common/mdb/mdb_memio.c

	mdb_memio.c revision 843e19887f64dde75055cf8842fc4db2171eff45
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * Memory I/O backend.
 *
 * Simple backend that has main memory as its backing store.
 */

#include <mdb/mdb_io_impl.h>
#include <mdb/mdb.h>

typedef struct mem_data {
    char *md_buf;
    size_t md_size;
    offset_t md_off;
} mem_data_t;

static ssize_t
memio_read(mdb_io_t *io, void *buf, size_t nbytes)
{
    mem_data_t *mdp = io->io_data;

    if (io->io_next == NULL) {
        if (mdp->md_off + nbytes > mdp->md_size)
            nbytes = (mdp->md_size - mdp->md_off);
        bcopy(mdp->md_buf + mdp->md_off, buf, nbytes);
        mdp->md_off += nbytes;
        return (nbytes);
    }

    return (IOP_READ(io->io_next, buf, nbytes));
}

static off64_t
memio_seek(mdb_io_t *io, off64_t offset, int whence)
{
    mem_data_t *mdp = io->io_data;

    if (io->io_next == NULL) {
        switch (whence) {
        case SEEK_SET:
            mdp->md_off = offset;
            break;
        case SEEK_CUR:
            mdp->md_off += offset;
            break;
        case SEEK_END:
            mdp->md_off = mdp->md_size + offset;
            if (mdp->md_off > mdp->md_size)
                mdp->md_off = mdp->md_size;
            break;
        default:
            return (-1);
        }

        return (mdp->md_off);
    }

    return (IOP_SEEK(io->io_next, offset, whence));
}

static const mdb_io_ops_t memio_ops = {
    memio_read,
    no_io_write,
    memio_seek,
    no_io_ctl,
    no_io_close,
    no_io_name,
    no_io_link,
    no_io_unlink,
    no_io_setattr,
    no_io_suspend,
    no_io_resume
};

mdb_io_t *
mdb_memio_create(char *buf, size_t size)
{
    mdb_io_t *io = mdb_alloc(sizeof (mdb_io_t), UM_SLEEP);
    mem_data_t *mdp = mdb_alloc(sizeof (mem_data_t), UM_SLEEP);

    mdp->md_buf = buf;
    mdp->md_size = size;
    mdp->md_off = 0;

    io->io_ops = &memio_ops;
    io->io_data = mdp;
    io->io_next = NULL;
    io->io_refcnt = 0;

    return (io);
}