/* @file

 * Decompression of the Huffman encoding used for HTTP fields in HPACK (HTTP/2)

 * and QPACK (HTTP/3)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <epan/tvbuff.h>

#include <epan/nghttp2_hd_huffman.h>

static wmem_strbuf_t *

get_hpack_huffman_strbuf(wmem_allocator_t *scope, const uint8_t *ptr, size_t len)

{

    wmem_strbuf_t *strbuf;

    strbuf = wmem_strbuf_new_sized(scope, len + 1);

    nghttp2_huff_decode node = {0, 0};

    const nghttp2_huff_decode *nodep = &node;

    while (len > 0) {

        uint8_t ch = *ptr++;

        nodep = &huff_decode_table[nodep->fstate & 0x1ff][ch >> 4];

        if (nodep->fstate & NGHTTP2_HUFF_SYM) {

            wmem_strbuf_append_c(strbuf, nodep->sym);

        }

        nodep = &huff_decode_table[nodep->fstate & 0x1ff][ch & 0xf];

        if (nodep->fstate & NGHTTP2_HUFF_SYM) {

            wmem_strbuf_append_c(strbuf, nodep->sym);

        }

        len--;

    }

    if (!(nodep->fstate & NGHTTP2_HUFF_ACCEPTED)) {

        wmem_strbuf_destroy(strbuf);

        return NULL;

    }

    return strbuf;

}

wmem_strbuf_t *

tvb_get_hpack_huffman_strbuf(wmem_allocator_t *scope, tvbuff_t *tvb, const unsigned offset, const unsigned len)

{

    return get_hpack_huffman_strbuf(scope, tvb_get_ptr(tvb, offset, len), len);

}

tvbuff_t*

tvb_child_uncompress_hpack_huff(tvbuff_t* parent, unsigned offset, unsigned length)

{

    tvbuff_t* tvb = NULL;

    wmem_strbuf_t *strbuf;

    char* data;

    size_t len;

    strbuf = tvb_get_hpack_huffman_strbuf(NULL, parent, offset, length);

    if (strbuf) {

        len = wmem_strbuf_get_len(strbuf);

        data = wmem_strbuf_finalize(strbuf);

        tvb = tvb_new_child_real_data(parent, (const uint8_t*)data, (unsigned)len, (unsigned)len);

        tvb_set_free_cb(tvb, g_free);

    }

    return tvb;

}