Trait Read

Source

pub trait Read: ErrorType {
    // Required method
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error>;

    // Provided method
    fn read_exact(
        &mut self,
        buf: &mut [u8],
    ) -> Result<(), ReadExactError<Self::Error>> { ... }
}

Expand description

Blocking reader.

This trait is the embedded-io equivalent of [std::io::Read].

Required Methods§

Source

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

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

If no bytes are currently available to read, this function blocks until at least one byte is available.

If bytes are available, a non-zero amount of bytes is read to the beginning of buf, and the amount is returned. It is not guaranteed that all available bytes are returned, it is possible for the implementation to read an amount of bytes less than buf.len() while there are more bytes immediately available.

If the reader is at end-of-file (EOF), Ok(0) is returned. There is no guarantee that a reader at EOF will always be so in the future, for example a reader can stop being at EOF if another process appends more bytes to the underlying file.

If buf.len() == 0, read returns without blocking, with either Ok(0) or an error. The Ok(0) doesn’t indicate EOF, unlike when called with a non-empty buffer.

Provided Methods§

Source

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

Read the exact number of bytes required to fill buf.

This function calls read() in a loop until exactly buf.len() bytes have been read, blocking if needed.

If you are using ReadReady to avoid blocking, you should not use this function. ReadReady::read_ready() returning true only guarantees the first call to read() will not block, so this function may still block in subsequent calls.