g_read_data9
Read/write data from/to geom consumer
Part of g_data(9).
Usage
#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);
Overview
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 ⟨sys/param.h⟩).
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; otherwise an error code is returned.
Errors
Possible errors:
- [EIO]
-
An I/O error occurred while reading from or writing to the consumer.