int db_env_set_func_read(ssize_t (*func_read)(int fd, void *buf, size_t nbytes));
Replace Berkeley DB calls to the IEEE/ANSI Std 1003.1 (POSIX) read function with func_read, which must conform to the standard interface.
The db_env_set_func_read interface affects the entire application, not a single database or database environment.
Although the db_env_set_func_read interface may be used to configure Berkeley DB at any time during the life of the application, it should normally be called before making any calls to the db_env_create or db_create functions.
The db_env_set_func_read function returns a non-zero error value on failure and 0 on success.
The db_env_set_func_read function may fail and return a non-zero error for the following conditions:
The db_env_set_func_read function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the db_env_set_func_read function may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.
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