int Decode(Huffman *h)
{
int len; /* current number of Bits in code */
int code; /* len Bits being decoded */
int first; /* first code of length len */
int count; /* number of Codes of length len */
int index; /* index of first code of length len in symbol table */
int bitbuf; /* Bits from stream */
int left; /* Bits left in next or left to process */
short *next; /* next number of Codes */
bitbuf = this.bitbuf;
left = bitcnt;
code = first = index = 0;
len = 1;
next = h->count + 1;
while (true)
{
while (left-- != 0)
{
code |= bitbuf & 1;
bitbuf >>= 1;
count = *next++;
if (code < first + count) /* if length len, return symbol */
{
this.bitbuf = bitbuf;
bitcnt = (bitcnt - len) & 7;
return(h->symbol[index + (code - first)]);
}
index += count; /* else update for next length */
first += count;
first <<= 1;
code <<= 1;
len++;
}
left = (MAXBITS + 1) - len;
if (left == 0)
{
break;
}
if (incnt == inlen)
{
throw new InvalidDataException("Output of input"); //longjmp(env, 1); /* out of input */
}
//if (incnt == inlen) throw new Exception("Out of length");
bitbuf = inBuffer[incnt++];
if (incnt == incntToJump)
{
JumpToNextSourceChunk();
}
if (left > 8)
{
left = 8;
}
}
return(-9); /* ran out of Codes */
}
int Construct(Huffman *h, short *length, int n)
{
int symbol; /* current symbol when stepping through length[] */
int len; /* current length when stepping through h->count[] */
int left; /* number of possible Codes left of current length */
short *offs = stackalloc short[MAXBITS + 1]; /* offsets in symbol table for each length */
/* count number of Codes of each length */
for (len = 0; len <= MAXBITS; len++)
{
h->count[len] = 0;
}
for (symbol = 0; symbol < n; symbol++)
{
(h->count[length[symbol]])++; /* assumes lengths are within bounds */
}
if (h->count[0] == n) /* no Codes! */
{
return(0); /* complete, but Decode() will fail */
}
/* check for an over-subscribed or incomplete set of lengths */
left = 1; /* one possible code of zero length */
for (len = 1; len <= MAXBITS; len++)
{
left <<= 1; /* one more bit, double Codes left */
left -= h->count[len]; /* deduct count from possible Codes */
if (left < 0)
{
return(left); /* over-subscribed--return negative */
}
} /* left > 0 means incomplete */
/* generate offsets into symbol table for each length for sorting */
offs[1] = 0;
for (len = 1; len < MAXBITS; len++)
{
offs[len + 1] = (short)(offs[len] + h->count[len]);
}
/*
* put symbols in table sorted by length, by symbol order within each
* length
*/
for (symbol = 0; symbol < n; symbol++)
{
if (length[symbol] != 0)
{
h->symbol[offs[length[symbol]]++] = (short)symbol;
}
}
/* return zero for complete set, positive for incomplete set */
return(left);
}
int Codes(Huffman *lencode, Huffman *distcode)
{
int symbol; /* decoded symbol */
int len; /* length for copy */
uint dist; /* distance for copy */
/* Decode literals and length/distance pairs */
do
{
symbol = Decode(lencode);
if (symbol < 0)
{
return(symbol); /* invalid symbol */
}
if (symbol < 256) /* literal: symbol is the byte */
/* write out the literal */
{
if (outBuffer != NIL)
{
if (outcnt == outlen)
{
return(1);
}
outBuffer[outcnt] = (byte)symbol;
}
outcnt++;
}
else if (symbol > 256) /* length */
/* get and compute length */
{
symbol -= 257;
if (symbol >= 29)
{
return(-9); /* invalid fixed code */
}
len = lens[symbol] + Bits(lext[symbol]);
/* get and check distance */
symbol = Decode(distcode);
if (symbol < 0)
{
return(symbol); /* invalid symbol */
}
dist = (uint)(dists[symbol] + Bits(dext[symbol]));
if (dist > outcnt)
{
return(-10); /* distance too far back */
}
/* copy length bytes from distance bytes back */
if (outBuffer != NIL)
{
if (outcnt + len > outlen)
{
return(1);
}
while (len-- != 0)
{
outBuffer[outcnt] = outBuffer[outcnt - dist];
outcnt++;
}
}
else
{
outcnt += (uint)len;
}
}
} while (symbol != 256); /* end of block symbol */
/* done with a valid fixed or dynamic block */
return(0);
}
