/* 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.
*/


/* RunLengthDecode filter */
#include "stdio_.h"		/* includes std.h */
#include "memory_.h"
#include "strimpl.h"
#include "srlx.h"

/* ------ RunLengthDecode ------ */

private_st_RLD_state();

/* Set defaults */
static void
s_RLD_set_defaults(stream_state * st)
{
    stream_RLD_state *const ss = (stream_RLD_state *) st;

    s_RLD_set_defaults_inline(ss);
}

/* Initialize */
static int
s_RLD_init(stream_state * st)
{
    stream_RLD_state *const ss = (stream_RLD_state *) st;

    return s_RLD_init_inline(ss);
}

/* Refill the buffer */
static int
s_RLD_process(stream_state * st, stream_cursor_read * pr,
              stream_cursor_write * pw, bool last)
{
    stream_RLD_state *const ss = (stream_RLD_state *) st;
    register const byte *p = pr->ptr;
    register byte *q = pw->ptr;
    const byte *rlimit = pr->limit;
    byte *wlimit = pw->limit;
    int left;
    int status = 0;

top:
    if ((left = ss->copy_left) > 0) {
        /*
         * We suspended because the output buffer was full:;
         * try again now.
         */
        uint avail = wlimit - q;
        int copy_status = 1;

        if (left > avail)
            left = avail;
        if (ss->copy_data >= 0)
            memset(q + 1, ss->copy_data, left);
        else {
            avail = rlimit - p;
            if (left >= avail) {
                copy_status = 0;
                left = avail;
            }
            memcpy(q + 1, p + 1, left);
            p += left;
        }
        q += left;
        if ((ss->copy_left -= left) > 0) {
            status = copy_status;
            goto x;
        }
    }
    while (p < rlimit) {
        int b = *++p;

        if (b < 128) {
            if (++b > rlimit - p || b > wlimit - q) {
                ss->copy_left = b;
                ss->copy_data = -1;
                goto top;
            }
            memcpy(q + 1, p + 1, b);
            p += b;
            q += b;
        } else if (b == 128) {	/* end of data */
            if (ss->EndOfData) {
                status = EOFC;
                break;
            }
        } else if (p == rlimit) {
            p--;
            break;
        } else if ((b = 257 - b) > wlimit - q) {
            ss->copy_left = b;
            ss->copy_data = *++p;
            goto top;
        } else {
            memset(q + 1, *++p, b);
            q += b;
        }
    }
x:  pr->ptr = p;
    pw->ptr = q;
    return status;
}

/* Stream template */
const stream_template s_RLD_template = {
    &st_RLD_state, s_RLD_init, s_RLD_process, 1, 1, NULL,
    s_RLD_set_defaults
};
