using System;
using System.IO;
using System.IO.Compression;
using System.Text;

namespace CSharpUtil
{

    /// <summary>
    /// 压缩工具类
    /// </summary>
    class CompressUtil
    {
        /// <summary>
        /// 数据最大长度不宜超过1M
        /// </summary>
        const int MaxDataLenght = 1024 * 1024;
        /// <summary>
        /// 利用deflate算法压缩字节数组
        /// </summary>
        /// <param name="data">字节数组(不宜超过1M)</param>
        /// <param name="compressMode">压缩模式(压缩/解压)</param>
        /// <exception cref="OutOfMemoryException">数据不建议超过1M</exception>
        /// <returns></returns>

        public static byte[] Deflate(byte[] data, CompressionMode compressMode = CompressionMode.Compress)
        {
            if (data.Length > MaxDataLenght)
            {
                throw new OutOfMemoryException("传入的数据过大(不接受超过1M的数据)!");
            }
            else
            {
                byte[] buffer = null;
                using (MemoryStream outms = new MemoryStream())
                {
                    using (DeflateStream df = new DeflateStream(outms, compressMode, true))
                    {
                        df.Write(data, 0, data.Length);
                    }
                    outms.Position = 0;
                    buffer = outms.ToArray();
                }
                return buffer;
            }
        }
        /// <summary>
        /// 解压deflate数据
        /// </summary>
        /// <param name="data">被压缩的内容</param>
        /// <exception cref="OutOfMemoryException">数据不建议超过1M</exception>
        /// <returns></returns>
        public static byte[] InFlate(byte[] data)
        {
            // todo: 这种写法在system.io.compress模式下是支持的.
            return Deflate(data, CompressionMode.Decompress);
        }

        public static string InFlate(byte[] data, Encoding encoder)
        {
            using (MemoryStream inputStream = new MemoryStream(data))
            using (DeflateStream gzip = new DeflateStream(inputStream, CompressionMode.Decompress))
            using (StreamReader reader = new StreamReader(gzip, GlobalConfig.Encoding))
            {
                return reader.ReadToEnd();
            }
        }

    }

}