Function evaluate_storage 

pub fn evaluate_storage(
    path: &Path,
    dst: &Path,
    expected_sha256: Option<&str>,
) -> Result<(bool, bool), DatasetError>

Evaluate the storage state for a dataset file.

This helper ensures the target directory exists and checks whether the destination file is already present and valid. If expected_sha256 is None, any existing file at dst is accepted without validation.

Parameters

• path - Directory path where the dataset will be stored.
• dst - Destination file path for the dataset.
• expected_sha256 - Optional expected SHA256 hash for the dataset file. If None, any existing file at dst is accepted without validation.

Returns

• (need_acquire, need_overwrite) - Flags indicating whether a new file needs to be prepared and whether an existing file should be overwritten.

Errors

• DatasetError::IoError - Returned when creating the directory fails or when file I/O operations fail during hash verification.

Example

use dataset_core::utils::evaluate_storage;
use std::path::Path;
use std::io::Write;

let test_dir = "./evaluate_storage_example";
let dir_path = Path::new(test_dir);
let file_path = dir_path.join("data.txt");

// Case 1: Directory doesn't exist yet
let (need_acquire, need_overwrite) = evaluate_storage(
    dir_path,
    &file_path,
    None,
).unwrap();
assert!(need_acquire);     // File doesn't exist, a new file must be prepared
assert!(!need_overwrite);  // Nothing to overwrite

// Case 2: File exists with correct hash
let mut file = std::fs::File::create(&file_path).unwrap();
file.write_all(b"hello world").unwrap();
drop(file);

let correct_hash = "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9";
let (need_acquire, need_overwrite) = evaluate_storage(
    dir_path,
    &file_path,
    Some(correct_hash),
).unwrap();
assert!(!need_acquire);    // File exists with correct hash
assert!(!need_overwrite);

// Case 3: File exists but hash doesn't match
let wrong_hash = "0000000000000000000000000000000000000000000000000000000000000000";
let (need_acquire, need_overwrite) = evaluate_storage(
    dir_path,
    &file_path,
    Some(wrong_hash),
).unwrap();
assert!(need_acquire);     // Hash mismatch, a new file must be prepared
assert!(need_overwrite);   // Existing file needs to be replaced

// Clean up (dispensable)
std::fs::remove_dir_all(test_dir).unwrap();