anychain-core 0.1.8

A core support for cryptocurrency wallets
Documentation 
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//! no-std io replacement
use crate::no_std::Vec;
use core::{cmp, fmt, mem};

pub trait Read {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>;
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>;
}

impl<R: Read + ?Sized> Read for &mut R {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
        (**self).read(buf)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error> {
        (**self).read_exact(buf)
    }
}

impl Read for &[u8] {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
        let amt = cmp::min(buf.len(), self.len());
        let (a, b) = self.split_at(amt);

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if amt == 1 {
            buf[0] = a[0];
        } else {
            buf[..amt].copy_from_slice(a);
        }

        *self = b;
        Ok(amt)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error> {
        if buf.len() > self.len() {
            return Err(Error);
        }
        let (a, b) = self.split_at(buf.len());

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if buf.len() == 1 {
            buf[0] = a[0];
        } else {
            buf.copy_from_slice(a);
        }

        *self = b;
        Ok(())
    }
}

pub trait Write {
    fn write(&mut self, buf: &[u8]) -> Result<usize, Error>;
    fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>;
}

impl<W: Write + ?Sized> Write for &mut W {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> Result<usize, Error> {
        (**self).write(buf)
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> Result<(), Error> {
        (**self).write_all(buf)
    }
}

impl Write for &mut [u8] {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> Result<usize, Error> {
        let amt = cmp::min(buf.len(), self.len());
        let (a, b) = mem::replace(self, &mut []).split_at_mut(amt);
        a.copy_from_slice(&buf[..amt]);
        *self = b;
        Ok(amt)
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> Result<(), Error> {
        let amt = cmp::min(buf.len(), self.len());
        let (a, b) = mem::replace(self, &mut []).split_at_mut(amt);
        a.copy_from_slice(&buf[..amt]);
        *self = b;

        if amt == buf.len() {
            Ok(())
        } else {
            Err(Error)
        }
    }
}

impl Write for Vec<u8> {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> Result<usize, Error> {
        self.extend_from_slice(buf);
        Ok(buf.len())
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> Result<(), Error> {
        self.extend_from_slice(buf);
        Ok(())
    }
}

#[derive(Debug)]
pub struct Error;

impl fmt::Display for Error {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        writeln!(f, "Error in no_std::io operation")
    }
}