/* Copyright (C) 2001-2023 Artifex Software, Inc.
   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied,
   modified or distributed except as expressly authorized under the terms
   of the license contained in the file LICENSE in this distribution.

   Refer to licensing information at http://www.artifex.com or contact
   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,
   CA 94129, USA, for further information.
*/


/* zlib decoding (decompression) filter stream */
#include "memory_.h"
#include "std.h"
#include "strimpl.h"
#include "szlibxx.h"

/* Initialize the filter. */
static int
s_zlibD_init(stream_state * st)
{
    stream_zlib_state *const ss = (stream_zlib_state *)st;
    int code = s_zlib_alloc_dynamic_state(ss);

    if (code < 0)
        return ERRC;    /****** WRONG ******/
    if (inflateInit2(&ss->dynamic->zstate,
                     (ss->no_wrapper ? -ss->windowBits : ss->windowBits))
        != Z_OK
        ) {
        s_zlib_free_dynamic_state(ss);
        return ERRC;    /****** WRONG ******/
    }
    st->min_left=1;
    return 0;
}

/* Reinitialize the filter. */
static int
s_zlibD_reset(stream_state * st)
{
    stream_zlib_state *const ss = (stream_zlib_state *)st;

    if (inflateReset(&ss->dynamic->zstate) != Z_OK)
        return ERRC;    /****** WRONG ******/
    return 0;
}

/* Process a buffer */
static int
s_zlibD_process(stream_state * st, stream_cursor_read * pr,
                stream_cursor_write * pw, bool ignore_last)
{
    stream_zlib_state *const ss = (stream_zlib_state *)st;
    z_stream *zs = &ss->dynamic->zstate;
    const byte *p = pr->ptr;
    int status;
    static const unsigned char jaws_empty[] = {0x58, 0x85, 1, 0, 0, 0, 0, 0, 1, 0x0A};

    /* Detect no input or full output so that we don't get */
    /* a Z_BUF_ERROR return. */
    if (pw->ptr == pw->limit)
        return 1;
    if (pr->ptr == pr->limit)
        return 0;
    zs->next_in = (Bytef *)p + 1;
    zs->avail_in = pr->limit - p;
    zs->next_out = pw->ptr + 1;
    zs->avail_out = pw->limit - pw->ptr;
    if (zs->total_in == 0 && zs->avail_in >= 10 && !memcmp(zs->next_in, jaws_empty, 10)) {
        /* JAWS PDF generator encodes empty stream as jaws_empty[].
         * The stream declares that the data block length is zero
         * but zlib routines regard a zero length data block to be an error.
         */
        pr->ptr += 10;
        return EOFC;
    }
    status = inflate(zs, Z_PARTIAL_FLUSH);
    pr->ptr = zs->next_in - 1;
    pw->ptr = zs->next_out - 1;
    switch (status) {
        case Z_OK:
            return (pw->ptr == pw->limit ? 1 : pr->ptr > p ? 0 : 1);
        case Z_STREAM_END:
            return EOFC;
        default:
            if (zs->msg && !strcmp("incorrect data check", zs->msg))
            {
                /* Ignore errors when zlib streams fail on the checksum.
                 * Adobe, Apple and xpdf don't fail on pdf:s where this happens,
                 * so neither should we. fixes bug 688716.
                 */
                dmprintf1(st->memory,
                          "warning: ignoring zlib error: %s\n", zs->msg);
                return EOFC;
            }
            return ERRC;
    }
}

/* Release the stream */
static void
s_zlibD_release(stream_state * st)
{
    stream_zlib_state *const ss = (stream_zlib_state *)st;

    if (ss->dynamic != NULL)
        inflateEnd(&ss->dynamic->zstate);
    s_zlib_free_dynamic_state(ss);
}

/* Stream template */
const stream_template s_zlibD_template = {
    &st_zlib_state, s_zlibD_init, s_zlibD_process, 1, 1, s_zlibD_release,
    s_zlib_set_defaults, s_zlibD_reset
};
