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/**
* The `node:v8` module exposes APIs that are specific to the version of [V8](https://developers.google.com/v8/) built into the Node.js binary. It can be accessed using:
*
* ```js
* const v8 = require('node:v8');
* ```
* @see [source](https://github.com/nodejs/node/blob/v20.13.1/lib/v8.js)
*/
declare module "v8" {
import { Readable } from "node:stream";
interface HeapSpaceInfo {
space_name: string;
space_size: number;
space_used_size: number;
space_available_size: number;
physical_space_size: number;
}
// ** Signifies if the --zap_code_space option is enabled or not. 1 == enabled, 0 == disabled. */
type DoesZapCodeSpaceFlag = 0 | 1;
interface HeapInfo {
total_heap_size: number;
total_heap_size_executable: number;
total_physical_size: number;
total_available_size: number;
used_heap_size: number;
heap_size_limit: number;
malloced_memory: number;
peak_malloced_memory: number;
does_zap_garbage: DoesZapCodeSpaceFlag;
number_of_native_contexts: number;
number_of_detached_contexts: number;
total_global_handles_size: number;
used_global_handles_size: number;
external_memory: number;
}
interface HeapCodeStatistics {
code_and_metadata_size: number;
bytecode_and_metadata_size: number;
external_script_source_size: number;
}
interface HeapSnapshotOptions {
/**
* If true, expose internals in the heap snapshot.
* @default false
*/
exposeInternals?: boolean;
/**
* If true, expose numeric values in artificial fields.
* @default false
*/
exposeNumericValues?: boolean;
}
/**
* Returns an integer representing a version tag derived from the V8 version,
* command-line flags, and detected CPU features. This is useful for determining
* whether a `vm.Script` `cachedData` buffer is compatible with this instance
* of V8.
*
* ```js
* console.log(v8.cachedDataVersionTag()); // 3947234607
* // The value returned by v8.cachedDataVersionTag() is derived from the V8
* // version, command-line flags, and detected CPU features. Test that the value
* // does indeed update when flags are toggled.
* v8.setFlagsFromString('--allow_natives_syntax');
* console.log(v8.cachedDataVersionTag()); // 183726201
* ```
* @since v8.0.0
*/
function cachedDataVersionTag(): number;
/**
* Returns an object with the following properties:
*
* `does_zap_garbage` is a 0/1 boolean, which signifies whether the `--zap_code_space` option is enabled or not. This makes V8 overwrite heap
* garbage with a bit pattern. The RSS footprint (resident set size) gets bigger
* because it continuously touches all heap pages and that makes them less likely
* to get swapped out by the operating system.
*
* `number_of_native_contexts` The value of native\_context is the number of the
* top-level contexts currently active. Increase of this number over time indicates
* a memory leak.
*
* `number_of_detached_contexts` The value of detached\_context is the number
* of contexts that were detached and not yet garbage collected. This number
* being non-zero indicates a potential memory leak.
*
* `total_global_handles_size` The value of total\_global\_handles\_size is the
* total memory size of V8 global handles.
*
* `used_global_handles_size` The value of used\_global\_handles\_size is the
* used memory size of V8 global handles.
*
* `external_memory` The value of external\_memory is the memory size of array
* buffers and external strings.
*
* ```js
* {
* total_heap_size: 7326976,
* total_heap_size_executable: 4194304,
* total_physical_size: 7326976,
* total_available_size: 1152656,
* used_heap_size: 3476208,
* heap_size_limit: 1535115264,
* malloced_memory: 16384,
* peak_malloced_memory: 1127496,
* does_zap_garbage: 0,
* number_of_native_contexts: 1,
* number_of_detached_contexts: 0,
* total_global_handles_size: 8192,
* used_global_handles_size: 3296,
* external_memory: 318824
* }
* ```
* @since v1.0.0
*/
function getHeapStatistics(): HeapInfo;
/**
* Returns statistics about the V8 heap spaces, i.e. the segments which make up
* the V8 heap. Neither the ordering of heap spaces, nor the availability of a
* heap space can be guaranteed as the statistics are provided via the
* V8 [`GetHeapSpaceStatistics`](https://v8docs.nodesource.com/node-13.2/d5/dda/classv8_1_1_isolate.html#ac673576f24fdc7a33378f8f57e1d13a4) function and may change from one V8 version to the
* next.
