/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011 Pawel Jakub Dawidek <pawel@dawidek.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <sys/endian.h>

#include <errno.h>
#include <string.h>
#include <strings.h>

#include <hast.h>
#include <lzf.h>
#include <nv.h>
#include <pjdlog.h>

#include "hast_compression.h"

static bool
allzeros(const void *data, size_t size)
{
        const uint64_t *p = data;
        unsigned int i;
        uint64_t v;

        PJDLOG_ASSERT((size % sizeof(*p)) == 0);

        /*
         * This is the fastest method I found for checking if the given
         * buffer contain all zeros.
         * Because inside the loop we don't check at every step, we would
         * get an answer only after walking through entire buffer.
         * To return early if the buffer doesn't contain all zeros, we probe
         * 8 bytes at the beginning, in the middle and at the end of the buffer
         * first.
         */

        size >>= 3;     /* divide by 8 */
        if ((p[0] | p[size >> 1] | p[size - 1]) != 0)
                return (false);
        v = 0;
        for (i = 0; i < size; i++)
                v |= *p++;
        return (v == 0);
}

static void *
hast_hole_compress(const unsigned char *data, size_t *sizep)
{
        uint32_t size;
        void *newbuf;

        if (!allzeros(data, *sizep))
                return (NULL);

        newbuf = malloc(sizeof(size));
        if (newbuf == NULL) {
                pjdlog_warning("Unable to compress (no memory: %zu).",
                    (size_t)*sizep);
                return (NULL);
        }
        size = htole32((uint32_t)*sizep);
        bcopy(&size, newbuf, sizeof(size));
        *sizep = sizeof(size);

        return (newbuf);
}

static void *
hast_hole_decompress(const unsigned char *data, size_t *sizep)
{
        uint32_t size;
        void *newbuf;

        if (*sizep != sizeof(size)) {
                pjdlog_error("Unable to decompress (invalid size: %zu).",
                    *sizep);
                return (NULL);
        }

        bcopy(data, &size, sizeof(size));
        size = le32toh(size);

        newbuf = malloc(size);
        if (newbuf == NULL) {
                pjdlog_error("Unable to decompress (no memory: %zu).",
                    (size_t)size);
                return (NULL);
        }
        bzero(newbuf, size);
        *sizep = size;

        return (newbuf);
}

/* Minimum block size to try to compress. */
#define HAST_LZF_COMPRESS_MIN   1024

static void *
hast_lzf_compress(const unsigned char *data, size_t *sizep)
{
        unsigned char *newbuf;
        uint32_t origsize;
        size_t newsize;

        origsize = *sizep;

        if (origsize <= HAST_LZF_COMPRESS_MIN)
                return (NULL);

        newsize = sizeof(origsize) + origsize - HAST_LZF_COMPRESS_MIN;
        newbuf = malloc(newsize);
        if (newbuf == NULL) {
                pjdlog_warning("Unable to compress (no memory: %zu).",
                    newsize);
                return (NULL);
        }
        newsize = lzf_compress(data, *sizep, newbuf + sizeof(origsize),
            newsize - sizeof(origsize));
        if (newsize == 0) {
                free(newbuf);
                return (NULL);
        }
        origsize = htole32(origsize);
        bcopy(&origsize, newbuf, sizeof(origsize));

        *sizep = sizeof(origsize) + newsize;
        return (newbuf);
}

static void *
hast_lzf_decompress(const unsigned char *data, size_t *sizep)
{
        unsigned char *newbuf;
        uint32_t origsize;
        size_t newsize;

        PJDLOG_ASSERT(*sizep > sizeof(origsize));

        bcopy(data, &origsize, sizeof(origsize));
        origsize = le32toh(origsize);
        PJDLOG_ASSERT(origsize > HAST_LZF_COMPRESS_MIN);

        newbuf = malloc(origsize);
        if (newbuf == NULL) {
                pjdlog_error("Unable to decompress (no memory: %zu).",
                    (size_t)origsize);
                return (NULL);
        }
        newsize = lzf_decompress(data + sizeof(origsize),
            *sizep - sizeof(origsize), newbuf, origsize);
        if (newsize == 0) {
                free(newbuf);
                pjdlog_error("Unable to decompress.");
                return (NULL);
        }
        PJDLOG_ASSERT(newsize == origsize);

        *sizep = newsize;
        return (newbuf);
}

const char *
compression_name(int num)
{

        switch (num) {
        case HAST_COMPRESSION_NONE:
                return ("none");
        case HAST_COMPRESSION_HOLE:
                return ("hole");
        case HAST_COMPRESSION_LZF:
                return ("lzf");
        }
        return ("unknown");
}

int
compression_send(const struct hast_resource *res, struct nv *nv, void **datap,
    size_t *sizep, bool *freedatap)
{
        unsigned char *newbuf;
        int compression;
        size_t size;

        size = *sizep;
        compression = res->hr_compression;

        switch (compression) {
        case HAST_COMPRESSION_NONE:
                return (0);
        case HAST_COMPRESSION_HOLE:
                newbuf = hast_hole_compress(*datap, &size);
                break;
        case HAST_COMPRESSION_LZF:
                /* Try 'hole' compression first. */
                newbuf = hast_hole_compress(*datap, &size);
                if (newbuf != NULL)
                        compression = HAST_COMPRESSION_HOLE;
                else
                        newbuf = hast_lzf_compress(*datap, &size);
                break;
        default:
                PJDLOG_ABORT("Invalid compression: %d.", res->hr_compression);
        }

        if (newbuf == NULL) {
                /* Unable to compress the data. */
                return (0);
        }
        nv_add_string(nv, compression_name(compression), "compression");
        if (nv_error(nv) != 0) {
                free(newbuf);
                errno = nv_error(nv);
                return (-1);
        }
        if (*freedatap)
                free(*datap);
        *freedatap = true;
        *datap = newbuf;
        *sizep = size;

        return (0);
}

int
compression_recv(const struct hast_resource *res __unused, struct nv *nv,
    void **datap, size_t *sizep, bool *freedatap)
{
        unsigned char *newbuf;
        const char *algo;
        size_t size;

        algo = nv_get_string(nv, "compression");
        if (algo == NULL)
                return (0);     /* No compression. */

        newbuf = NULL;
        size = *sizep;

        if (strcmp(algo, "hole") == 0)
                newbuf = hast_hole_decompress(*datap, &size);
        else if (strcmp(algo, "lzf") == 0)
                newbuf = hast_lzf_decompress(*datap, &size);
        else {
                pjdlog_error("Unknown compression algorithm '%s'.", algo);
                return (-1);    /* Unknown compression algorithm. */
        }

        if (newbuf == NULL)
                return (-1);
        if (*freedatap)
                free(*datap);
        *freedatap = true;
        *datap = newbuf;
        *sizep = size;

        return (0);
}