/*
 * tinflate  -  tiny inflate
 *
 * Copyright (c) 2003 by Joergen Ibsen / Jibz
 * All Rights Reserved
 *
 * http://www.ibsensoftware.com/
 *
 * This software is provided 'as-is', without any express
 * or implied warranty.  In no event will the authors be
 * held liable for any damages arising from the use of
 * this software.
 *
 * Permission is granted to anyone to use this software
 * for any purpose, including commercial applications,
 * and to alter it and redistribute it freely, subject to
 * the following restrictions:
 *
 * 1. The origin of this software must not be
 *    misrepresented; you must not claim that you
 *    wrote the original software. If you use this
 *    software in a product, an acknowledgment in
 *    the product documentation would be appreciated
 *    but is not required.
 *
 * 2. Altered source versions must be plainly marked
 *    as such, and must not be misrepresented as
 *    being the original software.
 *
 * 3. This notice may not be removed or altered from
 *    any source distribution.
 */

#include "tinf.h"

/* ------------------------------ *
 * -- internal data structures -- *
 * ------------------------------ */

typedef struct {
   unsigned short table[16];  /* table of code length counts */
   unsigned short trans[288]; /* code -> symbol translation table */
} TINF_TREE;

typedef struct {
   const unsigned char *source;
   unsigned int tag;
   unsigned int bitcount;

   unsigned char *dest;
   unsigned int *destLen;

   TINF_TREE ltree; /* dynamic length/symbol tree */
   TINF_TREE dtree; /* dynamic distance tree */
} TINF_DATA;

/* --------------------------------------------------- *
 * -- uninitialized global data (static structures) -- *
 * --------------------------------------------------- */

TINF_TREE sltree; /* fixed length/symbol tree */
TINF_TREE sdtree; /* fixed distance tree */

/* extra bits and base tables for length codes */
unsigned char length_bits[30];
unsigned short length_base[30];

/* extra bits and base tables for distance codes */
unsigned char dist_bits[30];
unsigned short dist_base[30];

/* special ordering of code length codes */
const unsigned char clcidx[] = {
   16, 17, 18, 0, 8, 7, 9, 6,
   10, 5, 11, 4, 12, 3, 13, 2,
   14, 1, 15
};

/* ----------------------- *
 * -- utility functions -- *
 * ----------------------- */

/* build extra bits and base tables */
static void tinf_build_bits_base(unsigned char *bits, unsigned short *base, int delta, int first)
{
   int i, sum;

   /* build bits table */
   for (i = 0; i < delta; ++i) bits[i] = 0;
   for (i = 0; i < 30 - delta; ++i) bits[i + delta] = i / delta;

   /* build base table */
   for (sum = first, i = 0; i < 30; ++i)
   {
      base[i] = sum;
      sum += 1 << bits[i];
   }
}

/* build the fixed huffman trees */
static void tinf_build_fixed_trees(TINF_TREE *lt, TINF_TREE *dt)
{
   int i;

   /* build fixed length tree */
   for (i = 0; i < 7; ++i) lt->table[i] = 0;

   lt->table[7] = 24;
   lt->table[8] = 152;
   lt->table[9] = 112;

   for (i = 0; i < 24; ++i) lt->trans[i] = 256 + i;
   for (i = 0; i < 144; ++i) lt->trans[24 + i] = i;
   for (i = 0; i < 8; ++i) lt->trans[24 + 144 + i] = 280 + i;
   for (i = 0; i < 112; ++i) lt->trans[24 + 144 + 8 + i] = 144 + i;

   /* build fixed distance tree */
   for (i = 0; i < 5; ++i) dt->table[i] = 0;

   dt->table[5] = 32;

   for (i = 0; i < 32; ++i) dt->trans[i] = i;
}

/* given an array of code lengths, build a tree */
static void tinf_build_tree(TINF_TREE *t, const unsigned char *lengths, unsigned int num)
{
   unsigned short offs[16];
   unsigned int i, sum;

   /* clear code length count table */
   for (i = 0; i < 16; ++i) t->table[i] = 0;

