1. andrew cooke
  2. c-orm


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What Does C-ORM Do?

C-ORM moves data between structs in C and tables in a relational database (ie "in SQL"). It's a little like Hibernate for Java, or SQLAlchemy for Python - it simplifies building structs from the data in the database, and also helps writing data in structs back out again.

Here's a quick example:

    typedef struct person {
      int id;
      char *name;
    } person;

    void find_by_name(isti_db *db, const char *text, person** result) {
      corm_person_select *s;
      corm_person_select_alloc(&s, db);
      s->name(s, "like", text)->_go_one(s, result);  // populate result from the database
      s->_free(s, 0);  // in "real" code, 0 is a chained status value

Where corm_person_select etc were generated by C-ORM. You can see (I hope) that this is searching for a person with a given name. The found instance is returned in result. For much more detail, with full error handling, please see the examples.

To do all this, C-ORM uses two things: a set of lower-level libraries and a small Python script to generate code for specific structs.

You can also use C-ORM just for the lower-level libraries, without using the Python script. Those libraries include support for SQL, strings and arrays.

What Are C-ORM's Main Limitations?

  • It's very much in beta right now. The basic functionality is there (although no sugar for updates, only int and char * data types, and only SQLite support), but the packaging and documentation leave a lot to be desired.

  • It's very simple. There is no support for joins or collections of related structs, for example, which are basic parts of Hibernate and SQLAlchemy. This is partly by design, and partly because implementing something like that in C (not C++!) would be quite difficult.

  • At the same time, some people might find C-ORM's approach too complex. Auto-generated C code, via Python and pre-processor macros, is fairly opaque. On the other hand, that work is done, and hidden away in the library - the code that uses C-ORM can be simple and transparent.

  • C-ORM was written to make non-critical, medium-sized projects easier. It has not been pushed to extremes of scale and does not try to be terribly efficient (in speed or space). People are often working in C because they face strong constraints, but C-ORM was not written with those cases in mind. Having said that, it may still be useful, and I am always happy to consider patches that improve behaviour - feel free to contact me if you have more questions.

For a more positive view, see Architecture and Coding Conventions.

Where Can I Learn More?

Start with the documentation here.