/*
 * 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 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include "streams_mmap.h"
#include "streams_common.h"

/*
 * Single-byte character memory map-based streams implementation
 */

static int
stream_mmap_prime(stream_t *str)
{
        char *nl;

        if (stream_is_primed(str))
                return (PRIME_SUCCEEDED);

        stream_set(str, STREAM_PRIMED);

        if (str->s_buffer_size == 0) {
                stream_set(str, STREAM_EOS_REACHED);
                return (PRIME_FAILED_EMPTY_FILE);
        }

        str->s_current.l_data.sp = str->s_buffer;
        str->s_type.SF.s_release_origin = str->s_buffer;
        if ((nl = (char *)memchr(str->s_buffer, '\n', str->s_buffer_size)) ==
            NULL) {
                warn(WMSG_NEWLINE_ADDED, str->s_filename);
                str->s_current.l_data_length = str->s_buffer_size;
        } else {
                str->s_current.l_data_length = nl - (char *)str->s_buffer;
        }

        str->s_current.l_collate.sp = NULL;
        str->s_current.l_collate_length = 0;

        __S(stats_incr_fetches());
        return (PRIME_SUCCEEDED);
}

/*
 * stream_mmap_fetch() sets the fields of str->s_current to delimit the next
 * line of the field.
 */
static ssize_t
stream_mmap_fetch(stream_t *str)
{
        ssize_t dist_to_buf_end;
        char *next_nl;

        ASSERT(stream_is_primed(str));
        ASSERT((str->s_status & STREAM_EOS_REACHED) == 0);

        /*
         * adding one for newline
         */
        str->s_current.l_data.sp = str->s_current.l_data.sp +
            str->s_current.l_data_length + 1;

        dist_to_buf_end = str->s_buffer_size - (str->s_current.l_data.sp
            - (char *)str->s_buffer);
        ASSERT(dist_to_buf_end >= 0 && dist_to_buf_end <= str->s_buffer_size);

        next_nl = memchr(str->s_current.l_data.sp, '\n', dist_to_buf_end);

        if (next_nl)
                str->s_current.l_data_length = next_nl
                    - str->s_current.l_data.sp;
        else {
                warn(WMSG_NEWLINE_ADDED, str->s_filename);
                str->s_current.l_data_length = dist_to_buf_end;
        }

        /*
         * adding one for newline
         */
        if (str->s_current.l_data.sp + str->s_current.l_data_length + 1 >=
            (char *)str->s_buffer + str->s_buffer_size)
                stream_set(str, STREAM_EOS_REACHED);

        str->s_current.l_collate_length = 0;

        __S(stats_incr_fetches());
        return (NEXT_LINE_COMPLETE);
}

static int
stream_mmap_is_closable(stream_t *str)
{
        if (str->s_status & STREAM_OPEN)
                return (1);
        return (0);
}

static int
stream_mmap_close(stream_t *str)
{
        if (str->s_type.SF.s_fd > -1) {
                (void) close(str->s_type.SF.s_fd);
                stream_unset(str, STREAM_OPEN);
                return (1);
        }

        return (0);
}

static int
stream_mmap_free(stream_t *str)
{
        if (!(str->s_status & STREAM_OPEN) ||
            (str->s_consumer != NULL &&
            str->s_consumer->s_status & STREAM_NOT_FREEABLE))
                return (0);

        if (str->s_buffer == NULL)
                return (1);

        if (munmap(str->s_buffer, str->s_buffer_size) < 0)
                die(EMSG_MUNMAP, str->s_filename);

        str->s_buffer = NULL;
        str->s_buffer_size = 0;

        stream_unset(str, STREAM_PRIMED);

        return (1);
}

static int
stream_mmap_eos(stream_t *str)
{
        int retval = 0;

        if (str == NULL || str->s_status & STREAM_EOS_REACHED)
                return (1);

        /*
         * If the file's size is known to be zero, then we are at EOS; the
         * remaining checks are only sensible if we successfully primed this
         * stream.  The additional character is for the optional newline.
         */
        if (str->s_filesize == 0 ||
            (stream_is_primed(str) && str->s_current.l_data.sp -
            (char *)str->s_buffer + str->s_current.l_data_length + 1 >=
            str->s_buffer_size)) {
                retval = 1;
                stream_set(str, STREAM_EOS_REACHED);
        }

        return (retval);
}

#define ALIGNED         (~(ulong_t)(PAGESIZE - 1))

/*
 * In certain cases, we know that we will never need the data on a page again
 * for the duration of the sort.  (These cases are associated with merges
 * involving temporary files.)  We can thus release all pages previous to the
 * page containing the current line, using the MADV_DONTNEED flag to
 * madvise(3C).  This additional memory management improves our chances of
 * avoiding a paging situation, by evicting pages we know are of no use.
 */
static void
stream_mmap_release_line(stream_t *str)
{
        caddr_t origin = str->s_type.SF.s_release_origin;
        size_t release = 0;

        while ((caddr_t)((ulong_t)str->s_current.l_data.sp & ALIGNED) -
            (origin + release) >= DEFAULT_RELEASE_SIZE)
                release += DEFAULT_RELEASE_SIZE;

        if (release == 0)
                return;

        if (madvise(origin, release, MADV_DONTNEED) == -1)
                warn(gettext("madvise failed"));

        str->s_type.SF.s_release_origin += release;
}

const stream_ops_t stream_mmap_ops = {
        stream_mmap_is_closable,
        stream_mmap_close,
        stream_mmap_eos,
        stream_mmap_fetch,
        NULL,
        stream_mmap_free,
        NULL,
        stream_mmap_prime,
        NULL,
        stream_mmap_release_line,
        NULL,
        stream_stdio_unlink
};