   /* scan symbol lengths, and sum code length counts */
   for (i = 0; i < num; ++i) t->table[lengths[i]]++;

   t->table[0] = 0;

   /* compute offset table for distribution sort */
   for (sum = 0, i = 0; i < 16; ++i)
   {
      offs[i] = sum;
      sum += t->table[i];
   }

   /* create code->symbol translation table (symbols sorted by code) */
   for (i = 0; i < num; ++i)
   {
      if (lengths[i]) t->trans[offs[lengths[i]]++] = i;
   }
}

/* ---------------------- *
 * -- decode functions -- *
 * ---------------------- */

/* get one bit from source stream */
static int tinf_getbit(TINF_DATA *d)
{
   unsigned int bit;

   /* check if tag is empty */
   if (!d->bitcount--)
   {
      /* load next tag */
      d->tag = *d->source++;
      d->bitcount = 7;
   }

   /* shift bit out of tag */
   bit = d->tag & 0x01;
   d->tag >>= 1;

   return bit;
}

/* read a num bit value from a stream and add base */
static unsigned int tinf_read_bits(TINF_DATA *d, int num, int base)
{
   unsigned int val = 0;

   /* read num bits */
   if (num)
   {
      unsigned int limit = 1 << (num);
      unsigned int mask;

      for (mask = 1; mask < limit; mask *= 2)
         if (tinf_getbit(d)) val += mask;
   }

   return val + base;
}

/* given a data stream and a tree, decode a symbol */
static int tinf_decode_symbol(TINF_DATA *d, TINF_TREE *t)
{
   int sum = 0, cur = 0, len = 0;

   /* get more bits while code value is above sum */
   do {

      cur = 2*cur + tinf_getbit(d);

      ++len;

      sum += t->table[len];
      cur -= t->table[len];

   } while (cur >= 0);

   return t->trans[sum + cur];
}

/* given a data stream, decode dynamic trees from it */
static void tinf_decode_trees(TINF_DATA *d, TINF_TREE *lt, TINF_TREE *dt)
{
   TINF_TREE code_tree;
   unsigned char lengths[288+32];
   unsigned int hlit, hdist, hclen;
   unsigned int i, num, length;

   /* get 5 bits HLIT (257-286) */
   hlit = tinf_read_bits(d, 5, 257);

   /* get 5 bits HDIST (1-32) */
   hdist = tinf_read_bits(d, 5, 1);

   /* get 4 bits HCLEN (4-19) */
   hclen = tinf_read_bits(d, 4, 4);

   for (i = 0; i < 19; ++i) lengths[i] = 0;

   /* read code lengths for code length alphabet */
   for (i = 0; i < hclen; ++i)
   {
      /* get 3 bits code length (0-7) */
      unsigned int clen = tinf_read_bits(d, 3, 0);

      lengths[clcidx[i]] = clen;
   }

   /* build code length tree */
   tinf_build_tree(&code_tree, lengths, 19);

   /* decode code lengths for the dynamic trees */
   for (num = 0; num < hlit + hdist; )
   {
      int sym = tinf_decode_symbol(d, &code_tree);

      switch (sym)
      {
      case 16:
         /* copy previous code length 3-6 times (read 2 bits) */
         {
            unsigned char prev = lengths[num - 1];
            for (length = tinf_read_bits(d, 2, 3); length; --length)
            {
               lengths[num++] = prev;
            }
         }
         break;
      case 17:
         /* repeat code length 0 for 3-10 times (read 3 bits) */
         for (length = tinf_read_bits(d, 3, 3); length; --length)
         {
            lengths[num++] = 0;
         }
         break;
      case 18:
         /* repeat code length 0 for 11-138 times (read 7 bits) */
         for (length = tinf_read_bits(d, 7, 11); length; --length)
         {
            lengths[num++] = 0;
         }
         break;
      default:
         /* values 0-15 represent the actual code lengths */
         lengths[num++] = sym;
         break;
      }
   }

   /* build dynamic trees */
   tinf_build_tree(lt, lengths, hlit);
   tinf_build_tree(dt, lengths + hlit, hdist);
}

/* ----------------------------- *
 * -- block inflate functions -- *
 * ----------------------------- */

