/*
 * Copyright (c) 1998 Michael Smith.
 * 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 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.
 */

#include <sys/cdefs.h>

#include "stand.h"

#include <sys/stat.h>
#include <string.h>
#include <zlib.h>

#define Z_BUFSIZE 16384 /* match NFSREAD_MAX_SIZE */

struct z_file
{
        int             zf_rawfd;
        off_t           zf_dataoffset;
        z_stream        zf_zstream;
        int             zf_endseen;
        unsigned char   zf_buf[Z_BUFSIZE];
};

static int zf_fill(struct z_file *z);
static int zf_open(const char *path, struct open_file *f);
static int zf_close(struct open_file *f);
static int zf_read(struct open_file *f, void *buf, size_t size, size_t *resid);
static off_t zf_seek(struct open_file *f, off_t offset, int where);
static int zf_stat(struct open_file *f, struct stat *sb);

struct fs_ops gzipfs_fsops = {
        .fs_name = "zip",
        .fo_open = zf_open,
        .fo_close = zf_close,
        .fo_read = zf_read,
        .fo_write = null_write,
        .fo_seek = zf_seek,
        .fo_stat = zf_stat,
        .fo_readdir = null_readdir
};

static int
zf_fill(struct z_file *zf)
{
        int     result;
        int     req;

        req = Z_BUFSIZE - zf->zf_zstream.avail_in;
        result = 0;

        /* If we need more */
        if (req > 0) {
                /* move old data to bottom of buffer */
                if (req < Z_BUFSIZE)
                        bcopy(zf->zf_buf + req, zf->zf_buf, Z_BUFSIZE - req);

                /* read to fill buffer and update availibility data */
                result = read(zf->zf_rawfd,
                    zf->zf_buf + zf->zf_zstream.avail_in, req);
                zf->zf_zstream.next_in = zf->zf_buf;
                if (result >= 0)
                        zf->zf_zstream.avail_in += result;
        }
        return (result);
}

/*
 * Adapted from get_byte/check_header in libz
 *
 * Returns 0 if the header is OK, nonzero if not.
 */
static int
get_byte(struct z_file *zf, off_t *curoffp)
{
        if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1))
                return (-1);
        zf->zf_zstream.avail_in--;
        ++*curoffp;
        return (*(zf->zf_zstream.next_in)++);
}

static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */

/* gzip flag byte */
#define ASCII_FLAG      0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC        0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD     0x04 /* bit 2 set: extra field present */
#define ORIG_NAME       0x08 /* bit 3 set: original file name present */
#define COMMENT         0x10 /* bit 4 set: file comment present */
#define RESERVED        0xE0 /* bits 5..7: reserved */

static int
check_header(struct z_file *zf)
{
        int     method; /* method byte */
        int     flags;  /* flags byte */
        uInt    len;
        int     c;

        zf->zf_dataoffset = 0;
        /* Check the gzip magic header */
        for (len = 0; len < 2; len++) {
                c = get_byte(zf, &zf->zf_dataoffset);
                if (c != gz_magic[len]) {
                        return (1);
                }
        }
        method = get_byte(zf, &zf->zf_dataoffset);
        flags = get_byte(zf, &zf->zf_dataoffset);
        if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
                return (1);
        }

        /* Discard time, xflags and OS code: */
        for (len = 0; len < 6; len++)
                (void) get_byte(zf, &zf->zf_dataoffset);

        if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
                len  =  (uInt)get_byte(zf, &zf->zf_dataoffset);
                len += ((uInt)get_byte(zf, &zf->zf_dataoffset))<<8;
                /* len is garbage if EOF but the loop below will quit anyway */
                while (len-- != 0 && get_byte(zf, &zf->zf_dataoffset) != -1)
                        ;
        }
        if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
                while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1)
                        ;
        }
        if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
                while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1)
                        ;
        }
        if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
                for (len = 0; len < 2; len++)
                        c = get_byte(zf, &zf->zf_dataoffset);
        }
        /* if there's data left, we're in business */
        return ((c == -1) ? 1 : 0);
}

static int
zf_open(const char *fname, struct open_file *f)
{
        char            *zfname;
        int             rawfd;
        struct z_file   *zf;
        char            *cp;
        int             error;
        struct stat     sb;
        size_t len;

        /* Have to be in "just read it" mode */
        if (f->f_flags != F_READ)
                return (EPERM);

        /* directory names are not compressed. */
        len = strlen(fname);
        if (len == 0 || fname[len - 1] == '/')
                return (ENOENT);

        /* If the name already ends in .gz or .bz2, ignore it */
        if ((cp = strrchr(fname, '.')) && (strcmp(cp, ".gz") == 0 ||
            strcmp(cp, ".bz2") == 0 || strcmp(cp, ".split") == 0))
                return (ENOENT);

