coreHTTP Client Library

This repository contains a C language HTTP client library designed for embedded platforms. It has no dependencies on any additional libraries other than the standard C library, llhttp, and a customer-implemented transport interface. This library is distributed under the MIT Open Source License.

This library has gone through code quality checks including verification that no function has a GNU Complexity score over 8. This library has also undergone both static code analysis from Coverity static analysis, and validation of memory safety and data structure invariance through the CBMC automated reasoning tool.

See memory requirements for this library here.

coreHTTP v3.0.0 source code is part of the FreeRTOS 202210.00 LTS release.

coreHTTP v2.0.0 source code is part of the FreeRTOS 202012.00 LTS release.

coreHTTP Config File

The HTTP client library exposes configuration macros that are required for building the library. A list of all the configurations and their default values are defined in core_http_config_defaults.h. To provide custom values for the configuration macros, a custom config file named core_http_config.h can be provided by the user application to the library.

By default, a core_http_config.h custom config is required to build the library. To disable this requirement and build the library with default configuration values, provide HTTP_DO_NOT_USE_CUSTOM_CONFIG as a compile time preprocessor macro.

The HTTP client library can be built by either:

• Defining a core_http_config.h file in the application, and adding it to the include directories for the library build. OR
• Defining the HTTP_DO_NOT_USE_CUSTOM_CONFIG preprocessor macro for the library build.

Building the Library

The httpFilePaths.cmake file contains the information of all source files and header include paths required to build the HTTP client library.

As mentioned in the previous section, either a custom config file (i.e. core_http_config.h) OR HTTP_DO_NOT_USE_CUSTOM_CONFIG macro needs to be provided to build the HTTP client library.

For a CMake example of building the HTTP library with the httpFilePaths.cmake file, refer to the coverity_analysis library target in test/CMakeLists.txt file.

Building Unit Tests

Platform Prerequisites

• For running unit tests, the following are required:
  • C90 compiler like gcc
  • CMake 3.13.0 or later
  • Ruby 2.0.0 or later is required for this repository's CMock test framework.
• For running the coverage target, the following are required:
  • gcov
  • lcov

Steps to build Unit Tests

1. Go to the root directory of this repository.

2. Run the cmake command: cmake -S test -B build -DBUILD_CLONE_SUBMODULES=ON

3. Run this command to build the library and unit tests: make -C build all

4. The generated test executables will be present in build/bin/tests folder.

5. Run cd build && ctest to execute all tests and view the test run summary.

CBMC

To learn more about CBMC and proofs specifically, review the training material here.

The test/cbmc/proofs directory contains CBMC proofs.

In order to run these proofs you will need to install CBMC and other tools by following the instructions here.

Reference examples

The AWS IoT Device SDK for Embedded C repository contains demos of using the HTTP client library here on a POSIX platform. These can be used as reference examples for the library API.

Documentation

Existing Documentation

For pre-generated documentation, please see the documentation linked in the locations below:

Location
AWS IoT Device SDK for Embedded C
FreeRTOS.org

Note that the latest included version of coreHTTP may differ across repositories.

Generating Documentation

The Doxygen references were created using Doxygen version 1.9.2. To generate the Doxygen pages, please run the following command from the root of this repository:

doxygen docs/doxygen/config.doxyfile

Contributing

See CONTRIBUTING.md for information on contributing.