bytebuffer internal structure

ByteBuffer internal structure

ByteBuffer important properties

• capacity: capacity. How much data can fit in the bytebuffer
• position: Read and write pointer. Index subscript
• limit: limit for reading and writing

In the beginning, the post is at the starting position, limit is the limit size of writing,

In write mode, 4 values ​​are written, position moves 4 positions, limit is the capacity to write.

After calling flip() method, turn on read mode, postion starts reading from 0 again, limit moves from capacity position to topOne step to read the position of the data, because the write only writes to the position of d, no need to read the position of the capacity.

The state after reading 4 bytes, after calling the get() method, the position moves to the limit position, and the reading is completed.

After calling clear method, switch to write mode and position returns to 0, limit returns to the position of capacity, which means that data of capacity size can be written.

compact method: For some reason, the data must be written before the data is read. The following original data contains four bytes of abcd data. After reading ab, it is necessary to write the data and call compact.The method is to start writing data from d, instead of writing data from 0, which prevents data loss.