/*

 * nghttp2 - HTTP/2 C Library

 *

 * Copyright (c) 2013 Tatsuhiro Tsujikawa

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 */

#include "nghttp2_hd_huffman.h"

#include <string.h>

#include <assert.h>

#include <stdio.h>

#include "nghttp2_hd.h"

#include "nghttp2_net.h"

size_t nghttp2_hd_huff_encode_count(const uint8_t *src, size_t len) {

  size_t i;

  size_t nbits = 0;

  for (i = 0; i < len; ++i) {

    nbits += huff_sym_table[src[i]].nbits;

  }

  /* pad the prefix of EOS (256) */

  return (nbits + 7) / 8;

}

int nghttp2_hd_huff_encode(nghttp2_bufs *bufs, const uint8_t *src,

                           size_t srclen) {

  const nghttp2_huff_sym *sym;

  const uint8_t *end = src + srclen;

  uint64_t code = 0;

  uint32_t x;

  size_t nbits = 0;

  size_t avail;

  int rv;

  avail = nghttp2_bufs_cur_avail(bufs);

  for (; src != end;) {

    sym = &huff_sym_table[*src++];

    code |= (uint64_t)sym->code << (32 - nbits);

    nbits += sym->nbits;

    if (nbits < 32) {

      continue;

    }

    if (avail >= 4) {

      x = htonl((uint32_t)(code >> 32));

      memcpy(bufs->cur->buf.last, &x, 4);

      bufs->cur->buf.last += 4;

      avail -= 4;

      code <<= 32;

      nbits -= 32;

      continue;

    }

    for (; nbits >= 8;) {

      rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 56));

      if (rv != 0) {

        return rv;

      }

      code <<= 8;

      nbits -= 8;

    }

    avail = nghttp2_bufs_cur_avail(bufs);

  }

  for (; nbits >= 8;) {

    rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 56));

    if (rv != 0) {

      return rv;

    }

    code <<= 8;

    nbits -= 8;

  }

  if (nbits) {

    rv = nghttp2_bufs_addb(

        bufs, (uint8_t)((uint8_t)(code >> 56) | ((1 << (8 - nbits)) - 1)));

    if (rv != 0) {

      return rv;

    }

  }

  return 0;

}

void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx) {

  ctx->fstate = NGHTTP2_HUFF_ACCEPTED;

}

nghttp2_ssize nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,

                                     nghttp2_buf *buf, const uint8_t *src,

                                     size_t srclen, int final) {

  const uint8_t *end = src + srclen;

  nghttp2_huff_decode node = {ctx->fstate, 0};

  const nghttp2_huff_decode *t = &node;

  uint8_t c;

  /* We use the decoding algorithm described in

      - http://graphics.ics.uci.edu/pub/Prefix.pdf [!!! NO LONGER VALID !!!]

      - https://ics.uci.edu/~dan/pubs/Prefix.pdf

      - https://github.com/nghttp2/nghttp2/files/15141264/Prefix.pdf */

  for (; src != end;) {

    c = *src++;

    t = &huff_decode_table[t->fstate & 0x1ff][c >> 4];

    if (t->fstate & NGHTTP2_HUFF_SYM) {

      *buf->last++ = t->sym;

    }

    t = &huff_decode_table[t->fstate & 0x1ff][c & 0xf];

    if (t->fstate & NGHTTP2_HUFF_SYM) {

      *buf->last++ = t->sym;

    }

  }

  ctx->fstate = t->fstate;

  if (final && !(ctx->fstate & NGHTTP2_HUFF_ACCEPTED)) {

    return NGHTTP2_ERR_HEADER_COMP;

  }

  return (nghttp2_ssize)srclen;

}

int nghttp2_hd_huff_decode_failure_state(nghttp2_hd_huff_decode_context *ctx) {

  return ctx->fstate == 0x100;

}