CRC

Overview

CRC is a small C library for calculating 8/16/32-bit checksums using standard, well-known polynomials. It provides simple, dependency-free functions and optional LUT-accelerated variants.

Supported Polynomials

• CRC8-ITU (Poly 0x07, Init 0x00, no input/output bit reflection, XorOut 0x55)
• CRC16-CCITT BLUETOOTH CCITT-TRUE V-41-LSB KERMIT (Poly 0x1021, Init 0x0000, input/output bit reflection, XorOut 0x0000)
• CRC16-MODBUS (Poly 0x8005, Init 0xFFFF, input/output bit reflection, XorOut 0x0000)
• CRC32-POSIX/cksum (Poly 0x04C11DB7, Init 0x00000000, no input/output bit reflection, XorOut 0xFFFFFFFF)

Core APIs

Headers:

• embetech/crc8.h
• embetech/crc16.h
• embetech/crc32.h

Version helper:

• CRC_GetVersionString() in embetech/crc.h

Representative functions:

• CRC-8 (ITU): CRC8_ITU_Init, CRC8_ITU_UpdateUsingFormula, CRC8_ITU_UpdateUsingLut, CRC8_ITU_Finalize
• CRC-16 CCITT: CRC16_CCITT_Init, CRC16_CCITT_UpdateUsingFormula, CRC16_CCITT_UpdateUsingLut, CRC16_CCITT_Finalize
• CRC-16 MODBUS: CRC16_MODBUS_Init, CRC16_MODBUS_UpdateUsingFormula, CRC16_MODBUS_UpdateUsingLut, CRC16_MODBUS_Finalize
• CRC-32 POSIX/cksum: CRC32_CKSUM_Init, CRC32_CKSUM_UpdateUsingFormula, CRC32_CKSUM_UpdateUsingLut, CRC32_CKSUM_Finalize

Installation

This project uses CPM.cmake for source consumption and also supports installable CMake package metadata.

Using CPM.cmake in your project:

# Download CPM.cmake (pin version as needed)
file(DOWNLOAD
  https://github.com/cpm-cmake/CPM.cmake/releases/download/v0.42.0/CPM.cmake
  ${CMAKE_BINARY_DIR}/cmake/CPM.cmake
  EXPECTED_HASH SHA256=2020b4fc42dba44817983e06342e682ecfc3d2f484a581f11cc5731fbe4dce8a
)
include(${CMAKE_BINARY_DIR}/cmake/CPM.cmake)

# Add crc (pin to a released tag or major stream)
CPMAddPackage("gh:embetech-official/crc@2")

add_executable(app main.c)
target_link_libraries(app PRIVATE embetech::crc)

Include headers via:

#include <embetech/crc.h>
#include <embetech/crc8.h>
#include <embetech/crc16.h>
#include <embetech/crc32.h>

Build

Use CMake Presets (Ninja Multi-Config) for a streamlined workflow:

cmake --workflow --preset native-gcc

The workflow configures, builds Debug, runs tests, and installs Debug+Release.

Options

• CRC_TESTS (default: ON if top-level): Builds unit tests (GoogleTest via CPM).
• CRC_DOC (default: ON if top-level): Builds Doxygen docs.
• CRC_EXAMPLES (default: ON if top-level): Builds example targets.
• CRC_INSTALL (default: ON): Enables install targets and generates CMake package config files.

Configure-time overrides, for example:

cmake --preset native-gcc -D CRC_TESTS=ON -D CRC_DOC=OFF -D CRC_EXAMPLES=ON

Dependencies

• Runtime: none.
• Tests: google/googletest (fetched via CPM when tests are enabled).
• Optional: if embetile is available, an additional API file is compiled and linked automatically.

Usage Example

Minimal example computing CRC-8, CRC-16 CCITT, and CRC-32 checksums:

#include <embetech/crc8.h>
#include <embetech/crc16.h>
#include <embetech/crc32.h>

int main(void) {
  unsigned char data[100] = {0};

  // CRC-8 ITU (formula or LUT variant)
  uint8_t c8 = CRC8_ITU_Init();
  c8 = CRC8_ITU_UpdateUsingLut(data, sizeof(data), c8);
  c8 = CRC8_ITU_Finalize(c8);

  // CRC-16 CCITT
  uint16_t c16 = CRC16_CCITT_Init();
  c16 = CRC16_CCITT_UpdateUsingLut(data, sizeof(data), c16);
  c16 = CRC16_CCITT_Finalize(c16);

  // CRC-32 POSIX/cksum
  uint32_t c32 = CRC32_CKSUM_Init();
  c32 = CRC32_CKSUM_UpdateUsingLut(data, sizeof(data), c32);
  c32 = CRC32_CKSUM_Finalize(c32);

  (void)c8; (void)c16; (void)c32;
  return 0;
}

Versioning

CRC_GetVersionString() returns the library version string. When built at the repository top-level, a short git commit id is appended (e.g., X.Y.Z+abcdef12).

Contributing

Issues and PRs are welcome. Please use the provided presets to build, run tests, and keep changes focused.