speedscope/asm-js.ts

type AsmJsSymbolMap = Map<string, string>

// This imports symbol maps generated by emscripten using the "--emit-symbol-map" flag.
// It allows you to visualize a profile captured in a release build as long as you also
// have the associated symbol map. To do this, first drop the profile into speedscope
// and then drop the symbol map. After the second drop, the symbols will be remapped to
// their original names.
export function importAsmJsSymbolMap(contents: string): AsmJsSymbolMap | null {
  const lines = contents.split('\n')
  if (!lines.length) return null

  // Remove a trailing blank line if there is one
  if (lines[lines.length - 1] === '') lines.pop()
  if (!lines.length) return null

  const map: AsmJsSymbolMap = new Map()
  const regex = /^([\$\w]+):([\$\w]+)$/

  for (const line of lines) {
    const match = regex.exec(line)
    if (!match) return null
    map.set(match[1], match[2])
  }

  return map
}