var bytes = [84,104,105,115,32,105,115,32,97,32,115,97,109,112,108,101,32,112,97,114,97,103,114,97,112,104,46];
var uint16 = new Uint16Array(bytes);
var uint8 = new Uint8Array(bytes);
function base64ArrayBuffer(arrayBuffer) {
var base64 = '';
var encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
var bytes = arrayBuffer;
var byteLength = bytes.byteLength;
var byteRemainder = byteLength % 3;
var mainLength = byteLength - byteRemainder;
var a, b, c, d;
var chunk;
// Main loop deals with bytes in chunks of 3
for (var i = 0; i < mainLength; i = i + 3) {
// Combine the three bytes into a single integer
chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
// Use bitmasks to extract 6-bit segments from the triplet
a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
b = (chunk & 258048) >> 12; // 258048 = (2^6 - 1) << 12
c = (chunk & 4032) >> 6; // 4032 = (2^6 - 1) << 6
d = chunk & 63; // 63 = 2^6 - 1
// Convert the raw binary segments to the appropriate ASCII encoding
base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
}
// Deal with the remaining bytes and padding
if (byteRemainder == 1) {
chunk = bytes[mainLength];
a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
// Set the 4 least significant bits to zero
b = (chunk & 3) << 4; // 3 = 2^2 - 1
base64 += encodings[a] + encodings[b] + '==';
} else if (byteRemainder == 2) {
chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1];
a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
b = (chunk & 1008) >> 4; // 1008 = (2^6 - 1) << 4
// Set the 2 least significant bits to zero;
c = (chunk & 15) << 2 // 15 = 2^4 - 1
base64 += encodings[a] + encodings[b] + encodings[c] + '=';
}
return base64;
}
globalThis.btoa(String.fromCharCode.apply(null, uint16));
base64ArrayBuffer(uint8);
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
String.fromCharCode & btoa | |
base64ArrayBuffer function |
Test name | Executions per second |
---|---|
String.fromCharCode & btoa | 2535201.0 Ops/sec |
base64ArrayBuffer function | 3994521.5 Ops/sec |
Let's dive into the world of JavaScript microbenchmarks!
Benchmark Definition Json
The provided JSON represents a benchmark test that compares two approaches for encoding binary data as base64 strings.
What is tested?
Two options are being compared:
btoa(String.fromCharCode.apply(null, uint16));
: This option uses the btoa()
function (a browser-specific function) to encode the binary data represented by the uint16
array.base64ArrayBuffer(uint8);
: This option uses a custom implementation of base64 encoding on an array buffer
(specifically, the uint8
array).Options Comparison
Here's a brief overview of each approach:
btoa(String.fromCharCode.apply(null, uint16));
btoa()
is available.base64ArrayBuffer(uint8);
Library Used:
In this benchmark, btoa()
is a built-in function in modern browsers (including Chrome). Its purpose is to encode a string into a base64-encoded string. The custom implementation in the second test case (base64ArrayBuffer
) achieves similar functionality but with more control over the encoding process.
Special JS Feature/ Syntax:
There are no special JavaScript features or syntax used in this benchmark, other than the apply()
method in the first test case (which is a common technique for calling functions with an array of arguments).
Other Alternatives:
If you're interested in exploring alternative approaches to base64 encoding, here are a few options:
Base64
module: A popular JavaScript library that provides a simple and efficient implementation of base64 encoding.atob()
function: The browser-specific function for decoding base64-encoded strings (the reverse of btoa()
).btoa()
.I hope this explanation helps you understand the benchmark and its various components!