/* given a stream and two trees, inflate a block of data */
static int tinf_inflate_block_data(TINF_DATA *d, TINF_TREE *lt, TINF_TREE *dt)
{
   /* remember current output position */
   unsigned char *start = d->dest;

   while (1)
   {
      int sym = tinf_decode_symbol(d, lt);

      /* check for end of block */
      if (sym == 256)
      {
         *d->destLen += d->dest - start;
         return TINF_OK;
      }

      if (sym < 256)
      {
         *d->dest++ = sym;

      } else {

         int length, dist, offs;
         int i;

         sym -= 257;

         /* possibly get more bits from length code */
         length = tinf_read_bits(d, length_bits[sym], length_base[sym]);

         dist = tinf_decode_symbol(d, dt);

         /* possibly get more bits from distance code */
         offs = tinf_read_bits(d, dist_bits[dist], dist_base[dist]);

         /* copy match */
         for (i = 0; i < length; ++i)
         {
            d->dest[i] = d->dest[i - offs];
         }

         d->dest += length;
      }
   }
}

/* inflate an uncompressed block of data */
static int tinf_inflate_uncompressed_block(TINF_DATA *d)
{
   unsigned int length, invlength;
   unsigned int i;

   /* get length */
   length = d->source[1];
   length = 256*length + d->source[0];

   /* get one's complement of length */
   invlength = d->source[3];
   invlength = 256*invlength + d->source[2];

   /* check length */
   if (length != (~invlength & 0x0000ffff)) return TINF_DATA_ERROR;

   d->source += 4;

   /* copy block */
   for (i = length; i; --i) *d->dest++ = *d->source++;

   /* make sure we start next block on a byte boundary */
   d->bitcount = 0;

   *d->destLen += length;

   return TINF_OK;
}

/* inflate a block of data compressed with fixed huffman trees */
static int tinf_inflate_fixed_block(TINF_DATA *d)
{
   /* decode block using fixed trees */
   return tinf_inflate_block_data(d, &sltree, &sdtree);
}

/* inflate a block of data compressed with dynamic huffman trees */
static int tinf_inflate_dynamic_block(TINF_DATA *d)
{
   /* decode trees from stream */
   tinf_decode_trees(d, &d->ltree, &d->dtree);

   /* decode block using decoded trees */
   return tinf_inflate_block_data(d, &d->ltree, &d->dtree);
}

/* ---------------------- *
 * -- public functions -- *
 * ---------------------- */

/* initialize global (static) data */
void tinf_init()
{
   /* build fixed huffman trees */
   tinf_build_fixed_trees(&sltree, &sdtree);

   /* build extra bits and base tables */
   tinf_build_bits_base(length_bits, length_base, 4, 3);
   tinf_build_bits_base(dist_bits, dist_base, 2, 1);

   /* fix a special case */
   length_bits[28] = 0;
   length_base[28] = 258;
}

/* inflate stream from source to dest */
int tinf_uncompress(void *dest, unsigned int *destLen,
                    const void *source, unsigned int sourceLen)
{
   TINF_DATA d;
   int bfinal;

   /* initialise data */
   d.source = (const unsigned char *)source;
   d.bitcount = 0;

   d.dest = (unsigned char *)dest;
   d.destLen = destLen;

   *destLen = 0;

   do {

      unsigned int btype;
      int res;

      /* read final block flag */
      bfinal = tinf_getbit(&d);

      /* read block type (2 bits) */
      btype = tinf_read_bits(&d, 2, 0);

      /* decompress block */
      switch (btype)
      {
      case 0:
         /* decompress uncompressed block */
         res = tinf_inflate_uncompressed_block(&d);
         break;
      case 1:
         /* decompress block with fixed huffman trees */
         res = tinf_inflate_fixed_block(&d);
         break;
      case 2:
         /* decompress block with dynamic huffman trees */
         res = tinf_inflate_dynamic_block(&d);
         break;
      default:
         return TINF_DATA_ERROR;
      }

      if (res != TINF_OK) return TINF_DATA_ERROR;

   } while (!bfinal);

   return TINF_OK;
}
