/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 (c) 1997-2001 by Sun Microsystems, Inc.
 * All rights reserved.
 */

/*
 * String I/O Backend
 *
 * Simple backend to provide the ability to perform i/o reads from an in-memory
 * string.  This allows us to mdb_eval() a string -- by creating an i/o object
 * out of it, we can then pass it to the parser as stdin.
 */

#include <mdb/mdb_modapi.h>
#include <mdb/mdb_io_impl.h>
#include <mdb/mdb_string.h>
#include <mdb/mdb_err.h>

typedef struct str_data {
        char *str_base;         /* Pointer to private copy of string */
        char *str_ptr;          /* Current seek pointer */
        size_t str_len;         /* Length of string */
} str_data_t;

static ssize_t
strio_read(mdb_io_t *io, void *buf, size_t nbytes)
{
        str_data_t *sd = io->io_data;
        size_t left = sd->str_base + sd->str_len - sd->str_ptr;

        if (left != 0) {
                size_t obytes = nbytes < left ? nbytes : left;
                (void) strncpy(buf, sd->str_ptr, obytes);
                sd->str_ptr += obytes;
                return (obytes);
        }

        return (0); /* At end of string: return EOF */
}

static off64_t
strio_seek(mdb_io_t *io, off64_t offset, int whence)
{
        str_data_t *sd = io->io_data;
        char *nptr;

        if (io->io_next != NULL)
                return (IOP_SEEK(io->io_next, offset, whence));

        switch (whence) {
        case SEEK_SET:
                nptr = sd->str_base + offset;
                break;
        case SEEK_CUR:
                nptr = sd->str_ptr + offset;
                break;
        case SEEK_END:
                nptr = sd->str_base + sd->str_len + offset;
                break;
        default:
                return (set_errno(EINVAL));
        }

        if (nptr < sd->str_base || nptr > sd->str_ptr + sd->str_len)
                return (set_errno(EINVAL));

        sd->str_ptr = nptr;
        return ((off64_t)(nptr - sd->str_base));
}

static void
strio_close(mdb_io_t *io)
{
        str_data_t *sd = io->io_data;

        strfree(sd->str_base);
        mdb_free(sd, sizeof (str_data_t));
}

static const char *
strio_name(mdb_io_t *io)
{
        if (io->io_next != NULL)
                return (IOP_NAME(io->io_next));

        return ("(string)");
}

static const mdb_io_ops_t strio_ops = {
        .io_read = strio_read,
        .io_write = no_io_write,
        .io_seek = strio_seek,
        .io_ctl = no_io_ctl,
        .io_close = strio_close,
        .io_name = strio_name,
        .io_link = no_io_link,
        .io_unlink = no_io_unlink,
        .io_setattr = no_io_setattr,
        .io_suspend = no_io_suspend,
        .io_resume = no_io_resume,
};

mdb_io_t *
mdb_strio_create(const char *s)
{
        mdb_io_t *io = mdb_alloc(sizeof (mdb_io_t), UM_SLEEP);
        str_data_t *sd = mdb_alloc(sizeof (str_data_t), UM_SLEEP);

        /*
         * Our parser expects each command to end with '\n' or ';'.  To
         * simplify things for the caller, we append a trailing newline
         * so the argvec string can be passed directly sans modifications.
         */
        sd->str_len = strlen(s) + 1;
        sd->str_base = strndup(s, sd->str_len);
        (void) strcat(sd->str_base, "\n");
        sd->str_ptr = sd->str_base;

        io->io_ops = &strio_ops;
        io->io_data = sd;
        io->io_next = NULL;
        io->io_refcnt = 0;

        return (io);
}

int
mdb_iob_isastr(mdb_iob_t *iob)
{
        mdb_io_t *io;

        for (io = iob->iob_iop; io != NULL; io = io->io_next) {
                if (io->io_ops == &strio_ops)
                        return (1);
        }

        return (0);
}