snarkvm-utilities 4.6.1

// Copyright (c) 2019-2026 Provable Inc.
// This file is part of the snarkVM library.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:

// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::{cmp, mem};

#[derive(Debug)]
pub struct Error;

pub type Result<T> = core::result::Result<T, Error>;

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

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

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

impl Read for &[u8] {
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
        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(())
    }
}

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

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

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

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