private static void HbMakeCodeLengths()

in src/ICSharpCode.SharpZipLib/BZip2/BZip2OutputStream.cs [1835:1985]
133 lines of code
25 McCabe index (conditional complexity)

		private static void HbMakeCodeLengths(char[] len, int[] freq, int alphaSize, int maxLen)
		{
			/*--
			Nodes and heap entries run from 1.  Entry 0
			for both the heap and nodes is a sentinel.
			--*/
			int nNodes, nHeap, n1, n2, j, k;
			bool tooLong;

			int[] heap = new int[BZip2Constants.MaximumAlphaSize + 2];
			int[] weight = new int[BZip2Constants.MaximumAlphaSize * 2];
			int[] parent = new int[BZip2Constants.MaximumAlphaSize * 2];

			for (int i = 0; i < alphaSize; ++i)
			{
				weight[i + 1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
			}

			while (true)
			{
				nNodes = alphaSize;
				nHeap = 0;

				heap[0] = 0;
				weight[0] = 0;
				parent[0] = -2;

				for (int i = 1; i <= alphaSize; ++i)
				{
					parent[i] = -1;
					nHeap++;
					heap[nHeap] = i;
					int zz = nHeap;
					int tmp = heap[zz];
					while (weight[tmp] < weight[heap[zz >> 1]])
					{
						heap[zz] = heap[zz >> 1];
						zz >>= 1;
					}
					heap[zz] = tmp;
				}
				if (!(nHeap < (BZip2Constants.MaximumAlphaSize + 2)))
				{
					Panic();
				}

				while (nHeap > 1)
				{
					n1 = heap[1];
					heap[1] = heap[nHeap];
					nHeap--;
					int zz = 1;
					int yy = 0;
					int tmp = heap[zz];
					while (true)
					{
						yy = zz << 1;
						if (yy > nHeap)
						{
							break;
						}
						if (yy < nHeap && weight[heap[yy + 1]] < weight[heap[yy]])
						{
							yy++;
						}
						if (weight[tmp] < weight[heap[yy]])
						{
							break;
						}

						heap[zz] = heap[yy];
						zz = yy;
					}
					heap[zz] = tmp;
					n2 = heap[1];
					heap[1] = heap[nHeap];
					nHeap--;

					zz = 1;
					yy = 0;
					tmp = heap[zz];
					while (true)
					{
						yy = zz << 1;
						if (yy > nHeap)
						{
							break;
						}
						if (yy < nHeap && weight[heap[yy + 1]] < weight[heap[yy]])
						{
							yy++;
						}
						if (weight[tmp] < weight[heap[yy]])
						{
							break;
						}
						heap[zz] = heap[yy];
						zz = yy;
					}
					heap[zz] = tmp;
					nNodes++;
					parent[n1] = parent[n2] = nNodes;

					weight[nNodes] = (int)((weight[n1] & 0xffffff00) + (weight[n2] & 0xffffff00)) |
						(int)(1 + (((weight[n1] & 0x000000ff) > (weight[n2] & 0x000000ff)) ? (weight[n1] & 0x000000ff) : (weight[n2] & 0x000000ff)));

					parent[nNodes] = -1;
					nHeap++;
					heap[nHeap] = nNodes;

					zz = nHeap;
					tmp = heap[zz];
					while (weight[tmp] < weight[heap[zz >> 1]])
					{
						heap[zz] = heap[zz >> 1];
						zz >>= 1;
					}
					heap[zz] = tmp;
				}
				if (!(nNodes < (BZip2Constants.MaximumAlphaSize * 2)))
				{
					Panic();
				}

				tooLong = false;
				for (int i = 1; i <= alphaSize; ++i)
				{
					j = 0;
					k = i;
					while (parent[k] >= 0)
					{
						k = parent[k];
						j++;
					}
					len[i - 1] = (char)j;
					tooLong |= j > maxLen;
				}

				if (!tooLong)
				{
					break;
				}

				for (int i = 1; i < alphaSize; ++i)
				{
					j = weight[i] >> 8;
					j = 1 + (j / 2);
					weight[i] = j << 8;
				}
			}
		}