Memory Leak in Encoder / Encoder.parse

[Aea]

I suspect this may be related to #32

Every instantiation of borc.Encoder whether explicit or through the use of the convenience function borc.decode leaks memory. The leak appears to be caused by the parse property (e.g. the ASM decoder object) holding onto memory.

Merely creating 50K Encoder objects in a loop consumes nearly 700MB.

node --expose-gc ...

'use strict';

const borc = require('borc')
const crypto = require('crypto')

const SAMPLES = 5e4;
const SAMPLE_RATE = 1e3;
const SEP = '\r';

const memory = (i, sep) => {
  i = i || 0;
  sep = sep || SEP;
  
  const padded = i.toString().padStart(9, ' ');
  const mem = process.memoryUsage().rss / 1024 ** 2;
  
  process.stdout.write(sep + `${i}\t\trss: ${mem.toFixed(1)}`);
};

// create decoder
console.info('\ncreate decode')
for(let i = 0; i <= SAMPLES; ++i) {
  new borc.Decoder();
  (i % SAMPLE_RATE == 0 || i == SAMPLES) && memory(i) && global.gc(); 
}

Output:

create decode
50000		rss: 695.0

node --expose-gc ...

'use strict';

const borc = require('borc')
const crypto = require('crypto')

const SAMPLES = 5e4;
const SAMPLE_RATE = 1e3;
const SEP = '\r';

const memory = (i, sep) => {
  i = i || 0;
  sep = sep || SEP;
  
  const padded = i.toString().padStart(9, ' ');
  const mem = process.memoryUsage().rss / 1024 ** 2;
  
  process.stdout.write(sep + `${i}\t\trss: ${mem.toFixed(1)}`);
};

// baseline
console.info('\nbaseline')
for(let i = 0; i <= SAMPLES; ++i) {
  crypto.randomBytes(2048).toString('base64');

  (i % SAMPLE_RATE == 0 || i == SAMPLES) && memory(i) && global.gc(); 
}

// encode 
console.info('\nencode')
for(let i = 0; i <= SAMPLES; ++i) {
  borc.encode(crypto.randomBytes(2048).toString('base64'));

  (i % SAMPLE_RATE == 0 || i == SAMPLES) && memory(i) && global.gc(); 
}

// external decode
console.info('\nexternal decode')
const decoder = new borc.Decoder();

for(let i = 0; i <= SAMPLES; ++i) {
  decoder.decodeAll(borc.encode(crypto.randomBytes(2048).toString('base64')));

  (i % SAMPLE_RATE == 0 || i == SAMPLES) && memory(i) && global.gc(); 
}

// helper decode
console.info('\nhelper decode')
for(let i = 0; i <= SAMPLES; ++i) {
  borc.decode(borc.encode(crypto.randomBytes(2048).toString('base64')));

  (i % SAMPLE_RATE == 0 || i == SAMPLES) && memory(i) && global.gc();
}

Output

baseline
50000		rss: 36.7
encode
50000		rss: 39.4
external decode
50000		rss: 45.3
helper decode
50000		rss: 718.5