The libflom programming kompass for C developers

FLoM API is very easy to understand and use; these are the basic concepts:

• flom.h is the header file you must include
• flom_handle_t is the data type you must use to communicate with FLoM (you must treat this type of objects as opaque objects: for every useful property there’s a getter/setter method and you don’t have to mind what’s the meaning of the object content)
• you can use a “static programming style”, allocating flom_handle_t objects on the stack or you can use a “dynamic programming style”, allocating flom_handle_t objects in the heap: that’s your choice and FLoM API does not force you to use a specific style

Static programming style example

basic_static.c example can be considered the hello world FLoM equivalent for static programming style:

1. allocate a flom_handle_t object on the stack declaring it
2. initialize the object using method (function) flom_handle_init
3. synchronize your program using method (function) flom_handle_lock
4. do everything your program must perform inside the synchronization window
5. desynchronize your program using method (function) flom_handle_unlock
6. clean-up the object using method (function) flom_handle_clean

Note: you must clean-up every initialized flom_handle_t object; if you don’t clean-up every object you will generate memory leaks.

Dynamic programming style example

basic_dynamic.c example can be considered the hello world FLoM equivalent for dynamic programming style:

1. declare a flom_handle_t object pointer
2. create a new object using method (function) flom_handle_new
3. synchronize your program using method (function) flom_handle_lock
4. do everything your program must perform inside the synchronization window
5. desynchronize your program using method (function) flom_handle_unlock
6. delete the object using method (function) flom_handle_delete

Note: you must delete every created flom_handle_t object; if you don’t delete every object you will generate memory leaks.

Static and dynamic programming styles

Note: the availability of two different programming styles does not mean you can mix them!
If you defined a static flom_handle_t object, you could not apply flom_handle_delete method against it.
If you created a dynamic flom_handle_t object, you could not apply flom_handle_init and flom_handle_clean methods against it.
Don’t mix the styles, that pattern is not supported.

Advanced examples

Basic examples do not explain as you can specify the name of the logical resource, the quantity of a numerical resource and the other parameters you typically use with flom command line.
advanced_static.c and advanced_dynamic.c examples show how some properties can be set before entering in the synchronization phase.
The complete list of the available setter/getter methods can be retrieved from:

• functions C API page
• flom_handle.h header file

Transactional example

Some resources, for example unique sequences, can be declared as transactional.
A transactional resource has an associated state and it needs an explicit unlock to commit the state.
If a transactional resource is not committed due to a program crash, the state will be rolled back.
Function flom_handle_unlock_rollback has been introduced to force a state rollback during the unlock phase, even if a program does not crash.
An example is available in this source code: transactional.c.