用于存储byte[]的buf

当多线程处理数据的时候,我们需要环形buf用于数据的缓存

public class MyRingBuf {

    private static final String TAG = MyRingBuf.class.getSimpleName();

    private static final boolean DEBUG_SHOW_ADD = false && com.physicaloid.BuildConfig.DEBUG;
    private static final boolean DEBUG_SHOW_GET = false && com.physicaloid.BuildConfig.DEBUG;

    private int mRingBufSize;
    private byte[] mRingBuf;
    private int mAddIndex;     // top of data index  private int mGetIndex;     // tail of data index   public long Last_write_time = System.currentTimeMillis();
    /**  * Ring buffer  * @param bufferSize buffer size. It needs enough size e.g.1024  */  public MyRingBuf(int bufferSize) {
        mRingBufSize = bufferSize+1;
        mRingBuf = new byte[mRingBufSize];
        mAddIndex = 0;
        mGetIndex = 0;
    }

    /**  * Gets ring buffer size  * @return ring buffer size  */  public int getRingBufferSize() {
        return mRingBufSize-1;
    }

    /**  * Gets buffered length  * @return buffered length  */  public int getBufferdLength() {
        if(mAddIndex >= mGetIndex) {
            return mAddIndex - mGetIndex;
        } else {
            return mAddIndex + (mRingBufSize - mGetIndex);
        }
    }

    /**  * Adds byte array to ring buffer  * @param buf byte array  * @param length added length  * @return actually added length  */  public synchronized int add(byte[] buf, int length) {
        int addLen = length;

        if(mAddIndex > mGetIndex) {
            if((mAddIndex + length) >= mRingBufSize) {                          // addした結果1周をまたぐ場合  if((mRingBufSize - mAddIndex) + (mGetIndex - 1) < length ) {    // 1周をまたいでなおlength以上になる場合  addLen = (mRingBufSize - mAddIndex) + (mGetIndex-1);        // 追い抜かないサイズに修正  }
            }
        } else if(mAddIndex < mGetIndex){ // 1周をまたいでいる場合  if((mGetIndex - 1) - mAddIndex < length) {
                addLen = (mGetIndex - 1) - mAddIndex;
            }
        }

        if(buf.length < addLen) {
            addLen = buf.length;
        }

        if((mAddIndex+addLen) >= mRingBufSize) { // storeがバッファ終端をまたぐ場合  int remain = mAddIndex + addLen - mRingBufSize;
            int copyLen = addLen-remain;
            if(copyLen != 0) {
                System.arraycopy(buf, 0, mRingBuf, mAddIndex, copyLen);
                if(DEBUG_SHOW_ADD){ Log.d(TAG, "add(" + length + ") : copy buf[0:" + (copyLen - 1) + "] to mRingBuf[" + mAddIndex + ":" + (mAddIndex + copyLen - 1) + "]"); }
            }

            mAddIndex = 0;

            if(remain != 0) {
                System.arraycopy(buf, copyLen, mRingBuf, mAddIndex, remain);
                if(DEBUG_SHOW_ADD){ Log.d(TAG,"add("+length+") : copy buf["+(copyLen)+":"+(addLen-1)+"] to mRingBuf[0:"+(remain-1)+"]"); }
                mAddIndex = remain;
            }

            if(DEBUG_SHOW_ADD){ Log.d(TAG,"add("+length+") : addOffset = "+mAddIndex+", getOffset = "+mGetIndex); }
            Last_write_time = System.currentTimeMillis();
            return addLen;
        } else {
            System.arraycopy(buf, 0, mRingBuf, mAddIndex, addLen);

            if(DEBUG_SHOW_ADD){ Log.d(TAG,"add("+length+") : copy buf[0:"+(addLen-1)+"] to mRingBuf["+mAddIndex+":"+(mAddIndex+addLen-1)+"]"); }

            mAddIndex += addLen;

            if(DEBUG_SHOW_ADD){ Log.d(TAG,"add("+length+") : addOffset = "+mAddIndex+", getOffset = "+mGetIndex);}
            Last_write_time = System.currentTimeMillis();
            return addLen;
        }
    }

// long click;  /**  * Gets ring buffer to byte array  * @param buf byte array  * @param length gotten length  * @return actually gotten length  */  public synchronized int get(byte[] buf, int length) {
// click = System.currentTimeMillis();  int getLen = length;
        if(mAddIndex == mGetIndex) {
            return 0;
        } else if(mGetIndex < mAddIndex) { // 通常  if(mAddIndex - mGetIndex < length) {  // get要求サイズがバッファされているサイズより大きい場合  getLen = mAddIndex - mGetIndex;     // 今バッファされているサイズを返す  }
        } else {// インデックスが1周をまたいでいる場合  if(mAddIndex + (mRingBufSize-mGetIndex) < length) {     // get要求サイズがバッファされているサイズより大きい場合  getLen = mAddIndex + (mRingBufSize - mGetIndex);    // 今バッファされているサイズを返す  }
        }

        if(buf.length < getLen) {
            getLen = buf.length;
        }

        if((mGetIndex+getLen) >= mRingBufSize) {
            int remain = mGetIndex + getLen - mRingBufSize;
            int copyLen = getLen - remain;
            if( copyLen != 0) {
                System.arraycopy(mRingBuf, mGetIndex, buf, 0, copyLen);
                if(DEBUG_SHOW_GET){ Log.d(TAG,"get("+length+") : copy mRingBuf["+mGetIndex+":"+(mGetIndex+copyLen-1)+"] to buf[0:"+(copyLen-1)+"]"); }
            }

            mGetIndex = 0;

            if(remain !=0) {
                System.arraycopy(mRingBuf, mGetIndex, buf, copyLen, remain);
                if(DEBUG_SHOW_GET){ Log.d(TAG,"get("+length+") : copy mRingBuf[0:"+(remain-1)+"] to buf["+copyLen+":"+(remain-1)+"]"); }
                mGetIndex = remain;
            }

            if(DEBUG_SHOW_GET){  Log.d(TAG,"get("+length+") : addOffset = "+mAddIndex+", getOffset = "+mGetIndex); }
            return getLen;
        } else {
            System.arraycopy(mRingBuf, mGetIndex, buf, 0, getLen);

            if(DEBUG_SHOW_GET){ Log.d(TAG,"get("+length+") : copy mRingBuf["+mGetIndex+":"+(mGetIndex+getLen-1)+"] to buf[0:"+(getLen-1)+"]");}

            mGetIndex += getLen;

            if(DEBUG_SHOW_GET){ Log.d(TAG,"get("+length+") : addOffset = "+mAddIndex+", getOffset = "+mGetIndex); }

            return getLen;
        }
    }


    /**  * Clear ring buffer  */  public synchronized void clear() {
        mAddIndex = 0;
        mGetIndex = 0;
    }


}

使用方法:

读取:

public int read(byte[] buf, int size) {
    return mBuffer.get(buf, size);
}
增加:
public int write(byte[] buf, int size) {
    if (buf == null) {
        return 0;
    }
    int add = mBuffer.add(buf, size);
    return add;
}

写入数据

write(buf, size);

byte[] templ_buf = new byte[2048];
int item_len = read(templ_buf, 4096);
每次读取后会清楚Ringbuf的数据,返回读取的数据长度;