/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Klara, Inc.
 *
 * 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 AUTHOR 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 AUTHOR 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.
 */

/* This file is #included by gzip.c */

static off_t
unzstd(int in, int out, char *pre, size_t prelen, off_t *bytes_in)
{
        static char *ibuf, *obuf;
        ZSTD_inBuffer zib;
        ZSTD_outBuffer zob;
        ZSTD_DCtx *zds;
        ssize_t res;
        size_t zres;
        size_t bytes_out = 0;
        int eof = 0;

        if (ibuf == NULL)
                ibuf = malloc(BUFLEN);
        if (obuf == NULL)
                obuf = malloc(BUFLEN);
        if (ibuf == NULL || obuf == NULL)
                maybe_err("malloc");

        zds = ZSTD_createDStream();
        ZSTD_initDStream(zds);

        zib.src = pre;
        zib.size = prelen;
        zib.pos = 0;
        if (bytes_in != NULL)
                *bytes_in = prelen;
        zob.dst = obuf;
        zob.size = BUFLEN;
        zob.pos = 0;

        while (!eof) {
                if (zib.pos >= zib.size) {
                        res = read(in, ibuf, BUFLEN);
                        if (res < 0)
                                maybe_err("read");
                        if (res == 0)
                                eof = 1;
                        infile_newdata(res);
                        zib.src = ibuf;
                        zib.size = res;
                        zib.pos = 0;
                        if (bytes_in != NULL)
                                *bytes_in += res;
                }
                zres = ZSTD_decompressStream(zds, &zob, &zib);
                if (ZSTD_isError(zres)) {
                        maybe_errx("%s", ZSTD_getErrorName(zres));
                }
                if (zob.pos > 0) {
                        res = write(out, obuf, zob.pos);
                        if (res < 0)
                                maybe_err("write");
                        zob.pos = 0;
                        bytes_out += res;
                }
        }
        ZSTD_freeDStream(zds);
        return (bytes_out);
}