private int huft_build(int[] b, // code lengths in bits (all assumed <= BMAX)
int bindex,
int n, // number of codes (assumed <= 288)
int s, // number of simple-valued codes (0..s-1)
int[] d, // list of base values for non-simple codes
int[] e, // list of extra bits for non-simple codes
int[] t, // result: starting table
int[] m, // maximum lookup bits, returns actual
int[] hp,// space for trees
int[] hn,// hufts used in space
int[] v // working area: values in order of bit length
){
// Given a list of code lengths and a maximum table size, make a set of
// tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
// if the given code set is incomplete (the tables are still built in this
// case), Z_DATA_ERROR if the input is invalid (an over-subscribed set of
// lengths), or Z_MEM_ERROR if not enough memory.
int a; // counter for codes of length k
int f; // i repeats in table every f entries
int g; // maximum code length
int h; // table level
int i; // counter, current code
int j; // counter
int k; // number of bits in current code
int l; // bits per table (returned in m)
int mask; // (1 << w) - 1, to avoid cc -O bug on HP
int p; // pointer into c[], b[], or v[]
int q; // points to current table
int w; // bits before this table == (l * h)
int xp; // pointer into x
int y; // number of dummy codes added
int z; // number of entries in current table
// Generate counts for each bit length
p = 0; i = n;
do {
c[b[bindex+p]]++; p++; i--; // assume all entries <= BMAX
}while(i!=0);
if(c[0] == n){ // null input--all zero length codes
t[0] = -1;
m[0] = 0;
return Z_OK;
}
// Find minimum and maximum length, bound *m by those
l = m[0];
for (j = 1; j <= BMAX; j++)
if(c[j]!=0) break;
k = j; // minimum code length
if(l < j){
l = j;
}
for (i = BMAX; i!=0; i--){
if(c[i]!=0) break;
}
g = i; // maximum code length
if(l > i){
l = i;
}
m[0] = l;
// Adjust last length count to fill out codes, if needed
for (y = 1 << j; j < i; j++, y <<= 1){
if ((y -= c[j]) < 0){
return Z_DATA_ERROR;
}
}
if ((y -= c[i]) < 0){
return Z_DATA_ERROR;
}
c[i] += y;
// Generate starting offsets into the value table for each length
x[1] = j = 0;
p = 1; xp = 2;
while (--i!=0) { // note that i == g from above
x[xp] = (j += c[p]);
xp++;
p++;
}
// Make a table of values in order of bit lengths
i = 0; p = 0;
do {
if ((j = b[bindex+p]) != 0){
v[x[j]++] = i;
}
p++;
}
while (++i < n);
n = x[g]; // set n to length of v
// Generate the Huffman codes and for each, make the table entries
x[0] = i = 0; // first Huffman code is zero
p = 0; // grab values in bit order
h = -1; // no tables yet--level -1
w = -l; // bits decoded == (l * h)
u[0] = 0; // just to keep compilers happy
q = 0; // ditto
z = 0; // ditto
// go through the bit lengths (k already is bits in shortest code)
for (; k <= g; k++){
a = c[k];
while (a--!=0){
// here i is the Huffman code of length k bits for value *p
// make tables up to required level
while (k > w + l){
h++;
w += l; // previous table always l bits
// compute minimum size table less than or equal to l bits
z = g - w;
z = (z > l) ? l : z; // table size upper limit
if((f=1<<(j=k-w))>a+1){ // try a k-w bit table
// too few codes for k-w bit table
f -= a + 1; // deduct codes from patterns left
xp = k;
if(j < z){
while (++j < z){ // try smaller tables up to z bits
if((f <<= 1) <= c[++xp])
break; // enough codes to use up j bits
f -= c[xp]; // else deduct codes from patterns
}
}
}
z = 1 << j; // table entries for j-bit table
// allocate new table
if (hn[0] + z > MANY){ // (note: doesn't matter for fixed)
return Z_DATA_ERROR; // overflow of MANY
}
u[h] = q = /*hp+*/ hn[0]; // DEBUG
hn[0] += z;
// connect to last table, if there is one
if(h!=0){
x[h]=i; // save pattern for backing up
r[0]=(byte)j; // bits in this table
r[1]=(byte)l; // bits to dump before this table
j=i>>(w - l);
r[2] = (int)(q - u[h-1] - j); // offset to this table
System.Array.Copy(r, 0, hp, (u[h-1]+j)*3, 3); // connect to last table
}
else{
t[0] = q; // first table is returned result
}
}
// set up table entry in r
r[1] = (byte)(k - w);
if (p >= n){
r[0] = 128 + 64; // out of values--invalid code
}
else if (v[p] < s){
r[0] = (byte)(v[p] < 256 ? 0 : 32 + 64); // 256 is end-of-block
r[2] = v[p++]; // simple code is just the value
}
else{
r[0]=(byte)(e[v[p]-s]+16+64); // non-simple--look up in lists
r[2]=d[v[p++] - s];
}
// fill code-like entries with r
f=1<<(k-w);
for (j=i>>w;j<z;j+=f){
System.Array.Copy(r, 0, hp, (q+j)*3, 3);
}
// backwards increment the k-bit code i
for (j = 1 << (k - 1); (i & j)!=0; j >>= 1){
i ^= j;
}
i ^= j;
// backup over finished tables
mask = (1 << w) - 1; // needed on HP, cc -O bug
while ((i & mask) != x[h]){
h--; // don't need to update q
w -= l;
mask = (1 << w) - 1;
}
}
}
// Return Z_BUF_ERROR if we were given an incomplete table
return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
}
