Benchmark: Decoding ascii: TextDecoder vs Js

Script Preparation code:

// needed to create bytes array
var encoder = new TextEncoder();
// string length, multiple of 4 - vary to get different results
var n = 8;
var arr = encoder.encode(Array((n / 4) | 0).fill('abcd'));
var decoder = new TextDecoder();
function decodeNative(arr) {
  return decoder.decode(arr);
}

function decoderJs(buffer) {
  var start = 0;
  var end = buffer.byteLength;

  if (end - start < 1) {
    return "";
  }

  var str = "";
  for (var i = start; i < end;) {
    var t = buffer[i++];

    if (t <= 0x7F) {
      str += String.fromCharCode(t);
    } else if (t >= 0xC0 && t < 0xE0) {
      str += String.fromCharCode((t & 0x1F) << 6 | buffer[i++] & 0x3F);
    } else if (t >= 0xE0 && t < 0xF0) {
      str += String.fromCharCode((t & 0xF) << 12 | (buffer[i++] & 0x3F) << 6 | buffer[i++] & 0x3F);
    } else if (t >= 0xF0) {
      var t2 = ((t & 7) << 18 | (buffer[i++] & 0x3F) << 12 | (buffer[i++] & 0x3F) << 6 | buffer[i++] & 0x3F) - 0x10000;
      str += String.fromCharCode(0xD800 + (t2 >> 10));
      str += String.fromCharCode(0xDC00 + (t2 & 0x3FF));
    }
  }
  return str;
}

Tests:

decodeNative
decodeNative(arr)
decoderJs
decoderJs(arr)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
decodeNative
decoderJs

Fastest: N/A

Slowest: N/A

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Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:99.0) Gecko/20100101 Firefox/99.0

Browser/OS: Firefox 99 on Linux

View result in a separate tab

Test name	Executions per second
decodeNative	6869119.0 Ops/sec
decoderJs	4343496.0 Ops/sec

Decoding ascii: TextDecoder vs Js (version: 0)

Measure performance of ascii decoding for various string lengths.

Comparing performance of: decodeNative vs decoderJs

Created: 2 years ago by: Registered User

Jump to the latest result

decodeNative

decoderJs

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A