libexif Nuget Package

This project builds a libexif Nuget package with static libexif libraries and header files for the x64 platform and Debug/ Release configurations.

Visit libexif website for additional information about the libexif project and library documentation:

https://github.com/libexif/libexif

Package Configuration

The libexif static library appropriate for the platform and configuration selected in a Visual Studio solution is explicitly referenced within this package and will appear within the solution folder tree after the package is installed. The solution may need to be reloaded to make the library file visible. This library may be moved into any solution folder after the installation.

Note that the libexif library path in this package is valid only for build configurations named Debug and Release and will not work for any other configuration names. Do not install this package for projects with configurations other than Debug and Release.

See StoneSteps.libexif.VS2022.Static.props and StoneSteps.libexif.VS2022.Static.targets for specific package configuration details and file locations.

Libraries in this package do not have libexif localization enabled and will return field names only in ASCII. This should not affect EXIF data, which may contain characters other than ASCII, even though EXIF requires ASCII. Many software packages will store UTF-8 characters in EXIF fields, which is a willful violation of the EXIF specification.

Building a Nuget Package

This project can build a Nuget package for libexif either locally or via a GitHub workflow. In each case, following steps are taken.

• libexif source archive is downloaded from libexif's website and its SHA-256 signature is verified.

• The default config.h.in is patched to work with Visual C++ 2022.

• VS2022 Community Edition is used to build libexif libraries locally and Enterprise Edition to build libraries on GitHub.

• Build artifacts for all platforms and configurations are collected in staging directories under nuget/build/native/lib.

• nuget.exe is used to package staged files with the first three version components used as a libexif version and the last version component used as a package revision. See Package Version section for more details.

• The Nuget package built on GitHub is uploaded to nuget.org. The package built locally is saved in the root project directory.

Package Version

Package Revision

Nuget packages lack package revision and in order to repackage the same upstream software version, such as libexif v0.6.24, the 4th component of the Nuget version is used to track the Nuget package revision.

Nuget package revision is injected outside of the Nuget package configuration, during the package build process, and is not present in the package specification file.

Specifically, nuget.exe is invoked with -Version=0.6.24.123 to build a package with the revision 123.

Version Locations

libexif version is located in a few places in this repository and needs to be changed in all of them for a new version of libexif.

• nuget/StoneSteps.libexif.VS2022.Static.nuspec (version)
• devops/make-package.bat (PKG_VER, PKG_REV, LIBEXIF_FNAME, LIBEXIF_SHA256)
• .github/workflows/build-nuget-package.yml (name, PKG_VER, PKG_REV, LIBEXIF_FNAME, LIBEXIF_SHA256)

LIBEXIF_SHA256 ia a SHA-256 checksum of the libexif package file and needs to be changed when a new version of libexif is released.

Verify that the new libexif archive follows the directory name pattern used in the LIBEXIF_DNAME variable.

In the GitHub workflow YAML, PKG_REV must be reset to 1 (one) every time libexif version is changed. The workflow file must be renamed with the new version in the name. This is necessary because GitHub maintains build numbers per workflow file name.

For local builds package revision is supplied on the command line and should be specified as 1 (one) for a new version of libexif.

GitHub Build Number

Build number within the GitHub workflow YAML is maintained in an unconventional way because of the lack of build maturity management between GitHub and Nuget.

For example, using build management systems, such as Artifactory, every build would generate a Nuget package with the same version and package revision for the upcoming release and build numbers would be tracked within the build management system. A build that was successfully tested would be promoted to the production Nuget repository without generating a new build.

Without a build management system, the GitHub workflow in this repository uses the pre-release version as a surrogate build number for builds that do not publish packages to nuget.org, so these builds can be downloaded and tested before the final build is made and published to nuget.org. This approach is not recommended for robust production environments because even though the final published package is built from the exact same source, the build process may still potentially introduce some unknowns into the final package (e.g. build VM was updated).

Building Package Locally

You can build a Nuget package locally with make-package.bat located in devops. This script expects VS2022 Community Edition installed in the default location. If you have other edition of Visual Studio, edit the file to use the correct path to the vcvarsall.bat file.

Run make-package.bat from the repository root directory with a package revision as the first argument. There is no provision to manage build numbers from the command line and other tools should be used for this (e.g. Artifactory).

Sample Application

A Visual Studio project is included in this repository under sample-libexif to test the Nuget package built by this project. This application dumps all EXIF tags found in a supplied image file.

In order to build sample-libexif.exe, open Nuget Package manager in the solution and install either the locally-built Nuget package or the one from nuget.org.