Class CharPool

src/ink/screen.ts:21–53

// so blitRegion can copy IDs directly (no re-interning) and
// diffEach can compare IDs as integers (no string lookup).
export class CharPool {
  private strings: string[] = [' ', ''] // Index 0 = space, 1 = empty (spacer)
  private stringMap = new Map<string, number>([
    [' ', 0],
    ['', 1],
  ])
  private ascii: Int32Array = initCharAscii() // charCode → index, -1 = not interned

  intern(char: string): number {
    // ASCII fast-path: direct array lookup instead of Map.get
    if (char.length === 1) {
      const code = char.charCodeAt(0)
      if (code < 128) {
        const cached = this.ascii[code]!
        if (cached !== -1) return cached
        const index = this.strings.length
        this.strings.push(char)
        this.ascii[code] = index
        return index
      }
    }
    const existing = this.stringMap.get(char)
    if (existing !== undefined) return existing
    const index = this.strings.length
    this.strings.push(char)
    this.stringMap.set(char, index)
    return index
  }

  get(index: number): string {
    return this.strings[index] ?? ' '
  }
}

// Hyperlink string pool shared across all screens.
// Index 0 = no hyperlink.