Method write_unhashed

atomic-core/src/change/format_v3/writer/sections.rs:172–205

Write the optional UNHASHED section. This section is NOT included in the content hash. It's intended for data that shouldn't affect the change's identity: AI transcripts, reasoning traces, editor state, review comments, etc. The payload is provided as raw bytes (typically JSON-serialized). The writer compresses it with zstd but does NOT feed it through the blake3 hasher. # Arguments `data` - T

(&mut self, data: &[u8])

    /// - Zstd compression errors.
    /// - I/O errors.
    pub fn write_unhashed(&mut self, data: &[u8]) -> FormatResult<()> {
        self.ensure_metadata_complete()?;
        self.transition_to_at_least(WriterState::WritingContent)?;

        if self.state == WriterState::WroteUnhashed || self.state == WriterState::Finalized {
            return Err(FormatError::UnexpectedSection {
                got: "UNHASHED".to_string(),
                expected: format!(
                    "UNHASHED can only be written once, state is {}",
                    self.state.name()
                ),
            });
        }

        // Compress the data
        let compressed = zstd::encode_all(data, self.options.compression_level())
            .map_err(|e| FormatError::Compress(e.to_string()))?;

        // Write section header + compressed payload
        let section_header = SectionHeader::new(SectionType::Unhashed, compressed.len() as u32);
        section_header.write_to(self.writer)?;
        self.writer.write_all(&compressed)?;

        // NOTE: Do NOT feed through hasher — unhashed section is excluded
        // from the content hash by design.

        self.stats.sections_written += 1;
        self.stats.total_uncompressed += data.len() as u64;
        self.stats.total_compressed += compressed.len() as u64;
        self.stats.total_bytes_written += (SectionHeader::SIZE + compressed.len()) as u64;

        self.state = WriterState::WroteUnhashed;
        Ok(())
    }
}