Struct Multireader 

pub struct Multireader<R: Seek> { /* private fields */ }

Structure that provides seeking and reading in a sequence of underlying readables.

Note: all readers except for the last one MUST have constant size so that we can rely on offsets for indexing across them. This will be true for the case of reading logrotated files.

Usage

Create a Multireader from a collection of items. Items are required to implement Seek, and must additionally support Read and BufRead to provide such functionality on resulting aggregate.

let inner_items = vec![Cursor::new(vec![1, 2, 3]), Cursor::new(vec![4, 5])];
// we get result here because Multireader performs seek
// (fallible operation) under the hood to determine sizes
let mut reader = Multireader::new(inner_items)?;
reader.read_to_end(&mut buf)?;
assert_eq!(buf, vec![1, 2, 3, 4, 5]);

Multireader allows seeking inside multiple underlying items as if you only had one big buffer.

reader.seek(SeekFrom::Start(3))?;
assert_eq!(reader.get_global_offset(), 3);
// you can get index of current item as well as offset into it
assert_eq!(reader.get_current_item_index(), 1);
assert_eq!(reader.get_local_offset(), 0);

Implementations

impl<R: Seek> Multireader<R>

pub fn new(items: Vec<R>) -> Result<Self>

Create a Multireader from a nonempty collection of readers.

This function returns io::Result because it will use seek to determine sizes which can fail.

pub fn get_global_offset(&self) -> u64

Offset amoung all underlying items.

pub fn get_local_offset(&self) -> u64

Offset inside current item.

pub fn len(&self) -> usize

Number of underlying items.

pub fn get_current_item_index(&self) -> usize

index of an item that is currently read.

pub fn into_inner(self) -> Vec<R>

Destroy the struct and return underlying readers.

pub fn get_total_size(&mut self) -> Result<u64>

Get total size of underlying items.

Computes total size of underlying items. This method requires mut ref and returns io::Result because we need to seek inside last item to determine its size at the moment of call.

pub fn seek_current_item(&mut self, pos: SeekFrom) -> Result<u64>

Seek current underlying reader properly updating any internal state.

Returns current local offset after seek.

pub fn seek_to_item_start(&mut self, item_index: usize) -> Result<u64>

Perform seek to 0 offset in item identified by item_index.

pub fn seek_by_local_index( &mut self, item_index: usize, pos: SeekFrom, ) -> Result<u64>

Seek globally by providing local pos inside item at index item_index.

Provided pos must be inside indexed item. Returns current local offset.

pub fn get_current_item_size(&self) -> Option<u64>

Returns item size of item. If it is last, returns None instead.

To determine size of last item, use get_last_item_size.

pub fn get_bytes_before_current_item(&self) -> u64

Computes global offset from which current item starts.

pub fn get_last_item_size(&mut self) -> Result<u64>

Computes last item size.

Last file in this reader may still be written into, so this number may soon become invalid.

Trait Implementations

impl<R: BufRead + Seek> BufRead for Multireader<R>

fn fill_buf(&mut self) -> Result<&[u8]>

Returns the contents of the internal buffer, filling it with more data, via Read methods, if empty.

fn consume(&mut self, amt: usize)

Marks the given amount of additional bytes from the internal buffer as having been read. Subsequent calls to read only return bytes that have not been marked as read.

fn has_data_left(&mut self) -> Result<bool, Error>

🔬This is a nightly-only experimental API. (buf_read_has_data_left)

Checks if there is any data left to be read.

fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes into buf until the delimiter byte or EOF is reached.

fn skip_until(&mut self, byte: u8) -> Result<usize, Error>

Skips all bytes until the delimiter byte or EOF is reached.

fn read_line(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until a newline (the 0xA byte) is reached, and append them to the provided String buffer.

fn split(self, byte: u8) -> Split<Self>

where Self: Sized,

Returns an iterator over the contents of this reader split on the byte byte.

fn lines(self) -> Lines<Self>

where Self: Sized,

Returns an iterator over the lines of this reader.

impl<R: Read + Seek> Read for Multireader<R>

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Reads the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Reads the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Read.

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

impl<R: Seek> Seek for Multireader<R>

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.