/// <summary>
/// 读取文件
/// 20M分段读取
/// </summary>
/// <param name="path"></param>
/// <param name="mapName"></param>
public async void ReadAllSegmentFileAsync(string path, string mapName = null)
{
IsComplete = false;
FileInfo file = new FileInfo(path);
if (!file.Exists)
{
return;
}
long offset = 0;
long len = 0;
long size = DefaultSize;
FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, fsCacheSize);
len = fs.Length;
//读取文件，capacity参数不能小于文件长度；
//但是capacity只是一个值，并不是就需要这么大内存
//内存在下一步创建视图时确定大小
//需要把视图部分加载到内存
using (MemoryMappedFile memoryFile = MemoryMappedFile.CreateFromFile(fs, mapName, 0, MemoryMappedFileAccess.Read, HandleInheritability.None, true))
{
while (len > 0)
{
//20M读取
//
size = len > DefaultSize ? DefaultSize : len;
//offset,size参数决定了当前访问位置及内存中大小。
using (var accessor = memoryFile.CreateViewAccessor(offset, size, MemoryMappedFileAccess.Read))
{
int index = 0; //当前读取
int r = 0; //当前读取长度
offset += size; //设置便宜值
len -= size; //剩余长度
while (true)
{
BaseBuffer <byte[]> item = null;
if (mapPool.TryGetBuffer(out item, 1000))
{
MemoryMapBuffer buf = (MemoryMapBuffer)item;
r = accessor.ReadArray <byte>(index, buf.Data, buf.OffSet, buf.Capacity);
index += r;
buf.Size = r;
lock (lock_obj)
{
lstData.Add(buf);
}
if (r < buf.Size || index >= DefaultSize)
{
//20M读取完成
break;
}
}
else
{
Console.WriteLine("MemoryMapStream:无法获取缓存，业务处理慢");
}
}
}
}
}
IsComplete = true;
fs.Close();
}
