using System;

namespace Unity.IO.Compression
{
	internal class InputBuffer
	{
		private byte[] buffer;

		private int start;

		private int end;

		private uint bitBuffer;

		private int bitsInBuffer;

		public int AvailableBits
		{
			get
			{
				return bitsInBuffer;
			}
		}

		public int AvailableBytes
		{
			get
			{
				return end - start + bitsInBuffer / 8;
			}
		}

		public bool EnsureBitsAvailable(int count)
		{
			if (bitsInBuffer < count)
			{
				if (NeedsInput())
				{
					return false;
				}
				bitBuffer |= (uint)(buffer[start++] << bitsInBuffer);
				bitsInBuffer += 8;
				if (bitsInBuffer < count)
				{
					if (NeedsInput())
					{
						return false;
					}
					bitBuffer |= (uint)(buffer[start++] << bitsInBuffer);
					bitsInBuffer += 8;
				}
			}
			return true;
		}

		public uint TryLoad16Bits()
		{
			if (bitsInBuffer < 8)
			{
				if (start < end)
				{
					bitBuffer |= (uint)(buffer[start++] << bitsInBuffer);
					bitsInBuffer += 8;
				}
				if (start < end)
				{
					bitBuffer |= (uint)(buffer[start++] << bitsInBuffer);
					bitsInBuffer += 8;
				}
			}
			else if (bitsInBuffer < 16 && start < end)
			{
				bitBuffer |= (uint)(buffer[start++] << bitsInBuffer);
				bitsInBuffer += 8;
			}
			return bitBuffer;
		}

		private uint GetBitMask(int count)
		{
			return (uint)((1 << count) - 1);
		}

		public int GetBits(int count)
		{
			if (!EnsureBitsAvailable(count))
			{
				return -1;
			}
			int result = (int)(bitBuffer & GetBitMask(count));
			bitBuffer >>= count;
			bitsInBuffer -= count;
			return result;
		}

		public int CopyTo(byte[] output, int offset, int length)
		{
			int num = 0;
			while (bitsInBuffer > 0 && length > 0)
			{
				output[offset++] = (byte)bitBuffer;
				bitBuffer >>= 8;
				bitsInBuffer -= 8;
				length--;
				num++;
			}
			if (length == 0)
			{
				return num;
			}
			int num2 = end - start;
			if (length > num2)
			{
				length = num2;
			}
			Array.Copy(buffer, start, output, offset, length);
			start += length;
			return num + length;
		}

		public bool NeedsInput()
		{
			return start == end;
		}

		public void SetInput(byte[] buffer, int offset, int length)
		{
			this.buffer = buffer;
			start = offset;
			end = offset + length;
		}

		public void SkipBits(int n)
		{
			bitBuffer >>= n;
			bitsInBuffer -= n;
		}

		public void SkipToByteBoundary()
		{
			bitBuffer >>= bitsInBuffer % 8;
			bitsInBuffer -= bitsInBuffer % 8;
		}
	}
}