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/*
* Copyright (c) 1996-1998 University of Utah and the Flux Group.
* All rights reserved.
*
* This file is part of the Flux OSKit. The OSKit is free software, also known
* as "open source;" you can redistribute it and/or modify it under the terms
* of the GNU General Public License (GPL), version 2, as published by the Free
* Software Foundation (FSF). To explore alternate licensing terms, contact
* the University of Utah at csl-dist@cs.utah.edu or +1-801-585-3271.
*
* The OSKit is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GPL for more details. You should have
* received a copy of the GPL along with the OSKit; see the file COPYING. If
* not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
*/
/*
* Implementation of simple oskit_blkio subsetting objects,
* e.g., for representing individual partitions on a disk.
*/
#include <stdlib.h>
#include <string.h>
#include <oskit/io/blkio.h>
struct sub {
oskit_blkio_t ioi; /* Interface to this object */
oskit_u32_t refs; /* Our reference count */
oskit_blkio_t *io; /* Reference to underlying I/O object */
oskit_off_t offset; /* Offset in underlying object */
oskit_off_t size; /* Size of our I/O segment */
};
/*
* Query a subset I/O object for its interfaces.
* This is extremely easy because we only export one interface
* (plus its base type, IUnknown).
*/
static OSKIT_COMDECL
query(oskit_blkio_t *io, const oskit_iid_t *iid, void **out_ihandle)
{
struct sub *s = (struct sub*)io;
if (memcmp(iid, &oskit_iunknown_iid, sizeof(*iid)) == 0 ||
memcmp(iid, &oskit_blkio_iid, sizeof(*iid)) == 0) {
*out_ihandle = &s->ioi;
++s->refs;
return 0;
}
*out_ihandle = NULL;
return OSKIT_E_NOINTERFACE;
}
/*
* Clone a reference to our block I/O interface.
*/
static OSKIT_COMDECL_U
addref(oskit_blkio_t *io)
{
struct sub *s = (struct sub*)io;
return ++s->refs;
}
/*
* Release a reference to our I/O interface.
*/
static OSKIT_COMDECL_U
release(oskit_blkio_t *io)
{
struct sub *s = (struct sub*)io;
if (--s->refs > 0)
return s->refs;
oskit_blkio_release(s->io);
free(s);
return 0;
}
/*
* Return the block size of this block I/O object.
*/
static OSKIT_COMDECL_U
getblocksize(oskit_blkio_t *io)
{
struct sub *s = (struct sub*)io;
return oskit_blkio_getblocksize(s->io);
}
/*
* Read from the block I/O subset object,
* clipping accesses to the range of this subset.
*/
static OSKIT_COMDECL
read(oskit_blkio_t *io, void *buf,
oskit_off_t off, oskit_size_t count, oskit_size_t *amount)
{
struct sub *s = (struct sub*)io;
if (off >= s->size) {
*amount = 0;
return 0;
}
if (off + count > s->size) {
count = s->size - off;
}
return oskit_blkio_read(s->io, buf, s->offset + off, count, amount);
}
/*
* Write data to the block I/O subset object,
* clipping accesses to the range of this subset.
*/
static OSKIT_COMDECL
write(oskit_blkio_t *io, const void *buf,
oskit_off_t off, oskit_size_t count, oskit_size_t *amount)
{
struct sub *s = (struct sub*)io;
if (off >= s->size) {
*amount = 0;
return 0;
}
if (off + count > s->size) {
count = s->size - off;
}
return oskit_blkio_write(s->io, buf, s->offset + off, count, amount);
}
/*
* Return the size of this subset I/O object.
*/
static OSKIT_COMDECL
getsize(oskit_blkio_t *io, oskit_off_t *out_size)
{
struct sub *s = (struct sub*)io;
*out_size = s->size;
return 0;
}
/*
* Attempt to set the size of this object,
* which never succeeds in our case.
*/
static OSKIT_COMDECL
setsize(oskit_blkio_t *io, oskit_off_t new_size)
{
return OSKIT_E_NOTIMPL;
}
/*
* Operations vector for the subset block I/O interface.
*/
static struct oskit_blkio_ops ops = {
query,
addref,
release,
getblocksize,
read,
write,
getsize,
setsize
};
oskit_error_t oskit_blkio_subset(oskit_blkio_t *io, oskit_off_t offset,
oskit_off_t size, oskit_blkio_t **out_io)
{
struct sub *s;
unsigned blksize;
/* Sanity-check the offset and size */
blksize = oskit_blkio_getblocksize(io);
if ((offset & (blksize-1)) || (size & (blksize-1)))
return OSKIT_E_INVALIDARG;
/* Create the new object */
s = malloc(sizeof(*s));
if (s == NULL)
return OSKIT_E_OUTOFMEMORY;
s->ioi.ops = &ops;
s->refs = 1;
s->io = io;
oskit_blkio_addref(io);
s->offset = offset;
s->size = size;
*out_io = &s->ioi;
return 0;
}
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