CFGPack Documentation

A MessagePack-based configuration library for embedded systems.

Embedded profile: no heap allocation. All buffers are caller-owned. Hard caps: max 128 schema entries.

Contents:

• Getting Started
  • Quick Start
  • Map Format
  • Building
• CFGPack API Reference
  • Errors
  • Values
  • Schema
  • Runtime API
  • Typed Convenience Functions
  • Usage Example
  • Dynamic Allocation Example
  • File I/O Wrappers (Optional)
  • LittleFS I/O Wrappers (Optional)
  • MessagePack Helpers (Internal-Facing)
• Schema Versioning & Remapping
  • Reserved Index
  • Detecting Schema Version
  • Migrating Between Schema Versions
  • Default Restoration During Remap
  • Type Widening Rules
  • Migration Workflow
  • Working Examples
• Compression Support
  • API
  • Usage Example
  • Implementation Notes
  • Compression Workflow
  • Compression Tool
  • Schema Pack Tool
  • Schema Validate Tool
  • Third-Party Libraries
• LittleFS Storage Wrappers
  • API
  • Scratch Buffer Layout
  • Usage Example
  • Composable I/O Pattern
  • Building
  • Error Codes
  • Working Example
  • Third-Party Library
• Stack Usage Analysis
  • Recommendations for Embedded Targets
  • Measurement Method
  • Per-Function Stack Frame Sizes
  • Worst-Case Call Chain Depths
  • Configuration Knobs Affecting Stack Usage
• Fuzz Testing
  • Why Fuzz the Parsers?
  • Fuzz Targets
  • Prerequisites
  • Building
  • Seed Corpus
  • Running
  • Investigating Crashes
  • Architecture

Features

• Fixed-cap schema (up to 128 entries) with typed values (u/i 8-64, f32/f64, str/fstr)

• Parses .map, JSON, and MessagePack binary schemas into caller-owned storage; no heap allocations

• Default values for schema entries, automatically applied at initialization

• Set/get by index and by schema name with type/length validation

• MessagePack encoding/decoding with size caps

• CRC-32C integrity checking on all serialized blobs (always on, verified on pagein)

• Measure-then-allocate for serialization via cfgpack_pageout_measure()

• Schema versioning with embedded schema name for version detection

• Index remapping and type widening for schema migrations

• Optional LZ4/heatshrink decompression support

• Optional LittleFS storage wrappers for flash-based embedded systems

Indices and tables

• Index

• Search Page