bao-tree 0.16.0

//! Define a number of newtypes and operations on these newtypes
//!
//! Most operations are concerned with node indexes in an in order traversal of a binary tree.
use std::{
    fmt,
    ops::{Add, Div, Mul, Sub},
};

use range_collections::range_set::RangeSetEntry;

/// A number of blake3 chunks.
///
/// This is a newtype for u64.
/// The blake3 chunk size is 1024 bytes.
#[repr(transparent)]
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct ChunkNum(pub u64);

impl std::fmt::Debug for ChunkNum {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        if f.alternate() {
            write!(f, "ChunkNum({:#x})", self.0)
        } else {
            write!(f, "{}", self.0)
        }
    }
}

impl std::fmt::Display for ChunkNum {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        std::fmt::Debug::fmt(self, f)
    }
}

impl RangeSetEntry for ChunkNum {
    fn min_value() -> Self {
        ChunkNum(0)
    }

    fn is_min_value(&self) -> bool {
        self.0 == 0
    }
}

impl Mul<u64> for ChunkNum {
    type Output = ChunkNum;

    fn mul(self, rhs: u64) -> Self::Output {
        ChunkNum(self.0 * rhs)
    }
}

impl Div<u64> for ChunkNum {
    type Output = ChunkNum;

    fn div(self, rhs: u64) -> Self::Output {
        ChunkNum(self.0 / rhs)
    }
}

impl Sub<u64> for ChunkNum {
    type Output = ChunkNum;

    fn sub(self, rhs: u64) -> Self::Output {
        ChunkNum(self.0 - rhs)
    }
}

impl Sub<ChunkNum> for ChunkNum {
    type Output = ChunkNum;

    fn sub(self, rhs: ChunkNum) -> Self::Output {
        ChunkNum(self.0 - rhs.0)
    }
}

impl Add<u64> for ChunkNum {
    type Output = ChunkNum;

    fn add(self, rhs: u64) -> Self::Output {
        ChunkNum(self.0 + rhs)
    }
}

impl Add<ChunkNum> for ChunkNum {
    type Output = ChunkNum;

    fn add(self, rhs: ChunkNum) -> Self::Output {
        ChunkNum(self.0 + rhs.0)
    }
}

impl PartialEq<u64> for ChunkNum {
    fn eq(&self, other: &u64) -> bool {
        self.0 == *other
    }
}

impl PartialEq<ChunkNum> for u64 {
    fn eq(&self, other: &ChunkNum) -> bool {
        *self == other.0
    }
}

impl PartialOrd<u64> for ChunkNum {
    fn partial_cmp(&self, other: &u64) -> Option<std::cmp::Ordering> {
        self.0.partial_cmp(other)
    }
}

impl ChunkNum {
    /// Convert to usize or panic if it doesn't fit.
    pub fn to_usize(self) -> usize {
        usize::try_from(self.0).expect("usize overflow")
    }
}

pub(crate) const BLAKE3_CHUNK_SIZE: usize = 1024;

/// A block size.
///
/// Block sizes are powers of 2, with the smallest being 1024 bytes.
/// They are encoded as the power of 2, minus 10, so 1 is 1024 bytes, 2 is 2048 bytes, etc.
///
/// Since only powers of 2 are valid, the log2 of the size in bytes / 1024 is given in the
/// constructor. So a block size of 0 is 1024 bytes, 1 is 2048 bytes, etc.
///
/// The actual size in bytes can be computed with [BlockSize::bytes].
#[repr(transparent)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct BlockSize(pub(crate) u8);

impl fmt::Display for BlockSize {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(&self, f)
    }
}

impl BlockSize {
    /// Create a block size from the log2 of the size in bytes / 1024
    ///
    /// 0 is 1024 bytes, 1 is 2048 bytes, etc.
    pub const fn from_chunk_log(chunk_log: u8) -> Self {
        Self(chunk_log)
    }

    /// Get the log2 of the number of 1 KiB blocks in a chunk.
    pub const fn chunk_log(self) -> u8 {
        self.0
    }

    /// The default block size, 1024 bytes
    ///
    /// This means that blocks and blake3 chunks are the same size.
    pub const ZERO: BlockSize = BlockSize(0);

    /// Number of bytes in a block at this level
    pub const fn bytes(self) -> usize {
        BLAKE3_CHUNK_SIZE << self.0
    }

    /// Compute a block size from bytes
    pub const fn from_bytes(bytes: u64) -> Option<Self> {
        if bytes.count_ones() != 1 {
            // must be a power of 2
            return None;
        }
        if bytes < 1024 {
            // must be at least 1024 bytes
            return None;
        }
        Some(Self((bytes.trailing_zeros() - 10) as u8))
    }

    /// Convert to an u32 for comparison with levels
    pub(crate) const fn to_u32(self) -> u32 {
        self.0 as u32
    }
}

impl ChunkNum {
    /// Start (inclusive) of the chunk group that this chunk is in
    pub const fn chunk_group_start(start: ChunkNum, block_size: BlockSize) -> ChunkNum {
        ChunkNum((start.0 >> block_size.0) << block_size.0)
    }

    /// End (exclusive) of the chunk group that this chunk the end for
    pub const fn chunk_group_end(end: ChunkNum, block_size: BlockSize) -> ChunkNum {
        let mask = (1 << block_size.0) - 1;
        let part = ((end.0 & mask) != 0) as u64;
        let whole = end.0 >> block_size.0;
        ChunkNum((whole + part) << block_size.0)
    }

    /// number of chunks that this number of bytes covers
    ///
    /// E.g. 1024 bytes is 1 chunk, 1025 bytes is 2 chunks
    pub const fn chunks(size: u64) -> ChunkNum {
        let mask = (1 << 10) - 1;
        let part = ((size & mask) != 0) as u64;
        let whole = size >> 10;
        ChunkNum(whole + part)
    }

    /// number of chunks that this number of bytes covers
    ///
    /// E.g. 1024 bytes is 1 chunk, 1025 bytes is still 1 chunk
    pub const fn full_chunks(size: u64) -> ChunkNum {
        ChunkNum(size >> 10)
    }

    /// number of bytes that this number of chunks covers
    pub const fn to_bytes(&self) -> u64 {
        self.0 << 10
    }
}