R: InputStream classes

InputStream {arrow} | R Documentation

## InputStream classes

### Description

`RandomAccessFile` inherits from `InputStream` and is a base class for: `ReadableFile` for reading from a file; `MemoryMappedFile` for the same but with memory mapping; and `BufferReader` for reading from a buffer. Use these with the various table readers.

### Factory

The `$create()` factory methods instantiate the `InputStream` object and take the following arguments, depending on the subclass:

- `path` For `ReadableFile`, a character file name

- `x` For `BufferReader`, a Buffer or an object that can be made into a buffer via `buffer()`.

To instantiate a `MemoryMappedFile`, call `mmap_open()`.

### Methods

- `$GetSize()`:

- `$supports_zero_copy()`: Logical

- `$seek(position)`: go to that position in the stream

- `$tell()`: return the position in the stream

- `$close()`: close the stream

- `$Read(nbytes)`: read data from the stream, either a specified `nbytes` or all, if `nbytes` is not provided

- `$ReadAt(position, nbytes)`: similar to `$seek(position)$Read(nbytes)`

- `$Resize(size)`: for a `MemoryMappedFile` that is writeable

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