[英]Read memory mapped file
我必须读取内存映射文件,写入似乎有效,但我不知道如何正确读取它。 这是我编写文件的方式:
public static void writeMapped(ArrayList<Edge> edges) throws FileNotFoundException, IOException{
// Create file object
File file = new File("data.txt");
//Delete the file; we will create a new file
file.delete();
// Get file channel in readonly mode
FileChannel fileChannel = new RandomAccessFile(file, "rw").getChannel();
// Get direct byte buffer access using channel.map() operation
// 7 values * 8 bytes(double = 8byte)
MappedByteBuffer buffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, (7*8)*edges.size());
//Write the content using put methods
for(Edge e : edges){
buffer.putDouble(e.X1);
buffer.putDouble(e.Y1);
buffer.putDouble(e.X2);
buffer.putDouble(e.Y2);
buffer.putDouble(e.color.getHue());
}
System.out.print("mapped done!");
}
我必须读取文件并创建与我编写文件时完全相同的数组列表。
这将是沿着这些路线的东西,尽管它可能需要一些改进:
File file = new File("data.txt");
FileChannel fileChannel = new RandomAccessFile(file, "r").getChannel();
MappedByteBuffer buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size());
List<Edge> edges= new ArrayList<Edge>();
while(buffer.hasRemaining())
{
Edge e = new Edge();
e.X1 = buffer.getDouble();
e.Y1 = buffer.getDouble();
e.X2 = buffer.getDouble();
e.Y2 = buffer.getDouble();
// here you will need to set the color Object first !!
// e.color.setHue(buffer.getDouble());
edges.add(e);
}
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