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51Degrees Common Code Library

51Degrees 51Degrees Common C Code

Reference Documentation


The 51Degrees Common Code Library groups common methods and structures used in 51Degrees APIs. This includes methods to stream from files, data sets, collections of items, arrays, memory management among other things. Anything which is not specific to a functional API is contained here as generic implementations which can be reused in multiple specific use cases.

Naming Conventions

All public methods and structures are prefixed by fiftyoneDegrees then the name of the area they belong to, e.g. the fiftyoneDegreesCollection prefix indicates it exists in collection.c/h.

The next part of a method name is the verb which describes what the method does, common terms are:

Verb Meaning
Init Initializes a structure which has already been allocated. This will take a pointer to the structure which is to initialized.
Create Allocates and initializes a new structure, then returns the pointer.
Size Returns the number of bytes which will be allocated by the accompanying create or init method. Implicitly, create or init methods which have no accompanying size method do not allocate any memory.
Get Returns a value or pointer which may need to be released after use.
Add Add an item to a structure, this may or may not allocate memory.
Process Processes data and populates a structure which is passed in.
Free Frees the memory allocated to a structure.
Release Releases a resource back to the resource manager or whatever structure in charge of handing out references to that particular resource.

e.g. the fiftyoneDegreesDataSetGet returns a pointer to a data set which will need to be released with the fiftyoneDegreesDataSetRelease method.

Finally, the optional last part completes the description of the method's use, e.g. fiftyoneDegreesDataSetInitFromMemory or fiftyoneDegreesDataSetInitFromFile.



When compiling on Linux, there is a dependency on libatomic. This is usually already present as part of the C libraries, and is included as part of GCC 5 and abover. On other systems, can be installed with:

sudo apt-get install libatomic1

Using CMake

To build the make files required to build, open a bash or Visual Studio Developer Command Prompt terminal and run

mkdir build
cd build
cmake ..

Note: on an x64 Windows system, it is neccessary to add -A x64 as CMake will build a Win32 Solution by default.

Then build the whole solution with

cmake --build . --config Release

Libraries are output to the lib/ directory, and executables like examples and tests are output to the bin/ directory.

Using Visual Studio

Calling CMake in an MSVC environment (as described in the Using CMake section) will produce a Visual Studio solution with projects for all libraries, examples, and tests. However, it is preferable to use the dedicated Visual Studio solution in the VisualStudio/ directory.


  • Required Visual Studio 2019 or equivalent C++ build tool
    • Minimum Platform Toolset Version v142
    • Minimum Windows SDK Version 10.0.18362.0

Build Options


In memory only operation compiling without stream capabilities using the FIFTYONE_DEGREES_MEMORY_ONLY directive results in performance improvements. By removing the unnecessary jumps to methods which are only used in stream operation, the performance of in memory collections is improved.

The option is enabled using the FIFTYONE_DEGREES_MEMORY_ONLY compile flag, which can also be set through CMake using the -DMemoryOnly=YES option, or through Visual Studio using the the Debug-MemoryOnly or Release-MemoryOnly build configurations.


In single threaded operation compiling without threading using the FIFTYONE_DEGREES_NO_THREADING directive results in performance improvements. By removing logic needed to keep operations thread safe, the performance of many operations are improved.

The option is enabled using the FIFTYONE_DEGREES_NO_THREADING compile flag, which can also be set through CMake using the -DNoThreading=YES option, or through Visual Studio using the Debug-Single or Release-Single build configurations.

WARNING: This option should only be enabled in single threaded environments, as it means operations will not be thread safe.


Exceptions are handled in the common library using the fiftyoneDegreesException structure. This logic can be disabled using the FIFTYONE_DEGREES_EXCEPTIONS_DISABLED directive, resulting in performance improvements.

The options is enabled using the FIFTYONE_DEGREES_EXCEPTIONS_DISABLED compile flag, which can also be set through CMake using the -DExceptionsDisabled=YES option.

WARNING: When exception handling is disabled, using the functionality in this library incorrectly can result in a segmentation fault instead of an exception being set.


All unit, integration, and performance tests are built using the Google test framework.


CMake automatically pulls in the latest Google Test from GitHub.

Building the project builds the test executable CommonTests to the bin/ directory. This can be run directly from a terminal.

These can be run by calling


If CMake has been used in an MSVC environment, then the tests will be set up and discoverable in the Visual Studio solution 51DegreesCommon created by CMake.

Visual Studio

Tests in the Visual Studio solution automatically install the GTest dependency via a NuGet package. However, in order for the tests to show up in the Visual Studio test explorer, the Test Adapter for Google Test extension must be installed.

The VisualStudio solution includes FiftyOne.Common.Tests, which can be run through the standard Visual Studio test runner.

Referencing the library


When building using CMake, static libraries are built in stages. These can be included in an executable just as they are in the examples. If these are included through a CMake file, the dependencies will be resolved automatically. However, if linking another way, all dependencies will need to be included from the lib/ directory. For example, to use the Common C library, the fiftyone-common-c static library would need to be included, and for C++, fiftyone-common-cxx is needed in addition.

Visual Studio

The Visual Studio solution contains static libraries which have all the dependencies set up correctly, so referencing these in a Visual Studio solution should be fairly self explanatory.