nordisk/edda

crates/gunnar-bitmap/src/error.rs

//! One error type for the whole crate.

/// Everything that can go wrong reading or writing a `.bitmap`.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum Error {
    #[error("expected {wanted} but the input ended")]
    /// The input ran out where a field was expected.
    UnexpectedEof {
        /// What the parser was looking for.
        wanted: &'static str,
    },
    #[error("corrupt ewah bitmap: {reason}")]
    /// The compressed stream does not describe a well-formed chunk sequence.
    CorruptEwah {
        /// Why the stream was rejected.
        reason: &'static str,
    },
    #[error("not a bitmap index: expected the magic {expected:?}, got {actual:?}")]
    /// The file does not start with `BITM`.
    Magic {
        /// Always `BITM`.
        expected: &'static [u8; 4],
        /// What was there instead.
        actual: [u8; 4],
    },
    #[error("unsupported bitmap index version {actual}, only version 1 exists")]
    /// A version other than 1, which is the only one that exists.
    Version {
        /// The version that was found.
        actual: u16,
    },
    #[error(
        "the BITMAP_OPT_FULL_DAG flag (0x1) is required by the format but flags are {flags:#06x}"
    )]
    /// The mandatory `BITMAP_OPT_FULL_DAG` flag is absent.
    MissingFullDag {
        /// The flags as read.
        flags: u16,
    },
    #[error(
        "bit {bit} was set after bit_size had already reached {bit_size}; \
             set_bit needs strictly ascending positions"
    )]
    /// [`crate::Builder::set_bit`] was given a non-ascending position.
    BitsOutOfOrder {
        /// The offending position.
        bit: u32,
        /// How far the builder had already got.
        bit_size: u64,
    },
    #[error("entry {entry} is xor-compressed against entry {entry} - {offset}, which is before the start of the file")]
    /// An entry names an XOR base that lies before the first entry.
    XorBeforeStart {
        /// Index of the entry at fault.
        entry: usize,
        /// The offset it asked for.
        offset: u8,
    },
    #[error("the trailing bytes are not a whole number of 32-bit name hashes ({tail} bytes left)")]
    /// The bytes after the entries are not a whole number of name hashes.
    TrailingBytes {
        /// How many bytes were left over.
        tail: usize,
    },
    #[error("no bitmap is stored for commit at pack index position {pos}")]
    /// The index stores no bitmap for the requested commit.
    NoBitmapForCommit {
        /// The pack index position asked for.
        pos: u32,
    },
    /// The trailing checksum does not match the file body.
    #[error(
        "the bitmap's trailing checksum {expected} does not match its contents; \
         the file is corrupt or truncated"
    )]
    ChecksumMismatch {
        /// The checksum the file claims.
        expected: gix_hash::ObjectId,
    },
    /// The object count derived from the file disagrees with the pack.
    #[error("the bitmap covers {in_bitmap} objects but the pack holds {in_pack}")]
    ObjectCountMismatch {
        /// Objects the bitmap's name-hash cache accounts for.
        in_bitmap: u32,
        /// Objects actually in the pack.
        in_pack: u32,
    },
    #[error("io error")]
    /// Reading or writing the file failed.
    Io(#[from] std::io::Error),
}