        /* Try to open the compressed datafile */
        rawfd = open(fname, O_RDONLY | F_GZIP);
        if (rawfd == -1) {
                /* add .gz sufix and try again */
                zfname = malloc(strlen(fname) + 4);
                if (zfname == NULL)
                        return (ENOMEM);
                sprintf(zfname, "%s.gz", fname);
                rawfd = open(zfname, O_RDONLY);
                free(zfname);
                if (rawfd == -1)
                        return (ENOENT);
        }

        if (fstat(rawfd, &sb) < 0) {
                printf("zf_open: stat failed\n");
                close(rawfd);
                return (ENOENT);
        }
        if (!S_ISREG(sb.st_mode)) {
                close(rawfd);
                return (EISDIR);        /* best guess */
        }

        /* Allocate a z_file structure, populate it */
        zf = malloc(sizeof (struct z_file));
        if (zf == NULL)
                return (ENOMEM);
        bzero(zf, sizeof (struct z_file));
        zf->zf_rawfd = rawfd;

        /* Verify that the file is gzipped */
        if (check_header(zf)) {
                close(zf->zf_rawfd);
                free(zf);
                return (EFTYPE);
        }

        /* Initialise the inflation engine */
        if ((error = inflateInit2(&(zf->zf_zstream), -15)) != Z_OK) {
                printf("zf_open: inflateInit returned %d : %s\n", error,
                    zf->zf_zstream.msg);
                close(zf->zf_rawfd);
                free(zf);
                return (EIO);
        }

        /* Looks OK, we'll take it */
        f->f_fsdata = zf;
        return (0);
}

static int
zf_close(struct open_file *f)
{
        struct z_file   *zf = (struct z_file *)f->f_fsdata;

        inflateEnd(&(zf->zf_zstream));
        close(zf->zf_rawfd);
        free(zf);
        return (0);
}

static int
zf_read(struct open_file *f, void *buf, size_t size, size_t *resid)
{
        struct z_file   *zf = (struct z_file *)f->f_fsdata;
        int             error;

        zf->zf_zstream.next_out = buf;          /* where and how much */
        zf->zf_zstream.avail_out = size;

        while (zf->zf_zstream.avail_out && zf->zf_endseen == 0) {
                if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1)) {
                        printf("zf_read: fill error\n");
                        return (EIO);
                }
                if (zf->zf_zstream.avail_in == 0) { /* oops, unexpected EOF */
                        printf("zf_read: unexpected EOF\n");
                        if (zf->zf_zstream.avail_out == size)
                                return (EIO);
                        break;
                }

                /* decompression pass */
                error = inflate(&zf->zf_zstream, Z_SYNC_FLUSH);
                if (error == Z_STREAM_END) {    /* EOF, all done */
                        zf->zf_endseen = 1;
                        break;
                }
                if (error != Z_OK) {            /* argh, decompression error */
                        printf("inflate: %s\n", zf->zf_zstream.msg);
                        return (EIO);
                }
        }
        if (resid != NULL)
                *resid = zf->zf_zstream.avail_out;
        return (0);
}

static int
zf_rewind(struct open_file *f)
{
        struct z_file   *zf = (struct z_file *)f->f_fsdata;

        if (lseek(zf->zf_rawfd, zf->zf_dataoffset, SEEK_SET) == -1)
                return (-1);
        zf->zf_zstream.avail_in = 0;
        zf->zf_zstream.next_in = NULL;
        zf->zf_endseen = 0;
        (void) inflateReset(&zf->zf_zstream);

        return (0);
}

static off_t
zf_seek(struct open_file *f, off_t offset, int where)
{
        struct z_file   *zf = (struct z_file *)f->f_fsdata;
        off_t           target;
        char            discard[16];

        switch (where) {
        case SEEK_SET:
                target = offset;
                break;
        case SEEK_CUR:
                target = offset + zf->zf_zstream.total_out;
                break;
        default:
                errno = EINVAL;
                return (-1);
        }

        /* rewind if required */
        if (target < zf->zf_zstream.total_out && zf_rewind(f) != 0)
                return (-1);

        /* skip forwards if required */
        while (target > zf->zf_zstream.total_out) {
                errno = zf_read(f, discard, min(sizeof (discard),
                    target - zf->zf_zstream.total_out), NULL);
                if (errno != 0)
                        return (-1);
        }
        /* This is where we are (be honest if we overshot) */
        return (zf->zf_zstream.total_out);
}


static int
zf_stat(struct open_file *f, struct stat *sb)
{
        struct z_file   *zf = (struct z_file *)f->f_fsdata;
        int             result;
        off_t           pos1, pos2;
        uint32_t        size;

        /* stat as normal, but indicate that size is unknown */
        if ((result = fstat(zf->zf_rawfd, sb)) == 0) {
                if (sb->st_size == -1)
                        return (result);
                pos1 = lseek(zf->zf_rawfd, 0, SEEK_CUR);
                pos2 = lseek(zf->zf_rawfd, sb->st_size - 4, SEEK_SET);
                if (pos2 != -1) {
                        if (read(zf->zf_rawfd, &size, 4) == 4)
                                sb->st_size = (off_t)size;
                        else
                                sb->st_size = -1;
                } else
                        sb->st_size = -1;

                pos1 = lseek(zf->zf_rawfd, pos1, SEEK_SET);
        }
        return (result);
}