/* given a data stream, decode dynamic trees from it */
static int tinf_decode_trees(TINF_DATA *d, TINF_TREE *lt, TINF_TREE *dt)
{
unsigned char lengths[288+32];
unsigned int hlit, hdist, hclen, hlimit;
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, temporarily use length tree */
tinf_build_tree(lt, lengths, 19);
/* decode code lengths for the dynamic trees */
hlimit = hlit + hdist;
for (num = 0; num < hlimit; )
{
int sym = tinf_decode_symbol(d, lt);
unsigned char fill_value = 0;
int lbits, lbase = 3;
/* error decoding */
if (sym < 0) return sym;
switch (sym)
{
case 16:
if (num == 0) {
return TINF_DATA_ERROR;
}
/* copy previous code length 3-6 times (read 2 bits) */
fill_value = lengths[num - 1];
lbits = 2;
break;
case 17:
/* repeat code length 0 for 3-10 times (read 3 bits) */
lbits = 3;
break;
case 18:
/* repeat code length 0 for 11-138 times (read 7 bits) */
lbits = 7;
lbase = 11;
break;
default:
/* values 0-15 represent the actual code lengths */
lengths[num++] = sym;
/* continue the for loop */
continue;
}
/* special code length 16-18 are handled here */
length = tinf_read_bits(d, lbits, lbase);
if (num + length >= hlimit) return TINF_DATA_ERROR;
for (; length; --length)
{
lengths[num++] = fill_value;
}
}
/* build dynamic trees */
tinf_build_tree(lt, lengths, hlit);
tinf_build_tree(dt, lengths + hlit, hdist);
return TINF_OK;
}
/* 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);
}
