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IPC

As mentioned in the previous chapter on JS Syscalls, ckb-js-vm supports Spawn. Building on top of Spawn, we implemented an additional abstraction layer called IPC, which also provides a similar set of APIs for use in JavaScript.

(While using JavaScript as a server is technically supported, the overhead of ckb-js-vm is significant, so we do not recommend doing so.)

spawnCellServer​

Spawns a new IPC server process using the provided code hash and hash type.

Syntax​

export function spawnCellServer(
  codeHash: ArrayBuffer,
  hashType: number,
  argv: string[]
): [Pipe, Pipe];

Parameters​

  • codeHash: The code hash to search for (must be 32 bytes)
  • hashType: The type of hash to search for (type or data)
  • argv: An array of strings representing the arguments to pass to the new process.

Return​

A tuple of two Pipe objects representing the read and write pipes for the parent process, or throws an Error if an error occurs.

spawnServer​

Same to spawnCellServer, but spawn from a specified source

Syntax​

export function spawnServer(
  index: number,
  source: SourceType,
  argv: string[],
): [Pipe, Pipe] {

Parameters​

  • index : The index of the source to spawn from
  • source : The type of source (use SOURCE_* constants)
  • argv: An array of strings representing the arguments to pass to the new process.

Return​

A tuple of two Pipe objects representing the read and write pipes for the parent process, or throws an Error if an error occurs.

runServer​

Runs the server with the provided service implementation. This function listens for incoming requests, processes them using the provided service, and sends back the responses. It uses the inherited file descriptors for communication.

Syntax​

export function runServer(handler: RequestHandler): void;

Parameters​

handler : The service implementation that handles the requests and generates the responses.

Return​

Never returns unless an error occurs, in which case it throws an Error.

Channel​

The Channel class facilitates IPC communication between a client and a server. It handles the transmission of requests from the client to the server and the reception of responses from the server to the client.

Channel.constructor​

Creates a new Channel instance

Syntax​

constructor(reader: Read, writer: Write);

Parameters​

  • reader : Responsible for reading data from the channel
  • writer : Responsible for writing data to the channel

Channel.execute​

Executes the server loop, processing incoming requests and sending responses.

Syntax​

execute(handler: RequestHandler): void

Parameters​

handler : A service that handles requests and generates responses

Channel.call​

Sends a request to the server and waits for a response.

This method handles the complete request-response cycle by sending the request to the server and then waiting for and returning the server's response.

Syntax​

call(req: RequestPacket): ResponsePacket

Parameters​

  • req : The request packet to send to the server

Return​

The response packet received from the server

Channel.sendErrorCode​

Sends an error code to the client

Syntax​

sendErrorCode(errorCode: number): void

Parameters​

  • errorCode - The error code to send

RequestHandler​

Interface for a service that can handle requests and generate responses

Syntax​

export interface RequestHandler {
  serve(req: RequestPacket): ResponsePacket;
}