The code for the SLAPI_PLUGIN_PRE_SEARCH_FN function, testpreop_search(), is preceded by three macros. Search testpreop.c for #define LOG1(format). The purpose of these macros is only to render the subsequent logging statements more compact, making the code easier to decipher. The digits in LOG1, LOG2, and LOG3 reflect the number of parameters each macro takes. The actual number of parameters that you pass to the log functions varies, as the log functions let you format strings in the style of printf().