io.vertx.core.file

## Interface AsyncFile

- All Superinterfaces:
    ReadStream<Buffer>, StreamBase, WriteStream<Buffer>

      public interface AsyncFile
      extends ReadStream<Buffer>, WriteStream<Buffer>

  Represents a file on the file-system which can be read from, or written to asynchronously.

  This class also implements `ReadStream` and `WriteStream`. This allows the data to be pumped to and from other streams, e.g. an `HttpClientRequest` instance, using the `Pump` class

  Author:
    Tim Fox

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `close()` Close the file.
    `void` | `close(Handler<AsyncResult<Void>> handler)` Close the file.
    `AsyncFile` | `drainHandler(Handler<Void> handler)` Set a drain handler on the stream.
    `AsyncFile` | `endHandler(Handler<Void> endHandler)` Set an end handler.
    `AsyncFile` | `exceptionHandler(Handler<Throwable> handler)` Set an exception handler on the read stream.
    `AsyncFile` | `flush()` Flush any writes made to this file to underlying persistent storage.
    `AsyncFile` | `flush(Handler<AsyncResult<Void>> handler)` Same as `flush()` but the handler will be called when the flush is complete or if an error occurs
    `AsyncFile` | `handler(Handler<Buffer> handler)` Set a data handler.
    `AsyncFile` | `pause()` Pause the `ReadSupport`.
    `AsyncFile` | `read(Buffer buffer, int offset, long position, int length, Handler<AsyncResult<Buffer>> handler)` Reads `length` bytes of data from the file at position `position` in the file, asynchronously.
    `AsyncFile` | `resume()` Resume reading.
    `AsyncFile` | `setReadPos(long readPos)` Sets the position from which data will be read from when using the file as a `ReadStream`.
    `AsyncFile` | `setWritePos(long writePos)` Sets the position from which data will be written when using the file as a `WriteStream`.
    `AsyncFile` | `setWriteQueueMaxSize(int maxSize)` Set the maximum size of the write queue to `maxSize`.
    `AsyncFile` | `write(Buffer data)` Write some data to the stream.
    `AsyncFile` | `write(Buffer buffer, long position, Handler<AsyncResult<Void>> handler)` Write a `Buffer` to the file at position `position` in the file, asynchronously.

    - ### Methods inherited from interface io.vertx.core.streams.WriteStream

      `writeQueueFull`

- - ### Method Detail

    - #### handler

          AsyncFile handler(Handler<Buffer> handler)

      Description copied from interface: `ReadStream`
      Set a data handler. As data is read, the handler will be called with the data.
      Specified by:
        `handler` in interface `ReadStream<Buffer>`
      Returns:
        a reference to this, so the API can be used fluently

    - #### pause

          AsyncFile pause()

      Description copied from interface: `ReadStream`
      Pause the `ReadSupport`. While it's paused, no data will be sent to the `dataHandler`
      Specified by:
        `pause` in interface `ReadStream<Buffer>`
      Returns:
        a reference to this, so the API can be used fluently

    - #### resume

          AsyncFile resume()

      Description copied from interface: `ReadStream`
      Resume reading. If the `ReadSupport` has been paused, reading will recommence on it.
      Specified by:
        `resume` in interface `ReadStream<Buffer>`
      Returns:
        a reference to this, so the API can be used fluently

    - #### endHandler

          AsyncFile endHandler(Handler<Void> endHandler)

      Description copied from interface: `ReadStream`
      Set an end handler. Once the stream has ended, and there is no more data to be read, this handler will be called.
      Specified by:
        `endHandler` in interface `ReadStream<Buffer>`
      Returns:
        a reference to this, so the API can be used fluently

    - #### write

          AsyncFile write(Buffer data)

      Description copied from interface: `WriteStream`
      Write some data to the stream. The data is put on an internal write queue, and the write actually happens asynchronously. To avoid running out of memory by putting too much on the write queue, check the `WriteStream.writeQueueFull()` method before writing. This is done automatically if using a `Pump`.
      Specified by:
        `write` in interface `WriteStream<Buffer>`
      Parameters:
        `data` - the data to write
      Returns:
        a reference to this, so the API can be used fluently