*
* The value returned is an array of objects containing the following properties:
*
* ```json
* [
* {
* "space_name": "new_space",
* "space_size": 2063872,
* "space_used_size": 951112,
* "space_available_size": 80824,
* "physical_space_size": 2063872
* },
* {
* "space_name": "old_space",
* "space_size": 3090560,
* "space_used_size": 2493792,
* "space_available_size": 0,
* "physical_space_size": 3090560
* },
* {
* "space_name": "code_space",
* "space_size": 1260160,
* "space_used_size": 644256,
* "space_available_size": 960,
* "physical_space_size": 1260160
* },
* {
* "space_name": "map_space",
* "space_size": 1094160,
* "space_used_size": 201608,
* "space_available_size": 0,
* "physical_space_size": 1094160
* },
* {
* "space_name": "large_object_space",
* "space_size": 0,
* "space_used_size": 0,
* "space_available_size": 1490980608,
* "physical_space_size": 0
* }
* ]
* ```
* @since v6.0.0
*/
function getHeapSpaceStatistics(): HeapSpaceInfo[];
/**
* The `v8.setFlagsFromString()` method can be used to programmatically set
* V8 command-line flags. This method should be used with care. Changing settings
* after the VM has started may result in unpredictable behavior, including
* crashes and data loss; or it may simply do nothing.
*
* The V8 options available for a version of Node.js may be determined by running `node --v8-options`.
*
* Usage:
*
* ```js
* // Print GC events to stdout for one minute.
* const v8 = require('node:v8');
* v8.setFlagsFromString('--trace_gc');
* setTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
* ```
* @since v1.0.0
*/
function setFlagsFromString(flags: string): void;
/**
* This is similar to the [`queryObjects()` console API](https://developer.chrome.com/docs/devtools/console/utilities#queryObjects-function)
* provided by the Chromium DevTools console. It can be used to search for objects that have the matching constructor on its prototype chain
* in the heap after a full garbage collection, which can be useful for memory leak regression tests. To avoid surprising results, users should
* avoid using this API on constructors whose implementation they don't control, or on constructors that can be invoked by other parties in the
* application.
*
* To avoid accidental leaks, this API does not return raw references to the objects found. By default, it returns the count of the objects
* found. If `options.format` is `'summary'`, it returns an array containing brief string representations for each object. The visibility provided
* in this API is similar to what the heap snapshot provides, while users can save the cost of serialization and parsing and directly filter the
* target objects during the search.
*
* Only objects created in the current execution context are included in the results.
*
* ```js
* import { queryObjects } from 'node:v8';
* class A { foo = 'bar'; }
* console.log(queryObjects(A)); // 0
* const a = new A();
* console.log(queryObjects(A)); // 1
* // [ "A { foo: 'bar' }" ]
* console.log(queryObjects(A, { format: 'summary' }));
*
* class B extends A { bar = 'qux'; }
* const b = new B();
* console.log(queryObjects(B)); // 1
* // [ "B { foo: 'bar', bar: 'qux' }" ]
* console.log(queryObjects(B, { format: 'summary' }));
*
* // Note that, when there are child classes inheriting from a constructor,
* // the constructor also shows up in the prototype chain of the child
* // classes's prototoype, so the child classes's prototoype would also be
* // included in the result.
* console.log(queryObjects(A)); // 3
* // [ "B { foo: 'bar', bar: 'qux' }", 'A {}', "A { foo: 'bar' }" ]
* console.log(queryObjects(A, { format: 'summary' }));
* ```
* @param ctor The constructor that can be used to search on the prototype chain in order to filter target objects in the heap.
* @since v20.13.0
* @experimental
*/
function queryObjects(ctor: Function): number | string[];
function queryObjects(ctor: Function, options: { format: "count" }): number;
function queryObjects(ctor: Function, options: { format: "summary" }): string[];
/**
* Generates a snapshot of the current V8 heap and returns a Readable
* Stream that may be used to read the JSON serialized representation.
* This JSON stream format is intended to be used with tools such as
* Chrome DevTools. The JSON schema is undocumented and specific to the
* V8 engine. Therefore, the schema may change from one version of V8 to the next.
