# db_env_set_func_ioinfo

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    #include <db.h>

    int
    db_env_set_func_ioinfo(int (*func_ioinfo)(const char *path,
        int fd, u_int32_t *mbytesp, u_int32_t *bytesp, u_int32_t *iosizep));

# Description

The Berkeley DB library requires the ability to determine the size and I/O characteristics of a file. The func_ioinfo argument must conform to the following interface:

>     int ioinfo(const char *path, int fd,
>     u_int32_t *mbytesp, u_int32_t *bytesp, u_int32_t *iosizep);

The path argument is the pathname of the file to be checked, and the fd argument is an open file descriptor on the file.

If the mbytesp and bytesp arguments are non-NULL, the ioinfo function must return in them the size of the file: the number of megabytes in the file into the memory location to which the mbytesp argument refers, and the number of bytes over and above that number of megabytes into the memory location to which the bytesp argument refers.

In addition, if the iosizep argument is non-NULL, the ioinfo function must return the optimum granularity for I/O operations to the file into the memory location to which it refers.

The func_ioinfo interface must return the value of errno on failure and 0 on success.

The db_env_set_func_ioinfo method 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_ioinfo interface 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_ioinfo method returns a non-zero error value on failure and 0 on success.

# Errors

The db_env_set_func_ioinfo method may fail and return a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

The db_env_set_func_ioinfo method 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_ioinfo method may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

# See Also

Run-time configuration`

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