// SPDX-License-Identifier: GPL-2.0
/*
 * uncompress.c
 *
 * (C) Copyright 1999 Linus Torvalds
 *
 * cramfs interfaces to the uncompression library. There's really just
 * three entrypoints:
 *
 *  - cramfs_uncompress_init() - called to initialize the thing.
 *  - cramfs_uncompress_exit() - tell me when you're done
 *  - cramfs_uncompress_block() - uncompress a block.
 *
 * NOTE NOTE NOTE! The uncompression is entirely single-threaded. We
 * only have one stream, and we'll initialize it only once even if it
 * then is used by multiple filesystems.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/vmalloc.h>
#include <linux/zlib.h>
#include "internal.h"

static z_stream stream;
static int initialized;

/* Returns length of decompressed data. */
int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
{
        int err;

        stream.next_in = src;
        stream.avail_in = srclen;

        stream.next_out = dst;
        stream.avail_out = dstlen;

        err = zlib_inflateReset(&stream);
        if (err != Z_OK) {
                pr_err("zlib_inflateReset error %d\n", err);
                zlib_inflateEnd(&stream);
                zlib_inflateInit(&stream);
        }

        err = zlib_inflate(&stream, Z_FINISH);
        if (err != Z_STREAM_END)
                goto err;
        return stream.total_out;

err:
        pr_err("Error %d while decompressing!\n", err);
        pr_err("%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
        return -EIO;
}

int cramfs_uncompress_init(void)
{
        if (!initialized++) {
                stream.workspace = vmalloc(zlib_inflate_workspacesize());
                if (!stream.workspace) {
                        initialized = 0;
                        return -ENOMEM;
                }
                stream.next_in = NULL;
                stream.avail_in = 0;
                zlib_inflateInit(&stream);
        }
        return 0;
}

void cramfs_uncompress_exit(void)
{
        if (!--initialized) {
                zlib_inflateEnd(&stream);
                vfree(stream.workspace);
        }
}