*
* Creating a heap snapshot requires memory about twice the size of the heap at
* the time the snapshot is created. This results in the risk of OOM killers
* terminating the process.
*
* Generating a snapshot is a synchronous operation which blocks the event loop
* for a duration depending on the heap size.
*
* ```js
* // Print heap snapshot to the console
* const v8 = require('node:v8');
* const stream = v8.getHeapSnapshot();
* stream.pipe(process.stdout);
* ```
* @since v11.13.0
* @return A Readable containing the V8 heap snapshot.
*/
function getHeapSnapshot(options?: HeapSnapshotOptions): Readable;
/**
* Generates a snapshot of the current V8 heap and writes it to a JSON
* file. This file is intended to be used with tools such as Chrome
* DevTools. The JSON schema is undocumented and specific to the V8
* engine, and may change from one version of V8 to the next.
*
* A heap snapshot is specific to a single V8 isolate. When using `worker threads`, a heap snapshot generated from the main thread will
* not contain any information about the workers, and vice versa.
*
* Creating a heap snapshot requires memory about twice the size of the heap at
* the time the snapshot is created. This results in the risk of OOM killers
* terminating the process.
*
* Generating a snapshot is a synchronous operation which blocks the event loop
* for a duration depending on the heap size.
*
* ```js
* const { writeHeapSnapshot } = require('node:v8');
* const {
* Worker,
* isMainThread,
* parentPort,
* } = require('node:worker_threads');
*
* if (isMainThread) {
* const worker = new Worker(__filename);
*
* worker.once('message', (filename) => {
* console.log(`worker heapdump: ${filename}`);
* // Now get a heapdump for the main thread.
* console.log(`main thread heapdump: ${writeHeapSnapshot()}`);
* });
*
* // Tell the worker to create a heapdump.
* worker.postMessage('heapdump');
* } else {
* parentPort.once('message', (message) => {
* if (message === 'heapdump') {
* // Generate a heapdump for the worker
* // and return the filename to the parent.
* parentPort.postMessage(writeHeapSnapshot());
* }
* });
* }
* ```
* @since v11.13.0
* @param filename The file path where the V8 heap snapshot is to be saved. If not specified, a file name with the pattern `'Heap-${yyyymmdd}-${hhmmss}-${pid}-${thread_id}.heapsnapshot'` will be
* generated, where `{pid}` will be the PID of the Node.js process, `{thread_id}` will be `0` when `writeHeapSnapshot()` is called from the main Node.js thread or the id of a
* worker thread.
* @return The filename where the snapshot was saved.
*/
function writeHeapSnapshot(filename?: string, options?: HeapSnapshotOptions): string;
/**
* Get statistics about code and its metadata in the heap, see
* V8 [`GetHeapCodeAndMetadataStatistics`](https://v8docs.nodesource.com/node-13.2/d5/dda/classv8_1_1_isolate.html#a6079122af17612ef54ef3348ce170866) API. Returns an object with the
* following properties:
*
* ```js
* {
* code_and_metadata_size: 212208,
* bytecode_and_metadata_size: 161368,
* external_script_source_size: 1410794,
* cpu_profiler_metadata_size: 0,
* }
* ```
* @since v12.8.0
*/
function getHeapCodeStatistics(): HeapCodeStatistics;
/**
* @since v8.0.0
*/
class Serializer {
/**
* Writes out a header, which includes the serialization format version.
*/
writeHeader(): void;
/**
* Serializes a JavaScript value and adds the serialized representation to the
* internal buffer.
*
* This throws an error if `value` cannot be serialized.
*/
writeValue(val: any): boolean;
/**
* Returns the stored internal buffer. This serializer should not be used once
* the buffer is released. Calling this method results in undefined behavior
* if a previous write has failed.
*/
releaseBuffer(): Buffer;
/**
* Marks an `ArrayBuffer` as having its contents transferred out of band.
* Pass the corresponding `ArrayBuffer` in the deserializing context to `deserializer.transferArrayBuffer()`.
* @param id A 32-bit unsigned integer.
* @param arrayBuffer An `ArrayBuffer` instance.
