() // 1
arena.create_node() // 2
arena.create_node(STYLESHEET, 0, 0, 1, 1) // 1
arena.create_node(STYLESHEET, 0, 0, 1, 1) // 2
expect(arena.get_capacity()).toBe(3)

// This should trigger growth (count is now 3, capacity is 3)
const node3 = arena.create_node() // 3
const node3 = arena.create_node(STYLESHEET, 0, 0, 1, 1) // 3
expect(node3).toBe(3)
expect(arena.get_count()).toBe(4)
// Capacity should be ceil(3 * 1.3) = 4
Expand All @@ -47,17 +47,11 @@ describe('CSSDataArena', () => {
test('should preserve existing data when growing', () => {
const arena = new CSSDataArena(2)

const node1 = arena.create_node()
const node2 = arena.create_node()

// Set data on existing nodes
arena.set_type(node1, STYLESHEET)
arena.set_start_offset(node1, 100)
arena.set_type(node2, DECLARATION)
arena.set_start_offset(node2, 200)
const node1 = arena.create_node(STYLESHEET, 100, 0, 1, 1)
const node2 = arena.create_node(DECLARATION, 200, 0, 1, 1)

// Trigger growth
const node3 = arena.create_node()
const node3 = arena.create_node(STYLESHEET, 0, 0, 1, 1)

// Verify old data is preserved
expect(arena.get_type(node1)).toBe(STYLESHEET)
Expand All @@ -74,41 +68,37 @@ describe('CSSDataArena', () => {
describe('node reading and writing', () => {
test('should read default values for uninitialized nodes', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

expect(arena.get_type(node)).toBe(0)
expect(arena.get_type(node)).toBe(STYLESHEET)
expect(arena.get_flags(node)).toBe(0)
expect(arena.get_start_offset(node)).toBe(0)
expect(arena.get_length(node)).toBe(0)
})

test('should write and read node type', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(DECLARATION, 0, 0, 1, 1)

arena.set_type(node, STYLESHEET)
expect(arena.get_type(node)).toBe(STYLESHEET)
})

test('should write and read node flags', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(DECLARATION, 0, 0, 1, 1)

arena.set_flags(node, FLAG_IMPORTANT)
expect(arena.get_flags(node)).toBe(FLAG_IMPORTANT)
})

test('should write and read all node properties', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(DECLARATION, 100, 50, 5, 1)

arena.set_type(node, DECLARATION)
arena.set_flags(node, FLAG_IMPORTANT)
arena.set_start_offset(node, 100)
arena.set_length(node, 50)
arena.set_content_start(node, 110)
arena.set_content_start_delta(node, 10)
arena.set_content_length(node, 30)
arena.set_start_line(node, 5)

expect(arena.get_type(node)).toBe(DECLARATION)
expect(arena.get_flags(node)).toBe(FLAG_IMPORTANT)
Expand All @@ -121,14 +111,8 @@ describe('CSSDataArena', () => {

test('should handle multiple nodes independently', () => {
const arena = new CSSDataArena(10)
const node1 = arena.create_node()
const node2 = arena.create_node()

arena.set_type(node1, STYLESHEET)
arena.set_start_offset(node1, 0)

arena.set_type(node2, DECLARATION)
arena.set_start_offset(node2, 100)
const node1 = arena.create_node(STYLESHEET, 0, 0, 1, 1)
const node2 = arena.create_node(DECLARATION, 100, 0, 1, 1)

expect(arena.get_type(node1)).toBe(STYLESHEET)
expect(arena.get_start_offset(node1)).toBe(0)
Expand All @@ -140,10 +124,10 @@ describe('CSSDataArena', () => {
describe('tree linking', () => {
test('should append first child to parent', () => {
const arena = new CSSDataArena(10)
const parent = arena.create_node()
const child = arena.create_node()
const parent = arena.create_node(STYLESHEET, 0, 0, 1, 1)
const child = arena.create_node(STYLE_RULE, 0, 0, 1, 1)

arena.append_child(parent, child)
arena.append_children(parent, [child])

expect(arena.get_first_child(parent)).toBe(child)
expect(arena.has_children(parent)).toBe(true)
Expand All @@ -152,14 +136,12 @@ describe('CSSDataArena', () => {

test('should append multiple children as siblings', () => {
const arena = new CSSDataArena(10)
const parent = arena.create_node()
const child1 = arena.create_node()
const child2 = arena.create_node()
const child3 = arena.create_node()
const parent = arena.create_node(STYLESHEET, 0, 0, 1, 1)
const child1 = arena.create_node(STYLE_RULE, 0, 0, 1, 1)
const child2 = arena.create_node(STYLE_RULE, 0, 0, 1, 1)
const child3 = arena.create_node(STYLE_RULE, 0, 0, 1, 1)

arena.append_child(parent, child1)
arena.append_child(parent, child2)
arena.append_child(parent, child3)
arena.append_children(parent, [child1, child2, child3])

expect(arena.get_first_child(parent)).toBe(child1)
expect(arena.get_next_sibling(child1)).toBe(child2)
Expand All @@ -169,18 +151,16 @@ describe('CSSDataArena', () => {

test('should build complex tree structure', () => {
const arena = new CSSDataArena(10)
const root = arena.create_node()
const rule1 = arena.create_node()
const rule2 = arena.create_node()
const decl1 = arena.create_node()
const decl2 = arena.create_node()
const root = arena.create_node(STYLESHEET, 0, 0, 1, 1)
const rule1 = arena.create_node(STYLE_RULE, 0, 0, 1, 1)
const rule2 = arena.create_node(STYLE_RULE, 0, 0, 1, 1)
const decl1 = arena.create_node(DECLARATION, 0, 0, 1, 1)
const decl2 = arena.create_node(DECLARATION, 0, 0, 1, 1)

