Module atomic 

Atomic file I/O utilities for concurrency-safe cache operations.

This module provides:

• Atomic writes via temp-file + rename to prevent partial/corrupt files.
• Advisory file locking for coordinating concurrent access to cache directories.

Concurrency Guarantees

• A reader will never see a partially written file.
• Concurrent writers to the same path will not interleave bytes; the last rename wins, producing one complete file.
• Advisory locks coordinate cache-directory operations across processes.

Cross-Platform Notes

• On POSIX systems, rename(2) is atomic within the same filesystem.
• On Windows, std::fs::rename uses MoveFileEx with MOVEFILE_REPLACE_EXISTING, which is atomic for same-volume renames.

Structs

DirLock

An advisory file lock scoped to a directory.

Functions

atomic_write

Write data to path atomically by writing to a temporary sibling file and then renaming it into place.

atomic_write_sync

Synchronous version of atomic_write for use in contexts that cannot use async (e.g., the FileSystem trait).