*/
transferArrayBuffer(id: number, arrayBuffer: ArrayBuffer): void;
/**
* Write a raw 32-bit unsigned integer.
* For use inside of a custom `serializer._writeHostObject()`.
*/
writeUint32(value: number): void;
/**
* Write a raw 64-bit unsigned integer, split into high and low 32-bit parts.
* For use inside of a custom `serializer._writeHostObject()`.
*/
writeUint64(hi: number, lo: number): void;
/**
* Write a JS `number` value.
* For use inside of a custom `serializer._writeHostObject()`.
*/
writeDouble(value: number): void;
/**
* Write raw bytes into the serializer's internal buffer. The deserializer
* will require a way to compute the length of the buffer.
* For use inside of a custom `serializer._writeHostObject()`.
*/
writeRawBytes(buffer: NodeJS.TypedArray): void;
}
/**
* A subclass of `Serializer` that serializes `TypedArray`(in particular `Buffer`) and `DataView` objects as host objects, and only
* stores the part of their underlying `ArrayBuffer`s that they are referring to.
* @since v8.0.0
*/
class DefaultSerializer extends Serializer {}
/**
* @since v8.0.0
*/
class Deserializer {
constructor(data: NodeJS.TypedArray);
/**
* Reads and validates a header (including the format version).
* May, for example, reject an invalid or unsupported wire format. In that case,
* an `Error` is thrown.
*/
readHeader(): boolean;
/**
* Deserializes a JavaScript value from the buffer and returns it.
*/
readValue(): any;
/**
* Marks an `ArrayBuffer` as having its contents transferred out of band.
* Pass the corresponding `ArrayBuffer` in the serializing context to `serializer.transferArrayBuffer()` (or return the `id` from `serializer._getSharedArrayBufferId()` in the case of
* `SharedArrayBuffer`s).
* @param id A 32-bit unsigned integer.
* @param arrayBuffer An `ArrayBuffer` instance.
*/
transferArrayBuffer(id: number, arrayBuffer: ArrayBuffer): void;
/**
* Reads the underlying wire format version. Likely mostly to be useful to
* legacy code reading old wire format versions. May not be called before `.readHeader()`.
*/
getWireFormatVersion(): number;
/**
* Read a raw 32-bit unsigned integer and return it.
* For use inside of a custom `deserializer._readHostObject()`.
*/
readUint32(): number;
/**
* Read a raw 64-bit unsigned integer and return it as an array `[hi, lo]` with two 32-bit unsigned integer entries.
* For use inside of a custom `deserializer._readHostObject()`.
*/
readUint64(): [number, number];
/**
* Read a JS `number` value.
* For use inside of a custom `deserializer._readHostObject()`.
*/
readDouble(): number;
/**
* Read raw bytes from the deserializer's internal buffer. The `length` parameter
* must correspond to the length of the buffer that was passed to `serializer.writeRawBytes()`.
* For use inside of a custom `deserializer._readHostObject()`.
*/
readRawBytes(length: number): Buffer;
}
/**
* A subclass of `Deserializer` corresponding to the format written by `DefaultSerializer`.
* @since v8.0.0
*/
class DefaultDeserializer extends Deserializer {}
/**
* Uses a `DefaultSerializer` to serialize `value` into a buffer.
*
* `ERR_BUFFER_TOO_LARGE` will be thrown when trying to
* serialize a huge object which requires buffer
* larger than `buffer.constants.MAX_LENGTH`.
* @since v8.0.0
*/
function serialize(value: any): Buffer;
/**
* Uses a `DefaultDeserializer` with default options to read a JS value
* from a buffer.
* @since v8.0.0
* @param buffer A buffer returned by {@link serialize}.
*/
function deserialize(buffer: NodeJS.TypedArray): any;
/**
* The `v8.takeCoverage()` method allows the user to write the coverage started by `NODE_V8_COVERAGE` to disk on demand. This method can be invoked multiple
* times during the lifetime of the process. Each time the execution counter will
* be reset and a new coverage report will be written to the directory specified
* by `NODE_V8_COVERAGE`.
*
* When the process is about to exit, one last coverage will still be written to
* disk unless {@link stopCoverage} is invoked before the process exits.
