fn write_eif_to_regions()

in src/enclave_proc/resource_manager.rs [1093:1158]

• 59 lines of code
• 6 McCabe index (conditional complexity)

fn write_eif_to_regions(
    eif_file: &mut File,
    regions: &[MemoryRegion],
    image_write_offset: usize,
) -> NitroCliResult<()> {
    let file_size = eif_file
        .metadata()
        .map_err(|_| {
            new_nitro_cli_failure!(
                "Failed to obtain EIF file metadata",
                NitroCliErrorEnum::FileOperationFailure
            )
        })?
        .len() as usize;

    eif_file.rewind().map_err(|_| {
        new_nitro_cli_failure!(
            "Failed to seek to the beginning of the EIF file",
            NitroCliErrorEnum::FileOperationFailure
        )
    })?;

    let mut total_written: usize = 0;

    for region in regions {
        let offset_plus_file_size = file_size.checked_add(image_write_offset).ok_or_else(|| {
            new_nitro_cli_failure!(
                "Memory overflow when trying to write EIF file",
                NitroCliErrorEnum::MemoryOverflow
            )
        })?;

        if total_written >= offset_plus_file_size {
            // All bytes have been written.
            break;
        }

        let written_plus_region_size = total_written
            .checked_add(region.mem_size as usize)
            .ok_or_else(|| {
                new_nitro_cli_failure!(
                    "Memory overflow when trying to write EIF file",
                    NitroCliErrorEnum::MemoryOverflow
                )
            })?;

        if written_plus_region_size <= image_write_offset {
            // All bytes need to be skipped to get to the image write offset.
        } else {
            let region_offset = image_write_offset.saturating_sub(total_written);
            let file_offset = total_written.saturating_sub(image_write_offset);
            let size = std::cmp::min(
                region.mem_size as usize - region_offset,
                file_size - file_offset,
            );
            region
                .fill_from_file(eif_file, region_offset, size)
                .map_err(|e| {
                    e.add_subaction("Failed to fill region with file content".to_string())
                })?;
        }
        total_written += region.mem_size as usize;
    }

    Ok(())
}