Function read_column

nodedb/src/engine/timeseries/packed_partition.rs:337–350

Read a single column's data from a packed file using byte range. When `footer.payload_encrypted` is true, `kek` must be `Some`; the payload region (everything before the footer body) is decrypted first, then the column range is extracted from the plaintext. The NDPK footer itself is always plaintext.

(
    file_path: &Path,
    footer: &PackedFooter,
    column_name: &str,
    kek: Option<&WalEncryptionKey>,
)

/// column range is extracted from the plaintext. The NDPK footer itself is
/// always plaintext.
pub fn read_column(
    file_path: &Path,
    footer: &PackedFooter,
    column_name: &str,
    kek: Option<&WalEncryptionKey>,
) -> Result<Vec<u8>, PackedError> {
    let (offset, length) = footer
        .column_ranges
        .get(column_name)
        .ok_or_else(|| PackedError::Corrupt(format!("column '{column_name}' not in footer")))?;

    let data = std::fs::read(file_path).map_err(|e| PackedError::Io(format!("read: {e}")))?;
    read_column_from_bytes(&data, footer, *offset, *length, kek)
}

/// Read a single column from in-memory file bytes (for testing).
fn read_column_from_bytes(