* @since v15.1.0, v14.18.0, v12.22.0
*/
function takeCoverage(): void;
/**
* The `v8.stopCoverage()` method allows the user to stop the coverage collection
* started by `NODE_V8_COVERAGE`, so that V8 can release the execution count
* records and optimize code. This can be used in conjunction with {@link takeCoverage} if the user wants to collect the coverage on demand.
* @since v15.1.0, v14.18.0, v12.22.0
*/
function stopCoverage(): void;
/**
* The API is a no-op if `--heapsnapshot-near-heap-limit` is already set from the command line or the API is called more than once.
* `limit` must be a positive integer. See [`--heapsnapshot-near-heap-limit`](https://nodejs.org/docs/latest-v20.x/api/cli.html#--heapsnapshot-near-heap-limitmax_count) for more information.
* @experimental
* @since v18.10.0, v16.18.0
*/
function setHeapSnapshotNearHeapLimit(limit: number): void;
/**
* This API collects GC data in current thread.
* @since v19.6.0, v18.15.0
*/
class GCProfiler {
/**
* Start collecting GC data.
* @since v19.6.0, v18.15.0
*/
start(): void;
/**
* Stop collecting GC data and return an object. The content of object
* is as follows.
*
* ```json
* {
* "version": 1,
* "startTime": 1674059033862,
* "statistics": [
* {
* "gcType": "Scavenge",
* "beforeGC": {
* "heapStatistics": {
* "totalHeapSize": 5005312,
* "totalHeapSizeExecutable": 524288,
* "totalPhysicalSize": 5226496,
* "totalAvailableSize": 4341325216,
* "totalGlobalHandlesSize": 8192,
* "usedGlobalHandlesSize": 2112,
* "usedHeapSize": 4883840,
* "heapSizeLimit": 4345298944,
* "mallocedMemory": 254128,
* "externalMemory": 225138,
* "peakMallocedMemory": 181760
* },
* "heapSpaceStatistics": [
* {
* "spaceName": "read_only_space",
* "spaceSize": 0,
* "spaceUsedSize": 0,
* "spaceAvailableSize": 0,
* "physicalSpaceSize": 0
* }
* ]
* },
* "cost": 1574.14,
* "afterGC": {
* "heapStatistics": {
* "totalHeapSize": 6053888,
* "totalHeapSizeExecutable": 524288,
* "totalPhysicalSize": 5500928,
* "totalAvailableSize": 4341101384,
* "totalGlobalHandlesSize": 8192,
* "usedGlobalHandlesSize": 2112,
* "usedHeapSize": 4059096,
* "heapSizeLimit": 4345298944,
* "mallocedMemory": 254128,
* "externalMemory": 225138,
* "peakMallocedMemory": 181760
* },
* "heapSpaceStatistics": [
* {
* "spaceName": "read_only_space",
* "spaceSize": 0,
* "spaceUsedSize": 0,
* "spaceAvailableSize": 0,
* "physicalSpaceSize": 0
* }
* ]
* }
* }
* ],
* "endTime": 1674059036865
* }
* ```
*
* Here's an example.
*
* ```js
* const { GCProfiler } = require('v8');
* const profiler = new GCProfiler();
* profiler.start();
* setTimeout(() => {
* console.log(profiler.stop());
* }, 1000);
* ```
* @since v19.6.0, v18.15.0
*/
stop(): GCProfilerResult;
}
interface GCProfilerResult {
version: number;
startTime: number;
endTime: number;
statistics: Array<{
gcType: string;
cost: number;
beforeGC: {
heapStatistics: HeapStatistics;
heapSpaceStatistics: HeapSpaceStatistics[];
};
afterGC: {
heapStatistics: HeapStatistics;
heapSpaceStatistics: HeapSpaceStatistics[];
};
}>;
}
interface HeapStatistics {
totalHeapSize: number;
totalHeapSizeExecutable: number;
totalPhysicalSize: number;
totalAvailableSize: number;
totalGlobalHandlesSize: number;
usedGlobalHandlesSize: number;
usedHeapSize: number;
heapSizeLimit: number;
mallocedMemory: number;
externalMemory: number;
peakMallocedMemory: number;
}
interface HeapSpaceStatistics {
spaceName: string;
spaceSize: number;
spaceUsedSize: number;
spaceAvailableSize: number;
physicalSpaceSize: number;
}
/**
* Called when a promise is constructed. This does not mean that corresponding before/after events will occur, only that the possibility exists. This will
* happen if a promise is created without ever getting a continuation.
