holos-tda 0.9.0

Vietoris-Rips persistence and checked degree-Rips modules
Documentation 
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use crate::{Error, KineticEdgeKey, Result};

pub(super) fn decode_edges(
    reader: &mut Reader<'_>,
    vertex_count: usize,
    maximum: usize,
) -> Result<Vec<KineticEdgeKey>> {
    let count = reader.bounded_usize("edge count", maximum)?;
    if count > reader.remaining() / 16 {
        return Err(Error::InvalidInput(
            "coverage edge count exceeds the remaining bytes".into(),
        ));
    }
    let edges = (0..count)
        .map(|_| {
            Ok(KineticEdgeKey {
                u: reader.usize()?,
                v: reader.usize()?,
            })
        })
        .collect::<Result<Vec<_>>>()?;
    if edges
        .iter()
        .any(|edge| edge.u >= edge.v || edge.v >= vertex_count)
        || edges.windows(2).any(|pair| pair[0] >= pair[1])
    {
        return Err(Error::InvalidInput(
            "coverage edges are not canonical".into(),
        ));
    }
    Ok(edges)
}

pub(super) fn decode_usizes(reader: &mut Reader<'_>, maximum: usize) -> Result<Vec<usize>> {
    let count = reader.bounded_usize("integer list count", maximum)?;
    if count > reader.remaining() / 8 {
        return Err(Error::InvalidInput(
            "coverage integer list exceeds the remaining bytes".into(),
        ));
    }
    (0..count).map(|_| reader.usize()).collect()
}

pub(super) fn decode_indices(
    reader: &mut Reader<'_>,
    exclusive_maximum: usize,
    maximum_count: usize,
) -> Result<Vec<usize>> {
    let values = decode_usizes(reader, maximum_count)?;
    if values.iter().any(|value| *value >= exclusive_maximum)
        || values.windows(2).any(|pair| pair[0] >= pair[1])
    {
        return Err(Error::InvalidInput(
            "coverage index list is not canonical".into(),
        ));
    }
    Ok(values)
}

pub(in crate::coverage_synthesis::wire) struct Reader<'a> {
    bytes: &'a [u8],
    position: usize,
}

impl<'a> Reader<'a> {
    pub(in crate::coverage_synthesis::wire) fn new(bytes: &'a [u8]) -> Self {
        Self { bytes, position: 0 }
    }

    pub(super) fn remaining(&self) -> usize {
        self.bytes.len() - self.position
    }

    pub(super) fn take(&mut self, count: usize) -> Result<&'a [u8]> {
        let end = self
            .position
            .checked_add(count)
            .ok_or_else(|| Error::InvalidInput("coverage artifact position overflows".into()))?;
        if end > self.bytes.len() {
            return Err(Error::InvalidInput("coverage artifact is truncated".into()));
        }
        let value = &self.bytes[self.position..end];
        self.position = end;
        Ok(value)
    }

    pub(super) fn bounded_usize(&mut self, name: &str, maximum: usize) -> Result<usize> {
        let value = self.usize()?;
        if value > maximum {
            return Err(Error::InvalidInput(format!(
                "coverage {name} exceeds its limit"
            )));
        }
        Ok(value)
    }

    pub(super) fn u8(&mut self) -> Result<u8> {
        Ok(self.take(1)?[0])
    }

    pub(super) fn u16(&mut self) -> Result<u16> {
        Ok(u16::from_be_bytes(self.take(2)?.try_into().unwrap()))
    }

    pub(super) fn u32(&mut self) -> Result<u32> {
        Ok(u32::from_be_bytes(self.take(4)?.try_into().unwrap()))
    }

    pub(super) fn u64(&mut self) -> Result<u64> {
        Ok(u64::from_be_bytes(self.take(8)?.try_into().unwrap()))
    }

    pub(super) fn usize(&mut self) -> Result<usize> {
        usize::try_from(self.u64()?)
            .map_err(|_| Error::InvalidInput("coverage integer does not fit usize".into()))
    }

    pub(super) fn optional_u64(&mut self) -> Result<Option<u64>> {
        match self.u8()? {
            0 => Ok(None),
            1 => Ok(Some(self.u64()?)),
            _ => Err(Error::InvalidInput(
                "coverage optional integer flag is invalid".into(),
            )),
        }
    }

    pub(super) fn optional_usize(&mut self) -> Result<Option<usize>> {
        match self.u8()? {
            0 => Ok(None),
            1 => Ok(Some(self.usize()?)),
            _ => Err(Error::InvalidInput(
                "coverage optional integer flag is invalid".into(),
            )),
        }
    }

    pub(super) fn array32(&mut self) -> Result<[u8; 32]> {
        Ok(self.take(32)?.try_into().unwrap())
    }
}