Class FileImpl

packages/platform/deno/src/DenoFileSystem.ts:184–326

A file handle is stateful and must not be used concurrently.

/** A file handle is stateful and must not be used concurrently. */
class FileImpl implements FileSystem.File {
  readonly [FileSystem.FileTypeId]: typeof FileSystem.FileTypeId = FileSystem.FileTypeId
  private readonly file: Deno.FsFile
  private readonly append: boolean
  private position = BigInt(0)
  private nativePosition: bigint | undefined = undefined

  constructor(
    file: Deno.FsFile,
    append: boolean
  ) {
    this.file = file
    this.append = append
  }

  get stat() {
    return Effect.map(
      tryPromise("stat", undefined, () => this.file.stat()),
      makeFileInfo
    )
  }

  get sync() {
    return tryPromise("sync", undefined, () => this.file.sync())
  }

  seek(offset: FileSystem.SizeInput, from: FileSystem.SeekMode) {
    const size = FileSystem.Size(offset)
    return Effect.sync(() => {
      if (from === "start") {
        this.position = size
      } else {
        this.position += size
      }
      return FileSystem.Size(this.position)
    })
  }

  private readChunk(method: string, buffer: Uint8Array) {
    return Effect.suspend(() => {
      const position = this.position
      return Effect.map(
        tryPromise(
          method,
          undefined,
          async () => {
            if (this.nativePosition !== position) {
              this.file.seekSync(position, Deno.SeekMode.Start)
            }
            this.nativePosition = undefined
            return await this.file.read(buffer)
          }
        ),
        (bytesRead) => {
          const sizeRead = FileSystem.Size(bytesRead ?? 0)
          this.position = this.nativePosition = position + sizeRead
          return sizeRead
        }