// Build tree: root -> [rule1, rule2]
// rule1 -> [decl1, decl2]
arena.append_child(root, rule1)
arena.append_child(root, rule2)
arena.append_child(rule1, decl1)
arena.append_child(rule1, decl2)
arena.append_children(root, [rule1, rule2])
arena.append_children(rule1, [decl1, decl2])

// Verify root level
expect(arena.get_first_child(root)).toBe(rule1)
Expand All @@ -198,7 +178,7 @@ describe('CSSDataArena', () => {

test('should handle nodes with no children or siblings', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

expect(arena.has_children(node)).toBe(false)
expect(arena.has_next_sibling(node)).toBe(false)
Expand All @@ -210,7 +190,7 @@ describe('CSSDataArena', () => {
describe('flag management', () => {
test('should set and check individual flags', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

expect(arena.has_flag(node, FLAG_IMPORTANT)).toBe(false)

Expand All @@ -220,7 +200,7 @@ describe('CSSDataArena', () => {

test('should set multiple flags independently', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

arena.set_flag(node, FLAG_IMPORTANT)

Expand All @@ -230,7 +210,7 @@ describe('CSSDataArena', () => {

test('should clear individual flags without affecting others', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

arena.set_flag(node, FLAG_IMPORTANT)
arena.set_flag(node, FLAG_HAS_ERROR)
Expand All @@ -241,7 +221,7 @@ describe('CSSDataArena', () => {

test('should handle all flag combinations', () => {
const arena = new CSSDataArena(10)
const node = arena.create_node()
const node = arena.create_node(STYLESHEET, 0, 0, 1, 1)

// Set all flags at once using setFlags
const allFlags = FLAG_IMPORTANT | FLAG_HAS_ERROR
Expand Down
60 changes: 33 additions & 27 deletions src/arena.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -238,10 +238,8 @@ export class CSSDataArena {
this.view.setUint16(this.node_offset(node_index) + 8, length, true)
}

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

Expand Down Expand Up @@ -285,10 +283,8 @@ export class CSSDataArena {
this.view.setUint16(this.node_offset(node_index) + 36, column, true)
}

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

Expand All @@ -313,35 +309,45 @@ export class CSSDataArena {
this.capacity = new_capacity
}

// Allocate a new node and return its index
// The node is zero-initialized by default (ArrayBuffer guarantees this)
// Allocate and initialize a new node with core properties
// Automatically grows the arena if capacity is exceeded
create_node(): number {
create_node(
type: number,
start_offset: number,
length: number,
start_line: number,
start_column: number
): number {
if (this.count >= this.capacity) {
this.grow()
}
let node_index = this.count
const node_index = this.count
this.count++

const offset = node_index * BYTES_PER_NODE
this.view.setUint8(offset, type) // +0: type
this.view.setUint32(offset + 4, start_offset, true) // +4: startOffset
this.view.setUint16(offset + 8, length, true) // +8: length
this.view.setUint32(offset + 32, start_line, true) // +32: startLine
this.view.setUint16(offset + 36, start_column, true) // +36: startColumn

return node_index
}

// --- Tree Building Helpers ---

// Add a child node to a parent node
// This appends to the end of the child list using the sibling chain
// O(1) operation using lastChild pointer
append_child(parentIndex: number, childIndex: number): void {
let last_child = this.get_last_child(parentIndex)

if (last_child === 0) {
// No children yet, make this the first and last child
this.set_first_child(parentIndex, childIndex)
this.set_last_child(parentIndex, childIndex)
} else {
// Append to the current last child's sibling chain
this.set_next_sibling(last_child, childIndex)
// Update parent's last child pointer
this.set_last_child(parentIndex, childIndex)
// Link multiple child nodes to a parent
// Children are linked as siblings in the order provided
append_children(parent_index: number, children: number[]): void {
if (children.length === 0) return

const offset = this.node_offset(parent_index)
this.view.setUint32(offset + 20, children[0], true) // firstChild
this.view.setUint32(offset + 24, children[children.length - 1], true) // lastChild

// Chain siblings
for (let i = 0; i < children.length - 1; i++) {
this.set_next_sibling(children[i], children[i + 1])
}
}

Expand Down
16 changes: 9 additions & 7 deletions src/parse-anplusb.ts
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Expand Up @@ -265,21 +265,23 @@ export class ANplusBParser {
}

private create_anplusb_node(start: number, a_start: number, a_end: number, b_start: number, b_end: number): number {
const node = this.arena.create_node()
this.arena.set_type(node, NTH_SELECTOR)
this.arena.set_start_offset(node, start)
this.arena.set_length(node, this.lexer.pos - start)
this.arena.set_start_line(node, this.lexer.line)
const node = this.arena.create_node(
NTH_SELECTOR,
start,
this.lexer.pos - start,
this.lexer.line,
1
)

// Store 'a' coefficient in content fields if it exists (length > 0)
if (a_end > a_start) {
this.arena.set_content_start(node, a_start)
this.arena.set_content_start_delta(node, a_start - start)
this.arena.set_content_length(node, a_end - a_start)
}

// Store 'b' coefficient in value fields if it exists (length > 0)
if (b_end > b_start) {
this.arena.set_value_start(node, b_start)
this.arena.set_value_start_delta(node, b_start - start)
this.arena.set_value_length(node, b_end - b_start)
}

Expand Down
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