as-string-sink

String Sink

An efficient dynamically sized string buffer (aka String Builder) for AssemblyScript.

Interface

class StringSink {
  constructor(initial: string = "");

  get length(): i32;
  get capacity(): i32;

  write(src: string, start?: i32, end?: i32): void;
  writeLn(src: string, start?: i32, end?: i32): void;
  writeCodePoint(code: i32): void;

  shrink(): void;
  clear(): void;

  toString(): string;
}

Benchmark Results

StringSink can be up to 8700 times faster than naive string concatenation!

100 strings:
------------
String += JS:  0.016 ms
String += AS:  0.018 ms
StringSink AS: 0.0033 ms

50,000 strings:
---------------
String += JS:  2.86 ms
String += AS:  1133.24 ms
StringSink AS: 0.57 ms

200,000 strings:
----------------
String += JS:  11.44 ms
String += AS:  17867.35 ms
StringSink AS: 2.06 ms

Usage 1. String accumulation (+=)

non efficient example:

function toList(arr: string[]): string {
  let res = "";
  for (let i = 0, len = arr.length; i < len; i++) {
    res += arr[i] + "\n";
  }
  return res;
}

efficient with StringSink:

function toList(arr: string[]): string {
  let res = new StringSink();
  for (let i = 0, len = arr.length; i < len; i++) {
    res.write(arr[i] + "\n");
  }
  return res.toString();
}

even more efficient:

function toList(arr: string[]): string {
  let res = new StringSink();
  for (let i = 0, len = arr.length; i < len; i++) {
    res.writeLn(arr[i]);
  }
  return res.toString();
}

Usage 2. String accumulation (+=) only part of string

non efficient example:

function toListSliced(arr: string[]): string {
  let res = "";
  for (let i = 0, len = arr.length; i < len; i++) {
    res += arr[i].substring(1, 3);
  }
  return res;
}

more efficient with StringSink:

function toListSliced(arr: string[]): string {
  let res = new StringSink();
  for (let i = 0, len = arr.length; i < len; i++) {
    res.write(arr[i], 1, 3);
  }
  return res.toString();
}