namespace System.Net.ApiService.Compression.Brotli {
	/// <summary>Contains a collection of huffman trees with the same alphabet size.</summary>
	internal sealed class HuffmanTreeGroup {
		/// <summary>The maximal alphabet size in this group.</summary>
		private int alphabetSize;

		/// <summary>Storage for Huffman lookup tables.</summary>
		internal int[] codes;

		/// <summary>
		/// Offsets of distinct lookup tables in
		/// <see cref="codes"/>
		/// storage.
		/// </summary>
		internal int[] trees;

		/// <summary>Initializes the Huffman tree group.</summary>
		/// <param name="group">POJO to be initialised</param>
		/// <param name="alphabetSize">the maximal alphabet size in this group</param>
		/// <param name="n">number of Huffman codes</param>
		internal static void Init(System.Net.ApiService.Compression.Brotli.HuffmanTreeGroup group, int alphabetSize, int n) {
			group.alphabetSize = alphabetSize;
			group.codes = new int[n * System.Net.ApiService.Compression.Brotli.Huffman.HuffmanMaxTableSize];
			group.trees = new int[n];
		}

		/// <summary>Decodes Huffman trees from input stream and constructs lookup tables.</summary>
		/// <param name="group">target POJO</param>
		/// <param name="br">data source</param>
		internal static void Decode(System.Net.ApiService.Compression.Brotli.HuffmanTreeGroup group, System.Net.ApiService.Compression.Brotli.BitReader br) {
			int next = 0;
			int n = group.trees.Length;
			for (int i = 0; i < n; i++) {
				group.trees[i] = next;
				System.Net.ApiService.Compression.Brotli.Decode.ReadHuffmanCode(group.alphabetSize, group.codes, next, br);
				next += System.Net.ApiService.Compression.Brotli.Huffman.HuffmanMaxTableSize;
			}
		}
	}
}