g_data(9)

NAME

g_read_data, g_write_data - read/write data from/to GEOM

consumer

SYNOPSIS

#include <geom/geom.h>
void *
g_read_data(struct   g_consumer  *cp,  off_t  offset,  off_t
length,
        int *error);
int
g_write_data(struct g_consumer *cp, off_t offset, void *ptr,
        off_t length);

DESCRIPTION

The g_read_data() function reads length bytes of data from

the provider
attached to consumer cp, starting at offset offset. The

buffer returned
from g_read_data() is allocated with g_malloc(), so it

should be freed by
the caller with g_free() after use. If the operation fails,

an error
value will be stored in the error argument if it is not

NULL.

The g_write_data() function writes length bytes of data from

the buffer
pointed to by ptr to the provider attached to consumer cp,

starting at
offset offset.

RESTRICTIONS/CONDITIONS

The length argument should be a multiple of the provider's

sectorsize and
less than or equal to DFLTPHYS (DFLTPHYS is defined in

The topology lock must not be held.

RETURN VALUES

The g_read_data() function returns a pointer to a data

buffer or NULL if
an error occurred. In that case an error value is stored in

the error
argument unless it is NULL.

The g_write_data() function returns 0 if successful; other

wise an error
code is returned.

ERRORS

Possible errors:

[EIO] An I/O error occurred while reading from

or writing to

the consumer.

SEE ALSO

geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9),

g_bio(9),
g_consumer(9), g_event(9), g_geom(9), g_provider(9),
g_provider_by_name(9), g_wither_geom(9)

AUTHORS

This manual page was written by Pawel Jakub Dawidek

<pjd@FreeBSD.org>.

BSD January 16, 2004

BSD