* @since v17.1.0, v16.14.0
* @param promise The promise being created.
* @param parent The promise continued from, if applicable.
*/
interface Init {
(promise: Promise<unknown>, parent: Promise<unknown>): void;
}
/**
* Called before a promise continuation executes. This can be in the form of `then()`, `catch()`, or `finally()` handlers or an await resuming.
*
* The before callback will be called 0 to N times. The before callback will typically be called 0 times if no continuation was ever made for the promise.
* The before callback may be called many times in the case where many continuations have been made from the same promise.
* @since v17.1.0, v16.14.0
*/
interface Before {
(promise: Promise<unknown>): void;
}
/**
* Called immediately after a promise continuation executes. This may be after a `then()`, `catch()`, or `finally()` handler or before an await after another await.
* @since v17.1.0, v16.14.0
*/
interface After {
(promise: Promise<unknown>): void;
}
/**
* Called when the promise receives a resolution or rejection value. This may occur synchronously in the case of {@link Promise.resolve()} or
* {@link Promise.reject()}.
* @since v17.1.0, v16.14.0
*/
interface Settled {
(promise: Promise<unknown>): void;
}
/**
* Key events in the lifetime of a promise have been categorized into four areas: creation of a promise, before/after a continuation handler is called or
* around an await, and when the promise resolves or rejects.
*
* Because promises are asynchronous resources whose lifecycle is tracked via the promise hooks mechanism, the `init()`, `before()`, `after()`, and
* `settled()` callbacks must not be async functions as they create more promises which would produce an infinite loop.
* @since v17.1.0, v16.14.0
*/
interface HookCallbacks {
init?: Init;
before?: Before;
after?: After;
settled?: Settled;
}
interface PromiseHooks {
/**
* The `init` hook must be a plain function. Providing an async function will throw as it would produce an infinite microtask loop.
* @since v17.1.0, v16.14.0
* @param init The {@link Init | `init` callback} to call when a promise is created.
* @return Call to stop the hook.
*/
onInit: (init: Init) => Function;
/**
* The `settled` hook must be a plain function. Providing an async function will throw as it would produce an infinite microtask loop.
* @since v17.1.0, v16.14.0
* @param settled The {@link Settled | `settled` callback} to call when a promise is created.
* @return Call to stop the hook.
*/
onSettled: (settled: Settled) => Function;
/**
* The `before` hook must be a plain function. Providing an async function will throw as it would produce an infinite microtask loop.
* @since v17.1.0, v16.14.0
* @param before The {@link Before | `before` callback} to call before a promise continuation executes.
* @return Call to stop the hook.
*/
onBefore: (before: Before) => Function;
/**
* The `after` hook must be a plain function. Providing an async function will throw as it would produce an infinite microtask loop.
* @since v17.1.0, v16.14.0
* @param after The {@link After | `after` callback} to call after a promise continuation executes.
* @return Call to stop the hook.
*/
onAfter: (after: After) => Function;
/**
* Registers functions to be called for different lifetime events of each promise.
* The callbacks `init()`/`before()`/`after()`/`settled()` are called for the respective events during a promise's lifetime.
* All callbacks are optional. For example, if only promise creation needs to be tracked, then only the init callback needs to be passed.
* The hook callbacks must be plain functions. Providing async functions will throw as it would produce an infinite microtask loop.
* @since v17.1.0, v16.14.0
* @param callbacks The {@link HookCallbacks | Hook Callbacks} to register
* @return Used for disabling hooks
*/
createHook: (callbacks: HookCallbacks) => Function;
}
/**
* The `promiseHooks` interface can be used to track promise lifecycle events.
* @since v17.1.0, v16.14.0
*/
const promiseHooks: PromiseHooks;
type StartupSnapshotCallbackFn = (args: any) => any;
interface StartupSnapshot {
/**
* Add a callback that will be called when the Node.js instance is about to get serialized into a snapshot and exit.
* This can be used to release resources that should not or cannot be serialized or to convert user data into a form more suitable for serialization.
