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#[derive(Debug, Default)]
#[doc(hidden)]
pub struct Buffer(usize, Vec<u8>);
impl From<Buffer> for Vec<u8> {
    fn from(Buffer(offset, mut vec): Buffer) -> Self {
        vec.copy_within(offset.., 0);
        vec.truncate(vec.len() - offset);
        vec
    }
}
impl From<Vec<u8>> for Buffer {
    fn from(value: Vec<u8>) -> Self {
        Self(0, value)
    }
}
impl std::ops::Deref for Buffer {
    type Target = [u8];

    fn deref(&self) -> &Self::Target {
        &self.1[self.0..]
    }
}
impl std::ops::DerefMut for Buffer {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.1[self.0..]
    }
}
#[doc(hidden)]
impl Buffer {
    pub fn truncate(&mut self, n: usize) {
        if n == 0 {
            self.0 = 0;
            self.1.truncate(0);
        } else {
            self.1.truncate(self.0 + n);
        }
    }

    pub fn extend_from_slice(&mut self, slice: &[u8]) {
        self.1.extend_from_slice(slice);
    }

    pub fn ignore_front(&mut self, n: usize) {
        self.0 += n;
        if self.0 >= self.1.len() {
            self.1.truncate(0);
            self.0 = 0;
        }
    }

    pub fn len(&self) -> usize {
        self.1.len() - self.0
    }

    pub fn is_empty(&self) -> bool {
        self.1.len() == self.0
    }

    pub fn fill_capacity(&mut self) {
        self.1.resize(self.1.capacity(), 0);
    }

    pub fn with_capacity(capacity: usize) -> Self {
        Self(0, Vec::with_capacity(capacity))
    }

    pub fn expand(&mut self) {
        if self.1.len() == self.1.capacity() {
            self.1.reserve(32);
        }
        self.fill_capacity();
    }
}