#include <db.h> int db_env_set_func_seek(int (*func_seek)(int fd, off_t offset, int whence));
The Berkeley DB library requires the ability to specify that a subsequent read from or write to a file will occur at a specific location in that file.
The db_env_set_func_seek() function configures all operations performed by
a process and all of its threads of control, not operations confined
to a single database environment.
Although the db_env_set_func_seek() function may be called at any time
during the life of the application, it should normally be called
before making calls to the db_env_create or
db_create methods.
The db_env_set_func_seek()
function returns a non-zero error value on failure and 0 on success.
The func_seek parameter is the function which seeks to a specific location in a file.
The fd parameter is an open file descriptor on the file.
The seek function must cause a subsequent read from or write to the file to occur at the byte offset specified by the offset parameter.
The whence parameter specifies where in the file the byte offset is relative to, as described by the IEEE/ANSI Std 1003.1 (POSIX) lseek system call.
The func_seek function must return the value of errno on failure and 0 on success.