package tinyTCPServer.net;

public class DataBuffer {

private byte[] bf_ = null;

private int readBeginIdx_ = 0;

private int writeBeginIdx_ = 0;

public DataBuffer(int size) {

this.bf_ = new byte[size];

}

public int dataSize() {

return this.writeBeginIdx_ - this.readBeginIdx_;

}

public byte[] retrieveAllData() {

byte[] data = new byte[this.dataSize()];

System.arraycopy(this.bf_, this.readBeginIdx_, data, 0, this.dataSize());

this.reset();

return data;

}

public void setWriteIdx(int idx) {

this.writeBeginIdx_ = idx;

}

public void setReadIdx(int idx) {

this.readBeginIdx_ = idx;

}

public void reset() {

this.writeBeginIdx_ = 0;

this.readBeginIdx_ = 0;

}

public void append(byte[] bytes) {

int capcity = this.bf_.length - this.writeBeginIdx_;

if (capcity >= bytes.length) {

System.arraycopy(bytes, 0, this.bf_, this.writeBeginIdx_,

bytes.length);

this.writeBeginIdx_ = this.writeBeginIdx_ + bytes.length;

return;

} else {

int oldContentLen = this.writeBeginIdx_ - this.readBeginIdx_;

int totalEmptySize = this.bf_.length - oldContentLen;

int deltaSize = totalEmptySize - bytes.length;

if (deltaSize >= 0) {

// have enough place to handle the new content ,

// but need to adjust/move the buffer data then append the new

// data to the end

byte[] newBuff = new byte[this.bf_.length];

System.arraycopy(this.bf_, this.readBeginIdx_, newBuff, 0,

oldContentLen);

System.arraycopy(bytes, 0, newBuff, oldContentLen, bytes.length);

this.readBeginIdx_ = 0;

this.writeBeginIdx_ = this.readBeginIdx_ + oldContentLen

+ bytes.length;

this.bf_ = newBuff;

} else {

// Policy: enlarge the buffer size to double

int requireSize = (this.bf_.length + Math.abs(deltaSize)) * 2;

byte[] newBuff = new byte[requireSize];

System.arraycopy(this.bf_, 0, newBuff, 0, oldContentLen);

System.arraycopy(bytes, 0, newBuff, 0, bytes.length);

this.readBeginIdx_ = 0;

this.writeBeginIdx_ = this.readBeginIdx_ + oldContentLen

+ bytes.length;

this.bf_ = newBuff;

}

}

}

}