Function createJSHeapSnapshot

test/common/heap.js:22–63

(stream = getHeapSnapshot())

const { getHeapSnapshot } = require('v8');

function createJSHeapSnapshot(stream = getHeapSnapshot()) {
  stream.pause();
  stream.read(0);
  const dump = JSON.parse(stream.read(stream.readableLength));
  const meta = dump.snapshot.meta;

  const nodes =
    readHeapInfo(dump.nodes, meta.node_fields, meta.node_types, dump.strings);
  const edges =
    readHeapInfo(dump.edges, meta.edge_fields, meta.edge_types, dump.strings);

  for (const node of nodes) {
    node.incomingEdges = [];
    node.outgoingEdges = [];
  }

  let fromNodeIndex = 0;
  let edgeIndex = 0;
  for (const { type, name_or_index, to_node } of edges) {
    while (edgeIndex === nodes[fromNodeIndex].edge_count) {
      edgeIndex = 0;
      fromNodeIndex++;
    }
    const toNode = nodes[to_node / meta.node_fields.length];
    const fromNode = nodes[fromNodeIndex];
    const edge = {
      type,
      to: toNode,
      from: fromNode,
      name: typeof name_or_index === 'string' ? name_or_index : null,
    };
    toNode.incomingEdges.push(edge);
    fromNode.outgoingEdges.push(edge);
    edgeIndex++;
  }

  for (const node of nodes) {
    assert.strictEqual(node.edge_count, node.outgoingEdges.length,
                       `${node.edge_count} !== ${node.outgoingEdges.length}`);
  }
  return nodes;
}

function readHeapInfo(raw, fields, types, strings) {
  const items = [];