Exemplo n.º 1
0
        private int huft_build(int[] b, int bindex, int n, int s, int[] d, int[] e, int[] t, int[] m, int[] hp, int[] hn, int[] v)
        {
            // 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
            {
                this.c[b[bindex + p]]++;
                p++;
                i--; // assume all entries <= BMAX
            }while (i != 0);

            if (this.c[0] == n)
            {
                // null input--all zero length codes
                t[0] = -1;
                m[0] = 0;
                return(InfTree.Z_OK);
            }

            // Find minimum and maximum length, bound *m by those
            l = m[0];
            for (j = 1; j <= InfTree.BMAX; j++)
            {
                if (this.c[j] != 0)
                {
                    break;
                }
            }

            k = j; // minimum code length
            if (l < j)
            {
                l = j;
            }

            for (i = InfTree.BMAX; i != 0; i--)
            {
                if (this.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 -= this.c[j]) < 0)
                {
                    return(InfTree.Z_DATA_ERROR);
                }
            }

            if ((y -= this.c[i]) < 0)
            {
                return(InfTree.Z_DATA_ERROR);
            }

            this.c[i] += y;

            // Generate starting offsets into the value table for each length
            this.x[1] = j = 0;
            p         = 1;
            xp        = 2;
            while (--i != 0)
            {
                // note that i == g from above
                this.x[xp] = j += this.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[this.x[j]++] = i;
                }

                p++;
            }while (++i < n);
            n = this.x[g]; // set n to length of v

            // Generate the Huffman codes and for each, make the table entries
            this.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)
            this.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 = this.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) <= this.c[++xp])
                                    {
                                        break; // enough codes to use up j bits
                                    }

                                    f -= this.c[xp]; // else deduct codes from patterns
                                }
                            }
                        }

                        z = 1 << j; // table entries for j-bit table

                        // allocate new table
                        if (hn[0] + z > InfTree.MANY)
                        {
                            // (note: doesn't matter for fixed)
                            return(InfTree.Z_DATA_ERROR); // overflow of MANY
                        }

                        this.u[h] = q = hn[0]; // DEBUG
                        hn[0]    += z;

                        // connect to last table, if there is one
                        if (h != 0)
                        {
                            this.x[h] = i;                                         // save pattern for backing up
                            this.r[0] = (sbyte)j;                                  // bits in this table
                            this.r[1] = (sbyte)l;                                  // bits to dump before this table
                            j         = SharedUtils.URShift(i, w - l);
                            this.r[2] = q - this.u[h - 1] - j;                     // offset to this table
                            Array.Copy(this.r, 0, hp, (this.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
                    this.r[1] = (sbyte)(k - w);
                    if (p >= n)
                    {
                        this.r[0] = 128 + 64; // out of values--invalid code
                    }
                    else if (v[p] < s)
                    {
                        this.r[0] = (sbyte)(v[p] < 256 ? 0 : 32 + 64); // 256 is end-of-block
                        this.r[2] = v[p++];                            // simple code is just the value
                    }
                    else
                    {
                        this.r[0] = (sbyte)(e[v[p] - s] + 16 + 64);  // non-simple--look up in lists
                        this.r[2] = d[v[p++] - s];
                    }

                    // fill code-like entries with r
                    f = 1 << (k - w);
                    for (j = SharedUtils.URShift(i, w); j < z; j += f)
                    {
                        Array.Copy(this.r, 0, hp, (q + j) * 3, 3);
                    }

                    // backwards increment the k-bit code i
                    for (j = 1 << (k - 1); (i & j) != 0; j = SharedUtils.URShift(j, 1))
                    {
                        i ^= j;
                    }

                    i ^= j;

                    // backup over finished tables
                    mask = (1 << w) - 1; // needed on HP, cc -O bug
                    while ((i & mask) != this.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 ? InfTree.Z_BUF_ERROR : InfTree.Z_OK);
        }