# db_env_set_func_seek

`

###

    #include <db.h>

    int
    db_env_set_func_seek(int (*func_seek)(int fd, size_t pgsize,
        db_pgno_t pageno, u_int32_t relative, int rewind, int whence));

# Description

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 func_seek argument must conform to the following interface:

>     int seek(int fd, size_t pgsize, db_pgno_t pageno,
>     u_int32_t relative, int rewind, int whence);

The fd argument 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 a byte offset specified by the calculation:

>     (pgsize * pageno) + relative

If rewind is non-zero, the byte offset is treated as a backwards seek, not a forwards one.

The whence argument 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.

The db_env_set_func_seek interface affects the entire application, not a single database or database environment.

While the db_env_set_func_seek 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_seek function returns a non-zero error value on failure and 0 on success.

# Errors

EINVAL
  An invalid flag value or parameter was specified.

# See Also

db_env_set_func_close, db_env_set_func_dirfree, db_env_set_func_dirlist, db_env_set_func_exists, db_env_set_func_free, db_env_set_func_fsync, db_env_set_func_ioinfo, db_env_set_func_malloc, db_env_set_func_map, db_env_set_func_open, db_env_set_func_read, db_env_set_func_realloc, db_env_set_func_seek, db_env_set_func_sleep, db_env_set_func_unlink, db_env_set_func_unmap, db_env_set_func_write and db_env_set_func_yield.`

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