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backend/node_modules/fastify/lib/req-id-gen-factory.js

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+'use strict'
+
+/**
+ * @callback GenerateRequestId
+ * @param {Object} req
+ * @returns {string}
+ */
+
+/**
+ * @param {string} [requestIdHeader]
+ * @param {GenerateRequestId} [optGenReqId]
+ * @returns {GenerateRequestId}
+ */
+function reqIdGenFactory (requestIdHeader, optGenReqId) {
+  const genReqId = optGenReqId || buildDefaultGenReqId()
+
+  if (requestIdHeader) {
+    return buildOptionalHeaderReqId(requestIdHeader, genReqId)
+  }
+
+  return genReqId
+}
+
+function getGenReqId (contextServer, req) {
+  return contextServer.genReqId(req)
+}
+
+function buildDefaultGenReqId () {
+  // 2,147,483,647 (2^31 − 1) stands for max SMI value (an internal optimization of V8).
+  // With this upper bound, if you'll be generating 1k ids/sec, you're going to hit it in ~25 days.
+  // This is very likely to happen in real-world applications, hence the limit is enforced.
+  // Growing beyond this value will make the id generation slower and cause a deopt.
+  // In the worst cases, it will become a float, losing accuracy.
+  const maxInt = 2147483647
+
+  let nextReqId = 0
+  return function defaultGenReqId () {
+    nextReqId = (nextReqId + 1) & maxInt
+    return `req-${nextReqId.toString(36)}`
+  }
+}
+
+function buildOptionalHeaderReqId (requestIdHeader, genReqId) {
+  return function (req) {
+    return req.headers[requestIdHeader] || genReqId(req)
+  }
+}
+
+module.exports = {
+  getGenReqId,
+  reqIdGenFactory
+}