Abstract
The program gama-local is a part of GNU Gama project and allows adjustment of local geodetic networks. Before realization of this project the program gama-local supported only XML as an input. I designed and implemented support for the SQLite database and thanks to this extension gama-local can read input data from the SQLite database. This article is focused on the specifics of the use of callback functions in C++ using the native SQLite C/C++ Application Programming Interface. The article provides solution to safe calling of callback functions written in C++. Callback functions are called from C library and C library itself is used by C++ program. Provided solution combines several programing techniques which are described in detail, so this article can serve as a cookbook even for beginner programmers. This project was accomplished within my bachelor thesis.
Highlights
GNU Gama is a library and set of programs for adjustment of geodetic networks
Information provided in this paper was used for implementing SQLite support in gama-local
This paper presents something like reusable design pattern because this information can be used generally when interfacing C++ code with C code or library
Summary
GNU Gama is a library and set of programs for adjustment of geodetic networks. Project is licensed under the GNU GPL and is written in C++ programming language. Project GNU Gama uses interface using callback functions It was chosen for implementation because this interface is considered to be the most stable one in terms of changes between versions of SQLite C/C++ API. Catching all possible exceptions is not enough, it is necessary to report error to callback function caller (it is library function sqlite3_exec in our case). Consider the case we have to catch all exceptions, keep information about exception type and later use this exception This is the case of callback functions used with SqliteReader class. Class is derived from std::exception in order to add function what to interface and to allow handling standard exceptions and specific GNU Gama exceptions together when necessary. In SqliteReader implementation a wrapper function for sqlite3_exec function was introduced This wrapper ensures rethrowing of previously stored exception.
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