Fmtstruct

Format-agnostic configuration loader supporting no_std, alloc, and std.

fmtstruct provides a flexible, compile-time or runtime-extensible interface for loading and parsing configuration files from various sources (Memory, FileSystem) into Rust structs, with optional validation and preprocessing hooks.

Features

• Format Agnostic: Support for multiple formats (JSON, TOML, YAML, Postcard) via feature flags.
• Flexible Loading:
  • StaticLoader: Zero-cost abstraction for compile-time defined source/format pairs.
  • DynLoader: Runtime automatic format detection and dynamic dispatch.
• Source Abstraction:
  • MemorySource: Useful for testing or embedded no_std environments.
  • FileSource: Secure file system access with sandbox protection against path traversal.
• Advanced Lifecycle:
  • PreProcess: Hooks for data normalization or context injection before validation.
  • ValidateConfig: Optional integration with the validator crate for struct validation.
• Environment Support: designed for no_std (requires alloc), alloc, and std environments seamlessly.

Usage Examples

Check the examples directory for runnable code:

• Basic Usage: examples/basic.rs - Load a configuration from a file with automatic format detection.
• Dynamic Loading: tests/loader_tests.rs - Examples of auto-detecting formats and handling parsing errors.
• Validation: tests/validation_tests.rs - Integrate validator to enforce rules on configuration fields.
• Preprocessing: tests/preprocess_tests.rs - Inject context (like filenames) into the configuration struct during loading.
• No-Std/Embedded: src/source/memory.rs - Use MemorySource for environments without a file system.

Installation

[dependencies]
fmtstruct = { version = "0.2", features = ["full"] }

Feature Flags

License

Released under the MIT License © 2026 Canmi