* @since v18.6.0, v16.17.0
*/
addSerializeCallback(callback: StartupSnapshotCallbackFn, data?: any): void;
/**
* Add a callback that will be called when the Node.js instance is deserialized from a snapshot.
* The `callback` and the `data` (if provided) will be serialized into the snapshot, they can be used to re-initialize the state of the application or
* to re-acquire resources that the application needs when the application is restarted from the snapshot.
* @since v18.6.0, v16.17.0
*/
addDeserializeCallback(callback: StartupSnapshotCallbackFn, data?: any): void;
/**
* This sets the entry point of the Node.js application when it is deserialized from a snapshot. This can be called only once in the snapshot building script.
* If called, the deserialized application no longer needs an additional entry point script to start up and will simply invoke the callback along with the deserialized
* data (if provided), otherwise an entry point script still needs to be provided to the deserialized application.
* @since v18.6.0, v16.17.0
*/
setDeserializeMainFunction(callback: StartupSnapshotCallbackFn, data?: any): void;
/**
* Returns true if the Node.js instance is run to build a snapshot.
* @since v18.6.0, v16.17.0
*/
isBuildingSnapshot(): boolean;
}
/**
* The `v8.startupSnapshot` interface can be used to add serialization and deserialization hooks for custom startup snapshots.
*
* ```bash
* $ node --snapshot-blob snapshot.blob --build-snapshot entry.js
* # This launches a process with the snapshot
* $ node --snapshot-blob snapshot.blob
* ```
*
* In the example above, `entry.js` can use methods from the `v8.startupSnapshot` interface to specify how to save information for custom objects
* in the snapshot during serialization and how the information can be used to synchronize these objects during deserialization of the snapshot.
* For example, if the `entry.js` contains the following script:
*
* ```js
* 'use strict';
*
* const fs = require('node:fs');
* const zlib = require('node:zlib');
* const path = require('node:path');
* const assert = require('node:assert');
*
* const v8 = require('node:v8');
*
* class BookShelf {
* storage = new Map();
*
* // Reading a series of files from directory and store them into storage.
* constructor(directory, books) {
* for (const book of books) {
* this.storage.set(book, fs.readFileSync(path.join(directory, book)));
* }
* }
*
* static compressAll(shelf) {
* for (const [ book, content ] of shelf.storage) {
* shelf.storage.set(book, zlib.gzipSync(content));
* }
* }
*
* static decompressAll(shelf) {
* for (const [ book, content ] of shelf.storage) {
* shelf.storage.set(book, zlib.gunzipSync(content));
* }
* }
* }
*
* // __dirname here is where the snapshot script is placed
* // during snapshot building time.
* const shelf = new BookShelf(__dirname, [
* 'book1.en_US.txt',
* 'book1.es_ES.txt',
* 'book2.zh_CN.txt',
* ]);
*
* assert(v8.startupSnapshot.isBuildingSnapshot());
* // On snapshot serialization, compress the books to reduce size.
* v8.startupSnapshot.addSerializeCallback(BookShelf.compressAll, shelf);
* // On snapshot deserialization, decompress the books.
* v8.startupSnapshot.addDeserializeCallback(BookShelf.decompressAll, shelf);
* v8.startupSnapshot.setDeserializeMainFunction((shelf) => {
* // process.env and process.argv are refreshed during snapshot
* // deserialization.
* const lang = process.env.BOOK_LANG || 'en_US';
* const book = process.argv[1];
* const name = `${book}.${lang}.txt`;
* console.log(shelf.storage.get(name));
* }, shelf);
* ```
*
* The resulted binary will get print the data deserialized from the snapshot during start up, using the refreshed `process.env` and `process.argv` of the launched process:
*
* ```bash
* $ BOOK_LANG=es_ES node --snapshot-blob snapshot.blob book1
* # Prints content of book1.es_ES.txt deserialized from the snapshot.
* ```
*
* Currently the application deserialized from a user-land snapshot cannot be snapshotted again, so these APIs are only available to applications that are not deserialized from a user-land snapshot.
*
* @experimental
* @since v18.6.0, v16.17.0
*/
const startupSnapshot: StartupSnapshot;
}
declare module "node:v8" {
export * from "v8";
}