    - #### setWriteQueueMaxSize

          AsyncFile setWriteQueueMaxSize(int maxSize)

      Description copied from interface: `WriteStream`
      Set the maximum size of the write queue to `maxSize`. You will still be able to write to the stream even if there is more than `maxSize` bytes in the write queue. This is used as an indicator by classes such as `Pump` to provide flow control.
      Specified by:
        `setWriteQueueMaxSize` in interface `WriteStream<Buffer>`
      Parameters:
        `maxSize` - the max size of the write stream
      Returns:
        a reference to this, so the API can be used fluently

    - #### drainHandler

          AsyncFile drainHandler(Handler<Void> handler)

      Description copied from interface: `WriteStream`
      Set a drain handler on the stream. If the write queue is full, then the handler will be called when the write queue has been reduced to maxSize / 2. See `Pump` for an example of this being used.
      Specified by:
        `drainHandler` in interface `WriteStream<Buffer>`
      Parameters:
        `handler` - the handler
      Returns:
        a reference to this, so the API can be used fluently

    - #### exceptionHandler

          AsyncFile exceptionHandler(Handler<Throwable> handler)

      Description copied from interface: `ReadStream`
      Set an exception handler on the read stream.
      Specified by:
        `exceptionHandler` in interface `ReadStream<Buffer>`
      Specified by:
        `exceptionHandler` in interface `StreamBase`
      Specified by:
        `exceptionHandler` in interface `WriteStream<Buffer>`
      Parameters:
        `handler` - the exception handler
      Returns:
        a reference to this, so the API can be used fluently

    - #### close

          void close()

      Close the file. The actual close happens asynchronously.

    - #### close

          void close(Handler<AsyncResult<Void>> handler)

      Close the file. The actual close happens asynchronously. The handler will be called when the close is complete, or an error occurs.
      Parameters:
        `handler` - the handler

    - #### write

          AsyncFile write(Buffer buffer,
                          long position,
                          Handler<AsyncResult<Void>> handler)

      Write a `Buffer` to the file at position `position` in the file, asynchronously.

      If `position` lies outside of the current size of the file, the file will be enlarged to encompass it.

      When multiple writes are invoked on the same file there are no guarantees as to order in which those writes actually occur

      The handler will be called when the write is complete, or if an error occurs.

      Parameters:
        `buffer` - the buffer to write
        `position` - the position in the file to write it at
        `handler` - the handler to call when the write is complete
      Returns:
        a reference to this, so the API can be used fluently

    - #### read

          AsyncFile read(Buffer buffer,
                         int offset,
                         long position,
                         int length,
                         Handler<AsyncResult<Buffer>> handler)

      Reads `length` bytes of data from the file at position `position` in the file, asynchronously.

      The read data will be written into the specified `Buffer buffer` at position `offset`.

      If data is read past the end of the file then zero bytes will be read.

      When multiple reads are invoked on the same file there are no guarantees as to order in which those reads actually occur.

      The handler will be called when the close is complete, or if an error occurs.

      Parameters:
        `buffer` - the buffer to read into
        `offset` - the offset into the buffer where the data will be read
        `position` - the position in the file where to start reading
        `length` - the number of bytes to read
        `handler` - the handler to call when the write is complete
      Returns:
        a reference to this, so the API can be used fluently

    - #### flush

          AsyncFile flush()

      Flush any writes made to this file to underlying persistent storage.

      If the file was opened with `flush` set to `true` then calling this method will have no effect.

      The actual flush will happen asynchronously.

      Returns:
        a reference to this, so the API can be used fluently

    - #### flush

          AsyncFile flush(Handler<AsyncResult<Void>> handler)

      Same as `flush()` but the handler will be called when the flush is complete or if an error occurs

    - #### setReadPos

          AsyncFile setReadPos(long readPos)

      Sets the position from which data will be read from when using the file as a `ReadStream`.
      Parameters:
        `readPos` - the position in the file
      Returns:
        a reference to this, so the API can be used fluently

    - #### setWritePos

          AsyncFile setWritePos(long writePos)

      Sets the position from which data will be written when using the file as a `WriteStream`.
      Parameters:
        `writePos` - the position in the file
      Returns:
        a reference to this, so the API can be used fluently

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